摘要:

Abstract.In this review we relate the physiological significance of C4photosynthesis to plant performance in nature. We begin with an examination of the physiological consequences of the C4pathway on photosynthesis, then discuss the ecophysiological performance of C4plants in contrasting environments. We then compare the performance of C3and C4plants when they occur together in similar habitats, and finally discuss the distribution of C4photosynthesis with respect to the physical environment, phylogeny, and life form.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1984.tb01194.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.Current opinion is divided on whether the free IAA in cereal shoots is derived from the coleoptile tip or from the grain. To date these hypotheses have been considered to be mutually exclusive. In this paper the idea is advanced that both sources may function in the supply of IAA in the shoot. Critical review of the literature shows that such an explanation best fits all the available evidence. It is argued that the relative importance of each source may vary between species of the Gramineae, with the supply of IAA inAvenashoots being derived predominantly from the grain, whereas inZeathe coleoptile tip is the more important source.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1984.tb01195.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.The export of assimilates from mature leaves towards the young leaves was investigated: 100% and 65% of constitutive matter of leaves of rank 0 (the youngest leaves at the top of the plant) and of rank 1, respectively, originated from other parts of the plant. Photosynthesis of a particular leaf covers the total carbon requirement of that leaf only when it reaches about two‐thirds of its mature size. When pairs of mature leaves were excised, the young leaves increased their own autotrophic growth while the level of assimilates exported by the remaining leaves remained unchanged. The existence of permanent pools in the leaves that export the assimilates was demonstrated; about 50% of the carbon, both in the soluble and insoluble fractions of mature and senescent leaves (ranks 5 to 8 from the apex), was not renewed by turnover. It is shown that the13C‐enrichment of the components of the starch‐malate sequence in young leaves results, at least in part, from the incorporation of imported carbon chains. The significance of the δ13C diagnosis in CAM determination is discussed in relation to the origin of the constitutive carbon of the

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1984.tb01196.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.A prolonged light treatment strongly increases responsivity to Pfr in many instances of phytochrome‐controlled biogenesis of flavone or cyanidin glycosides. The present investigation deals with the question of whether light also leads to a corresponding increase of responsivity towards Pfr in such photoresponses which are not related to synthesis of flavonoid pigments in outer tissue layers of seedlings. Phytochrome‐mediated accumulation of the chloroplast GPD (glyceraldehyde‐3‐phosphate dehydrogenase, EC 1.2.1.13) was chosen as a response and the milo shoot (Sorghum vulgarePers. cv. Weider, hybrid) as an appropriate subject. It was found that responsivity towards Pfr is extremely weak in a dark‐grown shoot while prolonged light pretreatments lead to a dramatic increase in responsivity. Blue and UV light are far more effective than red light in eliciting this effect within a few hours. High responsivity is only maintained in the light. When the seedlings are placed in darkness the level of responsivity drops rapidly with a half‐life of the order of 2 h. The data allow more complete explanations for intriguing phenomena of plant life under natural light/dark conditions such as shade detection or sensing of light → dar

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1984.tb01197.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.Fluence‐rate response curves were determined for the inhibition of hypocotyl growth in 54‐h‐old dark‐grownSinapis albaL. seedlings by continuous or hourly 5 min far‐red light irradiation (24 h). Just as in red light (Heim&Schäfer, 1982), a fluence‐rate dependence was observed for both kinds of irradiations, even if only 35% of the continuous light effect could be substituted for by hourly far‐red pulses. The same total fluence was used for the two different light regimes. Measurements of Pfr and Pfr/Ptot showed a strong fluence‐rate dependence under continuous light which only partially paralleled the fluence‐rate response curves for the inhibition of the hypocotyl growth. It was concluded that neither spectrophotometrically determined levels of Pfr nor Pfr/Ptot can be the only light‐dependent factor controlling hypocotyl lengthening under co

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1984.tb01198.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.An analysis of three biochemical parameters during growth of white mustard in continuous white light (WL) has been undertaken at 10°, 15° and 20°C. The time required for anthocyanin and chlorophyll content and nitrate reductase [E.C. 1661 NAD(P)H: nitrate oxidoreductase] activity (NRA) to reach a peak in the cotyledons is shown to be temperature dependent, the rise in chlorophyll content being delayed to a much greater extent than anthocyanin content. In addition, with NRA, there is a significant increase in the level of the peaks with a lowering of temperature.The NRA in dark‐grown plants has been investigated in detail at 10°C. The pre‐competence time for this response is increased to 20–24 h, compared with 14 h in seeds grown at 25°C. Other responses are affected far more by the lower temperature; for example, time for 50% loss of photoreversibility of a red (R) pulse in 48‐h‐old seeds is approximately 13 h, compared with 8 min in seeds grown at 25°C. At 25°C, light treatments during precompetence have been found to increase significantly the effectiveness of a subsequent R pulse on NRA; at 10°C, this effect appears to be almos

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1984.tb01199.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.Experiments were carried out onPinus radiata(D. Don) trees grown as cuttings from clonal parent stock. Some of these trees were about 0.4 m high while others were about 5 m high; all were grown in containers. The stem diameters at the tops and at the bottoms of the large trees, rates of photosynthesis, and needle water potentials were measured both when the trees were well watered and as they dehydrated after water was withheld. The water potentials of well‐watered plants was highest in the small trees and lowest at the top of the large trees. When water was withheld, photosynthesis was in most cases unaffected by a small reduction in water potential, but the rate of photosynthesis fell as water potentials declined further. The stems of the large trees expanded at a constant rate when the trees were well watered and for part of the dehydration period, while subsequent stem shrinkage and the fall in photosynthesis both occurred at approximately the same time.Water potentials increased little in the 24 h after rewatering, and significant rates of photosynthesis were not measured until 2 or 3 d later while renewed stem expansion was not measured until 2 d after rewatering.Water deficits reduced the lumen diameter of newly matured stem tracheids, but increased the thickness of their walls. After 1 month of water potentials of about −2.4 MPa, tracheid lumen diameter and wall thickness were both much reduced, and this reduction continued in tracheids maturing shortly after rewater

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1984.tb01200.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.Purified and crude phosphoenolpyruvate carboxylase from the CAM plantKalanchoë daigremontianaHamet et Perrier (Bryophyllum diagremontianum) was assayed at temperatures between 10 and 45° C. The optimum temperature of the enzyme activity changed with substrate availability and effector concentration in the assay.l‐malate inhibited the enzyme activity and lowered the optimum temperature. Glucose‐6‐phosphate raised the optimum temperature to 43°C.Kmvalues for phosphoenolpyruvate increased with assay temperature from 0.12 mol m‐3at 15° C to 0.36 molm−3at 35° C. Inhibition by malate increased with temperature and acidity of the assay. In the crude enzyme 50% of control activity was inhibited by 1.65 mol m‐3malate at 15° C and by 0.5 mol m‐3at 35° C (at pH 7.0). With purification malate sensitivity was lost (Kivalues for malate at least 10 times higher). The shift in optimum temperatures for PEP‐carboxylase activity thus results from changes in the kinetic parameters with temperature and allosteric effectors. The often low optimum temperatures for CO2fixation observed in nature may thus be the result of substrate and effector concentrations in the cytoplasm and the antagonistic effect of temperature on substrate affinity and effector efficiency on phosphoen

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1984.tb01201.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Books reviewed in this article:QUANTITATIVE PLANT ECOLOGY.3rd edn. By P. Greig‐SmithPHYSIOLOGY AND BIOCHEMISTRY OF SEEDS IN RELATION TO GERMINATION. By J. D. Bewley&M.blackPLANTS AND THE DAYLIGHT SPECTRUM. Edited by H. SmithWETLAND ECOLOGY. By J. R. EtheringtonTHE GERMINATION OF SEEDS. (3rd edn.) by A. M. Mayer&A. Poljakoff‐Ma

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1984.tb01202.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY