摘要:

Books reviewed in this article:NUCLEIC ACIDS IN PLANTS, Volume I. Edited by T. C. Hall&J. W. Davies(1979)

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11581811

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractThe nature of science and of scientific progress is discussed, with special reference to the role of mathematics, and the existence in biology of hierarchical organization and levels of description. A distinction is made between a description of a phenomenon, and an understanding of that phenomenon; if mathematics is applicable, this is reflected in the use of an empirical or a mechanistic model. Reductionism is considered in relation to alternative viewpoints, and some examples from cell biology and plant physiology of problems where reductionism alone may be leading to difficulties, are discussed. A possibly more effective research strategy is suggested.

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11581813

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractWater stress at a nonacclimating temperature (18–20°C) increased the cold hardiness ofMedicagosativaL. (alfalfa) plants. This increased cold hardiness was retained when the previously water‐stressed plants were cold acclimated (2–9°C) in the absence of water stress. Water stress during cold acclimation also increased cold hardiness. Alfalfa was demonstrated to suffer injury, measured as decreased growth following freezing, at sub‐lethal temperatures. During cold acclimation the turgor potential (ψ) of watered plants increased, whereas the solute potential and the water content per unit dry weight decreased. The large positive psgrdap of acclimated plants indicates that the decreased water content per unit dry weight is related to an increased proportion of tissue dry matter rather than to tissue d

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11581816

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractAlthough rice has long been recognized to be uniquely adapted for growth in low oxygen environments of flooded rice fields, rice weeds of theEchinochloa crus‐gallicomplex appear to be at least as well specialized for germination and growth under such unusual biological conditions.Seeds of two varieties ofE. crus‐galligerminate and grow for prolonged periods in a totally oxygen‐free environment.E. crus‐galligerminates as well as rice (Oryza sativa) under a total nitrogen atmosphere and produces as large a seedling in spite of its much smaller seed size. Like rice, the seedlings ofE. crus‐galliare unpigmented, the primary leaves do not emerge from the coleoptile and no root growth occurs without oxygen. Of particular interest is the ultrastructure of mitochondria from anaerobically‐grown seedlings. Mitochondrial profiles from the primary leaf of seedlings grown continuously in nitrogen are very similar to those grown aerobically. The size and shape of the mitochondria are similar and the cristae are numerous and normal in appearance. This is in sharp contrast to previous studies of other species which have reported that mitochondria were vesiculate and tended to lose their normal fine‐structure after similar periods without oxygen.Finally, based on ultrastructure and14C labeling studies, anaerobically‐grown seedlings are highly active metabolically, which may explain, at least forE. crus‐gallivar.oryzicola, its ability to germinate and emerge from fl

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11581818

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractFromSedum morganianum, which is a plant species known to have constitutive crassulacean acid metabolism (CAM), phosphoenolpyruvate (PEP) carboxylase (E.C.4.1.1.31) has been extracted and purified by (NH4)2SC4precipitation, ion exchange chromatography and gel electrophoresis. A specific antibody to this purified enzyme was obtained by immunization of a rabbit. This antibody was used to compare the antigen–antibody reaction of PEP‐carboxylases prepared from otherSedumspecies including constitutive, facultative and non‐CAM plants. The experiments revealed partial immunological indentity of PEP‐carboxylases obtained from the different

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11581821

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractA range of aliphatic, aromatic and amino acids at a concentration of 5 mol m‐3inhibited the extension of roots of barley seedlings. Acetic acid is one of the least toxic but its action has the greatest ecological significance because it can be formed in phytotoxic concentrations by micro‐organisms in soil. Its uptake and toxicity were greatest at low pH. Of the plant species which were examined, those most affected were barley, wheat and maize, followed by rape and clover. In aerobic conditions, microbial breakdown of the acid decreased its activity, but in atmospheres containing small concentrations of oxygen the acid prevented the germination of seeds. The toxicity could be partially alleviated by calcium carbonate applied as ground chalk to se

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11581824

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractBiomass increase, C and N content, C2H2reduction, percentage dry weight and chlorophyll a/b ratios were determined for clones ofAzolla carolinianaWilld.,A. filiculoidesLam.,A. mexicana Presl., andA. pinnataR. Br. as a function of nutrient solution, pH, temperature, photoperiod, and light intensity in controlled environment studies. These studies were supplemented by a glasshouse study. Under a 16 h, 26°C day at a light intensity of 200 μmol m−2s−1and an 8 h, 19° C dark period, there was no significant difference in the growth rates of the individual species on the five nutrient solutions employed. Growth was comparable from pH 5 to pH 8, but decreased at pH 9. Using the same photoperiod and light intensity but constant growth temperatures of 15–40°C, at 5°C intervals, the individual species exhibited maximum growth, nitro‐genase (N2ase) activity and N content at either 25° or 30°C. There was no difference in the temperature optima at pH 6 and pH 8. The tolerance of the individual species to elevated temperature was indicated to beA. mexicana>A. pinnata>A. caroliniana>A.filiculoides.At the optimum temperature, growth rates increased with increasing photoperiod at both pH 6 and pH 8 but N2ase activity was usually highest at a 16 h light period. At photon flux densities of 100, 200, 400 and 600 μmol m−2s−1, during a 16 h light period and optimum growth temperature of the individual species, N2ase activity was saturated at less than 200 μmol m−2s−1and growth at 400 μmol m−2s−1.No interacting effects of light and pH were noted for any species, nor were light intensities up to 1700 μmol m−2s−1detrimental to the growth rate or N content of any species in a 5 week glasshouse study with a natural 14.5 h light period and a constant temperature of 27.5°C. Using the optimum growth temperature, a 16 h light period, and a photon flux density of at least 400 μmol m−2s−1, theAzollaspecies all doubled their biomass in 2 days or less an

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11581825

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractTwo‐week old, glasshouse‐grown seedlings of spring and winter oats (Avena sativacv. Margam and Pennal respectively) were transferred to growth rooms where the daylength was 8 h and the temperature was either 20° or 5°C. Leaves from the 20°C treatment were harvested 1 week after transfer and those from the 5°C treatment after 3 weeks. Measurements were made, at temperatures in the range 5–20°C, of the rate of senescence of excised leaf sections; the rate ofin vivotetrazolium (TTC) reduction; the NADH‐MTT tetrazolium diaphorase (NMD) activity of a membrane preparation isolated by sucrose gradient centri‐fugation; and Hill activity of isolated chloroplasts. Data from these experiments, either untransformed or plotted in accordance with the Arrhenius equation, were analysed by the method of maximum likelihood for the occurrence of rate‐temperature discontinuities. Distinct breakpoints at 14.2–16.3°C were detected for senescence, TTC reduction and NMD in winter oat leaves from the 20°C treatment, but spring oats grown at the same temperature gave a significant discontinuity only in the rate of senescent yellowing. After the hardening treatment, 3 weeks at 5°C, senescence and TTC reduction in winter oats exhibited breakpoints at 10.1–12.4°C and spring oats gave breaks at 11.8–17.3°C. No breakpoint was observed for Hill activity from either variety under either temperature treatment. The use of this approach in studies of growth at chilling temperatures and its potential as a scr

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11581828

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractResponses of stomata to light and CO2were smaller when detached epidermis ofCommelina communisL. was incubated on a medium containing 50 mol m−3NaCl than when an equimolar KCl solution was used. Although opening in the light in the absence of CO2seemed to be the same whichever salt was present, apertures on KCl solutions were smaller in the dark or with CO2‐containing air. The response to 10−7mol dm−3ABA was similarly reduced in the presence of NaCl. If there is an optimal NaCl concentration for stomatal CO2and light responses it is at or below 25 mol m−3. These findings point towards control of stomatal movements by light, CO2and ABA at the level of cation uptake or

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11581831

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractIn the field successive leaves of winter wheat appear at a rate which varies because it depends strongly upon temperature. When plotted against ‘thermal time’, however (temperature accumulated above a fixed base of 0°C), leaf appearance was a strictly linear function of temperature. The mean rate of leaf appearance in thermal time,R′, was faster for a spring sowing than for an autumn sowing. The variation in R′ between sowings was better correlated with the rate at which daylength was changing when the plants emerged than with the mean daylength while leaves were a

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11581834

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY