摘要:

Books reviewed in this article:INTEGRATION OF ACTIVITY IN THE HIGHER PLANT. Edited by D. H. Jennings(1977)PLANT TISSUE AND CELL CULTURE. Edited by H. E. Street.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00750.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractLiving organisms use light as a source of energy and as a means of obtaining information about their environment. Photoreactivating enzyme, provitamins D, retinal (rhodopsins and bacteriorhodopsin), porphyrins (chlorophyll, protochlorophyll and heme), photosynthetic accessory pigments (carotenoids and bilins), phytochrome and riboflavin: these are the molecules which life has settled upon to play the role of light receptor. For some of these photoreceptor molecules a great deal is now known about the chemistry which they perform upon absorbing light; for others virtually nothing is known. Riboflavin, the molecule believed to be functioning in a variety of organisms as the receptor for physiological responses to blue light, is an especially interesting case. Its widespread occurrence in cellular roles other than photoreception make it difficult to separate out the particular flavin which functions as the photoreceptor. It represents a case of a photoreceptor which is at once ubiquitous and elusive.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00751.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractCurrent interest in seed hydration treatments for the improvement of level, rate and uniformity of germination or field emergence has revealed how little is known of the physiology of germination control under water stress. This review surveys briefly the responses of seeds held at different hydration levels, from normal germination in a free water supply to seed activation without germination under slight moisture stress, seed deterioration at greater moisture stress and the damage that can be caused to seeds in very dry conditions, as well as the responses to subsequent dehydration. Inhibition of germination, though not of seed activation, at certain levels of water stress is likened to various forms of dormancy, and the mechanism governing the initiation of cell elongation is suggested as the possible key to control over germination. Several lines of evidence on cell membrane integrity and action, and their responses to external factors, point to the role that the membrane may play in cell elongation (and hence germination) control, and membrane integrity may also be associated with the transition between seed deterioration at one hydration level and seed activation and repair at slightly higher hydration levels. Seed activation without germination is also considered in an ecological context.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00752.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractMembrane potentials (pd's) of epidermal bladder cells and green leaf cells ofMesembryanthemum crystallinumL. are rather low (between −10 and −40 mV). During growth on 400 mM NaCl membrane potentials decrease further. As shown previously, plants grown on 400 mM NaCl show the diurnal changes of malate levels typical for plants having crassulacean acid metabolism. Therefore, in this study membrane potentials were measured at different times of the day, but no diurnal variations of pd were correlated with diurnal oscillations of malate levels. Resting potentials are similar in bladder cells and in green leaf cells and are similar in continuous light and darkness. Both bladder and leaf cells display light‐triggered photosynthesis‐dependent oscillations of the membrane potential although the bladder cells do not appear to be photosynthetically very active. This suggests electrical coupling between the bladder cells and the underlying green cells. Over a larger distance (2 mm) in the leaves, however, there is no direct evidence for electrical coupling. Cl−, Na+, and K+concentrations are similar in bladder cells and in the photosynthetically active tissue of leaves and stems. Bladder cells appear to contain high concentrations of free oxalate. The present findings corroborate earlier conclusions that the epidermal bladder cells ofM. crystallinumfunction as peripheral water reservoirs providing protection from short term wat

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00753.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractEnough water is stored in the sapwood of large Douglas‐fir to significantly contribute to transpiration. Sapwood water content falls through the season, causing the wood's conductivity to fall. This leads to low leafwater potentials, stomatal closure, and reduced photosynthesis by the trees.The amount of water stored in the sapwood of Douglasfir 50‐60 m tall, growing in the Cascade Mountains of Oregon, was estimated periodically over two seasons from measurements of sapwood relative water content (Rs). The relationship between Rsand volume of water contained in the sapwood was determined in the laboratory, and an equation describing the variation of relative conductivity (K) with Rswas derived from the literature. Stomatal conductance (ks) and leaf water potentials were measured in the field.The relative conductivity of the sapwood was calculated from estimates of the flow rate through the tree and differences in water potential between dawn and the time of comparison. Flow rate was assumed to equal transpiration rate, calculated from the Penman‐Monteith equation using measured ksvalues. A sixfold decrease in K during the summer was attributed to changes in Rs. The maximum observed diurnal variation in K would require a change in RSestimated at 25%.About 270 m3ha−1(27 mm) of water were stored in sapwood, and 75% of that was in the stemwood. Withdrawal from this store reached 1.7 mm day−1on clear days after cloudy or rainy weather. Recharge could be almost as fast (up to 1.6 mm day−1) after rain, but was very slow if the foliage r

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00754.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractPhotoperiodism, known to control the level of CAM in different types of CAM plants (e.g.Kalanchoe blossfeldiana, Bryophyllum daigremontianum), would act as a reliable timer for seasonal coherent adaptation. Two different endogenous rhythms (malic enzyme activity, PEP carboxylase capacity) appear to be separately coupled to dawn and dusk, respectively, thus achieving time‐compartmentation of CAM; this feature suggests involvement of an ‘internal coincidence’ type of clock mechanism.Persistence in continuous darkness of the rhythm of malic enzyme activity (measured by label incorporation into pyruvate or by CO2output) establishes its endogenous character and shows that light is not necessary for malate decarboxylation. The role of the dawn signal would be to entrain the CAM system, i.e. to phase the endogenous rhythm of malic enzyme activity correctly to local time. The possibility of an effect of the phase of the PEP carboxylase rhythm on the phase of the decarboxylation rhythm is ruled out by the presence of the intermediary malate storage step. Phase responses to red and to far‐red show that phytochrome is involved in rephasing the rhythm of malic enzyme activity.The relative position of dusk affords a ‘measurement’ of the season by the CAM system entrained by dawn. According to the dusk‐dawn interval, the level of PEP carboxylase capacity (amount of active enzyme) is modified, resulting in changes of CAM level (high activity unde

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00755.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractGrowth and ethylene production by lentil root tips treated with varying concentrations of indolylacetic and indolylacrylic acids were measured. Stimulation of growth by low concentrations of auxin was accompanied by a reduced ethylene production; growth inhibition by high levels of auxin induced a diminished ethylene evolution. Application of a rhizobitoxine analogue increased growth and reduced ethylene evolution. Simultaneous application of auxin and rhizobitoxine analog reduced ethylene evolution even though growth was inhibited. This indicated the non‐dependency of auxin‐controlled root growth upon ethylene product

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00756.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe photoautotrophic procaryote,Anacystis nidulans, accumulates glycogen as a carbon reserve during illumination and nitrogen limitation. Glycogen phosphorylase participates in the mobilization of the polysaccharide in a dark period and was found to be a point of regulatory control of glycogen degradation. Specific enzyme activity of non‐dividing cells increased twofold upon transfer from light to dark and decreased again upon re‐illumination. This dark stimulation of enzyme activity was not inhibited by either rifampicin or chloramphenicol, whereas a light‐induced decrease was abolished by DCMU, an inhibitor of photosynthetic electron transport. Deactivation of glycogen phosphorylase could be simulated by dithiothreitolin vitro. A spheroplast lysate either with or without chromatophores and a partially purified glycogen‐enzyme complex responded to dithiothreitol.These results are compatible with an interpretation in terms of redox changes taking place with the enzyme in an activation/deactivation cycle. The inactive form maintained in a reduced state by photosynthetic electron transport is thought to be converted into an active form in t

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00757.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY