| 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 |
| 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 |
| [the effect of postradiation storage on the mutation process and germination of lettuce seeds (lactuca sativa) irradiated with co 60 gamma-rays]. | | 2001 | 5052700 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| [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 |