摘要:

Books reviewed in this article:THE MOLECULAR BIOLOGY OF PLANT CELLS. Edited by H. SmithPLANT GROWTH REGULATION. Proceedings of the 9th International Conference on Plant Growth Substances at Lausanne. Edited by P. E. Pilet

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00758.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractRelevant mathematical properties of the Richards function are described, along with references to its employment in previous work, and a brief description is given of some of the difficulties encountered in its use. Two introductory experiments were undertaken: firstly, applying the Richards function to leaf growth ofImpatiens parvifloraDC; and secondly, applying the function to artificial sets of data of differing variability and differing spreads of observation‐values along the growth curve. The purpose of the latter analysis was an attempt to elucidate some problems of fitting and interpretation arising in the first experiment. It was concluded that the prime aim in experimental work generally is the acquisition of data covering as large a range of sizes as possible; low variability of the replicate observations, while desirable, is not so important.
In another series of experiments, plants ofImpatiens parviflorawere grown at four different temperatures in the range 13–23°C inclusive. In terms of leaf dry weight, increase in temperature decreased the final size attained and increased the mean relative growth rate; the curvature of the growth curve and the mean absolute growth rate were, however, temperature independent. These results are brought together in a simple model which shows clearly how temperature affects the course of leaf dry weight increase in these plants. The results for leaf area are less clear, but both the mean absolute and relative growth rates increased with rise in temperature. The final area of a leaf and the curvature of the growth curve seemed to be little affected by temperatures in the range 16–23°C, but there was some evidence of differences in these features in leaves growing at 13°C. No model summary was attempted for leaf are

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00759.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractResults obtained withHydrodictyon africanum, and data from the literature, show that most green algae of the chlorophyte type (e.g.Chlorella, Chlamydomonas, Hydrodictyon) differ in their photosynthetic C fixation characteristics from most green algae of the charophyte type (e.g.Spirogyra, Chara) and from C3higher plants. The chlorophyte algae fix inorganic carbon by the photosynthetic carbon reduction cycle pathway, but have a low CO2compensation point in 250 μM O2, a low inhibition of CO2fixation from 10 μM CO2/250 μM O2when compared with 10 μM CO2/zero O2, and a low half‐saturation constant for CO2. These three characteristics are different from those of charophytes and C3higher plants, and resemble those of C4higher plants. It is suggested that these characteristics of chlorophyte algae are the result of a ‘CO2concentrating mechanism’ which increases the CO2/O2ratio at the site of ribulose bisphosphate carboxylase‐oxygenase action in a similar way to that achieved by the C4?C3acid cycle in C4plants. In the chlorophyte algae, however, CO2concentration probably involves active HCO3−transport at the inner membrane of the chloroplast envelope. Active HCO3−transport can occur at the plasmalemma of charophyte algae and submerged aquatic higher plants as well as chlorophyte algae, so it is unlikely to explain the differences between the two groups of aquatic green plants. Differences in the properties of ribulose bisphosphate carboxylase‐oxygenase, and differences in CO2production in the light, also seem inadequate to account for the different photosynthetic characteristics. The chlorophyte type of ‘C02concentrating mechanism’ appears to be common in other classes of eukaryotic algae, and in cyanophytes. Some of the ‘advanced’ members of these eukaryotic algal classes (including the chlorophytes) may lack the mechanism, while some ‘primitive’ charophytes may retain the mechanism which their a

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00760.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractEpidermal strips ofCommelina communiswith ‘isolated’ stomata were incubated on Trizma‐maleate buffer containing 0‐500 mM KCL, with or without 10−4M ABA, for 2.5 h. The resulting stomatal apertures indicate that there is no absolute requirement for live epidermal and subsidiary cells for ABA‐mediated closure. This implies that ABA has a direct effect on influx or efflux of K+into or out of the guard cells rather than on uptake of K+by the subsidiary cells. The possiblein vivorole of subsidiary cells in stomatal closure i

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00761.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe mechanism of paraquat tolerance was investigated in lines of perennial ryegrass (Lolium perenneL.) which had been selected for resistance to the herbicide. Uptake, metabolism and translocation of paraquat were studied. Susceptible cultivars and a tolerant line were not found to differ in uptake of radioactive paraquat applied to the leaf surface or supplied to the cut ends of excised leaves. Distribution of herbicide within leaf tissue was similar in tolerant and susceptible plants and no metabolites of14C‐paraquat were detected in tolerant or susceptible plants treated with sub‐lethal concentrations of the herbicide. Autoradiography and quantitative determinations showed much variation in translocation of14C‐paraquat out of treated leaves of intact plants, but the variation was not related to the degree of susceptibility to the herbicide. It is concluded that paraquat tolerance in perennial ryegrass is unlikely to depend upon reduced uptake, enhanced metabolism or altered translocation of the herb

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00762.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractRelative activities of superoxide dismutase, catalase and peroxidase have been determined in crude extracts of 4 paraquat‐tolerant lines and 11 paraquat‐susceptible cultivars of perennial ryegrass (Lolium perenne L.) grown under controlled conditions. Paraquat‐tolerant lines showed significantly higher activities of both catalase and superoxide dismutase than susceptible cultivars and some resistant lines exhibited in addition elevated peroxidase activity. Differences in superoxide dismutase levels in isolated chloroplasts appeared to parallel those in crude extracts. It is tentatively proposed that paraquat tolerance is due to destruction of O2−by elevated concentrations of superoxide dismutase and detoxification of the resulting hydrogen peroxide by increased levels of catalase and per

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00763.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThis paper describes experiments to test the suggestion that developing xylem vessels are the site of exudation of ions from the root to the shoot. Electron microscopy is used to define the stage of development of xylem vessels in young barley roots along the length of the root. The amino acid analogue p‐fluorophenyl‐alanine (FPA) is used to inhibit ion transport from the stele to the xylem vessels at varied distances from the apex. In the presence of FPA protein synthesis is not inhibited but ineffective proteins are formed. It is shown that exudation of Cl−from the root can be inhibited in this way in parts of the root where all the xylem vessels are mature. This is in contradiction to the suggestion that root exudation is due to the activity of developing vessels. The hypothesis is thus strengthened that ion transport proceeds into the xylem vessels, which are fully mature and devoid of cytoplasm, and is due to release from the xylem parenchyma

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00764.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe abscission of citrus leaf explants demonstrates the well‐known enhancing effect of ethylene and the delaying one of auxin when treatment is started at excision time. Total peroxidase activity increases differently in tissues of the blade, abscission zone, and petiole. The highest activity at zero time is recovered in abscission zone in which also the response to the abscission regulators is the most visible. Isoperoxidase profiles are modified in opposite directions by ethylene and auxin respectively. Both regulators affect the activity of the same cathodic and anodic isoperoxidases without any qualitative changes. By the same time, auxin‐like compounds increase in isolated abscission zones at 24 h from excision and decrease at 48 h. The level of one inhibitor complex undergoes an inverse variation.It is suggested that the increase in auxin during the first stage of abscission is necessary for influencing the growth of cells which is required to cause absciss

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00765.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractEffects of temperature on the ionic relations and energy metabolism ofChara corallinawere investigated. Measurements were made of the ionic content, tracer ion fluxes, and photosynthetic and dark CO2fixation in isolated cells, and of O2exchange in photosynthesis and respiration in isolated shoot apices.The total intracellular concentration of K+, Na+and Cl−was the same in cells held for 5 days in non‐growing medium at 15°C (the growth temperature) as in those held at 25°C or 5°C. The tracer influx in the light of all ions tested (Rb+, Na+, CH3NH3+, Cl−and H2PO4−) was lower at 5°C than at 15°C in experiments in which cells were subjected to 5°C for less than 24 hin toto. The influx at 25°C was greater than that at 15°C for H2PO−4, there was no difference between the two temperatures for Na+, while the influx at 25°C was less than that at 15°C for Cl−, Rb+and CH3NH3+For Cl−and H2PO−4similar results were found in later experiments with cells grown at 20—23°C. Photosynthetic CO2fixation and O2evolution, and respiratory O2uptake, are greater at 25°C, and lower at 5°C, than they are at the growth temperature of 15°C. In longer‐term pretreatments at the different temperatures, tracer Cl−influx at 15°C and particularly at 25°C were lower than in short‐term experiments, while the influx at 5°C was higher.It was concluded from these experiments, and from previous data on H+free energy differences across the plasmalemma, that (1) the maintenance of internal ion concentrations involves a close balancing of influx and efflux of K+, Na+and Cl−at all experimental temperatures; (2) the regulation of the tracer fluxes of the ions is kinetic rather than thermodynamic and (3) that the tracer fluxes at low temperatures are not restricted by the rate at which respiration o

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1978.tb00766.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY