ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01268.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01268.x_1

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.Peristomatal transpiration is defined as the relative high local rate of cuticular water loss from external and internal surfaces around the stomatal pore and its decisive role in the control of stomatal movement is re‐emphasized. As the resistance towards changes in air humidity is low in the pore surroundings, the state of turgor is particularly unsteady there. Due to the inherent instability the guard cell ‘senses’ fluctuations in the supply‐demand relationship of water and is thus the control unit proper. The environmental variables (supply and demand) are cross‐correlated within the subsidiary cell and the information is transmitted to the guard cell through the water potential gradient between the two cells. A conceptual segregation of a ‘humidity response’ by ‘passive’ stomatal movements is rejected.As ions always accumulate at the most distant point of the liquid path and as this point varies with pore width according to the prevailing water potential gradients, it is felt that the water stream is causing the characteristic pattern of ion distribution within the epidermis. Passive import of ions is attributed to local concentration gradients which are steepened by continuous supply and by water uptake into the guard cell in response to starch hydrolysis. A mechanistic model supplemen

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01269.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.Two strains ofDunaliella, both grown at 25°C were analysed for their α‐amino acid and neutral soluble carbohydrate content. Glycerol was found as a major cell constituent in both varieties; the amount was roughly proportional to the outside NaCI concentration between 0.5 and 3 kmol m−3, and varied from 3.4% to 45% of the total dry weight of packed cells. The sum of sugars and α‐amino acids did not amount to more than 2% of the total dry weight at any NaCI conce

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01270.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.The effect on seed germination of the red/far‐red ratio of light (ζ) as modified by a leaf canopy was studied. The artificial light sources used and daylight filtered through leaves appeared to have identical effects in tests with lettuce seed.The sensitivity of the seeds to ζ varied with the environmental conditions during pretreatment and during the actual germination test. Freshly harvested and dry‐stored seeds ofCirsium palustrewere strongly inhibited at low ζ; after stratification, the inhibition was much less. The fact thatC. palustreemerges mainly after the coppice is felled could not be explained from these results combined with field data on ζ and the response of germination to temperature.The ecological significance of inhibition at low ζ is to be found directly after dispersal. Seed germination will then be delayed until the following spring or later.Geum urbanumshowed primary dormancy, which was released by a stratification treatment. No inhibition of germination at low ζ was found in the spring and seeds germinated in light and darkness at low temperatures. These results explain why the species emerges early in spring regardless of the presence of the a

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01271.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Summary.Soluble potassium concentrations were determined for the slightly vacuolated, unicellular, walled alga Chlorella emersonii. Sap of cells grown in 1 mol m−3NaCI contained 140 mol m−3K+and sap of cells grown in 125, 200, and 335 mol m−3NaCI contained 160‐180 mol m−3K+.The possible regulation of K+concentrations by a system of lurgor and volume maintenance was investigated by supplying 3‐0‐methylglucose. This solute accumulates to 85‐230 mol m−3in C.emersonii, but is not metabolized. Accumulation of 3‐0‐methylglucose increased the volume of cells grown at both low and high NaCI by about 10%. Furthermore, accumulation of 3‐0‐methylglucose also increased turgor pressures of cells grown in 1 and 125 mol m−3NaCI by 0.3 and 0.2 MPa, respectively. (Similar measurements were not attempted for cells grown in 200 and 335 mol m−3NaCI, because of the insensitivity of available methods to measure turgor pressure of cells exposed to high external osmotic pressures.)At all NaCI concentrations, the K+concentrations of cells which had accumulated 3‐0‐methylglucose were only 10‐20 mol m−3lower than K+in cells which had not been supplied with 3‐0‐methylglucose. In contrast, accumulation of 3‐0‐methylglucose greatly decreased concentrations of the endogenous osmotic solutes, proline and sucrose, which accumulated in cells grown in 125 mol m−3and higher NaCI concentrations.It is concluded that K+concentrations in Chlorella emersonii are not controll

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01272.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.The patterns of growth in organs curving under the influence of gravity were analysed by time‐lapse photography of cress and cucumber hypocotyls which were delimited into 1 mm zones by ion‐exchange beads. Geotropic curvature resulted from changes in growth rate on both sides of the organ. Growth inhibition of varying degrees of intensity occurred in all the previously growing zones of the upper (concave) side. An absolute reduction in length due to compression frequently occurred in some zones. Also, in both species growth stimulation was observed on the lower (convex) side. The disparity in growth rate between the upper and lower surfaces varied with time, being more apparent in the subapical region in the first hour of curvature. A later promotion of growth rate on the lower surface subsequently increased the curvature of the more basal zones. Autotropic straightening occurred as a consequence of growth changes, both inhibitory and stimulatory, in the apical zones. These events indicate a polarity of response in which apical zones have precedence over basal zo

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01273.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.Published data of the concentration dependence of the uptake rate (uptake isotherms) of K+Na+, Cl−, SO2−4, and L‐lysine in barley roots, and glucose and 3‐O‐methylglucose in potato tuber tissue, were re‐examined. In as much as these isotherms yield non‐linear, concave upward Eadie‐Hofstee plots, they might have been termed ‘dual’ isotherms. In addition, all these isotherms have been considered to display discontinuous transitions in gradient. The following models that yield continuous isotherms were fitted to the isotherms: (1) the sum of a Michaelis‐Menten term and a linear term; (2) the sum of two Michaelis‐Menten terms; (3) the sum of two Michaelis‐Menten terms and a linear one. Goodness of fit was judged from: (i) the weighted mean square of deviates; (ii) the standard errors of the kinetic parameters; (iii) the algebraic significance of the terms; (iv) a Rankits plot of the residuals; (v) a Runs test on the residuals.For the precise and detailed isotherms of SO2−uptake, only model (3) gave a fit that was satisfactory in all respects. There appeared to be no reason to consider these isotherms as multiphasic. The same conclusion was reached for the L‐lysine uptake isotherms. For the other isotherms the results were less conclusive. Thai for K+and Na+ could, at any rate, be described satisfactorily by a continuous model, the best fit being obtained with model (2). The uptake isotherms of Cl−and 3‐0‐methylglucose could be best described by model (2), and that of glucose by model (3), only the result of the Runs test being unsatisfactory. It is concluded that there is hardly any evidence that the presumed ‘jumps’ or discontinuities or inflections in the gradient of uptake isotherms are not due to experimental error in the data. It is suggested that many uptake isotherms may be described by model (3), although the reason fo

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01274.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.Starch synthesis by developing wheat endosperm slices incubated in liquid media was more rapid, at optimum concentration, from sucrose as external substrate than from glucose and/or fructose. Fructose inhibited conversion of sucrose or glucose. The results are consistent with the hypothesis that sucrose is not hydrolysed in the apoplast before uptake.Besides a diffusional influx and efflux of labelled sucrose there was a non‐diffusional influx; it was inhibited by dinitrophenol, potassium arsenate, potassium iodide, and parachloromercuribenzene sulphonate (PCMBS). PCMBS inhibited both uptake and conversion of label from 150 molm−314C‐sucrose by 75%. Uptake and conversion of sucrose were stimulated by lowering pH and by fusicoccin, a promoter of proton extrusion.Extracellular solutes like raffinosc and polyethylene glycol stimulated net uptake of label from14C‐sucrose — the larger molecule being more effective — this being due to a non‐specific inhibition of diffusional efflux. At too high an osmotic concentration such solutes reduced net uptake; the larger the molecule the lower this transitional concentration.In conclusion, wheat endosperm is better equipped to convert apoplastic sucrose rather than the hydrolysis products to starch; active loading of sucrose possibly involves proton co‐transport; and large molecules in the extracellular solution reduce the diffusional elllux of l

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01275.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.Abscisic acid (ABA) is taken up by guard cells of isolated epidermata ofValerianella locustaonly at low external pH values. At pH 8.0, when nearly all ABA molecules are present as the union of ABA (ABA−), no uptake can be observed. ABA‐dependent movement of stomata was tested at external pH values between 5.0 and 8.0. Independent of the external pH, ABA induced stomatal closure at all tested ABA concentrations. It is concluded that ABA need not be taken up into the cytosol of the guard cells in order to induce slomatal closure. The primary site of ABA action at the guard cell plasmalemma must be located either at the outer surface of the plasmalemma or at least be easily accessible from outside. ABA− is as effective as undissociated ABA (

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01276.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY