摘要:

AbstractPublished seed storage data for 92 species derived from 13 localities were subjected to probit analysis to determine the half‐viability period (P50) for each sample. Estimates of half‐viability period for each species averaged over all 13 localities were calculated using a least square means procedure applied to known values for the half‐viability period for each species at each of its storage stations. The results reported here represent an initial step in the objective organization of seed longevity

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01693.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe traditional bulk elastic modulus approach to plant cell pressure‐volume relations is inconsistent with its definition. The relationship between the bulk modulus and Young's modulus that forms the basis of their usual application to cell pressure volume properties is demonstrated to be physically meaningless. The bulk modulus describes stress/strain relations of solid, homogeneous bodies undergoing small deformations, whereas the plant cell is best described as a thin‐shelled, fluid‐filled structure with a polymer base. Because cell walls possess a polymer structure, an alternative method of mechanical analysis is presented using polymer elasticity principles. This initial study presents the groundwork of polymer mechanics as would be applied to cell walls and discusses how the matrix and microfibrillar network induce nonlinear stress/ strain relationships in the cell wall in response to turgor pressure. In subsequent studies, these concepts will be expanded to include anisotropic expansion as regulated by the microfibrillar ne

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01694.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractA comparison was made of the content of total and some individual fatty acids in grains of nine barley varieties grown at six sites in Belgium. The varieties represented six‐ and two‐rowed winter types and two‐rowed spring types. The results showed that the winter types contain more linolenic acid (C18 : 3) than spring types and that six‐rowed barleys have less total fatty acids than two‐rowed barleys, due mainly to a low concentration of palmitic (C16:0), oleic (CI8 : 1) and linoleic (C18 : 2) acids. Analysis of variance showed that fatty acid content is affected by both the genotype and the environment and multiple regression analysis suggested that weather conditions before and after flowering affected lipid co

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01695.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractWe tested the hypothesis that electrogenic ion pumps, working at the parenchyma symplast/xylem interface of pea hypocotyls, provide the driving force for K+uptake from the xylem. Solutions of known composition were perfused through a hypocotyl segment. The K+activity of the solution flowing out of the xylem (K+out) increased (i.e. K+uptake decreased) when aerobic respiration was inhibited by lack of O2, and this was preceded by a decrease inVpx(electrical potential difference between parenchyma symplast and xylem). Perfusion with auxin (1AA) and fusicoccin (FC) stimulated the electrogenic activity of the ‘xylem pumps’ (111 and 205% respectively) and stimulated uptake of K+from the xylem (with 71% and 29% respectively). The close correlation between xylem pump activity and K+uptake corroborated the aforementioned hypothesis. Interestingly, inhibition of pump activity by anoxia was incomplete in the presence of FC. It is thought that FC increases the affinity of the ATP‐requiring xylem pump for ATP, thus ensuring that ATP production during fermentation is sufficient to fuel the pump in the absence

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01696.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractA method is described for perfusing xylem vessels in tap root segments of the halophyteP. maritima.Use of excised segments allowed recording of the trans‐root potential (TRP) at both ends of a segment. It was shown that there can be a spatial variation of electrogenic ion pump activity along the xylem in one root segment. The pH of perfusion solutions, differing in buffering capacity, was adjusted by the root segment to pH 5.1–5.6 during How through the xylem. This pH range was similar to that of sap produced by root pressure. The K+activity in the outflow solution (K+out) was rather constant at 12–13 mol m−l3despite input K+activities ranging from 8 to 20 mol m−l3. Addition of fusicoccin (10−l2mol m−l3) to the perfusion solution induced a strong acidification of the xylem sap, a decrease in K+outand an increase in Na+out. Inhibition of aerobic respiration through anoxia inhibited electrogenic proton pumping into the xylem and led to an increase in K+outand a decrease in Na+out. It is suggested that transport of K+and Na+to the shoot of the halophyteP. maritimais regulated in the tap root by means of ion exchange between xylem vessels and xylem parenchyma and that this exchange is energized by proton transloc

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01697.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractGrowth redistribution which occurs as a result of phototropic stimulation was studied in red light‐grown, maize (Zea maysL.) seedlings. The pattern of elongation of small areas (0.1mm2) of coleoptile epidermis on intact plants was analysed from time‐lapse, photomicrographic records. Growth following unilateral, pulse irradiation with blue light was depressed on the illuminated side and was stimulated on the shaded side. The time at which the change in growth rate occurred, on both illuminated and shaded sides, was significantly earlier in apical patches than it was in basal patches. Both kinds of change in the growth rate (stimulation and depression) occurred rapidly such that a new, constant growth rate was often established within five minutes. Micrographic, time‐lapse records were also obtained of growth changes induced by sub‐apical, unilateral application of a spot of an indole‐3‐acetic acid (IAA) and lanolin mixture. Growth on the side of the coleoptile to which IAA had been applied was similar to the growth on shaded sides of phototropically stimulated plants. The distance between apical and basal patches and the elapsed time between their changes in growth rate gave a velocity at which the growth response moved basipetally. Calculation of this velocity for blue light and auxin treatment gave values that were not significantly different. Thus, basipetal movement of a transverse auxin gradient could mediate growth changes that cause curvature of the coleoptile towards first positive fluences of

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01698.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractWith appropriate pretreatment of the seeds fluence‐response curves for the induction of germination ofArabidopsis thalianashow two phases. A proportion of the population responds to very low fluence (VLFR), 104–10−2μmolm−2establishing 10−4–10−2% of the total phytochrome in the far‐red absorbing form (Pfr) and a proportion of the population respond to low fluence (LFR), 1–1000 μmolm−2, establishing 1–75% Pfr. The VLFR is nol normally seen because the pre‐existing Pfr level satisfies the Pfr requirement or use of green safelight establishes more Pfr than necessary to saturate the VLFR. Endogenous Pfr was depicted by a 24 h 35°C treatment, presumably as a result of dark destruction and/or dark reversion to the red absorbing form of phytochrome (Pr), making it possible to visualize the VLFR. A short pulse of 35°C treatment in combination with an appropriate temperature regime is also able to sensitize a proportion of the seed population. The proportion of the population showing the VLFR is determined by the duration of the cold imbibition pretreatment as well as the duration of the 35°C treatment. Complex fluence‐response curves were observed in which a proportion of the seeds being promoted in the VLFR range, were inhibited at higher fluences before being further promoted in the LFR range. This was particularly clear for seed batches being sensitized by a short 35°C treatment. The VLFR may be of significance in the natural environment, enabling seeds buried in the upper layer of the soil to germinate, where the fluence rate falls off sharply and the LFR is not satisfied. A model is presented to explain the two phases

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01699.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractAn electrical analogue describing the phase and amplitude relations between transpiration, water potential and stem shrinkage for trees was developed. Observations of shrinking and swelling at various heights up aPinus radiatatree were obtained over several weeks in summer and autumn.The relative amplitude in shrinkage increased by a factor of two up the stem, but phase lags were small. The data obtained were used in conjunction with the electrical analogue of the How pathway to obtain an estimate of the relative magnitude of the capacitance of the living bark and the sapwood, and to predict phase lags between transpiration and leaf water potential, and lags in transpirational flux up the stem.The results suggest that if water potentials recover by dawn, phase lags in water potential down tree stems arc small and that the exchange between water stored in the sapwood and the transpiration stream is irreversible over the diurnal time scale.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01700.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractRaising ambient levels of CO2during the night, between 350 and 950cm3m−3, reduced the dark respiration rate ofMedicago sativumseedlings. The percentage effect was greater for maintenance respiration than for dark respiration as a whole, and when the plants were in a low photosynthate status. Twenty‐four h carbon balance studies confirmed a reduction in night time respiration and an increase of net carbon gain when night time [CO2] was high. Growth experiments showed a small but significant increase of dry weight inMedicago sativumseedlings exposed to high [CO2] (∼ 1200 cm3m−3) at night. This effect was greater for plants grown withRhizobiumnodules than for plants grown with nitrate in the absence ofRhizobium.A similar, but smaller and statistically non‐significant effect of high night time [CO2] on growth was found forXanthium strumariumseedlings. The significance of these findings is discussed in relation to the rising CO2content of the a

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01701.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Books reviewed in this article:THE PHYSIOLOGY AND BIOCHEMISTRY OF PLANT RESPIRATION.Edited by J. M. PalmerEMBRYOLOGY OF ANGIOSPERMS.Edited by B. M. Johri

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01702.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY