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role of cation and anion uptake in salt-stimulated elongation of lettuce hypocotyl sections.the role of cation and anion uptake in salt-stimulated growth of light-grown, ga(3)-treated lettuce (lactuca sativa l.) hypocotyl sections was investigated. potassium chloride (10 mm) causes a 2-fold increase in the growth rate of ga(3)-treated hypocotyl sections without affecting the growth rate of sections incubated in the absence of ga(3). salt uptake is the same in both treatments, and furthermore the uptake of cation and anion is stoichiometric during the first 24 hours under all incubation ...197816660256
temperature dependence of the gibberellin response in lettuce hypocotyls.the relationship between temperature and sensitivity to gibberellin a3 (ga3) was studied in lettuce seedlings (lactuca sativa l. cv. arctic). dose/response curves for hypocotyl elongation (10(-4) mol l(-1) to 10(-8) mol l(-1)) were constructed for a range of temperatures and the slope of the linear portion of the plots used as an indication of the sensitivity to ga3. hypocotyls were unresponsive to ga3 below 13°c but above this temperature sensitivity increased linearly. plots of growth rate aga ...197824414874
gibberellin metabolism in excised lettuce hypocotyls: response to ga9 and the conversion of [ (3)h]ga 9.elongation growth and gibberellin (ga9) metabolism in excised hypocotyls of lettuce (lactuca sativa l. cv. arctic) were investigated. exogenously supplied ga9 stimulates elongation of hypocotyl sections and this response is intermediate between that elicited by ga1 or ga20 and ga4/7 mixture. although uptake of radioactivity from [(3)h]ga9 increases with time, this gibberellin does not accumulate in the tissue but is rapidly converted to a compound with hplc properties resembling those of [(3)h]g ...197824414470
effects of colchicine and lumicolchicine on hypocotyl elongation, respiration rates and microtubules in gibberellic-acid-treated lettuce seedlings.gibberellic-acid (ga3)-induced hypocotyl elongation of intact lettuce (lactuca sativa l.) seedlings was inhibited by colchicine (4×10(-4) m) but not by lumicolchicine (4×10(-4) m). in excised lettuce hypocotyls, ga3 (10(-5) m) increased respiration over water controls, while both colchicine and lumicolchicine alone, or in combination with ga3, reduced respiration. microtubules were present in the hypocotyls of lumicolchicine-treated seedlings but absent in those treated with colchicine. it is su ...197824414274
degradation of the endosperm cell walls of lactuca sativa l., cv. grand rapids : timing of mobilisation of soluble sugars, lipid and phytate.the timing of mobilisation of lipid, sucrose, raffinose and phytate in lettuce seeds (achenes) (cv. grand rapids) has been examined. these reserves (33%, 1.5%, 0.7%, 1.4% of achene dry weight, respectively) are stored mostly in the cotyledons. except for a slight degradation of raffinose and increase in sucrose, there is no detectable reserve mobilisation during germination. the endosperm (8% of seed dry weight), which has thick, mannan-containing cell walls (carbohydrate, 3,4% of seed dry weigh ...197824414098
light effects upon dry lettuce seeds.germination of certain dry "seeds" (achenes) of lactuca sativa l. cv. grand rapids was increased to ca. 75% after irradiation with 665 nm red light (r; 1x10(3) j m(-2)); this response was eliminated by far-red light (fr) following the r. the response of dry seeds required an order of magnitude more light than that of wetted seeds, and was not maximal until 48 h after irradiation. other seeds, which could not be stimulated by r in dry state, showed a partial response after 10 min hydration. irrad ...197824408637
the role of acidification in gibberellic acid- and fusicoccin-induced elongation growth of lettuce hypocotyl sections.the roles of gibberellic acid (ga3) and fusicoccin (fc) in the elongation growth and acidification of the medium by excised hypocotyl sections of lettuce (lactuca sativa l.) were investigated. hypocotyl sections incubated in buffer without ga3 elongate optimally at ph 4.0-4.25 while sections incubated with ga3 show the same growth between ph 4.25 and 6.0. preincubation of sections at ph 6.0 for 6 h does not affect the subsequent elongation response to acidic medium (ph 4.25); however, the sectio ...197824408094
interaction of [(3)h]gibberellin a 1 with a sub-cellular fraction from lettuce (lactuca sativa l.) hypocotyls : requirement for protein synthesis.the relationship between protein synthesis and the incorporation of [(3)h]gibberellin a1 ([(3)h]ga1) into a 2,000xg pelletable (2kp) fraction from lettuce (lactuca sativa l.) hypocotyl sections has been investigated. concentrations of d-2-(4-methyl-2,6-dinitroanilino)-n-methylpropionamide (mdmp) between 10(-7) m and 10(-4) m caused increasing inhibition of growth, 2kp labelling and incorporation of [(14)c]leucine into soluble protein. growth and 2kp radioactivity were highly correlated (r=0.996) ...197924311043
abscisic acid localization and metabolism in barley aleurone layers.aleurone layers of hordeum vulgare, cv. ;himalaya' took up [(14)c]-abscisic acid (aba) when incubated for various times. radioactivity accumulated with time in a low speed, dna-containing pellet accounting for 1.6 to 2.3% of the radioactivity recovered in subcellular fractions at 18 hours. thin layer chromatography of ethanolic or methanolic extracts of the cytosol, which contained greater than 95% of the radioactivity taken up by layers, revealed that labeled aba was metabolized to phaseic acid ...197916660912
dependence of thermal responses of seeds on membrane transitions.transitions at 28-32 degrees c in membranes of many kinds of seeds influence their germination and subsequent growth. changes at 28-32 degrees c in the rates of loss of endogenous amino acids from imbibed barbarea verna and lactuca sativa seeds indicate permeation of the plasma membrane. a transition in the same temperature range is shown by the change in fluorescence with temperature of substituted naphthalenesulfonate probe molecules associated with membrane fragments isolated from the seeds. ...197916592623
action spectra for light-induced germination in dormant lettuce seeds : ii. blue region.light of wavelengths in the range 400-500 nm induces germination of seeds of lactuca sativa l. (cv. noran and may queen) when made light requiring by high temperature (thermodormancy) or prolonged exposure to far red light (far red dormancy). td seeds proved more sensitive to blue light than frd seeds by several orders of magnitude. blue induced germination could be reversed by far red. fluence response curves for this reversion are less steep for td than for frd seeds. the degree of germination ...197924408684
action spectra for light-induced germination in dormant lettuce seeds : i. red region.fluence response curves for red light-induced germination of thermodormant (td) seeds of lactuca sativa l. show two regions that differ in their light sensitivity. in the region of high sensitivity, the germination responses differ between seed batches and can be altered by dark storage or far red irradiation. induction of germination in far red dormant (frd) seeds requires far higher fluences. action spectra for induction to 60% germination were determined for these various response types. spec ...197924408683
inhibitory effects of full daylight on the germination of lactuca sativa l.using glass filters that transmit various spectral bands and different intensities of natural daylight, experiments with achenes of lettuce cv. vanquard were performed. germination during prolonged treatment depended both on the far red/red radiation ratio and on the irradiance. the promotive effect of red radiation present in natural light prevailed at low irradiances, the inhibitory effect of far red radiation at high irradiances. the dormancy imposed by prolonged white light of high intensity ...197924408682
mannanase production by the lettuce endosperm : control by the embryo.endo-β-mannanase (ec 3.2.1.78) is produced and secreted by the cells of the endosperm of lettuce (lactuca sativa l.) "seeds" (achenes). in imbibed intact seeds, production is prevented by inhibitors. if the endosperm is incubated alone, these inhibitors can be removed by leaching, allowing mannanase production. abscisic acid, a component of lettuce seeds, inhibits the production of mannanase in the isolated endosperm, and may be involved in regulation of mannanase production in intact seeds. dur ...197924407322
the growth physics and water relations of red-light-induced germination in lettuce seeds : iv. biochemical changes in the embryonic axes of red-and far-red-treated seeds.using lettuce (lactuca sativa l., cv. grand rapids) embryos in osmotica, we have demonstrated that when the growth rates of the embryonic axes of seeds treated with red (r) or far-red (fr) light are equalized, the axes of r-treated seeds develop a 3.4-bar decrease in water potential (paper no. iii).as axial growth begins, reserve protein and phytin decrease rapidly, concomitant with increases in reducing sugars, α-amino nitrogen, and inorganic and esterified soluble phosphates. however, no diffe ...197924407252
the growth physics and water relations of red-light-induced germination in lettuce seeds : iii. changes in the osmotic and pressure potential in the embryonic axes of red-and far-red-treated seeds.irradiation of grand rapids lettuce (lactuca sativa l.) seeds with red light (r) results in an increase in the growth response in the embryonic axes which enables them to overcome the mechanical restriction of the endosperm or the osmotic restriction of an external solution. when the growth rates of axes from r-and far-red(fr)-treated seeds are equalized with polyethylene-glycol-4000 solutions, a water potential difference of 3.4 bars between the axes is obtained. measurements of the osmotic pot ...197924407251
interaction of [(3)h] gibberellin a 1 with a sub-cellular fraction from lettuce (lactuca sativa l.) hypocotyls : ii. stability and properties of the association.radioactive 2,000 g pellets (2kp) derived from lettuce (lactuca sativa) hypocotyl sections incubated with [(3)h]gibberellin a1 ([(3)h]ga1) were subjected to a range of treatments to test the stability of labelling. the labelled association was stable in 0.1 m buffer at ph 3 and ph 9 and also in 1 m salt, organic solvents, protease or cellulase. both 1 m potassium hydroxide (koh) and a quaternary ammonium hydroxide tissue solubiliser effected an 80% release of incorporated [(3)h]. no radioactivit ...197924318190
interaction of [(3)h]gibberellin a 1 with a sub-cellular fraction from lettuce (lactuca sativa l.) hypocotyls : i. kinetics of labelling.the distribution of [(3)h]gibberellin a1 ([(3)h]ga1) amongst sub-cellular fractions from lettuce (lactuca sativa l.) hypocotyl sections was examined by differential centrifugation. material pelleting at 2000 g (2kp) accounted for 2-5% of the total tissue radioactivity and no other significant interactions were detected. after rigorous washing procedures, the 2kp fraction was found to consist mainly of cell wall material and the radioactivity remained associated during sucrose density-gradient ce ...197924318189
degradation of the endosperm cell walls of lactuca sativa l., cv. grand rapids in relation to the mobilisation of proteins and the production of hydrolytic enzymes in the axis, cotyledons and endosperm.the timing of changes in total nitrogen and soluble amino nitrogen content, and in the activities of proteinase (ph 7.0), isocitrate lyase, catalase, phytase, phosphatase (ph 5.0), α-galactosidase and β-mannosidase were studied in extracts from the cotyledons, axis and endosperms of germinating and germinated light-promoted lettuce seeds. the largest amount of total nitrogen (2.7% seed dry weight) occurs within the cotyledons, as storage protein. as this decreases the total nitrogen content of t ...197924318187
the influence of plant growth regulators on the growth of the embryonic axes of red- and far-red-treated lettuce seeds.the influence of several plant growth regulators on the growth of the embryonic axes from red- and far-red-(r- and fr-)treated lettuce (lactuca sativa l., cv. grand rapids) seeds was examined; as shown previously, the water potential of the axes from r-treated seeds has been lowered by 3.5-5.6 bars compared to that in axes from fr-treated ones. kinetin and abscisic acid (aba), when included in the incubation medium, reduced the elongation of the axes whereas fusicoccin stimulated it; however, th ...197924317869
effect of temperature on the short chain fatty acid-induced inhibition of lettuce seed germination.in lettuce, lactuca sativa short chain fatty acids (c(6) - c(9)) vary in their effectiveness as inhibitors of germination according to temperature; the higher the temperature, the greater the inhibition. a linear relationship exists between temperature and the dose causing half-maximal germination. nonanoic (c(9)) acid is the most effective.when extrapolated to the abscissa, really zero concentration of acid, the regression lines intercept at 36.8 c +/- 2.6 c. it may be that at this temperature ...197916660694
changes in the strength of lettuce endosperm during germination.the forces required to puncture intact lettuce (lactuca sativa) seed and pericarp, endosperm and embryo were measured by the instron universal testing machine. it required about 0.6 newton to puncture the endosperm in seeds imbibed in the dark at 6, 12 and 24 hours. endosperm of seeds imbibed in the light or in dark with gibberellic acid required about 4.2 newtons at 6 and at 12 hours and only about 0.15 newton at 24 hours. forces required to puncture embryo at all treatments and times remained ...197916660662
cyanide-insensitive, salicylhydroxamic acid-sensitive processes in potentiation of light-requiring lettuce seeds.phytochrome-mediated germination of lactuca sativa l. cv. waldmann's green seeds was inhibited strongly by 10 millimolar salicylhydroxamic acid (sham), but only slightly delayed by the same level of kcn. sham was most effective if applied within the 8-hour potentiation period (release from dormancy) following red light treatment, but much less effective with completely potentiated seeds. sham at 3 millimolar actually hastened completion of potentiation, whereas concentrations of 6.6 millimolar o ...197916660661
influence of after-ripening on phytochrome control of seed germination in two varieties of lettuce (lactuca sativa l.).the reversible photoreaction on seed germination of two varieties of lettuce differs remarkably not only with the variety but also with the germination temperature and the physiological conditions of seeds caused by after-ripening.grand rapids showed reversible photoreaction at 25 c with 0 to 6 months and at 30 c with 5 to 6 months after-ripening. msu 16 did not show any reversible photoreaction at 30 c with 0 to 6 months or at 25 c with 0 to 3 months after-ripening although they were completely ...198016661604
interaction of [(3)h]gibberellin a 1 with a sub-cellular fraction from lettuce (lactuca sativa l.) hypocotyls : the relationship between growth and incorporation.the relationship between elongation growth and the incorporation of [(3)h]gibberellin a1 ([(3)h]ga1) into a 2,000g pelletable (2kp) fraction from lettuce (lactuca sativa l., cv. arctic) hypocotyl sections has been examined. sections were loaded with incremental amounts of ga1 under conditions where growth was arrested (5° c) or permitted (30° c) and, after 16 h, all were transferred to a ga-free medium at 30° c. growth and 2kp radioactivity were measured at this point and after a further 24 h in ...198024310192
studies of the mechanism of enhancement of phytochrome-dependent lettuce seed germination by prechilling.temperature and kinetic studies were performed to examine the mechanism by which prechilling stimulates phytochrome-dependent seed germination in lettuce, lactuca sativa, l. cv. grand rapids. imbibed seeds were given a short far red irradiation and one day of dark incubation at 20 c to establish very low levels of the far red-absorbing form of phytochrome-(pfr). germination was greatly stimulated by subsequent prechilling treatments when they were followed by a second short far red irradiation. ...198016661408
stabilization of adenine nucleotide ratios at various values by an oxygen limitation of respiration in germinating lettuce (lactuca sativa) seeds.the concentrations of adenine nucleotides were determined in germinating lettuce (lactuca sativa) seeds after transitions from air to hypoxic or anoxic atmospheres. the ratio atp/adp and the energy charge were rapidly lowered after the transitions and remained stable at low values for hours. the energy charge in anoxia stabilized at a value close to 0.3. after 24 h in anoxia the energy charge rose rapidly to high values (0.9) when n2 was replaced by air. the metabolic properties of lettuce seeds ...19807447934
allelopathic effects of pakistani weeds: euphorbia granulata forssk.the aqueous extract of euphorbia granulata forssk., prepared in hoagland's nutrient solution; and underlying soil significantly inhibited germination and radicle growth of dichanthium annulatum, cynodon dactylon, setaria italica, pennisetum americanum, euphorbia pilulifera, oxalis corniculata and lactuca sativa invariably in laboratory bioassays. artificially decomposed e. granulata litter in a nutrient medium significantly reduced germination and fresh and dry weight of the aforementioned test ...198028309538
evidence for a race-specific resistance factor in some lettuce (lactuca sativa l.) cultivars previously considered to be universally susceptible to bremia lactucae regel.previously undetected race-specific resistance to bremia lactucae (downy mildew) was located in many lettuce cultivars hitherto considered to be universally susceptible to this disease. this resistance factor(s) may also be widely distributed in other cultivars known to carry combinations of already recognised factors r1 to r11. specific virulence to match this resistance is almost invariably present in pathogen collections. this situation may be either a relic of the evolutionary history of the ...198124276692
the effect of phytohormones produced by arthrobacter sp. on the phosphatase activity in plant roots.phytohormonal activity (auxins, gibberellins, cytokinins) was tested in the supernatant of a culture of arthrobacter sp. crude extract of the phytohormonal fraction was used as substrate for the growth of lactuca sativa seedlings. treating with bacterial hormones resulted in an increased plant develop- ment. furthermore, a sharp increase of the acid phosphatase activity was observed in the roots.19817262713
oxidative phosphorylation in germinating lettuce seeds (lactuca sativa) during the first hours of imbibition.experiments with lettuce seeds during the first hours of imbibition showed that oxygen is necessary to sustain high adenine nucleotide ratios and consequently, energy charge values are higher than 0.8 as is usually the case in normally metabolizing tissues.the energy charge value (0.2) of dry seeds soaked in aerated water increased to normal values (0.8) within 30 minutes. the energy charge value of seeds imbibed under cyanide or nitrogen stayed at low values, about 0.3 for 30 minutes. nitrogen ...198116661970
calcium and gibberellin-induced elongation of lettuce hypocotyl sections.the relationship between calcium ions and gibberellic acid (ga3)-induced growth in the excised hypocotyl of lettuce (lactuca sativa l.) was investigated. the short-term kinetics of growth responses were measured using a linear displacement transducer. test solutions were added either as drops to the filter paper on which the hypocotyl stood ("non-flow-past") or by switching solution flowing past the base of hypocotyl ("flow-past"), resulting in differences in growth behavior. drops of cacl2 adde ...198124301119
short-term kinetics of elongation growth of gibberellin-responsive lettuce hypocotyl sections.the short-term kinetics of growth of the excised lettuce (lactuca sativa l.) hypocotyl were characterized with respect to the effects of gibberellic acid (ga3), indole-3-acetic acid (iaa), kcl and ph. a hall-device-based, miniaturized, linear displacement transducer was developed to measure the growth of 2-mm hypocotyl sections with 1-μm resolution. following treatment with ga3, a lag time of less than 10 min was typically followed by an increase in growth rate with two acceleration phases, reac ...198124301118
red-light- and gibberellic-acid-enhanced α-galactosidase activity in germinating lettuce seeds, cv. grand rapids : control by the axis.dry lettuce (lactuca sativa l.) "seeds" (achenes) contain α-galactosidase (ec 3.2.122) at a level which is maintained in the imbibed dormant state in darkness. both red light (r) and gibberellic acid promote an increase in enzyme activity several hours prior to the completion of germination. germination and enzyme activity are not essentially linked, however, for the latter can increase while the former is inhibited. α-galactosidase activity increases within the cotyledons and the endosperm foll ...198124301117
[effect of aqueous extracts of tamus communis l. leaves on the germination of seeds of various species].the different influence of germination and growth inhibitors in aqueous extracts, at the same concentration, of tamus communis l. leaves, on germinating seeds and seedlings of nigra l., lactuca sativa l., medicago sativa l., has been shown. this action, very marked at the experimental concentrations, is not toxic, as the seeds and seedlings, if immersed in deionized water after treatments, recover their germination and growth. this recovery occurs however differently in the plants investigated.19817284097
growth physics and water relations of red-light-induced germination in lettuce seeds : v. promotion of elengation in the embryonic axes by gibberellins and phytochrome.red light (r) and gibberellins (ga) each induce a water potential decrease in the axes of lettuce (lactuca sativa l.) embryos resulting in germination of intact "seeds" (achenes) or an increase in growth of the axes of isolated embryos. the fruit coat and endosperm are a substantial barrier to the penetration of exogeneous ga. isolated embryos take up 35 times as much [(3)h]ga1 as the embryos of intact seeds and respond to less than 1·10(-10) m ga3 or ga4+7. we calculated that only 1·10(-8) m of ...198124302380
factors affecting the induction of secondary dormancy in lettuce.the relationship between the temperature at which germination of 50% of the seeds is inhibited in the light (gt(50) light) and secondary dormancy was investigated in three cultivars of lactuca sativa l. seeds were incubated for varying periods under non-germinating conditions and subsequent germination in response to red light (r) was determined over a wide range of temperatures. dark incubation at 32 c reduced the gt(50) light of cv. new york but did not affect germination at temperatures below ...198116661841
l-lactate dehydrogenase from leaves of higher plants. kinetics and regulation of the enzyme from lettuce (lactuca sativa l).1. l-lactate dehydrogenase from lettuce (lactuca sativa) leaves was purified to electrophoretic homogeneity by affinity chromatography. 2. in addition to its nad(h)-dependent activity with l-lactate and pyruvate, the enzyme also catalyses the reduction of hydroxypyruvate and glyoxylate. the latter activities are not due to a contamination of the enzyme preparations with hydroxypyruvate reductase. 3. the enzyme shows allosteric properties that are markedly by the ph. 4. atp is a potent inhibitor ...19817316976
effects of prolonged exposure to space flight factors for 175 days on lettuce seeds.we have studied the effects of prolonged (up to 175 days) exposure of lactuca sativa seeds to space flight factors, including primary cosmic radiation heavy ions. the data obtained evidence a significant fourfold increase of spontaneous mutagenesis in seeds both with regard to the total number of aberrant cells as well as the formation of single cells with multiple aberrations. comparison of the present experiment with earlier works shows that the frequency of such aberrations increases with the ...198111541723
endosperm and pericarp involvement in the supercooling of imbibed lettuce seeds.fully hydrated lettuce (lactuca sativa l.) seeds showed dual freezing exotherms (-9 and -18 degrees c), even after 10 hours imbibition. only the -9 degrees c exotherm was observed in seeds imbibed for 20 hours, but without external nucleation, all water in the embryo supercooled. results indicate that the endosperm acts as a barrier to ice propagation. other experiments suggest that the pericarp may also protect the embryo under certain freezing conditions.198216662720
dark metabolism of carbon monoxide in lettuce leaf discs.in the dark, leaf tissue of crisphead lettuce (lactuca sativa l.) metabolized (14)co to (14)co(2) and acid-stable products. tissue incubated at 2.5 degrees c for 3.5 hours and 48 hours converted about 1% and 17%, respectively, of the applied (14)co to (14)co(2), and incorporated about 0.04% and 0.6% of the (14)c in acid-stable products. examination of soluble acid-stable products from (14)co and (14)co(2)-treated leaf tissue revealed that the labeling patterns of both treatments were identical d ...198216662503
immunopurification and initial characterization of dicotyledonous phytochrome.antiserum was prepared against proteolytically undegraded phytochrome obtained from etiolated zucchini squash (cucurbita pepo l., cv. black beauty). the antiserum was prepared by injecting into a rabbit immunoprecipitates between zucchini phytochrome and specific antiserum against undegraded oat (avena sativa l., cv. garry) phytochrome. specific antiphytochrome immunoglobulins were purified from this crude serum by an affinity column consisting of conventionally purified undegraded pea phytochro ...198216662209
immobilized thylakoids in a cross-linked albumin matrix: effects of cations studied by electron microscopy, fluorescence emission, photoacoustic spectroscopy, and kinetic measurements.immobilization of lettuce (lactuca sativa) thylakoids has been performed by using glutaraldehyde and bovine serum albumin. confirming previous reports, a stabilization of the o(2) evolution activity of the photosystem ii (psii) under storage and functional conditions has been observed. the present work is devoted to the role played by mono-and divalent cations, during the immobilization process itself, on the o(2) production. four types of measurements have been employed: kinetic measurements, l ...198216662563
comparative phytochrome immunochemistry as assayed by antisera against both monocotyledonous and dicotyledonous phytochrome.preparation and characterization of antisera against lettuce (lactuca sativa l., cv. grand rapids) and pea (pisum sativum l., cv. alaska) phytochrome is described. these antisera, together with previously obtained antisera against zucchini (cucurbita pepo l., cv. black beauty) and oat (avena sativa l., cv. garry) phytochrome, were used to compare by ouchterlony double immunodiffusion phytochrome isolated from etiolated lettuce, pea, bean (phaseolus vulgaris l., cv. taylor horticultural bush), zu ...198216662599
the effects of colchicine and gibberellic acid on growth and microtubules in excised lettuce hypocotyls.the effect of colchicine on growth and microtubules in h2o-and gibberellic acid (ga3)-treated hypocotyls of lettuce (lactuca sativa l. cv. arctic) was examined. hypocotyls of seedlings from γ-irradiated as well as non-irradiated seedlings were used in order to establish that the drug was affecting cell elongation and not cell division. although colchicine inhibited elongation of ga3-treated hypocotyl sections at concentrations as low as 1 μm, it did not affect the growth of sections. rather, col ...198224276062
studies on herbal remedies i: analysis of herbal smoking preparations alleged to contain lettuce (lactuca sativa l.) and other natural products. 19827062258
[change in incidence of parasite eggs and larvae from vegetable in the markets of taegu]a survey on vegetables, which consisted of lettuce (lactuca sativa), young radish (raphanus sapivus), and chinese cabbage (brassica pekinensis) collected from 6 markets in the taegu city, was conducted for the discovery of helminth eggs and larvae, from july 1982 to june 1983. the results were compared with the data obtained from vegetables collected at the same markets by lee (1969) and choi and lee (1972). both sides of vegetable leaves were washed carefully with a hard brush, and the species ...198312902676
the aster yellows controversy: current status.evidence for and against the spiroplasmal etiology of aster yellows (ay) disease is examined. a spiroplasma, serologically identical to spiroplasma citri, was cultivated by some workers from lettuce (lactuca sativa l.) plants claimed to be naturally infected with ay. the isolated spiroplasma was shown to be infectious by injecting macrosteles fascifrons with the cultured organisms and then confining the injected leafhoppers on healthy plants. the reports claiming that a spiroplasma is the etiolo ...19836382826
an evaluation of acetone extracts from six plants in the ames mutagenicity test.acetone extracts from six plants were evaluated for mutagenic activity with the salmonella/mammalian-microsome mutagenicity test (ames) utilizing tester strains ta98 and ta100 and in the presence and absence of induced rat liver microsomes. extracts from alfalfa (medicago sativa), lettuce (lactuca sativa) and thread-leaf groundsel (senecio longilobus) produced only negative responses. comfrey (symphytum officinale) and tansy ragwort (senecio jacobaea) extracts produced toxic responses that were ...19836836587
long-term storage of dormant grand rapids lettuce seeds in the imbibed state: physiological and metabolic changes.grand rapids lettuce (lactuca sativa l.) seeds retained their viability for up to ten months when maintained in the fully imbibed state on moist filter paper at 25°c in darkness. the ability of red light (r) to promote their germination was essentially lost within one week from the start of imbibition; sensitivity to gibberellic acid was retained for two weeks longer. seeds which did not respond to either treatment had entered the state of secondary dormancy (skotodormancy). this could be reliev ...198324258141
enhancement of lettuce yield by manipulation of light and nitrogen nutrition.several levels of photosynthetic photon flux density (ppfd) were tested for effects on growth of 4 cultivars of lettuce (lactuca sativa l.) under controlled-environment conditions. growth of 'salad bowl', 'bibb', and 'ruby' was greater at 932 micromoles s-1 m-2 than at < or = 644 micromoles s-1 m-2 under a 16-hour photoperiod. thirty mm no3- or 5 mm nh4+ + 25 mm no3- increased leaf dry weight while reducing leaf chlorosis in 'salad bowl' and 'grand rapids' relative to that with 15 mm no3-, and r ...198311542284
inhibition of seed germination by quinolizidine alkaloids : aspects of allelopathy in lupinus albus l.germination of lactuca sativa l. was inhibited by mixtures of quinolizidine alkaloids. the alkaloid esters resulted in the strongest inhibition: 6 mm 13-tigloyloxylupanine inhibited germination by 100%, whereas the other lupin alkaloids, such as lupanine and sparteine, gave a 45 and 20% inhibition, respectively. seedlings of lupinus albus l., which are not affected by quinolizidine alkaloids, excrete lupanine and 13-tigloyloxylupanine into the surrounding medium by their roots. it is assumed tha ...198324264757
stimulation of lettuce productivity by manipulation of diurnal temperature and light.'salad bowl' and 'waldmann's green' leaf lettuce (lactuca sativa l.) were exposed to photosynthetic photon flux densities (ppfd) of 444 or 889 micromoles s-1 m-2 for 20 hours day-1 under a diurnal temperature regime of 25 degrees c days/15 degrees nights or 20 degrees days/15 degrees nights. leaf dry weight of both cultivars was highest under the high ppfd/warm temperature regime and lowest under the low ppfd/cool temperature regime. 'waldmann's green' yielded more than did 'salad bowl' at 889 m ...198311542283
synthesis of oxalic acid by enzymes from lettuce leaves.a rapid purification of lactate dehydrogenase and glycolate oxidase from lettuce (lactuca sativa) leaves is described. the kinetics of both enzymes are reported in relation to their possible roles in the production of oxalate. lettuce lactate dehydrogenase behaves like mammalian dehydrogenase, catalyzing the dismutation of glyoxylate to glycolate and oxalate. a model is proposed in which glycolate oxidase in the peroxisomes and lactate dehydrogenase in the cytosol are involved in the production ...198316662946
a role for α-galactosidase in the degradation of the endosperm cell walls of lettuce seeds, cv. grand rapids.isolated endosperms of grand rapids lettuce (lactuca sativa l.) seeds undergo extensive cell-wall degradation and sugars are released into the surrounding incubation medium. one sugar so released is galactose. α-galactosidase (ec 3.2.122) is present at the same level in both dry and imbibed isolated endosperms and is responsible for the release of galactose. however, this enzyme does not act upon the native endosperm cell wall, but requires first its partial hydrolysis and the production of olig ...198324264159
structural alterations in isolated endosperms of lactuca sativa l. achenes.endosperm tissue of lettuce (lactuca sativa l.) achenes germinating in the dark was isolated from the embryo after appropriate time periods of imbibition in the dark and was incubated in water or in gibberellic acid solution in the dark. it was found that endosperms which were dissected from achenes during the first to the eighth hours of imbibition do not show any structural alteration even after 24 h of incubation either in water or in ga(3) while endosperms excised after 9 hours of imbibition ...198423195506
changes in germination and respiratory potential of embryos of dormant grand rapids lettuce seeds during long-term imbibed storage, and related changes in the endosperm.grand rapids lettuce (lactuca sativa l.) seeds were stored in an imbibed state for up to two years. embryos dissected from stored seeds showed a progressive loss with time in their ability to germinate on polyethylene glycol (peg) solutions. little germination of dissected embryos from one-month imbibed seeds occurred on-6 bar peg but only after four months of storage did the dissected embryos fail to germinate on-4 bar peg. after two years storage 30% of dissected embryos still were able to ger ...198424253946
introduction of xylem differentiation in lactuca by ethylene.evidence was obtained to support the hypothesis that ethylene is involved in xylem differentiation in primary pith explants of lactuca sativa l. cv romaine cultured in vitro. xylem elements differentiated when explants were supplied indole-3-acetic acid (iaa) in combination with either the ethylene biosynthetic precursor 1-aminocyclopropane-1-carboxylic acid (acc), the ethylene-releasing agent 2-chloroethylphosphonic acid (cepa), or kinetin. in contrast, no xylem elements differentiated in the p ...198416663752
mechanism of seed priming in circumventing thermodormancy in lettuce.lettuce (lactuca sativa l. cv minetto) seeds were primed in aerated solutions of 1% k(3)po(4) or water at 15 degrees c in the dark for various periods of time to determine the manner by which seed priming bypasses thermodormancy. seeds which were not primed did not germinate at 35 degrees c, whereas those which were primed for 20 h in 1% k(3)po(4) or distilled h(2)o had up to 86% germination. the rate of water uptake and respiration during priming were similar regardless of soak solution. cell e ...198416663613
utilization of a response-surface technique in the study of plant responses to ozone and sulfur dioxide mixtures.a second order rotatable design was used to obtain polynomial equations describing the effects of combinations of sulfur dioxide (so(2)) and ozone (o(3)) on foliar injury and plant growth. the response surfaces derived from these equations were displayed as contour or isometric (3-dimensional) plots. the contour plots aided in the interpretation of the pollutant interactions and were judged easier to use than the isometric plots. plants of ;grand rapids' lettuce (lactuca sativa l.), ;cherry bell ...198416663598
phytochrome intermediates and action spectra for light perception by dry seeds.it has previously been demonstrated that far-red irradiation of dry lactuca sativa l. seeds results in inhibition of subsequent germination. although red has no effect on dry seeds, a red irradiation following a farred irradiation reverses the effect of far-red. this phenomenon is most noticeable in seeds with artificially raised levels of phytochrome in the far-red absorbing form. qualitatively similar results have been found for the seeds of plantago major l., sinapis arvensis l., and bromus s ...198416663467
effects of relative humidity and root temperature on calcium concentration and tipburn development in lettuce.growth chamber studies were undertaken with a tipburn-sensitive cultivar of romaine lettuce (lactuca sativa l. cv. lobjoits green cos) grown under a photosynthetic photon flux density of 320 micromoles s-1 m-2 for 16 hours; light and dark temperatures were 26.0 degrees and 12.5 degrees c, respectively. as the relative humidity (rh) during the light period was decreased from 74% to 51%, growth was retarded, ca concentration increased, and the onset of tipburn delayed. decreasing rh during the dar ...198411540812
effect of light and temperature on the germination of lettuce seeds.a short period (15-30 min) at 30° c promotes germination of seeds of lactuca sativa l. cv. repolhuda in darkness. far-red light reverses this stimulation, and the escape curves for phytochrome and high-temperature action are quite similar, indicating that the two factors act at a common point in the chain of events leading to germination. it is suggested that high temperature acts by decreasing the threshold of the active, far-red absorbing, form of phytochrome (pfr) needed to promote germinatio ...198424258424
reversion from light-induced inhibition of seed germination by respiratory inhibitors.treating of the dark-imbibed lettuce (lactuca sativa l.) seeds prior to light irradiation with 1 millimolar kcn or nan(3) in the dark for 3 hours prevented blue light and far-red light-induced inhibitions of phytochrome-mediated germination. similarly, salicylhydroxamic acid (sham) at 10 millimolar counteracted the blue and far-red light inhibitions, the combined application of kcn and sham being more effective than kcn or sham alone in some experiments. these respiratory inhibitors slightly inh ...198416663377
uptake of 2,4-d in higher plants from artificial rain.sinapis alba l., lapsana communis l., achillea millefolium l., brassica napus l., lactuca sativa l., and lycopersicum esculentum l. were exposed to 2,4-dichlorophenoxy [2-14c]acetic acid (2,4-d) at 10 micrograms liter-1 in artificial rain, ph 6.5 and 3.3. the 2,4-d was absorbed in all species tested. concentrations of parent 2,4-d appeared at the highest level in achillea (0.1 mg kg-1 dry wt), and at zero level in lycopersicum. twenty-one daily treatments at ph 6.5 for 30-min periods increased d ...19846428858
characterization by enzyme-linked immunosorbent assay of monoclonal antibodies to pisum and avena phytochrome.nine monoclonal antibodies to pea (pisum sativum l.) and 16 to oat (avena sativa l.) phytochrome are characterized by enzyme-linked immunosorbent assay against phytochrome from six different sources: pea, zucchini (cucurbita pepo l.), lettuce (lactuca sativa l.), oat, rye (secale cereale l.), and barley (hordeum vulgare l.). all antibodies were raised against phytochrome with a monomer size near 120,000 daltons. nevertheless, none of them discriminated qualitatively between 118/114-kilodalton oa ...198416663365
plant triose phosphate isomerase isozymes : purification, immunological and structural characterization, and partial amino acid sequences.we report the first complete purifications of the cytosolic and plastid isozymes of triose phosphate isomerase (tpi; ec 5.3.1.1) from higher plants including spinach (spinacia oleracea), lettuce (lactuca sativa), and celery (apium graveolens). both isozymes are composed of two isosubunits with approximate molecular weight of 27,000; in spinach and lettuce the plastid isozyme is 200 to 400 larger than the cytosolic isozyme. the two isozymes, purified from lettuce, had closely similar amino acid c ...198416663420
relative resistance of and delayed toxicity in undifferentiated plant cells to methyl mercury.meristematic cells of carrot (daucus carota l., ca68-10) and lettuce (lactuca sativa l., le-67) cultured in 71-v medium (with 0.15 microgram/ml 2, 4-d) were given one initial dose (0.0001, 0.001, or 0.01 microgram/ml) of methyl mercury (mehg) at 0 hr, cultured for 288 hr. and then subcultured for 4 weeks. in another experiment, mehg was added in four daily doses (0.05, 0.10, 0.50, 1.0, 2.5, or 5.0 micrograms/ml) starting at 72 hr for 120 hr and then subcultured for 168 hr. the resulting 50% grow ...19846510322
pathogenic variation and sexual reproduction in swedish populations of bremia lactucae.the host-pathogen interaction between lettuce (lactuca sativa) and downy mildew (bremia lactucae) is mainly differential and the resistance so far utilized in the host is vertical. as in many other obligate parasites, the introduction of cultivars with new vertical resistance has exerted a strong selection pressure on the pathogen resulting in significant changes in virulence frequencies and in the establishment of races with new combinations of virulence. genetic diversity in pathogen populatio ...198524253122
linkage analysis of genes for resistance to downy mildew (bremia lactucae) in lettuce (lactuca sativa).the genetics of specific resistance was studied in f2 populations which segregated for either one or two resistance genes. the resistance factors 1, 11 and 14 which had not previously been characterized genetically segregated as single dominant genes (dm). resistance was determined by three linkage groups; r 1/14, 2, 3, and 6 in the first, r 5/8, and 10 in the second and r 4, 7 and 11 in the third. cultivars of lettuce commonly used in the differential series to detect virulence to r3 and r10, w ...198524253062
blue and green light-induced phototropism in arabidopsis thaliana and lactuca sativa l. seedlings.exposure time-response curves for blue and green light-induced phototropic bending in hypocotyls of arabidopsis thaliana (l.) heynh. and lactuca sativa l. seedlings are presented. these seedlings show significant phototropic sensitivity up to 540 to 550 nanometers. since wave-lengths longer than 560 nanometers do not induce phototropic bending, it is suggested that the response to 510 to 550 nanometers light is mediated by the specific blue light photoreceptor of phototropism. we advise care in ...198516664021
activities of arginine and ornithine decarboxylases in various plant species.in extracts from the youngest leaves of avena sativa, hordeum vulgare, zea mays, pisum sativum, phaseolus vulgaris, lactuca sativa, and four pyrrolizidine alkaloid-bearing species of heliotropium, the activities of ornithine decarboxylase, close to v(max), ranged between traces and 1.5 nanomoles per hour per gram fresh weight when based on putrescine formed during incubation with labeled ornithine. the arginine decarboxylase activities in the same extracts ranged between 8 and 8000 nanomoles per ...198516664442
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 ...198516664360
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 ...19854026805
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 ...198516664144
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 ...19853994672
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 ...198511540836
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 ...198624232644
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. ...198616664963
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 ...198616664902
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 ...198624254736
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 ...198611539771
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 ...198624442367
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 ...198611539770
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 ...198711539702
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, ...198711539105
the genetics of esterase isozymes in lactuca sativa l. 19873435432
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 ...198724240222
role of benzoxazinones in allelopathy by rye (secale cereale l.).two phytotoxic compounds [2,4-dihydroxy-1,4(2h)-benzoxazin-3-one (diboa) and 2(3h)-benzoxazolinone (boa)] were previously isolated and identified in 35-day-old greenhouse-grown rye shoot tissue. both compounds were also detected by tlc in greenhouse-grown root and fieldgrown shoot tissue. the concentration of diboa varied in the tissues, with the greatest quantity detected in greenhouse-grown shoots. diboa and boa were compared with β-phenyllactic acid (pla) and β-hydroxybutyric acid (hba) for a ...198724302054
methyl mercury toxicity in plant cultures: modification of resistance and demethylation by light and/or 2,4-dichlorophenoxyacetic acid.cultures of daucus carota, ca-68-10, and lactuca sativa, le-67, were grown at increasing methyl mercury (mehg) concentrations ranging from initial doses of 0.05 to 5.0 micrograms/ml per day for 4 days with or without 0.15 microgram/ml 2,4-dichlorophenoxyacetic acid (2,4-d) in the presence or absence of light. the presence of 2,4-d interacted with light synergistically in the expression of mehg toxicity within the whole range of concentrations. demethylation patterns increased or decreased depend ...19873595486
transformation of lettuce (lactuca sativa) mediated by agrobacterium tumefaciens.lactuca sativa can be routinely transformed using ti plasmids of agrobacterium tumefaciens containing a chimeric kanamycin resistance gene (nos.nptii.nos). critical experimental variables were plant genotype, bacterial concentration, presence of a nurse culture and timing of transfers between tissue culture media. transformation was confirmed by the ability to callus and root in the presence of kanamycin, nopaline production, and by hybridization in southern blots. transformation has been achiev ...198724248927
a genetic map of lettuce (lactuca sativa l.) with restriction fragment length polymorphism, isozyme, disease resistance and morphological markers.a detailed linkage map of lettuce was constructed using 53 genetic markers including 41 restriction fragment length polymorphism (rflp) loci, five downy mildew resistance genes, four isozyme loci and three morphological markers. the genetic markers were distributed into nine linkage groups and cover 404 cm which may be 25-30% of the lettuce genome. the majority (31 of 34) of the rflp probes detected single segregating loci, although seven of these may have been homologous to further monomorphic ...198717246387
gibberellin-mediated synergism of xylogenesis in lettuce pith cultures.major gibberellins (gas) in lettuce (lactuca sativa l. cv romaine) pith explants have been identified by gas chromatography-mass spectrometry (gc-ms) or gc-selected ion monitoring (gc-sim) as ga(1), 3-epi-ga(1), ga(8), ga(19), and ga(20). treatment of pith explants with indole-3-acetic acid (iaa) (57 micromolar) plus kinetic (0.5 micromolar) induced xylogenesis. in this xylogenic treatment, the concentration of a biologically active, polar ga-like substance(s) increased during the first 2 days o ...198716665571
effect of temperature on infection and survival of rotylenchulus reniformis.from infestation of lettuce with preinfective females to egg deposition, populations of rotylenchulus reniformis from baton rouge, louisiana; lubbock and weslaco, texas; and mayaguez, puerto rico, required 41, 13, 7, and 7 days at 15, 20, 25, and 34 c, respectively. no nematode infection occurred at 10 c with any r. reniformis population, and the population from puerto rico did not reproduce at 15 c. nematode survival was not influenced by temperature, since populations from texas and louisiana ...198819290223
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 ...198816666455
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 ...198816666434
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 ...198816666236
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 ...198816666203
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 ...198811539044
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 ...198811539046
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