摘要:

AbstractLight transmitted through soil, and the leaf litter of two tree species, was measured using a spectroradiometer. In general, a greater penetration by longer wavelengths, especially far‐red, was noted. This was most marked in a dry sand sample. The effect was less in the case of clay‐loam aggregates. Moisture in the samples had an opposite effect in these two cases, causing an increase in transmission through sand but a decrease through clay loam aggregates. Reduction in particle size was found to reduce both the total light transmitted and the red/far‐red ratio (R : FR). Red wavelengths were also more attenuated by a layer of freshly fallen oak (Quercus rotrur) leaves than were far‐red wavelengths. A layer of Corsican pine (Pinus nigramaritima) needles however, was found to act as a neutral density filter over the 400 800 nm range.Prolonged exposure to soil‐filtered light was found to affect the germination of seven species tested.Plantago majordemonstrated an approximately linear decrease in germination with increasing depth.Rumex obtusifotiusshowed an apparent threshold response at 4 6 mm depth, as didCecropia obtusifoliabut at a slightly greater depth.Digitalis purpureagerminated very poorly in darkness, yet was extremely photosensitive with very high germination even at 10 mm depth.Galiutn aparineandChenopodium albumshowed a two‐phase response with germination reaching a peak at 2 mm depth.The implications for the function of the photoreceptor phytochrome in the control of germination are discussed in relation to soil‐transmitted light and with regard to the results of the germ

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01683.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractA previously described growth model of the vegetative grass crop is extended to include a simple representation of the root system, uptake of nitrogen from a soil nitrogen pool, and response to fertilizer application. The model simulates the processes of light interception, photosynthesis, partitioning of new growth, leaf area expansion, growth and maintenance respiration, ageing of plant tissues, senescence, recycling of substrates from senescing tissues, nitrogen uptake by the plant, leaching, mineralization, and fertilizer application. A principal component of the model, nitrogen uptake, is assumed to depend positively on plant carbon substrate concentration and soil nitrogen concentration, and to be inhibited by plant nitrogen substrate concentration. The dynamic responses to different levels of soil nitrogen, of shoot and root growth, nitrogen uptake and root activity, carbon and nitrogen plant substrate concentrations, and the fraction of substrate carbon used by the shoots, are examined; realistic behaviour is observed. The model predicts nitrogen fertilizer responses of yield and plant nitrogen content, which are compared directly with experimental data; good agreement is obtained.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01684.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractFrost avoidance mechanisms were studied inEspeletia spicataandEspeletia timotensis, two Andean giant rosette species. The daily courses of soil, air and tissue temperatures were measured at a site at circa 4000 m. Only the leaves were exposed to subzero temperatures; the apical bud and stem pith tissues were insulated by surrounding tissues. The leaf tissues avoided freezing by supercooling rather than by undergoing active osmotic changes. The temperatures at which ice formed in the tissues (the supercooling points) coincided with injury temperatures indicating thatEspeletiatissue does not tolerate any kind of ice formation. For insulated tissue (apical bud, stem pith, roots) the supercooling point was around ‐ 5°C coinciding with the injury temperature. Supercooling points of about –13 to ‐ 16°C were observed for leaves. These results contrast with those reported for Afroalpine giant rosettes which tolerate extracellular freezing. The significance of different adaptive responses of giant rosettes to similar cold tropical environments is di

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01685.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe spectra of incoming daylight and shadelight in a mature oak woodland were measured at intervals during the canopy cycle, and mean transmittance spectra were derived. Transmittance was spectrally neutral atca.0.55 during the light phase but, following leaf emergence, transmittance of PAR (400–700 nm) fell toca.0.1. Simultaneously, the red : far‐red transmittance ratio fell to circa 0.6. Both showed little change during the summer and autumn until senescence, indicating that the optical properties of the canopy were surprisingly stable. There was no evidence that cloud cover influenced mean canopy transmittance, although transient sunflecks introduced great variability which, in combination with sampling bias, might explain previous contradictory reports. The red : far‐red fluence rate ratio in the woodland showed a temporary increase in late summer, a result of a small increase in the red : far‐red ratio of incoming daylight during this period. Reflectance and transmittance spectra and pigment content of sun and shade leaves were measured. Leaf transmittance spectra showed changes correlated with those of the canopy, and were related to changes in pigment

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01686.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractNitrate uptake into intact pea seedlings (Pisum sativumL. cv. Feltham First) grown in hydroponic culture has been investigated. Following inoculation withRhizobium leguminosaruma twofold increase in net nitrate uptake was observed. Changes in morphological characteristics following inoculation were found todecreasethe effective area available for absorption.There was a two‐fold decrease in net nitrate uptake into intact seedlings grown in the presence of N compared with N free media. In the former case net nitrate uptake appeared to stall at regular intervals. In both cases only the initial rates of nitrate uptake were found to be responsive to the external nitrate concentration. The results are discussed in terms of current models for the regulation of NO−3uptake by higher pla

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01687.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractWe have devised an experimental system for simultaneous measurement of the activity of the xylem electrogenic ion pump, which is located on the inner cell membrane between the parenchyma symplast (p) and the xylem (x). and pH of the xylem exudate of a hypocotyl segment ofVigna unguiculataunder pressurized xylem perfusion. Anoxia caused immediate depolarization of the inner cell membrane followed by alkalization of the xylem exudate several minutes later. Activity of the xylem pump was recovered by reaeration and acidification of the xylem exudate took place. These results indicate that the xylem pump is the respiration‐dependent electrogenic proton‐pump extruding proton from the parenchyma symplast into the xy

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01688.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractYoung willow plants (Salix‘aquatica gigantea’) were grown in hydroponic culture media, and14C–labelled sodium bicarbonate was fed to the roots. Uptake of14C‐label in the leaves and shoots was assayed after two different feeding periods (6 h, 48 h). Even during the shortest feeding period,14C‐label had been transferred to the leaves and shoots. Compared with the longer feeding period, after the 6 h feeding period more label was in the form of acid‐labile products, whereas after the 48 h feeding period most of the label was in acid‐stable products.A second experiment was designed to test whether carbon uptake by roots affects the growth of young willow plants. Uniform rooted cuttings were grown in hydroponic cultures at five different levels of bicarbonate: 0, 0.015, 0.147 0.737, and 1.473 mol m−3NaHCO3. After a 4‐week growing period we determined the biomass of leaves, shoots, roots and cuttings.Production of total dry matter (shoots, leaves and roots) increased with increasing bicarbonate concentration. Saturation of dry matter production was reached at 0.737 mol m−3NaHCO3, but a higher concentration of NaHCO3(1.470 mol m−3) caused a slight decrease in the dry matter production. At 0.737 mol m−3NaHCO3the total dry weight increased by 31.1%, which suggests that uptake of dissolved carbon dioxide through the roots might affect carbon budgeting

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01689.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractA method is presented for the control of carbon dioxide concentrations within the roots ofFraxinus pennsylvanicaMarsh. The results indicated a linear fit of the root CO2concentrations to the CO2levels of the treatment gases:y= l.l.x+105 (r= 0.98, 18 d.f.). The method presented for controlling CO2can be easily modified for other gas mixtures and plant species.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01690.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractAn instrument for the generation and measurement of modulated chlorophyll fluorescence signals from leaves exposed to continuous, highintensity white light is described. Modulated fluorescence is generated in the leaf by pulsed diodes emitting low‐intensity yellow radiation and is detected with a photodiode whose output is fed to an amplifier locked in to the frequency of the lightemitting diodes. Comparisons are made between the modulated fluorescence signals measured with this instrument and the continuous fluorescence signals emitted from dark‐adapted leaf tissue and isolated thylakoids when photosynthetic activity is induced by exposure to a range of intensities of continuous broad‐band, blue‐green light. The modulated fluorescence signals were similar to the continuous fluorescence signals, but they were not always identical. The small differences between the two signals are mainly attributable to differences in the populations of chloroplasts being monitored in the two measurements as a result of differential penetration of the modulated and actinic light sources into the

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01691.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Books reviewed in this article:THE BIOSYNTHESIS AND METABOLISM OF PLANT HORMONES.Edited by A. Crosier&J. R. HillmanENCYLOPEDIA OF PLANT PHYSIOLOGY, NEW SERIES, VOLUME 10. HORMONAL REGULATION OF DEVELOPMENT II. THE FUNCTIONS OF HORMONES FROM THE LEVEL OF THE CELL TO THE WHOLE PLANT.Edited by TomK. ScottPLANT DISEASES. INFECTION, DAMAGE AND LOSS.Edited by R. K. S. Wood&G. J. JelusPLANT‐MICROBE INTERACTIONS. MOLECULAR AND GENETIC PERSPECTIVES.Vol. I. Edited by T. Kosuge&E. W. NesterPRINCIPLES OF GENE MANIPULATION: AN INTRODUCTION TO GENETIC ENGINEERING(3rd edn). By R. W. Old&S. B. Primro

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01692.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY