摘要:

Books reviewed in this article:SEEDS AND THEIR USES.By C. DUFFUS&C. SLAUGHTERBIOCHEMISTRY AND STRUCTURE OF CELL ORGANELLES. By R. A. REID&R. M. LEECHNATURE AND ORIGINS OF CARBOHYDRATES IN SOIL.By M. V. CHESHIREBIOLOGICAL MEMBRANES: THEIR STRUCTURE AND FUNCTION.By R. HARRISON&G. G. LUNTPLANT ORGANELLES. Edited by E. REIDVEGETATION OF THE EARTH AND ECOLOGICAL SYSTEMS OF THE GEO‐BIOSPHERE. By HEINRICHWALT

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb01042.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract.This paper (i) considers the measurement of light in terms of the flow of radiant energy or of particles in a vector field; (ii) derives terminology and units for the specification of light as a flow of radiant energy or of photons which satisfy both the requirements of SI and are physically consistent and (iii) recommends that this terminology is adopted by all plant scientists to avoid ambiguity, confusion and the proliferation of synonyms when reporting light measurements.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb01043.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract.ManyRumexspecies show similar seed dormancy characteristics but there is more information concerningR. crispusandR. obtusifoliusthan other species. These species respond positively to red or white light. Far‐red light applied for short periods may promote or inhibit germination depending on the timing of the irradiation in relation to temperature change; but long periods of far‐red inhibit germination. Seeds may also be stimulated to germinate in the dark by low‐temperature stratification at 15°C or less providing the temperature of the seeds is subsequently raised to a minimum of about 15°C. Seeds can, however, germinate at lower temperatures providing they have received other appropriate stimulatory treatment. Seeds also respond to alternating temperatures. In a diurnal cycle the minimum upper temperature required is about 15°C and the maximum lower temperature is about 25°C. The optimum period spent at the upper temperature is about 8 h when it is 15–25°C but the optimum period decreases as the upper temperature is increased above this range so that at 45°C, for example, it is only about 30 min. The period spent at the lower temperature in a diurnal cycle is not critical. Providing these criteria are met, the percentage germination increases with the number and amplitude of the cycles. The warming part of the cycle is necessary for the response but so far there is no convincing evidence that cooling itself is important. Secondary dormancy is induced at constant temperatures at a rate dependent on temperature, but apparently only in the presence of oxygen. This feature affects the optimum timing of a temperature change or exposure to light. Strong positive interactions are shown between stimulatory temperature treatments and white or red light. Unlike many other weed species the seeds respond only slightly to nitrate ions. The implications of these responses are discussed in relation to fi

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb01044.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract.It is widely believed that the root cap participates in geotropism by acting both as a sensor of the direction of gravity and as a source of at least one regulator of root growth, which may be abscisic acid (ABA). It has been suggested that this regulator accumulates within the prospective concave (or lower) half of the root and there causes a retardation of growth that brings about bending. A re‐examination of the evidence upon which this inhibitor hypothesis of geotropic control is based reveals that (1) it is derived almost entirely from microsurgical studies and the deductions from such experiments still require corro‐orations from analyses of inhibitor content and action; (2) the evidence that ABA is the inhibitor seems poor at present; (3) in maize and lentil, two well‐studied species, geocurvature is probably a consequence of accelerated growth within the prospective convex (or upper) half rather than inhibited growth within the concave (or lower) half; (4) the geotropic signal from the cap may be one that redirects a pre‐existing basipetal flow of inhibitor away from t

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb01031.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract.The belief that the shoot apex plays a special role in geotropism is shown to be erroneous and the implications of this widely held misconception are discussed.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb01032.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract.Characteristics of the geotropic response of de‐etiolated mung bean hypocotyls are presented. Geotropic sensitivity is not confined to the apical tissue but exists throughout the responding zone. The presentation time is estimated to lie between 0 and 30 s for this tissue. Anatomical features of the presumed geoperceptive tissues are described. Rapid sedimentation and cyclosis of statolith amyloplasts in living tissue are reported, which are fast enough not to preclude the possibility of receptor sites situated at or near the lateral wall of statocyte

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb01033.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract.Velocities of transport of IAA through long‐celled (dark‐grown) and short‐celled (light‐grown) coleoptile segments have been measured by the intercept method. Transport is faster through short‐celled segments, and the difference is highly significant. Calculations show that this finding is consistent with a model for polar auxin transport which postulates a pumping mechanism between cells and movement through the cell by

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb01034.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract.Conflicting data have appeared in the literature concerning the necessity for DNA synthesis prior to xylem cell differentiation. In some systems DNA synthesis is not required before differentiation, while in other systems DNA synthesis appears to be an absolute necessity. The construction of a model for the cell cycle in which the G1 phase is subdivided into a separate ‘early’ and ‘late’ phase can resolve this apparent c

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb01035.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract.Twenty cultivars of spring wheat were examined for variation in abscisic acid (ABA) accumulation following partial dehydration of excised leaves. A 3‐fold range of ABA concentration was obtained.A cross between two cultivars which differed in drought‐induced ABA accumulation was used to study the heritability of ABA accumulation and to develop lines differing in their capacity to accumulate ABA. Broad sense heritability was 0–32 between the F2and F3generations and 0–70 between the F3and F4generations. Apparent homozygosity for ABA accumulation was achieved in several selections at the F4. The possible significance for drought resistance of differences in capacity to accumulate ABA is di

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb01036.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract.Measurements of the efflux of CO2from 5–6 year old container grown apple trees, in the dark at a range of temperatures (T), indicated that respiration rate (R) can be described by the equation R = SL ekT. The temperature coefficient k, was the same at all times of the year and for all components of the trees, but the values of a varied. At the same temperature respiration rates were low when the trees were dormant, rose rapidly to a peak in spring (before full bloom) and then declined steadily through the season. When respiration was expressed as a flux density, rates for different components of the tree were usually similar. Differences were sometimes statistically significant but no clear pattern emerged. The results obtained are similar to those published for other plants and the equation can be used in the calculation of the carbon balance of apple tree

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1981.tb01037.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY