Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
|---|
| biochar potential in intensive cultivation of capsicum anuum l. (sweet pepper): crop yield and plant protection. | the influence of various biochars on crop yield and disease resistance of capsicum anuum l. (sweet pepper) under modern, high-input, intensive net house cultivation was tested over the course of 2011 to 2014 in the arava desert region of israel. a pot experiment with lactuca sativa l. (lettuce) grown in the absence of fertilizer employed the 3-year old field trial soils to determine if biochar treatments contributed to soil intrinsic fertility. | 0 | 28612389 |
| evaluation of borage extracts as potential biostimulant using a phenomic, agronomic, physiological, and biochemical approach. | biostimulants are substances able to improve water and nutrient use efficiency and counteract stress factors by enhancing primary and secondary metabolism. premise of the work was to exploit raw extracts from leaves (le) or flowers (fe) of borago officinalis l., to enhance yield and quality of lactuca sativa 'longifolia,' and to set up a protocol to assess their effects. to this aim, an integrated study on agronomic, physiological and biochemical aspects, including also a phenomic approach, has ... | 0 | 28638392 |
| lettuce flavonoids screening and phenotyping by chlorophyll fluorescence excitation ratio. | environmentally induced variation and the genotypic differences in flavonoid and phenolic content in lettuce can be reliably detected using the appropriate parameters derived from the records of rapid non-invasive fluorescence technique. the chlorophyll fluorescence excitation ratio method was designed as a rapid and non-invasive tool to estimate the content of uv-absorbing phenolic compounds in plants. using this technique, we have assessed the dynamics of accumulation of flavonoids related to ... | 0 | 28303392 |
| arsenic uptake by lettuce from as-contaminated soil remediated with pteris vittata and organic amendment. | leaching of inorganic arsenic (as) from chromated copper arsenate (cca)-treated wood may elevate soil as levels. thus, an environmental concern arises regarding as accumulation in vegetables grown in these soils. in this study, a greenhouse experiment was conducted to investigate the ability of as-hyperaccumulator p. vittata and organic amendments in reducing as uptake by lettuce (lactuca sativa) from a soil contaminated from cca-treated wood (63.9 mg kg(-1) as). p. vittata was grown for 150 d i ... | 0 | 28273532 |
| simultaneous detection of sulfoxaflor and its metabolites, x11719474 and x11721061, in lettuce using a modified quechers extraction method and liquid chromatography-tandem mass spectrometry. | an analytical method has been developed to quantify the residual levels of sulfoxaflor and its metabolites (x11719474 and x11721061) in/on cultivated lettuce grown under greenhouse conditions. samples were extracted and purified using a quick, easy, cheap, effective, rugged, and safe 'quechers' method (original version) following systematic method optimization and were analyzed by liquid chromatography-tandem mass spectrometry (lc-ms/ms). good linearity with coefficient of determination ≥0.9930 ... | 0 | 27995654 |
| growth promotion of lactuca sativa in response to volatile organic compounds emitted from diverse bacterial species. | agrochemicals are currently used in horticulture to increase crop production. nevertheless, their indiscriminate use is a relevant issue for environmental and legal aspects. alternative tools for reducing fertilizers and synthetic phytohormones are being investigated, such as the use of volatile organic compounds (vocs) as growth inducers. some soil bacteria, such as pseudomonas and bacillus, stimulate arabidopsis and tobacco growth by releasing vocs, but their effects on vegetables have not bee ... | 0 | 27825485 |
| chemical composition and allelopathic potential of essential oils from citharexylum spinosum l. grown in tunisia. | citharexylum spinosum l. (verbenaceae) also known as citharexylum quadrangulare jacq. or citharexylum fruticosum l. is an exotic tree introduced many years ago in tunisia, specially used as a street and park ornamental tree. essential oils (eos) were obtained by hydrodistillation of the different parts (roots, stems, leaves, flowers and fruits; drupes) collected from trees grown in the area of monastir (tunisia). in total, 84 compounds, representing 90.1 - 98.4% of the whole oil composition, wer ... | 0 | 27685082 |
| chemical composition and allelopathic potential of essential oils from tipuana tipu (benth.) kuntze cultivated in tunisia. | in tunisia, tipuana tipu (benth.) kuntze is an exotic tree, which was introduced many years ago and planted as ornamental street, garden, and park tree. the present work reported, for the first time, the chemical composition and evaluates the allelopathic effect of the hydrodistilled essential oils of the different parts of this tree, viz., roots, stems, leaves, flowers, and pods gathered in the area of sousse, a coastal region, in the east of tunisia. in total, 86 compounds representing 89.9 - ... | 0 | 26916976 |
| c15083. chemical composition and allelopathic potential of essential oils from tipuana tipu (benth.) kuntze cultivated in tunisia. | in tunisia, tipuana tipu (benth.) kuntze is an exotic tree, which was introduced many years ago and planted as ornamental street, garden, and park tree. the present work reported, for the first time, the chemical composition and evaluates the allelopathic effect of the hydrodistilled essential oils of the different parts of this tree, viz., roots, stems, leaves, flowers and pods gathered in the area of sousse, a coastal region, in the east of tunisia. in total, 86 compounds representing 89.9-94. ... | 0 | 26864905 |
| phytotoxicity of three plant-based biodiesels, unmodified castor oil, and diesel fuel to alfalfa (medicago sativa l.), lettuce (lactuca sativa l.), radish (raphanus sativus), and wheatgrass (triticum aestivum). | the wide use of plant-based oils and their derivatives, in particular biodiesel, have increased extensively over the past decade to help alleviate demand for petroleum products and improve the greenhouse gas emissions profile of the transportation sector. biodiesel is regarded as a clean burning alternative fuel produced from livestock feeds and various vegetable oils. although in theory these animal and/or plant derived fuels should have less environmental impact in soil based on their simplifi ... | 0 | 26283287 |
| effect of a non-woven fabric covering on the residual activity of pendimethalin in lettuce and soil. | lettuce (lactuca sativa l.) is a crop that is very sensitive to herbicide contamination owing to its short growing season. the use of long-residual herbicides and non-woven fabric coverings could therefore influence pendimethalin concentrations in soil and lettuce. | 0 | 27558779 |
| non-destructive prediction of pigment content in lettuce based on visible-nir spectroscopy. | lettuce (lactuca sativa l.) is one of the most important salad vegetables in the world, with a number of head shapes, leaf types and colors. the lettuce pigments play important physiological functions, such as photosynthetic processes and light stress defense, but they also benefit human health because of their antioxidant action and anticarcinogenic properties. in this study three lettuce cultivars were grown under different farming systems, and partial least squares models were built to predic ... | 0 | 27553517 |
| uptake of antibiotics from irrigation water by plants. | the capacity of carrot (daucus corota l.) and lettuce (lactuca sativa l.), two plants that are usually eaten raw, to uptake tetracycline and amoxicillin (two commonly used antibiotics) from irrigated water was investigated in order to assess the indirect human exposure to antibiotics through consumption of uncooked vegetables. antibiotics in potted plants that had been irrigated with known concentrations of the antibiotics were extracted using accelerated solvent extraction and analyzed on a liq ... | 0 | 27213239 |
| bioavailability and risk assessment of potentially toxic elements in garden edible vegetables and soils around a highly contaminated former mining area in germany. | although soil contamination by potentially toxic elements (ptes) in europe has a history of many centuries, related problems are often considered as having been dealt with due to the enforcement of tight legislations. however, there are many unsolved issues. we aimed to assess pte levels in highly contaminated soils and in garden edible vegetables using human health risk indices in order to evaluate the availability and mobilization of arsenic (as), copper (cu), manganese (mn), mercury (hg), lea ... | 0 | 27117508 |
| stability of carotenoids and tocopherols in ready-to-eat baby-leaf lettuce and salad rocket during low-temperature storage. | minimally processed ready-to-eat baby-leaf vegetables (blvs) are the most convenient source to include the health beneficial bioactive in the daily diet. in the present study, the visual quality and storage stability of carotenoids, tocopherols were investigated in lettuce (green and red romaine) and salad rocket blvs. the commercially packed samples of blvs were stored at 0 °c and 4 °c in dark conditions and analyzed after 0, 2, 4, 8 and 12 days of storage. all the studied samples were found in ... | 0 | 27075434 |
| anti-inflammatory and antioxidant activity of polyphenolic extracts from lactuca sativa (var. maravilla de verano) under different farming methods. | besides their nutritional value, vegetables are a source of health-promoting compounds, such as polyphenols, and their content can be influenced by the particular farming method. in this study polyphenolic extracts from lactuca sativa (var. maravilla de verano) plants cultivated with different farming methods were chemically characterised and tested in vitro and ex vivo inflammation models. | 0 | 26777118 |
| elucidating the genetic basis of antioxidant status in lettuce (lactuca sativa). | a diet rich in phytonutrients from fruit and vegetables has been acknowledged to afford protection against a range of human diseases, but many of the most popular vegetables are low in phytonutrients. wild relatives of crops may contain allelic variation for genes determining the concentrations of these beneficial phytonutrients, and therefore understanding the genetic basis of this variation is important for breeding efforts to enhance nutritional quality. in this study, lettuce recombinant inb ... | 0 | 26640696 |
| dissipation and distribution of chlorpyrifos in selected vegetables through foliage and root uptake. | dissipation, distribution and uptake pathways of chlorpyrifos were investigated in pakchoi (brassica chinensis l.) and lettuce (lactuca sativa) with foliage treatments under a greenhouse trial and root treatments under a hydroponic experiment. the dissipation trends were similar for chlorpyrifos in pakchoi and lettuce with different treatments. more than 94% of chlorpyrifos was degraded in the samples for both of the vegetables 21 days after the foliage treatments. for the root treatment, the di ... | 0 | 26363321 |
| [structure of outgrowths produced by lactuca sativa l. (belle de mai variety) under the action of the ethyl ester of 2,-4 d]. | 1953 | 13067405 | |
| depth controlled deuteron irradiation of lactuca sativa seeds. ii. energy loss in the outer seed layers. | 1958 | 16655140 | |
| depth controlled deuteron irradiation of lactuca sativa seeds. i. effects on germination and growth. | 1958 | 16655139 | |
| mediation of phytochrome in the inductive action of low temperature on dark germination of lettuce seed at supra-optimal temperature. | the induction of dark germination in light-requiring lettuce (lactuca sativa) seed at supraoptimal temperatures by cold treatment (in darkness) was partly reversed by a brief far-red irradiation made at time of transfer, and even more so when the irradiation was made at the beginning of the cold pretreatment. when the inhibitory far-red irradiation was followed by additional cold treatment, the promotion was greatly restored. the promotive effects of brief irradiations with red light were furthe ... | 1966 | 16656362 |
| germination of lettuce induced by inhibitors of protein synthesis. | l-threo chloramphenicol and actinomycin d act like d-chloramphenicol in being able to promote germination of light-requiring seeds of lactuca sativa in darkness. the two isomers of chloramphenicol at relatively low concentrations also prevent the development of skotodormancy. protein synthesis, measured by the incorporation of tritiated leucine, occurs in dormant seeds in darkness; evidence suggests that this occurs most intensively in the endosperm. the stimulation of germination by chloramphen ... | 1967 | 24553746 |
| temperature and other factors affecting chloramphenicol stimulation of the germination of light-sensitive lettuce seeds. | d-threo-chloramphenicol at concentrations ranging from 1000 to 3000 μg/ml stimulated the germination of the light-sensitive seeds of the lettuce (lactuca sativa l.) varieties attractie and grand rapids. this stimulatory effect of chloramphenicol was markedly temperature dependent, increasing with decrereasing temperature. seeds showed little response to chloramphenicol at temperatures of 28°c and above except in the case of light treated attractie seed. the failure of one batch of grand rapids s ... | 1967 | 24522609 |
| [an action spectrum of photomorphogenesis under high energy conditions and its interpretation on the basis of phytochrome (hypocotyl growth inhibition in lactuca sativa l)]. | 1967 | 4384903 | |
| induction of light sensitive dormancy in seed of lactuca sativa l. (lettuce) by patulin. | 1967 | 16656588 | |
| correlative studies on plant growth and metabolism. iii. metabolic changes accompanying inhibition of the longitudinal growth of stem and root by kinetin. | kinetin-induced expansion of lettuce (lactuca sativa) cotyledons and inhibition of root are accompanied by parallel changes in protein nitrogen. however, during its inhibition of the longitudinal growth and water uptake of hypocotyl and pea (pisum sativum) epicotyl sections kinetin markedly stimulates protein synthesis. kinetin seems to separate auxin induced effects on protein synthesis and water uptake and indicates that water uptake and protein synthesis may not necessarily be correlated.in c ... | 1967 | 16656545 |
| chemical form and physiological availability of iodine in lettuce (lactuca sativa). | 1967 | 6030612 | |
| far-red sensitive dark processes essential for light- and gibberellin-induced germination of lettuce seed. | the action of prolonged far-red on seed germination was studied in lactuca sativa l. var. grand rapids. exposure of imbibed seeds to 6 hours far-red before the application of gibberellic acid (ga(3)) and thiourea completely prevented germination. using ga(3), this far-red was effective after the sixth hour of imbibition. at 6, 12, and 18 hours of imbibition equal durations of far-red had equal effects. the kinetics of far-red action was investigated: it was found that although far-red for severa ... | 1968 | 16656733 |
| stimulation of lettuce seed germination by ethylene. | ethylene increased the germination of freshly imbibed lettuce (lactuca sativa l. var. grand rapids) seeds. seeds receiving either red or far-red light or darkness all showed a positive response to the gas. however, ethylene was apparently without effect on dormant seeds, those which failed to germinate after an initial red or far-red treatment. carbon dioxide, which often acts as a competitive inhibitor of ethylene, failed to clearly reverse ethylene-enhanced seed germination. while light double ... | 1969 | 16657056 |
| biosynthesis of phytoquinones. homogentisic acid: a precursor of plastoquinones, tocopherols and alpha-tocopherolquinone in higher plants, green algae and blue-green algae. | 1. by means of (14)c tracer experiments and isotope competition experiments the roles of d-tyrosine, p-hydroxyphenylpyruvic acid, p-hydroxyphenylacetic acid, phenylacetic acid, homogentisic acid and homoarbutin (2-methylquinol 4-beta-d-glucoside) in the biosynthesis of plastoquinones, tocopherols and alpha-tocopherolquinone by maize shoots was investigated. it was established that d-tyrosine, p-hydroxyphenylpyruvic acid and homogentisic acid can all be utilized for this purpose, whereas p-hydrox ... | 1970 | 4986835 |
| the contents of sterol derivatives (sterols + esters, glycosides and acylated glycosides) have been determined using thin layer chromatography in leaves and bulky and organs from carrots (daucus carota l.) potato (solanum tuberosum l.), onion (allium cepa l.) two varieties of radish (raphanus sativus l.) and gentiana purpurea l. plants. ether-soluble lipids of leaves contain 2.8-5.2%, those of storage tissue 3.1-8.9% sterol derivatives. the fractionation of lettuce (lactuca sativa l., burpee's r ... | 1970 | 11945480 | |
| food, feeding rates and assimilation in woodland snails. | analyses of the faeces of seven species of woodland, litterdwelling snails (marpessa laminata, clausilia bidentata, oxychilus cellarius, o. alliarius, discus rotundatus, arianta arbustorum and hygromia striolata), showed that all feed predominently on higher plant material, be it living or dead. h. striolata and a. arbustorum took more chlorophyll-containing plant material than the other species, d. rotundatus had a significant amount of fungus in its faeces, while the faeces of o. cellarius and ... | 1970 | 28309717 |
| water content and phytochrome-induced potential germination responses in lettuce seeds. | grand rapids lettuce seeds (lactuca sativa l.) with 6 to 8% water content show no light-induced germination responses, whereas in seeds with 15% or more water content, germination is promoted or retarded by red and far red light respectively. by adjusting seed water content, persistent potentiated responses to light are induced in the seeds at seed water levels much below that required for germination itself. alternate moistening and drying of seeds in conjunction with red and far red irradiatio ... | 1971 | 16657591 |
| two effects of prolonged far red light on the response of lettuce seeds to exogenous gibberellin. | prolonged far red irradiation of imbibed lettuce seeds (lactuca sativa l. cv. grand rapids) makes them unresponsive to subsequent treatment with gibberellin. it has been found that this effect is overcome by supplying gibberellin buffered at a low ph. on the basis of this and other evidence it is suggested that an extended far-red exposure causes a loss of gibberellin sensitivity through an effect on the permeability of the endosperm. in seeds treated simultaneously with gibberellin and far red ... | 1972 | 16657995 |
| ethylene synthesis in lettuce seeds: its physiological significance. | the germination and pregermination ethylene production of grand rapids lettuce seeds (lactuca sativa l.) incubated at 20 c after a red light treatment are inhibited if the seeds are first imbibed at 30 c for 36 hours. in this study, low concentrations of ethylene were found to enhance the germination of seeds pretreated at 30 c more than that of untreated controls. in the presence of high concentrations of ethylene, pretreated seeds and controls germinated at a similar rate. these results are co ... | 1972 | 16658250 |
| polysome formation in light-controlled dormancy. | lettuce (lactuca sativa) seeds var. grand rapids could be maintained many weeks in the dark without germination. following illumination with white light, a gradual increase in polyribosome population up to the time of germination was demonstrated by sucrose gradient centrifugation. polysomes could not be detected in imbibed seeds maintained continuously in the dark. thus, polysome formation and therefore the capacity for a high rate of protein synthesis required for germination and growth, is no ... | 1972 | 16658240 |
| phytochrome transformation in lettuce seed irradiated at various temperatures. | phototransformation of phytochrome in lettuce seeds (lactuca sativa l. var. grand rapids) was examined by testing germination responses of seeds irradiated at various temperatures. temperature variations from 0 to 50 c had no influence on the germination of partially hydrated seeds (about 15% water content) irradiated with either red or far red light prior to imbibition. at -15 c far red light more effectively retarded germination than red light promoted it. no effective phototransformation was ... | 1972 | 16658150 |
| antagonistic effects of high and low temperature pretreatments on the germination and pregermination ethylene synthesis of lettuce seeds. | red light-induced germination of grand rapids lettuce seeds (lactuca sativa l.) incubated at 20 c was inhibited if the seeds were first imbibed at 30 c for 36 hours. this effect was counteracted by exogenous ethylene and associated with a reduction in the rate at which the seeds produced ethylene throughout the pregermination period. a chilling treatment reversed the effect of a prior imbibition at 30 c on both germination and ethylene production. the possibility that the pretreatments influence ... | 1972 | 16658141 |
| interaction of carbon dioxide and ethylene in overcoming thermodormancy of lettuce seeds. | the combination of ethylene with co(2) will completely overcome the thermodormancy of lettuce (lactuca sativa l.) seeds at 35 c. this combination is effective if it is added to seeds either at the start or after several days of imbibition. the action of ethylene is dependent upon the co(2) level present in the atmosphere surrounding the seeds. when co(2) is trapped by koh the ethylene effect is essentially nil. | 1972 | 16658074 |
| phytochrome and temperature relations in lactuca sativa l. grand rapids seed germination after thermo-dormancy. | 1972 | 4621828 | |
| [morphological variability of myeoplasma-like bodies in the phloem of lactuca sativa l]. | 1972 | 4679140 | |
| incidence of parasites found on vegetables collected from markets and vegetable gardens in taegu area. | a parasitic survey on vegetables collected from markets and vegetable gardens in taegu area was conducted for the discovery of human parasitic eggs and larvae. three species of vegetable, lettuce (lactuca sativa), young radish(raphanus sapivus) and chinese cabbage (brassica pekinensis) were selected. all vegetable leaves were washed with a hard brush, and then species of parasites and the approximate mean number of parasitic eggs per 200 grams of vegetable leaves were investigated. when vegetabl ... | 1972 | 12913510 |
| pathogenicity of meloidogyne hapla to lettuce as affected by inoculum level, plant age at inoculation and temperature. | pathogenicity of meloidogyne hapla to lettuce was influenced by inoculum level, age of plant at inoculation and temperature. top weight of 'minetto' lettuce was reduced 32% when 2-week-old lettuce plants were each inoculated with five egg masses. higher inoculum levels did not further decrease top weight significantly. inoculation at seeding reduced top growth more than inoculation of 1-, 2- or 3-week-old seedlings. m. hapla reduced growth more at the intermediate (21.1 c night and 26.7 c day), ... | 1973 | 19319317 |
| growth of plants in solution culture containing low levels of chromium. | chromium was not required for normal growth of romaine lettuce (lactuca sativa l. subsp. longifolia), tomato (lycopersicon esculentum mill.), wheat (triticum aestivum l.), or bean (phaseolus vulgaris l.) in solution culture containing 3.8 x 10(-4) mum cr. plants grown on this purified nutrient solution contained an average of 22 ng cr/g dry weight. duckweed (lemna sp.) grew and reproduced normally on a dilute nutrient solution containing 3.8 x 10(-5) mum cr. | 1973 | 16658503 |
| application of chemicals in organic solvents to dry seeds. | various chemicals were applied to dry seeds by means of organic solvents. the gibberellic acid-treated (1 mm) lettuce seeds (lactuca sativa l.) germinated nearly 100% in the dark even after prolonged storage, and those treated with abscisic acid (1 mm or 0.5 mm) failed to germinate in the light. the seedlings emerging from morphactin-treated (1 mm) cucumber seeds (cucumis sativus l.) exhibited profound changes in morphology. different combinations of hormones applied to lettuce seeds caused a pr ... | 1973 | 16658505 |
| a temperature-dependent source of variability in estimates of germination behaviour of lettuce fruits. | germination of fruits of lactuca sativa l. cv. "arctic king" showed a sharp upper temperature maximum at 31±1.0°c on an agar substrate in light. in a series of 60 tests carried out over 2 years, above, below and in the region of this maximum it was demonstrated that variability of germination counts was greater in the transition zone around this maximum. this is important when single controlled temperatures are chosen to compare effects of chemical or physical stresses on germination, where the ... | 1973 | 24468990 |
| polyribosome formation and protein synthesis in imbibed but dormant lettuce seeds. | dormancy is maintained in grand rapids lettuce (lactuca sativa) seeds imbibed on water in darkness at 25 c. polyribosome formation and protein synthesis occur early in the imbibition phase and considerable polysomal material is also present after 24 and 48 hours, even though the seeds have failed to germinate. incorporation of labeled leucine into protein following a 24-hour preincubation period shows that these polysomes are active in protein synthesis. | 1973 | 16658614 |
| vanadium and plant nutrition: the growth of lettuce (lactuca sativa l.) and tomato (lycopersicon esculentum mill.) plants in nutrient solutions low in vanadium. | lettuce (lactuca sativa l.) and tomato (lycopersicon esculentum mill.) plants were grown in purified nutrient solutions with and without the addition of 50 nanograms per milliliter v. these experiments showed that lettuce and tomato plants can be grown to maturity on nutrient solutions containing less than 0.04 nanogram per milliliter v with tissue concentrations of less than 2 to 18 nanograms per gram v. growth and dry matter yield were comparable to those of plants grown on nutrient solutions ... | 1973 | 16658525 |
| the effect of arsenate and other inhibitors on early events during the germination of lettuce seeds (lactuca sativa l.). | the effect of arsenate, arsenite, 2,4-dinitrophenol, and anaerobiosis on early events in seed germination was investigated using both intact and punched seeds of lettuce (lactuca sativa l.). it was found that punching the seed removes penetration barriers to the entrance of inhibitors without an undue loss of germination or light responses. the kinetics of the action of germination inhibitors were established by 2-hour pulse experiments. arsenate and 2, 4-dinitrophenol have very different kineti ... | 1973 | 16658515 |
| promotion of seed germination by cyanide. | potassium cyanide at 3 mum to 10 mm promotes germination of amaranthus albus, lactuca sativa, and lepidium virginicum seeds. l-cysteine hydrogen sulfide lyase, which catalyzes the reaction of hcn with l-cysteine to form beta-l cyanoalanine, is active in the seeds. beta-l-cyanoalanine is the most effective of the 23 alpha-amino acids tested for promoting germination of a. albus seeds. aspartate, which is produced by enzymatic hydrolysis of asparagine formed by hydrolysis from beta-cyanoalanine, i ... | 1973 | 16658492 |
| the role of phytochrome in an interaction with ethylene and carbon dioxide in overcoming lettuce seed thermodormancy. | ethylene and co(2) were used to control induction of germination in thermodormant lettuce seed (lactuca sativa l.). these experiments ultimately showed that germination depends on the presence of an active form of the phytochrome. the phytochrome system is functional and stable at 35 c, a temperature which completely inhibits germination. phytochrome responses to red or far red light and darkness showed that this inhibition of germination under light must be due to some other block(s) rather tha ... | 1973 | 16658472 |
| the relation between photophosphorylation and delayed light emission in chloroplasts. | one millisecond delayed light emission has been studied in isolated coupled lettuce (lactuca sativa var. romaine) chloroplasts. delayed light emission was increased upon addition of ferricyanide or 2,3,5,6-tetramethyl-p-phenylene diamine. in the presence of ferricyanide, the magnitude of the signal was increased by the addition of adp (in the absence of orthophosphate), atp, di0-9, or phlorizin. the signal was also increased by the addition of nacl and by the addition of nh(4)cl in the presence ... | 1973 | 16658467 |
| dark reversion of phytochrome in lettuce seeds stored in a water-saturated atmosphere. | dark reversion of the far red-absorbing form of phytochrome, which does not occur in dry lettuce (lactuca sativa var. grand rapids) seeds, appears to take place in seeds stored in a water-saturated atmosphere. the water content (approximately 70% after 10 days) of such seeds is insufficient to support germination; however the treatment enhances germination in seeds stored for 1 to 5 days, but this enhancement subsequently disappears, and the effect of extended storage (up to 28 days) is inhibiti ... | 1973 | 16658351 |
| results of cytogenetic studies of seeds after their extended orbital flight aboard the salyut orbital scientific station. | air-dry seeds of lactuca sativa (lettuce) with a different level of spontaneous mitagenesis were used in these experiments. a part of the seeds was given pre-flight gamma radiation in doses of 1 and 10 krads. comparison of the results for the in-flight experiments, laboratory and "transport" control showed an increase of cells with chromosome aberrations and an increase of radiobiological effect in irradiated seeds flown aboard the salyut scientific station. a comparative analysis was made of th ... | 1973 | 11998856 |
| photodormant lettuce seeds: phytochrome-induced protein and lipid degradation. | photodormant lettuce (lactuca sativa l.) seeds were incubated in mannitol to prevent germination. under these conditions, red light induced an extensive degradation of protein and a moderate one of lipid in the cortical cells of the radicle 24 h after treatment. it is suggested that the previously reported phytochrome-caused lowering of the water potential in light-treated embryos, which enables these embryos to overcome the resistance of the surrounding layers of the seed, is caused by lowering ... | 1974 | 24458467 |
| effects of germination-promoting substances given in conjunction with red light on the phytochrome-mediated germination of dormant lettuce seeds (lactuca sativa l.). | ethylene or thiourea can substitute for gibberellic acid but not for red light in breaking the secondary dormancy induced by extended dark storage of fully hydrated lettuce seeds (lactuca sativa cv. grand rapids). after 10 days of storage, ethylene, thiourea, or gibberellic acid applied either separately or in any combination in conjunction with red light induced near maximal germination. when applied separately without red light, none of the substances promoted germination of seeds stored 10 da ... | 1974 | 16658988 |
| hormone-solute interactions in the lettuce hypocotyl hook. | the hypocotyl hook of the lettuce (lactuca sativa cv. grand rapids) seedling is stimulated to a high degree of curvature through a synergistic interaction of ethylene and gibberellic acid in the light. presentation of various inorganic salts to the seedlings caused extensive alteration of the hormone-induced curvatures, with ammonium and sulfate being the most stimulatory of curvature, and potassium and carbonate being the most inhibitory of curvature. experiments using organic buffers indicated ... | 1974 | 16658876 |
| phytochrome-mediated germination responses in gamma-irradiated lettuce seeds. | sublethal doses of gamma-radiation and far red light have some-what analogous, red light reversible, effects on the germination of lettuce seeds (lactuca sativa l. var. grand rapids). however, the mechanism by which gamma-radiation retards germination appears to differ from that of far red light. compared to controls, gamma-radiation retarded germination for the first 24 hours; but after 36 or 48 hours of imbibition gemination of treated seeds was higher than that of the controls, whether or not ... | 1974 | 16658841 |
| seed aging: chromosome stability and extended viability of seeds stored fully imbided. | increase in moisture content of seeds of lactuca sativa l. and fraxinus americana l. in air-dry storage caused a rapid decline in longevity and an increase in the rate of accumulation of chromosome aberrations. storage of seeds fully imbibed but unable to germinate allowed a high germination capacity to be maintained for long periods, together with a very low incidence of chromosome aberrations. seedlings grown from dry-stored seeds showed an increase in morphological abnormalities with length o ... | 1974 | 16658808 |
| persistence of red light induction in lettuce seeds of varying hydration. | incubation of lettuce seeds (lactuca sativa l. cv. grand rapids) in 0.3 m mannitol allows sufficient water uptake to make seeds fully sensitive to red light. but germination is possible only after lowering the osmotic potential of the incubation medium. the red light induction of these incompletely hydrated seeds can be reversed by far red light. their reversibility declines with time at a slower rate than seeds incubated in water. about half the seeds in 0.3 m mannitol respond to far red light ... | 1974 | 16658732 |
| actions of gibberellic acid and phytochrome on the germination of grand rapids lettuce seeds. | red light and gibberellic acid were about equally effective in promoting germination of grand rapids lettuce (lactuca sativa l.) seeds. with initial far red light treatment more than 80% remained dormant in subsequent dark storage. after 2 days of dark storage, red light effectively promoted germination, while gibberellic acid action was weak. with between 2 and 10 days of dark storage, gibberellic acid had little effect, while promotion by red light decreased slowly and finally disappeared. aft ... | 1974 | 16658688 |
| the structure of the lettuce endosperm. | the two-cell-layered endosperm of lettuce (lactuca sativa l.) is characterized by thick cell walls and dense cytoplasm. the periodic-acid-schiff's(pas)-positive cell wall forms numerous peg-like projections which extend into the cytoplasm. the dense cytoplasm contains organelles of protein and lipid storage. the protein bodies are numerous and appear to be interconnected by narrow extensions of their envelopes. spherosomes are also numerous; they occupy a peripheral position in the cytoplasm. ot ... | 1974 | 24442777 |
| patterns of food utilization by the germinating lettuce seeds. | the embryo excised from seed of grand rapids lettuce (lactuca sativa l.) can be cultured in distilled water. complete digestion of the endosperm and transfer of nutrients from the endosperm to the embryo occur in the germinating seed with fat as the source of food. the fat is utilized for respiration, synthesis of amino acids, and to a degree, converted to sucrose. (14)c-glucose administered to the seed is quickly converted to sucrose in the endosperm and translocated to the embryo. radioactivit ... | 1974 | 16658653 |
| promotion of seed germination by nitrate, nitrite, hydroxylamine, and ammonium salts. | action and uptake of azides, nitrates, nitrites, hydroxylamines, and ammonium salts were measured on germination of amaranthus albus, lactuca sativa, phleum pratense, barbarea vulgaris, b. verna, and setaria glauca seeds. nitrate and nitrite reductase activities were measured in vivo for each of these kinds of seeds. activities were measured in vitro for catalase, peroxidase, glycolate oxidase, and pyridine nucleotide quinone reductase on extracts of a. albus and l. sativa seeds before and after ... | 1974 | 16658878 |
| effect of gibberellic acid, kinetin, and ethylene plus carbon dioxide on the thermodormancy of lettuce seed (lactuca sativa l. cv. mesa 659). | the effects of gibberellic acid and kinetin with ethylene plus carbon dioxide on the thermodormancy of lettuce seeds (lactuca sativa l. cv. mesa 659) at 35 c in the dark were studied. the combination of gibberellic acid plus kinetin with ethylene plus carbon dioxide was most effective in overcoming thermodormancy in these great lakes type seeds, alleviating any induced light requirement. gibberellic acid action required at least a minimal level of ethylene plus carbon dioxide. kinetin action was ... | 1975 | 16659403 |
| endogenous abscisic acid levels in germinating and nongerminating lettuce seed. | the concentrations of abscisic acid in grand rapids lettuce (lactuca sativa l.) seeds imbibed under conditions which promote or inhibit germination were determined by electron capture-gas chromatography. the concentration of abscisic acid in dry seeds was 12 to 14 nanograms per 100 milligrams. during 24-hour imbibition, the abscisic acid content diminished more rapidly during conditions which allow germination (25 c in light) than in conditions which inhibited germination (35 c in light or darkn ... | 1975 | 16659382 |
| [purification and characterization of chloroplast carbonate dehydratase from leaves of lactuca sativa (author's transl)]. | two isoenzymes of carbonate dehydratase were identified in green leaf tissue of lactuca sativa. their molecular weights were found to be 195 000 and 250 000. the lighter isoenzyme (i) was further characterized. it is localized in the chloroplast fraction. with polyacrylamide gel electrophoresis in the presence of dodecyl sulphate, subunits with a molecular weight of 34 000 and higher aggregates of this size could be detected. this is interpreted as an indication of an hexameric enzyme structure. ... | 1975 | 812792 |
| photomanipulation of phytochrome in lettuce seeds. | seeds of lettuce (lactuca sativa l. cv. grand rapids) were imbibed and given either short irradiation with red or far red light prior to drying or dried under continuous red or far red light. seeds treated with either short or continuous red germinate in darkness, whereas seeds treated with either short or continuous far red require a short exposure to red light, after a period of imbibition, to stimulate germination. irradiation of dry red seeds with far red light immediately before sowing resu ... | 1975 | 16659296 |
| gibberellin response in lettuce hypocotyl sections. | excised lettuce (lactuca sativa l.) hypocotyl sections retain the ability to elongate in response to gibberellic acid (ga(3)) addition. in 48 hr at 30 c a ga(3)-treated segment more than doubles while a control segment elongates less than 50%. auxin has no detectable effect on this system. sensitivity to ga(3) is not decreased by apex or root removal. of the experimental variables tested, temperature, sucrose, and preincubation in water affect growth both with and without ga(3). blue and far red ... | 1975 | 16659285 |
| additive and synergistic effects of kinetin and ethrel on germination, thermodormany, and polyribosome formation in lettuce seeds. | the inhibition of germination of grand rapids lettuce (lactuca sativa l.) seeds at 35 c was removed to a marked extent by kinetin and 2-chloroethylphosphonic acid (ethrel). when both compounds were used together, an additive effect was observed. a synergistic effect was, however, noted when ethrel promoted the kinetin reversal of abscisic acid inhibition of seed germination (light- as well as gibberellic acid-, induced). both kinetin and ethrel increased the total ribosomal material and the perc ... | 1975 | 16659284 |
| light-induced de-epoxidation of violaxanthin in lettuce chloroplasts. iv. the effects of electron-transport conditions on violaxanthin availability. | 1. in isolated chloroplasts of lactuca sativa var. manoa, the size of the violaxanthin fraction which is available for de-epoxidation is not directly dependent on electron transport but rather related to the reduced level of some electron carrier between the photosystems. this is concluded from the effects of various electron-transport conditions on violaxanthin availability: under conditions of electron transport through both photosystems, availability was saturated at a lower electron-transpor ... | 1975 | 1125284 |
| [natural infection by broad bean wilt virus in head lettuce (lactuca sativa l.) (author's transl)]. | 1975 | 1242248 | |
| lettuce seed germination: modulation of pregermination protein synthesis by gibberellic acid, abscisic acid, and cytokinin. | protein synthesis in gibberellin-treated lettuce (lactuca sativa) seeds has been studied during the lag phase between the beginning of imbibition and the first signs of radicle protrusion. when compared to the water-imbibed controls, both polyribosome populations and radioactive leucine incorporation into protein increase in the embryos of ga(3)- induced seeds early in the imbibition period. since these results are contradictory to previously published studies, the reasons for the differences ar ... | 1976 | 16659711 |
| light-induced de-epoxidation in lettuce chloroplasts: vi. de-epoxidation in grana and in stoma lamellae. | grana and stroma lamellae fractions prepared from illuminated chloroplasts (lactuca sativa l. var. manoa) by french press treatment contained less violaxanthin and more zeaxanthin than the corresponding fractions from dark controls. in both fractions, only part of the total violaxanthin was de-epoxidized under illumination, and the ratio of de-epoxidized and unchanged violaxanthin was similar. this not only shows that the de-epoxidation system is present in both grana and stroma thylakoids but a ... | 1976 | 16659604 |
| effects of 35 c heat treatments on photosensitive grand rapids lettuce seed germination. | grand rapids lettuce (lactuca sativa l.) seeds were given 35 c heat treatments to increase photodormancy in a subsequent 20 c dark period. short heat treatments (1-5 hours) induced a significant germination percentage increase of from 16% to over 50% depending on seed lot. with longer heat treatments dark germination percentage was gradually reduced to zero. if given at the end of 35 c, far red or red followed by far red further increased the amount of dark germination.thermodormancy also delaye ... | 1976 | 16659537 |
| promotive effects of organic solvents and kinetin on dark germination of lettuce seeds. | significant promotion in dark germination was observed when grand rapids lettuce (lactuca sativa l.) seeds were soaked in acetone or dichloromethane, vacuum-dried, and imbibed at 25 c. permeation of kinetin via these organic solvents further enhanced the dark germination. those seeds that were affected by acetone and acetone-kinetin treatments and germinated in the dark escaped red-far red photocontrol of germination. although abscisic acid was not detected in the organic solvent leachates, they ... | 1976 | 16659500 |
| effects of red light and ethylene on growth of etiolated lettuce seedlings. | low concentrations of ethylene inhibit hypocotyl elongation of etiolated lettuce seedlings (lactuca sativa cv. grand rapids), whereas red light does not inhibit it. the plumular hook tightens in response to either ethylene or red light. a combination of these two factors gives an additive response. red light has no effect on ethylene production and red light will cause hook closure even under hypobaric pressure which removes endogenous ethylene. this suggests that ethylene and red light act inde ... | 1976 | 16659495 |
| the involvement of indole acetic acid in the thermodormancy of lettuce fruits, lactuca sativa cv. grand rapids. | at 20° c and at 30° c in darkness, concentrations of indole acetic acid (iaa) greater than 10(-7) m inhibited the germination of grand rapids lettuce at 24 h and 48 h after the beginning of imbibition. there was no marked, readily defined period of inhibition during germination that could be associated solely with an effect of iaa on suppressing radicle extension. gibberellin a4+7, benzyladenine and red light were capable of reversing the effects of iaa. there was no consistent pattern of change ... | 1976 | 24424836 |
| abscisic acid as an endogenous component in lettuce fruits, lactuca sativa l. cv. grand rapids. does it control thermodormancy? | abscisic acid (aba) has been unequivocally identified as an endogenous component of seeds of grand rapids lettuce. both "free" and "bound" aba levels were followed during imbibition at various temperatures but no clear role for aba in the imposition of thermodormancy emerged. furthermore it was apparent that different seed batches showed different ratios of "free" to "bound" aba and patterns of changes. an unsuccessful attempt was made to identify "bound" aba, presumed to be the glucosyl ester. | 1976 | 24424821 |
| an enzyme to degrade lettuce endosperm cell walls. appearance of a mannanase following phytochrome- and gibberellin-induced germination. | lettuce seeds (lactuca sativa l. cv. grand rapids) stimulated to germinate by gibberellin and red light produce large amounts of endo-β-mannanase. this enzyme increases markedly following radicle emergence and is capable of degrading mannose-containing polysaccharides, which are the major components of the endosperm cell wall. non-germinated seeds contain little enzyme and under conditions where gibberellin- or red light-stimulated germination is prevented (eg. by abscisic acid or prolonged far ... | 1976 | 24424598 |
| variation in germination and amino acid leakage of seeds with temperature related to membrane phase change. | leakages of amino acids and/or fluorescent material as functions of temperature between 15 and 40 c are reported for imbibed seeds of avena fatua l., lactuca sativa l., barbarea vulgaris r. br., amaranthus albus l., abutilon theophrasti medic., lychnis alba mill., daucus carota l., setaria faberi herrm., setaria viridis (l.) beauv., and datura stramonium l. the leakage indicates prominent increase in permeability of the plasmalemma in the 30 to 35 c range for 8 of the 10 kinds of seeds studied. ... | 1976 | 16659623 |
| attempts to detect cyclic adenosine 3':5'-monophosphate in higher plants by three assay methods. | endogenous levels of cyclic adenosine-3':5'-monophosphate in coleoptile first leaf segments of oat (avena sativa l.), potato (solanum tuberosum l.) tubers, tobacco (nicotiana tabacum l.) callus, and germinating seeds of lettuce (lactuca sativa l.) were measured with a modified gilman binding assay and a protein kinase activation assay. the incorporation of adenosine-8-(14)c into compounds with properties similar to those of cyclic amp was also measured in studies with germinating lettuce seeds. ... | 1976 | 16659419 |
| growth and gibberellin a(1) metabolism in excised lettuce hypocotyls. | excised lettuce (lactuca sativa l. cv. arctic) hypocotyls retain the ability to elongate in response to exogenously supplied gibberellic acid and gibberellin a(1) (ga(1)). we have studied the relationship between metabolism of ga(1) and elongation in this tissue. in 24 hours at 28 c, hypocotyls treated with 3 mum ga(1) double in length while controls elongate less than 45%. after an exogenous hormone supply is removed, hypocotyls continue to grow faster than untreated controls, although as the h ... | 1977 | 16659819 |
| apparent destruction and reutilization of heterologous dna applied to seeds of lactuca sativa [proceedings]. | 1977 | 79399 | |
| breaking of seed dormancy by catalase inhibition. | germination of some dormant seeds is promoted by solutions of thiourea, sodium nitrite, and hydroxylamine salts. the promotions are accompanied by irreversible inhibition of catalase (ec 1.11.1.6) in extracts from the seeds. the seeds are also promoted in germination by catechol and pyrogallol solutions. these effects are recorded for lettuce (lactuca sativa l. cv. grand rapids) and pigweed (amaranthus albus l.) seeds. the results indicae that metabolically derived hydrogen peroxide, spared from ... | 1977 | 235126 |
| occupational dermatitis from lactuca sativa (lettuce) and cichorium (endive). simultaneous occurrence of immediate and delayed allergy as a cause of contact dermatitis. | four patients with occupational contact dermatitis to lactuca sativa had cross-sensitivity to cichorium endivia. one of the patients also had contact urticaria to lactuca and cichorium, and another reacted positively to scratch tests with these plants as a sign of immediate allergy. in two cases such immediate allergy was considered the cause of a vesicular, intense itching eruption within a few minutes of contact with fresh leaves of lactuca on previously eczematous skin. the severe chronic der ... | 1977 | 139283 |
| mode of action of gibberellic acid and light on lettuce seed germination. | the seeds of lettuce (lactuca sativa l. cv. grand rapids) germinate in darkness at 25 c when treated by gibberellic acid (ga(3)) for 1 hour following 2 hours of imbibition. the time of ga(3) application influences the rate and the final percentage of seeds that germinate. in contrast, red light illumination given at different times affects only the rate and not the final germination percentage. the early process(es) of germination initiated by ga(3) or light treatment can be arrested by subjecti ... | 1977 | 16660140 |
| reversal of induced dormancy in lettuce by ethylene, kinetin, and gibberellic acid. | the germination of lettuce seeds (lactuca sativa l., cv. premier great lakes) was significantly inhibited by high temperature (32 c), 0.1 mm abscisic acid or 0.4 m mannitol. ethylene (16 mul/1 of air) partially reversed the dormancy induced by all three inhibitors but only in the presence of 1 mm gibberellic acid (ga) or light. neither ethylene plus ga nor ethylene plus light were able to promote germination when thermal inhibition was imposed at 36 c. addition of 0.01 mm kinetin to the ethylene ... | 1977 | 16660064 |
| polypeptide composition of chlorophyll-protein complexes from romaine lettuce. | the protein moiety of the two major chlorophyll-protein complexes associated with chloroplast membranes of outer, dark green leaves of a romaine lettuce shoot (lactuca sativa l. var. romana) has been analyzed by discontinuous sodium dodecyl sulfate-polyacrylamide disc gel electrophoresis. complex ii, also termed light-harvesting chlorophyll-protein complex, is shown to consist of a major polypeptide of 25 kilodaltons (kd) and two minor ones of 27.5 and 23 kd. the 25 kd subunit is the single larg ... | 1977 | 16660046 |
| hormonal activity in detached lettuce leaves as affected by leaf water content. | the interrelationship between water deficiency and hormonal makeup in plants was investigated in detached leaves of romaine lettuce (lactuca sativa l. cv. ;hazera yellow'). water stress was imposed by desiccating the leaves for several hours in light or darkness at different air temperatures and relative humidity. in the course of desiccation, a rise in abscisic acid content and a decline in gibberellin and cytokinin activity were observed by gas-liquid chromatography, by both the barley endospe ... | 1977 | 16660015 |
| release of esterase following germination of lettuce seed (lactuca sativa l.). | light-insensitive lettuce seeds, lactuca sativa l. cv. great lakes, release esterases for a period following radicle protrusion. very little or no enzymes are released prior to 24 hours or after 48 hours of germination. as compared to intact seeds, half-seeds readily release esterases and the release is not affected by far red irradiation. bulk of the released esterases are derived from the endosperm tissue and presumably exists in the intact seed as a component of the extraembryonic fluid. | 1977 | 16659992 |
| gibberellin metabolism in excised lettuce hypocotyls: evidence for the formation of gibberellin a1 glucosyl conjugates. | the properties of the water-soluble metabolites of [(3)h]gibberellin a1 ([(3)h]ga1) from lettuce (lactuca sativa l.) hypocotyls were compared with those of authentic samples of gibberellin (ga) glucosyl esters and ethers. partitioning against l-butanol at high and low ph was not an efficient method of differentiating between ester and ether conjugates of ga1 or ga3. extraction into l-butanol at ph 2.5 was, however, useful as a group purification step. gel-filtration on acrylamide indicated a mea ... | 1977 | 24420400 |
| cell elongation and cell division in elongating lettuce hypocotyl sections. | the roles of cell division and cell elongation in the growth of sections excised from hypocotyls of lettuce (lactuca sativa l. cv. arctic) were investigated. elongation of sections incubated in the light is inhibited compared to dark-grown sections and this inhibition is reversed by gibberellic acid (ga3). the elongation of both dark-grown and ga3-treated, light-grown sections can be enhanced by 10mm kcl. under all conditions of incubation, elongation growth is greatest in the uppermost quarter ... | 1977 | 24420091 |
| roles of extensibility and turgor in gibberellin- and dark-stimulated growth. | the elongation response elicited by incubating excised hypocotyl sections of lettuce (lactuca sativa l.) in light in gibberellin (ga) can be enhanced by the addition of cl(-), br(-), and no(3) (-) salts of k(+) and na(+). sections incubated in light in the absence of ga do not elongate in response to the addition of salts. in contrast, excised hypocotyls incubated in darkness elongate equally in both ga and water, and their elongation can also be enhanced by kcl treatment. growth stimulation by ... | 1977 | 16659790 |
| effect of weightlessness and of artificial gravity on irradiated lettuce seeds. | in our previous studies on board the artificial earth satellite cosmos 368, the cosmic apparatus zond 8 and the orbital station salyut it has been demonstrated that space-flight factors (sff) have a definite effect on poorly active biological systems, such as dry lettuce seeds. the technical possibilities on board the biosatellite cosmos 782 (the availability of an on-board centrifuge) allowed us to obtain some new data concerning the mechanisms of the sff effects. irradiated seeds of lettuce (l ... | 1977 | 11962502 |
| effects of ethylene and carbon dioxide on the germination of osmotically inhibited lettuce seed. | lettuce seeds (lactuca sativa l.) used in this study germinated 98% at 25 c in light or dark. their germination was completely inhibited by 0.20 m nacl, 0.35 m mannitol, or polyethylene glycol 6000 (-7 bars) under continuous light when germination tests were made in petri dishes. approximately 50% germination occurred in sealed flasks due to endogenously produced c(2)h(4) and co(2). removal of either or both gases prevented germination. in the presence of endogenous co(2), addition of c(2)h(4) ( ... | 1978 | 16660541 |
| endogenous gibberellin and abscisic acid content as related to senescence of detached lettuce leaves. | levels of gibberillins (gas) and of abscisic acid (aba) in attached leaves of romaine lettuce (lactuca sativa l.) declined as the leaf became older. the time course of changes in hormone levels, determined in detached lettuce leaves kept in darkness, revealed that a sharp decline in gas accompanied by a moderate rise in aba occurred before the onset of chlorophyll degradation. as senescence advanced, no gas could be detected and a considerable rise of aba was observed. a similar sequence of horm ... | 1978 | 16660490 |
| induction of phenylalanine ammonia-lyase and increase in phenolics in lettuce leaves in relation to the development of russet spotting caused by ethylene. | russet spotting (rs), consisting of numerous small brown spots on the midrib of head lettuce (lactuca sativa), is a physiological disorder induced by exposure to ethylene. in leaves suffering rs, the increase in spotting was accompanied by a parallel increase in the amount of phenolic compounds. of these, chlorogenic acid and isochlorogenic acid were identified. ethylene induced high phenylalanine ammonia-lyase (pal) activity and rs formation in the susceptible cultivar salinas, but not in the r ... | 1978 | 16660463 |
| light penetration and light-induced seed germination in soil. | light penetration through a drummer silty clay loam and a broomfield sand was measured spectrophotometrically and biologically. the spectrophotometric measurements showed that less than 1% of the incident light penetrated 2.2 millimeters at any wavelength between 350 and 780 nanometers for ped sizes up to 1 millimeter. biological measurements with light-sensitive lettuce (lactuca sativa) seeds in soil showed that an exposure to light equivalent to about 1 sunny day induced some germination of se ... | 1978 | 16660344 |