| isolation and identification of a potent allelopathic substance in rice root exudates. | a search for growth inhibitors in rice root exudates was undertaken in order to clarify the allelopathic system in rice (oryza sativa l.). rice seedlings inhibited the growth of cress (lepidium sativum l.) and lettuce (lactuca sativa l.) seedlings when the cress and lettuce were grown with rice seedlings. the putative compound causing the inhibitory effect of rice seedlings was isolated from their culture solution, and the chemical structure of the inhibitor was determined by spectral data as mo ... | 2002 | 12081533 |
| [disinfection treatment for lettuces (lactuca sativa) and strawberries (fragatia chiloensis)]. | the disinfection of vegetables and fruits is a treatment applied in order to reduce their natural contamination or processes to the product along the different steps of the food chain until its consumption. in the present work the effect of two disinfectants products was studied: grapefruit seed extract (400 ppm) for 10 min and peracetic acid (2000 ppm) for 1 min (action times assayed according to the manufacturer recommendations) and other additional times. the germicidal action was carried out ... | 2001 | 12012564 |
| polyoxygenated cyclohexenes from the chinese tree, uvaria purpurea. | four new polyoxygenated cyclohexenes, 2-o-acetyl-6-o-methylzeylenol (2), 2-o-benzoyl-3-o-debenzoylzeylenone (5), 3-o-debenzoylzeylenone (6) and 3-o-debenzoylgrandiflorone (8), were isolated from the leaves of uvaria purpurea. 2-o-acetyl-6-o-benzoylzeylenol (3) was also isolated for the first time as a natural product. compounds 5-7 each showed inhibitory activity against the root growth of lactuca sativa. their structures were established by spectroscopic and chemical methods. | 2002 | 12005046 |
| involvement of putative chemical wound signals in the induction of phenolic metabolism in wounded lettuce. | cutting leaves of romaine lettuce (lactuca sativa l. cv. longifolia) produces a wound signal that induces the synthesis of phenylalanine ammonia lyase (pal, ec 4.3.1.5) and the accumulation of phenolic compounds in cells up to 2 cm from the site of injury, and tissue browning near the site of injury. the response of leaves within a head of romaine lettuce to putative chemical wound signals [abscisic acid (aba), jasmonate (ja) and methyl jasmonate (meja)] differed significantly with leaf age. exp ... | 2002 | 11982937 |
| characterization of "lettucine", a serine-like protease from lactuca sativa leaves, as a novel enzyme for milk clotting. | in this work we focused on the characterization of a novel plant rennet purified from lettuce leaves (lactuca sativa l. cv romana). the lettuce protease, lettucine, showed trypsin-like, sv8-like, and caseinolytic activities. although the enzyme did not recognize peptides having hydrophobic amino acid residues in the p(1) position of the target bond, it did show milk-clotting activity, suggesting that different bonds rather than the phe(105)-met(106) of the kappa-casein might be cleaved, still in ... | 2002 | 11929310 |
| halogenated auxins affect microtubules and root elongation in lactuca sativa. | we studied the effect of 4,4,4-trifluoro-3-(indole-3-)butyric acid (tfiba), a recently described root growth stimulator, and 5,6-dichloro-indole-3-acetic acid (dciaa) on growth and microtubule (mt) organization in roots of lactuca sativa l. dciaa and indole-3-butyric acid (iba) inhibited root elongation and depolymerized mts in the cortex of the elongation zone, inhibited the elongation of stele cells, and promoted xylem maturation. both auxins caused the plane of cell division to shift from ant ... | 2000 | 11762379 |
| hysteresis and positive cooperativity of iceberg lettuce polyphenol oxidase. | a kinetic study of the diphenolase activity of latent polyphenol oxidase (ppo), purified from iceberg lettuce (lactuca sativa l), revealed a sigmoid relationship between the reaction rate and the substrate concentration with a high hill coefficient (n(h) = 3.8). this positive cooperativity had not been previously described for any ppo. furthermore, the enzyme showed a lag phase in the expression of this activity, suggesting a hysteretic nature of the enzyme. the kinetic behavior, the latency and ... | 2001 | 11726215 |
| lyc1, a transgenic mutant of lactuca sativa (lettuce) tightly linked to chloroplast biogenesis. | a t-dna tagging mutant of lettuce was studied. the transgenic lettuce mutant, designated light yellowish cotyledon1 (lyc1), exhibited a chloroplast mutant phenotype in which the chloroplast development was arrested at the cotyledon stage and the cotyledon became a light yellowish due to the reduced level of chlorophyll content. a microscopic observation of the mutant showed that the chloroplasts failed to position along the cell wall, but were scattered in the cytoplasm. the number of chloroplas ... | 2001 | 11710531 |
| prediction of uptake of copper from solution by lettuce (lactuca sativa romance). | we studied effects of free copper ion activity and total copper concentration on copper uptake by lettuce from nutrient solution and a model was developed. in ethylenediaminetetraacetic acid and dissolved organic matter treatments, when ph and free copper ion activity were the same, root copper concentration did not change with the total copper concentration. however, at fixed ph and total copper concentration, root copper concentration increased with, and was log-log linearly related to free co ... | 2001 | 11699781 |
| evidence for a tetrameric form of iceberg lettuce (lactuca sativa l.) polyphenol oxidase: purification and characterization. | polyphenol oxidase from iceberg lettuce (lactuca sativa l.) chloroplasts was released from the thylakoid-membrane by sonication, and it was extensively purified to homogeneity as judged by sds-page. purification was achieved by ammonium sulfate fractionation, gel-filtration chromatography, and ion-exchange chromatography. two molecular forms were separated by gel-filtration chromatography with apparent molecular masses of 188 and 49 kda. both forms were characterized by sedimentation analysis wi ... | 2001 | 11600037 |
| calcium localization and tipburn development in lettuce leaves during early enlargement. | tissue concentrations of ca, mg, and k were determined across immature leaves of lettuce (lactuca sativa l. 'buttercrunch') at different stages of enlargement using electron microprobe x-ray analysis. the analysis was with a wavelength dispersive spectrometer to permit detection of low concentrations of ca. patterns of mineral accumulation in immature leaves that were exposed were compared to patterns of accumulation in leaves that were enclosed within a developing head. the leaves developing wi ... | 2000 | 11543566 |
| initiation and elongation of lateral roots in lactuca sativa. | lactuca sativa cv. baijianye seedlings do not normally produce lateral roots, but removal of the root tip or application of auxin, especially indole-butyric acid, triggered the formation of lateral roots. primordia initiated within 9 h and were fully developed after 24 h by activating the pericycle cells opposite the xylem pole. the pericycle cells divided asymmetrically into short and long cells. the short cells divided further to form primordia. the effect of root tip removal and auxin applica ... | 1999 | 11542270 |
| four polyoxygenated cyclohexenes from the chinese tree, uvaria purpurea. | two novel polyoxygenated cyclohexenes, 6-methoxyzeylenol (3) and 2-acetoxyzeylenone (4), together with two known compounds, zeylenol (1) and zeylenone (2), were isolated from the heartwood of the chinese tree, uvaria purpurea. zeylenol (1) and zeylenone (2) both showed inhibitory activity toward the root growth of lactuca sativa. their structures were established by spectroscopic and chemical methods. | 2001 | 11471741 |
| allelopathy, dimboa production and genetic variability in accessions of triticum speltoides. | a screening was conducted to study the allelopathic potential of australian-held accessions of triticum speltoides. of 26 accessions, four were found to inhibit root growth in the indicator species, lettuce (lactuca sativa). the methanol leaf extracts of these accessions significantly reduced the root length of wild oat (avena spp.). in all but one case, alellopathic accessions contained higher amounts of dimboa than did nonallelopathic accessions. since some variation in allelopathic response w ... | 2001 | 11446298 |
| responses of plant growth rate to nitrogen supply: a comparison of relative addition and n interruption treatments. | this paper investigates the effects of uptake of nitrate and the availability of internal n reserves on growth rate in times of restricted supply, and examines the extent to which the response is mediated by the different pools of n (nitrate n, organic n and total n) in the plant. hydroponic experiments were carried out with young lettuce plants (lactuca sativa l.) to compare responses to either an interruption in external n supply or the imposition of different relative n addition rate (rar) tr ... | 2001 | 11283176 |
| preparation and biological activity of four epiprogoitrin myrosinase-derived products. | (5r)-5-vinyl-1,3-oxazolidine-2-thione, (2s)-1-cyano-2-hydroxy-3-butene, and two diastereoisomeric erythro-(2s)- and threo-(2s)-1-cyano-2-hydroxy-3,4-epithiobutanes were prepared in pure form starting from (2s)-2-hydroxybut-3-enyl glucosinolate (epiprogoitrin). this glucosinolate was isolated in almost pure form using ripe seeds of crambe abyssinica and then hydrolyzed under different conditions. the hydrolysis was carried out using either myrosinase immobilized on nylon, to produce (5r)-5-vinyl- ... | 2001 | 11170613 |
| effect of wounding on phenolic enzymes in six minimally processed lettuce cultivars upon storage. | the effect of wounding on polyphenol oxidase (ppo), peroxidase (pod), and phenylalanine ammonia-lyase (pal) was studied in six minimally processed lettuce (lactuca sativa l.) cultivars upon storage for 7 days at 5 degrees c (iceberg mikonos (im), i. green queen (igq), i. asdrúbal (ia), little gem sandra (lgs), romaine cazorla (rc), and r. modelo (rm)). wounding of lettuce tissue midribs (because of minimal processing) caused an exponential increase in ppo activity due to the activation process f ... | 2001 | 11170594 |
| abscisic acid and hypoxic induction of anoxia tolerance in roots of lettuce seedlings. | lettuce (lactuca sativa l.) seedlings were subjected to anoxic stress after aba-pretreatment (aba-pt) or hypoxic-pretreatment (h-pt). the h-pt increased the survivability of the anoxia in roots of the seedlings by 5.2-fold compared to that of non-pretreated (n-pt) seedlings. aba-pt also increased the survivability at concentrations greater than 1 microm, and the survivability increased with increasing aba doses. at 100 microm aba, the survivability was 4.5-fold greater than that of n-pt seedling ... | 2000 | 11113172 |
| the action spectrum for maximal photosensitivity of germination. | fruits of garden lettuce, imbibed in 0.01 m kno3, were depleted of maternal active phytochrome b by saturating deep-red exposure and photosensitized by chilling for 1 week at 4 degrees c. twenty saturated fluence-response curves for photoinduced germination were elaborated between 300 and 800 nm, using exposure periods from 6 to 600 s at 22.5 degrees c; there is linear and closely parallel regression in the logarithmic probability net. the reciprocals of the half-response fluences obtained gave ... | 2000 | 11091963 |
| inactivation of dna replication origins by the cell cycle regulator, trigonelline, in root meristems of lactuca sativa. | the effects of trigonelline (trg) on the cell cycle in root meristems of lactuca sativa l. were examined in the knowledge that trg is a cell cycle regulator that causes cell arrest in g2, and prevents ligation of replicons in s-phase. the hypothesis was tested that continuous exposure to trg would perturb dna replication which, in turn, would lengthen the cell cycle and impair root elongation. using dna fibre autoradiography, mean replicon size was 31 and 13 microm in the trg (3 mm) and control ... | 2000 | 10923713 |
| inhibition of plant asparagine synthetase by monoterpene cineoles. | asparagine (asn) synthetase (as) is the key enzyme in asn biosynthesis and plays an important role in nitrogen mobilization. despite its important physiological function, little research has been done documenting inhibitors of plant as. plant growth inhibition caused by the natural monoterpene 1,4-cineole and its structurally related herbicide cinmethylin was reversed 65% and 55%, respectively, by providing 100 microm asn exogenously. reversion of the phytotoxic effect was dependent on the conce ... | 2000 | 10859202 |
| characterization of monophenolase activity of polyphenol oxidase from iceberg lettuce. | polyphenol oxidase (ec 1.14.18.1), a thylakoid membrane-bound enzyme, was isolated by sonication of osmotically shocked chloroplasts from iceberg lettuce (lactuca sativa). the enzyme showed monophenolase activity when assayed on (p-hydroxyphenyl)propionic acid with 3-methyl-2-benzothiazolinone hydrazone in a reliable continuous spectrophotometric method, with high sensitivity, accuracy, and precision. the monophenolase activity showed a lag period before the steady-state rate (v(ss)) was reached ... | 1999 | 10563992 |
| determination of ametryn herbicide by bioassay and gas chromatography-mass spectrometry in analysis of residues in drinking water. | a simple, rapid and quantitative bioassay method was compared to a gas chromatography/mass spectrometry (gc/ms) procedure for the analysis of ametryn in surface and groundwater. this method was based on the activity of ametryn in inhibiting the growth of the primary root and shoot of germinating letuce, lactuca sativa l. seed. the procedure was sensitive to 0.01 microgram/l and was applicable from this concentration up to 0.6 microgram/l. initial surface sterilization of the seed, selection of p ... | 1999 | 10464973 |
| toxicity of formulated glycol deicers and ethylene and propylene glycol to lactuca sativa, lolium perenne, selenastrum capricornutum, and lemna minor | laboratory studies were conducted to determine the toxicity of ethylene glycol (eg) and propylene glycol (pg) as well as two formulated glycol aircraft deicing/anti-icing fluids (adafs) to lettuce (lactuca sativa), perennial ryegrass (lolium perenne), a green alga (selenastrum capricornutum), and duckweed (lemna minor). seedling emergence, root length, and shoot length were measured in lettuce and ryegrass; cell growth of the alga and frond growth, chlorophyll a, and pheophytin a of the duckweed ... | 1999 | 10341039 |
| mapping morphological genes relative to molecular markers in lettuce (lactuca sativa l.) | two f2 populations were generated by crossing morphologically diverse genetic stocks in order to map 10 morphological traits relative to polymerase chain reaction-based molecular markers (rapds). using one segregating population generated from crossing the experimental line, 'dwarf-2', with the butterhead cultivar, 'saffier', the dwarf phenotype conditioned by the dwf2 locus was mapped using bulked segregation analysis to within 38 cm of the adh3 locus. using the second segregating population ge ... | 1999 | 10336698 |
| postharvest analysis of vitamin c and inorganic cations in lettuce by cze. | in the present work, we used capillary zone electrophoresis (cze) for the analysis of vitamin c and inorganic cations (potassium, sodium, calcium, and magnesium) in lettuce (lactuca sativa) during postharvest storage. the leaves of the creasphead lettuce samples were treated with 18 m omega water for cation analysis and, alternatively, with 3% wt/vol oxalic acid solution for ascorbic acid extraction. they were then homogenized and centrifuged, and the supernatants were introduced into the capill ... | 2013 | 10327371 |
| microsatellite retrieval in lettuce (lactuca sativa l.). | by using enriched genomic libraries, microsatellite-containing sequences were isolated from lettuce (lactuca sativa) with high efficiency. with this approach, a sizeable fraction (up to 55%) of the clones contained a microsatellite. in about half of these clones, primers could be designed for pcr amplification of the microsatellite. this yielded 28 primer sets amplifying unambiguously scorable products, of which 26 showed polymorphisms in a test set of six lettuce varieties. practically all micr ... | 1999 | 10208007 |
| phylogenetic relationships among lactuca (asteraceae) species and related genera based on its-1 dna sequences. | internal transcribed spacer (its-1) sequences from 97 accessions representing 23 species of lactuca and related genera were determined and used to evaluate species relationships of lactuca sensu lato (s.l.). the its-1 phylogenies, calculated using paup and phylip, correspond better to the classification of feráková than to other classifications evaluated, although the inclusion of sect. lactuca subsect. cyanicae is not supported. therefore, exclusion of subsect. cyanicae from lactuca sensu ferák ... | 1998 | 21680311 |
| regulation of thermal dissipation of absorbed excitation energy and violaxanthin deepoxidation in the thylakoids of lactuca sativa. photoprotective mechanism of a population of photosystem ii centers | non-photochemical quenching of chlorophyll a fluorescence is thought to be mainly associated with thermal dissipation of excitation energy taking place within the antenna and reaction center of ps ii. in this report, non-photochemical fluorescence quenching was investigated in the fluorescence yields induced by a series of short and high-energy flashes after dark adaptation. the observation of period four fluorescence oscillations with increasing flash number indicates functioning o2 evolving ce ... | 1998 | 9507102 |
| kinetic study of the suicide inactivation of latent polyphenoloxidase from iceberg lettuce (lactuca sativa) induced by 4-tert-butylcatechol in the presence of sds. | in plants, polyphenoloxidase undergoes an irreversible inactivation during the oxidation of o-diphenol to o-quinones. in the present paper, using latent polyphenoloxidase from iceberg lettuce (lactuca sativa), in the presence of an activating agent, sds, the kinetic parameters that characterize the enzyme during its action on the suicide substrate 4-tert-butylcatechol have been determined. the effect of ph has also been considered. it was seen that the presence of sds in the reaction medium chan ... | 1997 | 9187250 |
| endo-[beta]-mannanase activity present in cell wall extracts of lettuce endosperm prior to radicle emergence. | lettuce (lactuca sativa l.) endosperm cell walls isolated prior to radicle emergence underwent autohydrolysis, the rate of which was correlated with whether radicle emergence would subsequently occur. extraction of endosperm cell walls with 6 m licl suppressed autohydrolysis, and the desalted extract possessed activity that was capable of hydrolyzing purified locust bean galactomannan but not arabinogalactan, carboxymethylcellulose, glucomannan, polygalacturonic acid, tomato galactomannan, or na ... | 1997 | 12223598 |
| influence of fertilizer and sewage sludge compost on yield and heavy metal accumulation by lettuce grown in urban soils. | previous research has demonstrated that many urban soils are enriched in pb, cd and zn. culture of vegetable crops in these soils could allow transfer of potentially toxic metals to foods. 'tanya' lettuce (lactuca sativa l.) was grown in pots of five urban garden soils and one control agricultural soil to assess the effect of urban-soil metal enrichment, and the effect of soil amendments, on heavy metal uptake by garden vegetables. the amendments included npk fertilizer, limestone, ca(h2po4)2, a ... | 1996 | 24194408 |
| an automated plant monitoring system using machine vision. | a plant growth chamber equipped with a machine vision (mv) system was developed for the continuous, non-contact sampling and near-real-time evaluation of the top projected leaf area (tpla) of lettuce (lactuca sativa, cv. ostinata) seedlings. a rotary table enabled automatic, individual presentation of the lettuce plants to the imaging system. hourly measurements were continuously made for 16 plants from the first true leaf stage through 30 days from seeding. a near-infrared radiation source illu ... | 1996 | 11541581 |
| effect of dissolved oxygen concentration on lettuce growth in floating hydroponics. | lettuce (lactuca sativa l., cv. ostinata) growth experiments were carried out to study the effect of dissolved oxygen (do) concentration on plant growth in a floating hydroponic system. pure o2 and n2 gas were supplied to the hydroponic system for precise do control. this system made it easy to increase the do concentration beyond the maximum (or saturation) concentration possible when bubbling air into water. eleven day old lettuce seedlings were grown for 24 days under various do concentration ... | 1996 | 11541573 |
| a system and methodology for measuring volatile organic compounds produced by hydroponic lettuce in a controlled environment. | a system and methodology were developed for the nondestructive qualitative and quantitative analysis of volatile emissions from hydroponically grown 'waldmann's green' leaf lettuce (lactuca sativa l.). photosynthetic photon flux (ppf), photoperiod, and temperature were automatically controlled and monitored in a growth chamber modified for the collection of plant volatiles. the lipoxygenase pathway products (z)-3-hexenal, (z)-3-hexenol, and (z)-3-hexenyl acetate were emitted by lettuce plants af ... | 1996 | 11539353 |
| violaxanthin de-epoxidase. | violaxanthin de-epoxidase catalyzes the de-epoxidation of violaxanthin to antheraxanthin and zeaxanthin in the xanthophyll cycle. its activity is optimal at approximately ph 5.2 and requires ascorbate. in conjunction with the transthylakoid ph gradient, the formation of antheraxanthin and zeaxanthin reduces the photochemical efficiency of photosystem ii by increasing the nonradiative (heat) dissipation of energy in the antennae. previously, violaxanthin de-epoxidase had been partially purified. ... | 1996 | 8742341 |
| linking plant tissue concentrations and soil copper pools in urban contaminated soils. | copper tissue concentrations of radish (raphanus sativa cv. cherry belle), lettuce (lactuca sativa cv. buttercrunch) and ryegrass (lolium perenne cv. barmultra) grown in a greenhouse in urban contaminated soils are compared to total, soluble and free ion copper pools. the tissue concentrations of copper vary between 8.1 and 82.6 mg cu kg(-1) dry tissue and the total soil copper content varies between 32 and 640 mg cu kg(-1) dry soil. the linear regressions with cupric ion activity and total soil ... | 1996 | 15093501 |
| effect of co2 levels on nutrient content of lettuce and radish. | atmospheric carbon-dioxide enrichment is known to affect the yield of lettuce and radish grown in controlled environments, but little is known about co2 enrichment effects on the chemical composition of lettuce and radish. these crops are useful model systems for a controlled ecological life-support system (celss), largely because of their relatively short production cycles. lettuce (lactuca sativa l.) cultivar 'waldmann's green' and radish (raphanus sativus l.) cultivar 'giant white globe' were ... | 1996 | 11538818 |
| effect of crop development on biogenic emissions from plant populations grown in closed plant growth chambers. | the biomass production chamber at john f. kennedy space center is a closed plant growth chamber facility that can be used to monitor the level of biogenic emissions from large populations of plants throughout their entire growth cycle. the head space atmosphere of a 26-day-old lettuce (lactuca sativa cv. waldmann's green) stand was repeatedly sampled and emissions identified and quantified using gc-mass spectrometry. concentrations of dimethyl sulphide, carbon disulphide, alpha-pinene, furan and ... | 1995 | 7669278 |
| occurrence of the carotenoid lactucaxanthin in higher plant lhc ii. | the pigment composition of the light-harvesting complexes of photosystem ii (lhc ii) has been determined for lettuce (lactuca sativa). in common with other members of the composite, the photosynthetic tissues of this species may contain large amounts of the carotenoid lactucaxanthin (ε, ε-carotene-3,3'-diol) in addition to their normal compliment of carotenoids. the occurrence and distribution of lactucaxanthin in lhc ii has been examined using isoelectric focusing of bby particles followed by r ... | 1995 | 24306850 |
| influence of growth conditions on the value of crisphead lettuce. 4. quality changes during storage. | crisphead lettuce (lactuca sativa l. var capitata cvs. marius and saladin) were grown with a nitrogen supply from 50 to 200 kg n/hectare. heads were stored for one or two weeks at 1 degree c in cold storage or ice bank cooling. samples were taken for measurement of dry matter, sugars, vitamin c and nitrate. the content of dry matter, sugars (glucose, fructose) and vitamin c decreased with increasing level of nitrogen, and the content of nitrate increased. except for nitrate the contents of the o ... | 1995 | 7792264 |
| phloem sap collection from lettuce (lactuca sativa l.): chemical comparison among collection methods. | the chemical composition of phloem sap from lettuce, collected by three different methods, was compared. phloem sap from stylectomy samples contained sucrose and 14 amino acids. honeydew and edta chelation samples showed considerable breakdown of sucrose into fructose and glucose, several additional amino acids, and large differences in relative concentrations of amino acids, when compared to stylectomy samples. honeydew contained considerable amounts of other oligosaccharides, and few proteins ... | 1994 | 24241986 |
| phloem sap collection from lettuce (lactuca sativa l.): methodology and yield. | three methods to collect phloem sap on different lettuce lines were optimized and are described in detail. the success ratio for stylectomy of aphids was over 80% through the combination of a specially designed setup and electrical penetration graphs to monitor phloem sap ingestion. for unknown reasons on some lettuce lines stylets never showed sustained exudation. there were clear differences in stylet exudation between two aphid species on the same lettuce line. honeydew collection in hexadeca ... | 1994 | 24241985 |
| differentiation of nearly identical germplasm accessions by a combination of molecular and morphologic analyses. | polymerase chain reaction (pcr) based random amplified polymorphic dna (rapd) markers were used to study the extent of redundancy (duplication of genetic materials) within a genetic resources collection. nine nearly phenotypically and identical accessions of butterhead lettuce (lactuca sativa l.) were assayed for their genetic identities. a nonuniform, heterogeneous butterhead line and a crisphead cultivar were added for population comparison. pcr amplification using 13 oligonucleotide primers g ... | 1994 | 18470101 |
| growth and gas exchange by lettuce stands in a closed, controlled environment. | two studies were conducted in which 'waldmann's green' lettuce (lactuca sativa l.) was grown hydroponically from seed to harvest in a large (20-m2), atmospherically closed growth chamber for the national aeronautics and space administration's controlled ecological life support system (celss) program. the first study used metal-halide (mh) lamps [280 micromoles m-2 s-1 photosynthetic photon flux (ppf)], whereas the second used high-pressure sodium (hps) lamps (293 micromoles m-2 s-1). both studie ... | 1994 | 11538197 |
| intron loss from the nadh dehydrogenase subunit 4 gene of lettuce mitochondrial dna: evidence for homologous recombination of a cdna intermediate. | the mitochondrial gene coding for subunit 4 of the nadh dehydrogenase complex i (nad4) has been isolated and characterized from lettuce, lactuca sativa. analysis of nad4 genes in a number of plants by southern hybridization had previously suggested that the intron content varied between species. characterization of the lettuce gene confirms this observation. lettuce nad4 contains two exons and one group iia intron, whereas previously sequenced nad4 genes from turnip and wheat contain three group ... | 1994 | 8190077 |
| analysis of a detailed genetic linkage map of lactuca sativa (lettuce) constructed from rflp and rapd markers. | a detailed genetic map has been constructed from the f2 population of a single intraspecific cross of lactuca sativa (n = 9). it comprises 319 loci, including 152 restriction fragment length polymorphism (rflp), 130 random amplified polymorphic dna (rapd), 7 isozyme, 19 disease resistance, and 11 morphological markers. thirteen major, four minor linkage groups and several unlinked markers are identified for this genome which is estimated to be approximately 1950 cm. rflp and rapd markers show si ... | 1994 | 7912217 |
| membrane barriers and mehler-peroxidase reaction limit the ascorbate available for violaxanthin de-epoxidase activity in intact chloroplasts. | the presence of an acidic lumen and the xanthophylls, zeaxanthin and antheraxanthin, are minimal requirements for induction of non-radiative dissipation of energy in the pigment bed of photosystem ii. we recently reported that ascorbate, which is required for formation for these xanthophylls, also can mediate the needed lumen acidity through the mehler-peroxidase reaction [neubauer and yamamoto (1992) plant physiol 99: 1354-1361]. it is demonstrated that in non-co2-fixing intact chloroplasts and ... | 1994 | 24311066 |
| cell-wall autohydrolysis in isolated endosperms of lettuce (lactuca sativa l.). | cell walls prepared from the endosperm tissue of hydrated lettuce (lactuca sativa l.) seeds undergo autohydrolysis. release of carbohydrates is most rapid (0.4-0.6 [mu]g per endosperm) within the 1st h of incubation in buffer, but substantial autolysis is sustained for at least 10 h. autolysis is temperature sensitive, and the optimum rate occurs at ph 5. the rate of autolysis increases markedly in the period just prior to radicle emergence. the cell-wall polysaccharide composition in micropylar ... | 1994 | 12232113 |
| lettuce and carrot allergy: are they related? | lettuce is commonly included in many elimination diets of subjects with either food allergy or atopic dermatitis since ige-mediated allergic reactions have not been reported. we have observed a positive carrot skin test and/or rast in two clinically lettuce sensitive, ragweed allergic subjects and positive lettuce skin test and/or rast in two ragweed allergic patients with oral allergy syndrome to carrot. in this study lettuce allergy and the allergenic relationship between iceberg lettuce (lact ... | 2004 | 8005454 |
| transactivation of ds elements in plants of lettuce (lactuca sativa). | the maize transposable element, activator (ac), is being used to develop a transposon mutagenesis system in lettuce, lactuca sativa. in this paper, we describe somatic and germinal transactivation of ds by chimeric transposase genes in whole plants. constructs containing either the ds element or the ac transposase open reading frame (orf) were introduced into lettue. the ds element was located between either the 35s or the nos promoter and a chimeric spectinomycin resistance gene (which included ... | 1993 | 8246892 |
| infrequent transposition of ac in lettuce, lactuca sativa. | the maize transposable element activator (ac) is being used to develop a transposon mutagenesis system in lettuce, lactuca sativa. two constructs containing the complete ac from the waxy-m7 locus of maize were introduced into lettuce and monitored for activity using southern analysis and pcr amplification of the excision site. no transposition of ac was detected in over 32 transgenic r1 plants, although these constructs were known to provide frequent transposition in other species. also, no tran ... | 1993 | 8395257 |
| mehler-peroxidase reaction mediates zeaxanthin formation and zeaxanthin-related fluorescence quenching in intact chloroplasts. | induction of zeaxanthin formation and the associated nonphotochemical quenching in iodoacetamide-treated, non-co(2)-fixing intact chloroplasts of lactuca sativa l. cv romaine is reported. the electron transport needed to generate the required deltaph for zeaxanthin formation and nonphotochemical quenching are ascribed to the mehler-ascorbate peroxidase reaction. kcn, an inhibitor of ascorbate peroxidase, significantly affected these activities without affecting linear electron transport to methy ... | 1992 | 16669044 |
| importance of 'blue' photon levels for lettuce seedlings grown under red-light-emitting diodes. | light-emitting diodes (leds) with high-intensity output are being studied as a photosynthetic light source for plants. high-output leds have peak emission at approximately 660 nm concentrated in a waveband of +/- 30 nm. lettuce (lactuca sativa grand rapids') seedlings developed extended hypocotyls and elongated cotyledons when grown under these leds as a sole source of irradiance. this extension and elongation was prevented when the red led radiation was supplemented with more than 15 micromoles ... | 1992 | 11537611 |
| dark induction of zeaxanthin-dependent nonphotochemical fluorescence quenching mediated by atp. | zeaxanthin-dependent nonphotochemical fluorescence quenching is a light-induced activity in plants that apparently protects against the potentially damaging effects of excess light. we report a dark-induced nonphotochemical quenching in thylakoids of lactuca sativa l. cv. romaine mediated by atp. this effect is due to low lumen ph from hydrolysis-dependent proton pumping and hence required an active atpase. the induction was optimal at 0.3 mm atp, a physiological concentration, and occurred unde ... | 1992 | 1542689 |
| root growth-promoting activities of n-acyl-l-proline derivatives. | a number of n-acyl-l-proline derivatives were synthesized and their biological activities were investigated by using lettuce (lactuca sativa l. cv. sacramento) seedling test. a wide variety of these compounds promoted root growth at 25°c both under light and in darkness. of the compounds tested, n-(2-ftuorobenzoyl)-l-proline methyl ester (4) showed the highest activity and caused a 270% increase in the root elongation compared to the control. n-(2-naphthoyl)-l-proline methyl ester (14) promoted ... | 1992 | 27286207 |
| interactions of uptake of malate and nitrate into isolated vacuoles from lettuce leaves. | vacuoles were isolated from leaves of two lettuce (lactuca sativa l.) genotypes that differed significantly in their nitrate accumulation. the rate of nitrate uptake into the vacuoles did not differ between the genotypes, but the malate-uptake rate did. fitting a michaelis-menten equation, with or without the addition of a linear term, showed that the rates of malate and nitrate uptake can be best described by saturation kinetics for both genotypes. malate transport across the tonoplast showed a ... | 1991 | 24193527 |
| inhibition of lettuce seed germination by cycloheximide and chloramphenicol is alleviated by kinetin and oxygen. | kinetin alleviates cycloheximide inhibition and oxygen alleviates chloramphenicol inibition of germination of lettuce seeds (lactuca sativa l. cv grand rapids). the effect is not due to increased but rather a substitution for protein synthesis. a cytokinin and energy supply appear prime requirements for germination. | 1991 | 16668478 |
| calcium localization in lettuce leaves with and without tipburn: comparison of controlled-environment and field-grown plants. | an electron microprobe was used to determine tissue concentrations of ca across 20-mm-long leaves of 'green lakes' crisphead lettuce (lactuca sativa l.) with and without tipburn injury. concentrations within the fifth and 14th leaves, counted from the cotyledons, from plants grown under controlled-environment conditions were compared to concentrations within similar leaves obtained from plants grown under field conditions. only the 14th leaf from plants grown under controlled-environment conditi ... | 1991 | 11538112 |
| separation of light-induced [c]ent-kaurene metabolism and light-induced germination in grand rapids lettuce seeds. | the effect of light on the metabolism of [(14)c]kaurene in light-requiring lettuce seeds (lactuca sativa l. cv grand rapids) was investigated. seeds were soaked in a solution of [(14)c]ent-kaurene in methylene chloride with 0.01% tween-20, dried, and incubated in 20% polyethylene glycol (peg) to prevent seedling development. labeled metabolites were extracted and analyzed by high performance liquid chromatography and gas chromatography-radio counting. [(14)c]ent-kaurenol and [(14)c]ent-kaurenal ... | 1991 | 16668262 |
| the nutritional status of the apical meristem of lactuca sativa as affected by nacl salinization: an electron-probe microanalytic study. | a volume of tissue of lettuce (lactuca sativa l.) plants extending 2 mm basipetally from the apical meristem and including leaf primordia and young expanding leaves was surveyed using electron-probe microanalysis (epma) on both frozen-hydrated and freeze-dried samples. this analysis was carried out either 2 or 5 d following nacl salinization of the medium from the 10 mol · m(--3) control level up to 80 mol · m(--3). the objective was the investigation of possible changes in the nutritional statu ... | 1991 | 24194150 |
| complementary analysis of freeze-dried and frozen-hydrated plant tissue by electron-probe x-ray microanalysis: spectral resolution and analysis of calcium. | automated methods of peak determination including peak location, background determination and peak deconvolution are presented. special attention is given to the problem of severely overlapped peaks, such as the primary calcium peak (caka) and the secondary potassium peak (kkβ). a method, based on the principle of electronic transitional probabilities, is presented for estimating ca in the presence of a high background of k, and limitations of resolution are discussed. minimally detectable conce ... | 1991 | 24194149 |
| interspecific somatic hybridization between lettuce (lactuca sativa) and wild species l. virosa. | somatic hybrids between cultivated lettuce (lactuca sativa) and a wild species l. virosa were produced by protoplast electrofusion. hybrid selection was based on inactivation of l. sativa with 20mm iodoacetamide for 15 min, and the inability of l. virosa protoplasts to divide in the culture conditions used. protoplasts were cultured in agarose beads in a revised ms media. in all 71 calli were formed and 21 of them differentiated shoots on ls medium containing 0.1mg/l naa and 0.2mg/l ba. most reg ... | 1991 | 24220705 |
| light-emitting diodes as a radiation source for plants. | development of a more effective radiation source for use in plant-growing facilities would be of significant benefit for both research and commercial crop production applications. an array of light-emitting diodes (leds) that produce red radiation, supplemented with a photosynthetic photon flux (ppf) of 30 micromoles s-1 m-2 in the 400- to 500-nm spectral range from blue fluorescent lamps, was used effectively as a radiation source for growing plants. growth of lettuce (lactuca sativa l. grand r ... | 1991 | 11537727 |
| a water relations analysis of seed germination rates. | seed germination culminates in the initiation of embryo growth and the resumption of water uptake after imbibition. previous applications of cell growth models to describe seed germination have focused on the inhibition of radicle growth rates at reduced water potential (psi). an alternative approach is presented, based upon the timing of radicle emergence, to characterize the relationship of seed germination rates to psi. using only three parameters, a ;hydrotime constant' and the mean and stan ... | 1990 | 16667786 |
| direct isolation of vacuoles from leaf tissue of lettuce (lactuca sativa) retaining protoplasts within the leaves. | a procedure is described in which vacuoles are isolated from leaf tissue of lettuce (lactuca sativa l.). after incubation in an enzyme solution, the vacuoles are directly extracted from the leaf tissue by osmotic shock using a phosphate buffer. in this method no protoplasts are released from the leaf tissue. this procedure avoids the problems of separating vacuoles from protoplasts with similar density. to evaluate the purity of the vacuoles, the activity of glucan synthetase 11 (ec 2.4.1.34), n ... | 1990 | 21087281 |
| induced expression of a chimeric gene construct in transgenic lettuce plants using tobacco pathogenesis-related protein gene promoter region. | the expression of a stress- and salicylic acidinducible protein gene from tobacco, pr1a protein gene, was determined after its introduction to lettuce (lactuca sativa l.) plants. the 5' flanking 2.4 kb fragment from pr1a gene was joined to the bacterial β -glucuronidase (gus) gene (pr-gus) and introduced into lettuce cotyledons by agrobacterium-mediated gene transfer using a binary vector containing a kanamycin-resistance gene as a selectable marker. as a control with constitutive expression, th ... | 1990 | 24226367 |
| [effect of outer space factors on lettuce seeds (lactuca sativa) flown on "kosmos" biosatellites]. | the effect of cosmic radiation on air-dry lettuce (lactuca sativa) seeds was investigated. it was attempted to discriminate the effects of cosmic ionizing radiation per se and its combination with solar light radiation. it was found that the number of aberrant cells in the seeds exposed to solar light was smaller than that of cells chielded with 0.0008 to 0.0035 g/cm2 foil which could be attributed to photoreactivity. | 2006 | 2329764 |
| [effect of single exposure of the seeds of lactuca sativa to heavy ions of galactic cosmic radiation at orbital manned space stations "saliut-6" and "saliut-7"]. | this paper presents the results of measuring single heavy ions (hi) of galactic cosmic rays during 40- to 457-day flights of manned orbital stations salyut-6 and salyut-7. cytogenetic analysis of lactuca sativa seeds showed a significant increase of aberrant cells and cells with multiple chromosome aberrations in seeds hit with hi compared to non-hit++ seeds during flights of 123 to 457 days in duration. there was a good correlation between curves showing aberrant cells as a function of flight o ... | 2006 | 2625981 |
| kinetin enhanced 1-aminocyclopropane-1-carboxylic acid utilization during alleviation of high temperatures stress in lettuce seeds. | the thermoinhibition at 35 and 32 degrees c of pregermination ethylene production and germination in lettuce (lactuca sativa l. cv mesa 659) seeds was synergistically or additively alleviated by 0.05 millimolar kinetin (kin) and 10 millimolar 1-aminocyclopropane-1-carboxylic acid (acc). the synergistic effect of kin + acc on ethylene production and germination at 35 degrees c was inhibited by co(2+) (44-46%) but not by aminoethoxyvinyl glycine (avg). the uptake of acc by the seed was not influen ... | 1989 | 16667094 |
| chloroplast gene expression in lettuce grown under different irradiances. | chloroplast dna sequences have been used as hybridisation probes to measure the levels of rna transcripts present in low- and high-light-grown lettuce (lactuca sativa l.) plants. the transcript levels for rbc l, psa a, psb a and rdna are not different between these two light regimes. in contrast, transcript levels for atp be and pet bd are increased in high-light as a proportion of the chloroplast rna. three days after transfer from low-light into high-light, increased transcript levels were fou ... | 1989 | 24212551 |
| control processes in the induction and relief of thermoinhibition of lettuce seed germination : actions of phytochrome and endogenous ethylene. | germination of lettuce seeds (lactuca sativa l. cv grand rapids) in the dark was nearly 100% at 20 degrees c but was inhibited at 27 degrees c and higher temperatures (thermoinhibition). a single 5-minute exposure to red light completely overcame the inhibition at temperatures up to 28 degrees c, above which the effectiveness of single light exposures gradually declined to reach a negligible level at 32 degrees c. however, the promotive effect of light could be extended to 34 degrees c by repeat ... | 1989 | 16666755 |
| [combined effects of beta radiation and shock wave on the seeds of lettuce lactuca sativa l]. | the effect of shock wave (sw) and beta-radiation (beta) on lactuca sativa l. seeds was investigated. exposure to sw at an amplitude of 200 and 600 mpa in various combinations with beta caused a lower survival rate and development of abnormal plants. at an amplitude of 600 mpa, when the sw + beta protocol was used, the maximum amount of abnormalities was seen after 220-240 hours of wetting and when the beta + sw protocol was used the maximum amount of abnormalities was seen after 80-100 hours of ... | 2014 | 2716274 |
| effects of incandescent radiation on photosynthesis, growth rate and yield of 'waldmann's green' leaf lettuce. | effects of different ratios incandescent (ln) to fluorescent (fl) radiation were tested on growth of 'waldmann's green' leaf lettuce (lactuca sativa l.) in a controlled environment. after 4 days of treatment, dry weight, leaf area, relative growth rate (rgr), net assimilation rate (nar), leaf area ratio (lar) and photosynthetic rate (pn) were greater for plants grown at 84 rather than 16% of total irradiance (82 w m-2) from ln lamps. although leaf dry weight and area were 12-17% greater at 84% l ... | 1989 | 11539045 |
| effects of prolonged exposure of lettuce seeds to hze particles on orbital stations. | in a study of the biological effects of cosmic hze particles, lettuce (lactuca sativa) seeds were flown on the orbital stations salyut 6 and 7 for varying periods of time (from 40 to 457 days). the dependence of the biological damage on flight duration, physical parameters and the fact of passage of an hze particle through the seed was estimated using the criterion of the frequency of aberrant cells. the arrangement of the flight biological container biobloc made it possible to trace the locatio ... | 1989 | 11537348 |
| biological effects of galactic radiation hze particles in experiments on the orbital station salyut 7. | lettuce (lactuca sativa) seeds were flown on-board the orbital station salyut 7 for 66-457 days. it was found that a single heavy charged particle (hze) hitting a seed only slightly affects the subsequent plant growth. however, morphological anomalies of varying type in primordial leaves and roots were observed that show good correlation with the location of the particle track. the most severe damage detected by light and an electron microscopy were "channels" in dry and soaked seeds. the appear ... | 1989 | 11537347 |
| sodium and potassium compartmentation and transport in the roots of intact lettuce plants. | in this report, we consider the accumulation in roots, and transport to the shoot, of na(+) and k(+) in intact lettuce plants (lactuca sativa cv black-seeded simpson). plants were grown in modified hoagland medium supplemented with 10 moles nacl per cubic meter. at this salinity, significant levels of na(+) were accumulated in roots and shoots, but there was no reduction in plant growth. transport characteristics for both na(+) and k(+) were qualitatively similar to those previously reported, fo ... | 1988 | 16666455 |
| plant hormone interaction and phenolic metabolism in the regulation of russet spotting in iceberg lettuce. | russet spotting (rs) is a physiological disorder induced in iceberg lettuce (lactuca sativa l.) by exposure to parts per million levels of ethylene at 5 +/- 2 degrees c. ethylene induced phenylalanine ammonia-lyase and ionically bound peroxidase activities that correlated with development of rs symptoms. the ethylene-treated tissue had significantly higher lignin content than air control tissue with lignification localized in walls of rs-affected cells. ethylene also caused the accumulation of t ... | 1988 | 16666434 |
| synergistic enhancement of ethylene production and germination with kinetin and 1-aminocyclopropane-1-carboxylic acid in lettuce seeds exposed to salinity stress. | relief of salt (0.1 molar nacl) stress on germination of lettuce (lactuca sativa l., cv mesa 659) seeds occurred with applications of 0.05 millimolar kinetin (kin) and 1 to 10 millimolar 1-aminocyclopropane 1-carboxylic acid (acc). treatment with kin enhanced the pregermination ethylene production under saline condition. a synergistic or an additive enhancement of pregermination ethylene production and germination occurred under saline condition in the presence of kin and a saturating dose (10 m ... | 1988 | 16666236 |
| abscisic acid is an endogenous inhibitor in the regulation of mannanase production by isolated lettuce (lactuca sativa cv grand rapids) endosperms. | the production of mannanase, a cell-wall-degrading carbohydrase, can be manipulated in isolated lettuce (lactuca sativa cv grand rapids) endosperms by changes in the volume of buffer in which they are incubated. the enzyme is produced when endosperms are incubated in a large volume, but not when incubated in a small volume, which is suggestive that an endogenous, diffusible inhibitor of mannanase production is being lost from the endosperms in a large volume (jd bewley, p halmer 1980/1981 israel ... | 1988 | 16666203 |
| effects of co2 and photosynthetic photon flux on yield, gas exchange and growth rate of lactuca sativa l. 'waldmann's green.' | enrichment of co2 to 46 mmol m-3 (1000 mm3 dm-3) at a moderate photosynthetic photon flux (ppf) of 450 micromoles m-2 s-1 stimulated fresh and dry weight gain of lettuce leaves 39% to 75% relative to plants at 16 mmol m-3 co2 (350 mm3 dm-3). relative growth rate (rgr) was stimulated only during the first several days of exponential growth. elevating co2 above 46 mmol m-3 at moderate ppf had no further benefit. however, high ppf of 880-900 micromoles m-2 s-1 gave further, substantial increases in ... | 1988 | 11539044 |
| growth and yield characteristics of 'waldmann's green' leaf lettuce under different photon fluxes from metal halide or incandescent + fluorescent radiation. | 'waldmann's green' leaf lettuce (lactuca sativa l.) was grown either under 84% irradiance from incandescent (in) + 16% from fluorescence (fl) lamps, or 100% from metal halide (mh) lamps, both at 392 micromoles s-1 m-2 of photosynthetically active radiation (400-700 nm) from 11 to 19 days after seeding. no differences in leaf dry weight, leaf area, relative growth rate (rgr) or photosynthesis (pn) occurred after 8 days of exposure to these radiation treatments for 20 h day-1. however, a 23% reduc ... | 1988 | 11539046 |
| effect of salicylhydroxamic acid on endosperm strength and embryo growth of lactuca sativa l. cv waldmann's green seeds. | salicylhydroxamic acid (sham) stimulated germination of photosensitive lettuce (lactuca sativa l. cv waldmann's green) seeds in darkness. to determine whether sham acts on the embryo or the endosperm, we investigated separately effects of sham on growth potential of isolated embryos as well as on endosperm strength. embryo growth potential was quantified by incubating decoated embryos in various concentrations of osmoticum and measuring subsequent radicle elongation. growth potential of embryos ... | 1988 | 11538237 |
| stimulating productivity of hydroponic lettuce in controlled environments with triacontanol. | triacontanol (1-triacontanol) applied as a foliar spray at 10(-7) m to 4-day-old, hydroponically grown leaf lettuce (lactuca sativa l.) seedlings in a controlled environment increased leaf fresh and dry weight 13% to 20% and root fresh and dry weight 13% to 24% 6 days after application, relative to plants sprayed with water. when applied at 8 as well as 4 days after seeding, triacontanol increased plant fresh and dry weight, leaf area, and mean relative growth rate 12% to 37%. there was no benef ... | 1987 | 11539702 |
| the effects of nutrient solution sterilization on the growth and yield of hydroponically grown lettuce. | two methods of removing bacteria from hydroponic nutrient solution [ultraviolet (uv) radiation and submicronic filter] were evaluated for efficiency and for their effects on lettuce (lactuca sativa l.) production. both methods were effective in removing bacteria; but, at high intensity, the ultraviolet sterilizer significantly inhibited the production of plants grown in the treated solution. bacterial removal by lower intensity uv or a submicronic filter seemed to promote plant growth slightly, ... | 1987 | 11539105 |
| the genetics of esterase isozymes in lactuca sativa l. | | 1987 | 3435432 |
| comparison of restriction endonucleases and sources of probes for their efficiency in detecting restriction fragment length polymorphisms in lettuce (lactuca sativa l.). | as a first step in developing a detailed genetic map of lettuce (lactuca sativa l.), 156 cdna and 123 genomic dna clones of lettuce were compared for their efficiency to detect restriction fragment length polymorphism (rflp) between four lines of lettuce. polymorphism was detected 2.5 times more frequently with cdna probes than random genomic probes. less polymorphism was detected with cdna clones homologous to single copy than with cdna clones homologous to multiple copy dna sequences. a lower ... | 1987 | 24240222 |
| β-mannoside mannohydrolase and the mobilization of the endosperm cell wall of lettuce seeds, cv. grand rapids. | mobilization of the endosperm cell-wall reserves of lactuca sativa l. cv. grand rapids requires endo-β-mannanase and α-galactosidase activity. a third enzyme, β-mannoside mannohydrolase (ec 3.2.1.25) is also involved. we have determined the optimum extraction and assay conditions for this enzyme, which is soluble only in high-salt (1 m nacl) buffer. it is located exclusively within the cotyledons, in association with a cellulosic cell-wall fraction. its substrates are the products of endosperm c ... | 1986 | 24232644 |
| requirement for ethylene synthesis and action during relief of thermoinhibition of lettuce seed germination by combinations of gibberellic acid, kinetin, and carbon dioxide. | application of exogenous ethylene in combination with gibberellic acid (ga(3)), kinetin (kin), and/or co(2) has been reported to induce germination of lettuce seeds at supraoptimal temperatures. however, it is not clear whether endogenous ethylene also plays a mediatory role when germination under these conditions is induced by treatment regimes that do not include ethylene. therefore, possible involvement of endogenous ethylene during the relief of thermoinhibition of lettuce (lactuca sativa l. ... | 1986 | 16664963 |
| role of ethylene in lactuca sativa cv ;grand rapids' seed germination. | promotion of thermoinhibited (30 degrees c) lettuce (lactuca sativa cv ;grand rapids') seed germination by ethylene is similar to the action of the gas in other hormonal systems. ethylene was more active than propylene and ethane was inactive. an inhibitor of ethylene production, aminoethoxy-vinylglycine, reduced ethylene evolution and germination. inhibitors of ethylene action such as, 5-methyl-7-chloro-4-ethoxycarbonylmethoxy-2,1,3-benzothiadiazole, 2,5-norbornadiene, and silver thiosulfate in ... | 1986 | 16664902 |
| comparative toxicity of six test chemicals to lettuce using two root elongation test methods. | lettuce (lactuca sativa l., cv buttercrunch) was used to evaluate and compare the results from two different root elongation phytotoxicity test methods with the same six test substances. seeds were either germinated in the dark on an inclined filter paper substrate with one end immersed in test solution or germinated in 0.1 strength nutrient solution with a 16 hr light period in a glass bulb mixed and aerated with compressed air. sodium fluoride, monosodium methanearsonate and monuron reduced le ... | 1986 | 24254736 |
| effect of 16 and 24 hours daily radiation (light) on lettuce growth. | a 50% increase in total radiation by extending the photoperiod from 16 to 24 hr doubled the weight of all cultivars of loose-leaf lettuce (lactuca sativa l.) 'grand rapids forcing', 'waldmanns green', 'salad bowl', and 'rubyconn', but not a butterhead cultivar, 'salina'. when total daily radiation (moles of photons) was the same, plants under continuous radiation weighed 30% to 50% more than plants under a 16 hr photoperiod. by using continuous radiation on loose-leaf lettuce, fewer lamp fixture ... | 1986 | 11539771 |
| a study of factors which regulate the membrane appression of lettuce thylakoids in relation to irradiance. | factors that may influence the extent of thylakoid membrane appression have been examined using lettuce (lactuca sativa cv. celtuce) grown under different irradiances. electron microscopy and salt-induced chlorophyll fluorescence suggest that the percentage of membrane appression is increased in plants grown in low light (20 wm(-2)) compared with those grown in high light (150 wm(-2)). in high light plants surface charge, as measured by 9-aminoacridine, was found to be twice that measured in low ... | 1986 | 24442367 |
| effects of artificial enclosure of young lettuce leaves on tipburn incidence and leaf calcium concentration. | the young developing leaves of 20-day-old lettuce plants (lactuca sativa l. 'buttercrunch') were enclosed by aluminized polyethylene sheaths to decrease transpiration and reduce ca transport. the plants were grown in recirculating solution culture system using a modified half-strength hoagland's solution under cool-white fluorescent lamps with a photosynthetic photon flux of 350 micromoles s-1 m-2 in a 16:8-hr (light:dark) period. air temperature and humidity were 20 degrees c and 65%, respectiv ... | 1986 | 11539770 |
| interactions between mild nacl stress and red light during lettuce (lactuca sativa l. cv grand rapids) seed germination. | the sensitivity of lettuce (lactuca sativa l. cv grand rapids) seeds to red light was reduced by nacl concentrations which had no effect upon the germination of continuously illuminated seeds. the germination capacity of the seeds was fully restored by increased red light exposures. indirect evidence indicates that nacl does not affect the photoconversion of red-absorbing form of phytochrome to the far-red absorbing form of phytochrome. instead, the increased red light requirements are attributa ... | 1985 | 16664360 |
| sidedness studies of thylakoid phosphatidylglycerol in higher plants. | the transmembrane distribution of phosphatidylglycerol was determined in thylakoids from barley (hordeum vulgare), lettuce (lactuca sativa) and pea (pisum sativum) chloroplasts. phospholipase a2 and phospholipase d digestion and chemical-labelling methods were used. phosphatidylglycerol was preferentially localized in the outer (stromal) leaflet. the proportion of the phospholipid in this leaflet ranged from about 66% in pea to about 75% for barley and lettuce thylakoids. one of the main fatty a ... | 1985 | 4026805 |
| [effect of heavy charged particles in galactic cosmic radiation on seeds]. | the experiments were carried out on lactuca sativa seeds exposed for 20, 66, 123 and 308 days in a biostack also containing physical detectors of heavy charged particles. the purpose of the experiments was to measure the yield of aberrant cells and its dependence on the exposure time and the site where particles hit the object. the cytogenetic examination demonstrated a significant difference between the seeds that were or were not hit by heavy charged particles. this is indicative of a signific ... | 2006 | 4033049 |
| dual action of respiratory inhibitors: inhibition of germination and prevention of dormancy induction in lettuce seeds. | ;grand rapids' lettuce lactuca sativa l. seeds germinate readily at 15 degrees c but poorly at 25 degrees c in darkness. when held in dark at 25 degrees c for an extended period, the ungerminated seeds become dormant as shown by their inability to germinate or transfer to 15 degrees c in darkness. induction of dormancy at 25 degrees c was prevented by exposure to cn(-), azide, salicylhydroxamic acid (sham), dinitrophenol, and pure n(2) as determined by subsequent germination at 15 degrees c on r ... | 1985 | 16664144 |
| localization of chloroplastic fatty acid synthesis de novo in the stroma. | the synthesis of fatty acids de novo from [2-14c]malonyl-coa was studied in fractions from lettuce (lactuca sativa) and pea (pisum sativum) chloroplasts. when lettuce chloroplasts were subjected to osmotic lysis, disintegration through a yeda press and high-speed centrifugation, essentially all of the fatty-acid-synthetic activity was found to be soluble. the distribution of the activity in various chloroplast fractions was similar to that of soluble marker enzymes such as ribulose-1,5-bisphosph ... | 1985 | 3994672 |
| salicylhydroxamic acid potentiates germination of 'waldmann's green' lettuce seed. | a combination of salicylhydroxamic acid (sham) + cyanide (cn) is known to stimulate dark germination of lactuca sativa l. seeds. further studies were done to characterize sham and cn action in stimulating dark germination of lettuce seed. germination was stimulated slightly by either sham or cn, whereas when sham and cn were combined germination was greatly enhanced. treatment of seeds with sham + cn only during the first 8 hours of hydration stimulated germination as much as did treatment for 7 ... | 1985 | 11540836 |