摘要:

Books reviewed in this article:DIFFERENTIATION AND THE CONTROL OF DEVELOPMENT IN PLANTS—POTENTIAL FOR CHEMICAL MODIFICATION. Ed. E. C. George.ENVIRONMENTAL INSTRUMENTATION. By LeoJ. Fritschen&LloydW. GayADVANCES IN BOTANICAL RESEARCH, VOLUME 7. Ed. H. W. Woolhouse.PRINCIPLES OF GENE MANIPULATION: AN INTRODUCTION TO GENETIC ENGINEERING. By R. W. Oldand S. B. Primro

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb00830.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe spatial and temporal relationships between carbon (C) metabolism and nitrogen (N) nutrition in grain legumes are of great academic interest with the added bonus that any data for economically important species may ultimately prove useful to breeders and growers. So far there are no data which can be used to relate differences in carbon usage by any symbiotic association with differences in economic yield. Much research has focussed on the dependence of dinitrogen fixation on photosynthate supply, on the C–N relationships of nodulated roots and nodules and on diurnal and seasonal profiles of dinitrogen fixation. In all these aspects a plethora of responses have been described, often based on insufficiently proven measurement techniques; consequently unequivocal conclusions cannot be drawn. We know little about within‐species differences due to cultivar, strain ofRhi‐zobiumor environment, or about the proportions of any heritable variations which might be sufficiently large to merit inclusion among the selection criteria of grain legume bre

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb00831.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractSites of acid‐phosphatase activity were found in the differentiating root protophloem ofNymphoides peltataby lead‐salt and by azo‐dye methods. Different substrates revealed different subcellular locations of the enzyme. The substrates β‐glycerophosphate (β‐GP) and naphthol ASBI phosphate revealed enzyme activity at similar sites within the sieve element. These sites included plasmodesmata, dictyosomes and small vacuoles in the cytoplasm. The substrate p‐nitrophenylphosphate (p‐NPP), however, revealed additional sites of acid‐phosphatase activity which were not detectable by either naphthol ASBI phosphate or β‐GP. For example, the inner region of the wall in mature sieve elements showed conspicuous acid‐phosphatase activity only when p‐NPP was used as substrate. The significance of the different locations of acid phosphatase within the sieve element is discussed.The convoluted ER, characteristic of immature sieve elements ofN. peltata, failed to show acid‐phosphatase activity whichever substate was used. By contrast, the stacked ER found in the parietal layer of mature sieve elements showed prominent acid‐phosphatase activity regardless of the substrate used. The demonstration of acid‐phosphatase activity in the stacked ER, and by both lead‐salt and azo‐dye methods, suggests that this organelle is a true site of acid‐phosphatase activity.The onset of acid‐phosphatase activity in the ER in later stages of sieve‐element differentiation is compatible with the view that stacked ER plays a role in the final a

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb00832.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractCarbon fluxes in photosynthesis and photorespiration of water stressed leaves have been analysed in a steady state model based on the ribulose diphosphate carboxylase (RuDP carboxylase) and RuDP oxygenase enzyme activities and the CO2and O2concentrations in the leaf. Agreement between predicted and observed photorespiration (Lawlor&Fock, 1975) and C flux in the glycollate pathway is good over much of the range of water stress, but not at severe stress. An alternative source of respiratory CO2is suggested to explain the discrepancy. The model suggests that resistance to CO2fixation is mainly in the carboxylation reactions, not in CO2transport.Using the steady state model, the kinetics of14C incorporation into photosynthetic and photorespiratory intermediates are simulated. The predicted rate of14C incorporation is faster than observed and delay terms in the model are used to simulate the slow rates of mixing and metabolic reactions. Inactive pools of glycine and serine are suggested to explain the observed specific activities of glycine and serine. Three models of carbon flux between the glycollate pathway, the photosynthetic carbon reduction cycle and sucrose synthesis are considered. The most satisfactory simulation is for glycollate pathway carbon feeding into the PCR cycle pool of 3‐phosphoglyceric acid which provides the carbon for sucrose synthesis. Simulation of the specific activity of CO2released in photorespiration suggests that a source of unlabelled carbon may contribute to photorespiratio

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb00833.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractIn germinating seedlings ofSinapis albanitrate reductase activity as assayedin vivobecomes accessible to phytochrome control between 15 and 17 h after sowing. Phytochrome operates via the high irradiance reaction to control nitrate reductase activity in the period 15 to 20 h after sowing. Both continuous red light and far‐red light elicit this response with a strong fluence rate dependency being apparent in each case. The induction of nitrate reductase activity by light pulses at 20 h after sowing is greatly influenced by red light pre‐treatments (operating through phytochrome) given between 0 and 15 h after sowing. Low fluence rate pre‐treatments reduce the effectiveness of a subsequent pulse to below the level of a dark control whilst high fluence rate pre‐treatments greatly increase the effectiveness of a subsequen

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb00834.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractUnlike wheat chloroplasts, wheat protoplasts showed a pronounced restoration of the induction phase after a short period of darkness. This difference was used to investigate the relative roles of light‐induced reductive activation of enzymes and the auto‐catalytic increase in the level of substrates in the control of the rate of photosynthesis during induction. Light activation and dark inactivation of ribulose 5‐phosphate kinase, fructose 1,6‐biphosphatase and NADP+‐specific glyceraldehydephosphate dehydrogenase were measured. In this respect there was no appreciable difference between protoplasts and chloroplasts. In contrast, the level of photosynthetic intermediates remained constant in darkened isolated chloroplasts, but declined rapidly in chloroplasts isolated from darkened protoplasts. When fructose 1,6‐bisphosphatase was pre‐activated by treating protoplasts with dithiothreitol the lag was only slightly shortened. These results are discussed in terms of control of the rate of the photosynthesis during the lag by substrates rather than limitation imposed by activity of any of the enz

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb00835.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe changes in the levels of two different isozymes of cellulase (EC 3.2.1.4) have been followed during the abscission of the primary leaves of bean (Phaseolus vulgarisc.v. Red Kidney), using antibodies raised against the 9.5 form of the enzyme. Data from both radioimmune and direct assay show that the 9.5 form of cellulase is undetectable prior to the induction of abscission. After a 12 h lag this isozyme increases in activity, the increase preceding a decrease in integrity of the abscission zone cell walls. The results are consistent not only with the view that this specific isozyme is involved in wall hydrolysis but also with previous data which showed that cellulase is synthesized ‘de novo’.The 4.5 isozyme of cellulase is more widely spread throughout the plant, being most active in young tissues. During abscission the activity of this isozyme in the abscission layer falls and consequently it is not thought to be involved directly in the abscission proc

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb00836.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractAfter the onset of imbibition, the dormant seeds ofRumex obtusifoliusandR. crispusare stimulated to germinate by a change from an initial low temperature to a warmer temperature for a relatively brief period: the warmer that temperature the shorter is the optimum period spent at it, and this optimum value is unaffected by the initial temperature. The optimum period is more critical inR. crispusthan inR. obtusifolius(about 1 h and 2.5 to 4 h, respectively, for a warmer temperature of 35°C in the dark); in the light the length of the period at the warmer temperature is less critical in both species. The sensitivity of the seeds to the change to the warmer temperature increases with time from the start of imbibition at a rate which is positively related to the initial temperature. InR. obtusifoliusmaximum sensitivity was typically reached after 3 to 5 d when the initial temperature was 20°C and then remained constant, or declined only slightly, over the period investigated (10 d). At the same initial temperature, however,R. crispusshowed a cyclical pattern of sensitivity with peaks occurring at 3–4 d intervals from the start of imbibit

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb00837.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA theoretical analysis of yield components ofHevea brasiliensisis attempted in this paper. The effect of the major yield components, i.e. initial flow rate per unit length of tapping cut, length of the cut, percentage rubber content and plugging index on rubber yield is represented by the formulaVariation in yield within and between clones can be ascribed to variation to any one of the above components. The importance of high growth rate for maintaining high yield throughout the life cycle of the tree is theoretically elucidated. While the present contention of a theoretical maximum yield of 9.5 t ha−1with a stand of 350 trees is questioned, the theoretical possibility of attaining that yield by increasing the stand per ha to 600 is analyse

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb00838.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY