摘要:

AbstractInvestigations were conducted with etiolated seedlings of Avena on the influence of red, far red and blue light on:a.the growth of sections of coleoptile and mesocotylb.the geotropic reactions of coleoptile and mesocotylc.guttation of the seedlings.The experiments were carried out in darkness, the experimental irradiations excepted.Two systems of reactions to light appear to be present in the seedlings. One of them shows a very low saturation value of about 1 erg cm−2for red and far red light, the sensitivity to blue light being much lower than for the former wavelengths. This system was found in section growth and the geotropic reaction. The other system shows a dependency on the amount of light energy applied up to at least 105erg cm−2for red, far red and blue light. In this system the sensitivity to far red light is much lower than to red light and about as high as to blue light. This system was found to affect guttation and the shape of the geotropic curves of the seedlings.The latter system appears to exert its influence through changes in transport rates of water and solutes, as is indicated by its influence on guttation.From the results is concluded that this change in the rate of water transport influences the transport rates of auxins and, consequently, the relative growth rates of different parts of the seedlings.Connections of the conclusions drawn with some data from the literature on phototropism are discus

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00169.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractThe techniques for cultivating the young intact barley seedlings used in these absorption experiments are described in some detail.Sets of twelve selected seedlings were used and all data obtained refer to these units.In the experiments, proper absorption took place from dilute solutions of either potassium chloride alone or a mixture of potassium bromide and chloride, the total concentration of which was 0.001 M. Calcium sulphate was also present in all experimental solutions.Chloride is absorbed from the medium at an almost constant speed for a number of hours. This absorption is not influenced by subsequent distribution. At first, the root tissue tends to retain a large proportion of the chloride absorbed at the expense of the transfer of ions to the shoots. Gradually the transfer increases until a constant value is reached within a few hours.Identical results were obtained for total halides if absorption took place from a mixture of chloride and bromide. In addition it was found that chloride and bromide were absorbed at a ratio, which was constant and about twice as high as the ratio for the ions present in the medium. This ratio remained constant even in the dark when total absorption tended to decline slightly.In the transport processes following primary absorption, further discrimination between chloride and bromide ions takes place. The additional screening effect of the root tissue is very small. Nevertheless, important conclusions could be drawn from the behaviour of the Cl/Br ratios of the halides found in roots and shoots. For root tissue this ratio, which must equal the ratio for total absorption at the beginning of the experiment, decreases slightly until a somewhat lower but constant level is reached after a few hours. Although there is no doubt about this decrease for the root tissue, it proved to be so small that the simultaneous increase of the ratio for the shoot tissue was hardly discernable under normal conditions. It became so, if the transfer of ions to the shoot was reduced by a dark treatment.These results could be explained by assuming that the root tissue consists of at least two compartments, differing with respect to the Cl/Br ratio. Ions are brought from the medium into the first compartment by the primary absorption process and then transferred to either the second compartment or via the xylem vessels to the shoots.It is tempting to identify the first compartment with the symplasm of the root tissue, the second one with the vacuole system.The process that takes ions out of the symplasm into the vacuoles prefers bromide ions to chloride ions. Little preference, if any, for either chloride or bromide ions was found for the secretion of ions from the symplasm into the xylem vessels. This is consistent with the idea that the secretion is a simple leakage of a solution out of the tissue.Under conditions of suppressed transfer to the shoots, the accumulation of ions from the symplasm into the vacuoles becomes relatively more important. This causes greater shifts in the Cl/Br ratios found in the different compartments.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00170.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractThe effect of Ca on the uptake of the anion Br and the cations K (Rb) and Na was investigated, with emphasis on its relation to time.Absorption of the Br ion is stimulated in the presence of Ca ions. This stimulation is relatively stronger at low concentrations than at higher ones, and manifests itself without a lag‐phase. The effect of the Ca ion on Br uptake is independent of temperature; it appears at 1.5° C as well as at 20° C. Moreover, this stimulation is more or less independent of the pH in the range between 3.8 and 7.0. Further, the stimulating effect on Br uptake is not specific for the Ca ion because other cations such as K, Na, and Li also increase the Br absorption albeit to a less extent than the divalent Ca ion. The view is advanced that cations screen the negative charges on the cell surface, as a result of which more absorption sites come within the reach of the Br ion.The effect of the Ca ion on Na uptake is manifested at a pH of 5.3 in the form of a reduction in the total amount of Na entering the roots. It was found that the Na uptake can be divided into two fractions, a steady‐state Na uptake and an additional Na uptake taking place only over a limited period, viz. during the first two hours of the experimental time, and probably consisting of the adsorption of Na to cytoplasmatic sites. This additional Na uptake is entirely or partially eliminated by Ca, but, quite to the contrary, the steady‐state Na uptake is not at all influenced by Ca. Evidence is advanced indicating that the effect of Ca on this additional Na uptake is based not on competition for negative adsorption sites in the cytoplasm but on a reduction of the permeability of the outer plasma membrane under the influence of the Ca ion, by which admittance to the cytoplasmic sites behind this membrane is denied to the Na ion.The influence of the Ca ion on the K uptake at pH 5.4 manifests itself as inhibitory, stimulatory, or neutral depending upon the K concentration and the experimental time. At low K concentration (0.01 m.e./l), analogous to the situation with Na, there is an additional K uptake of limited extent and duration which is inhibited by Ca. As in the case of Na, this additional K uptake is assumed to consist of an adsorption of K ions to negative adsorption sites situated behind a membrane, the permeability of which is decreased by Ca. The steady‐state K uptake is in itself not Ca‐sentitive. At higher K concentrations (0.2 m.e./l) the additional K uptake is no longer abolished by the presence of Ca. The fact that in the absence of Ca at higher K concentrations (0.2 m.e./l and higher) the uptake rate diminishes quite considerably after a few hours is to be seen as the result of an efflux of K coming into operation as the K content of the root increases.The results are discussed in relation to the interpretations presented in the literature with respect to the influence of the Ca ion on ion uptake. An attempt is made to localize the various physiological processes involved in cation uptake at the cel

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00171.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractThe shift of phototropic dosage‐response curves by red light appears to be dependent on the time interval between red light treatment and phototropic induction. Red light enhances the maximum of the first positive curvature when administered before phototropic induction. Its effect, when given after induction, is only evident with plants exposed in addition to red light the day before the experimen

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00172.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractGrowth of three varieties of dwarf peas was compared with growth of a tall variety. Dwarfism is determined by light intensity. No difference was found between the effects of light of narrow spectral regions (460 mμ, 560 mμ, 589 mμ and 660 mμ) of high energy (17.000 ergs/sec/cm2).A transitory difference in growth inhibition was found between the dwarfs and the tall vari

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00173.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractDuring the germination of barley, the epidermal cells of the scutellum detach themselves from one another and grow to twice their former length.Aleuron proteins are dissolved in the first 3–4 days and subsequently the lipid contents of the spherosomes are digested. This coincides with the development and temporarily increased activity of all metabolic organelles, viz. endoplasmic reticulum, mitochondria, dictyosomes (Golgi apparatus) and leucoplasts.After ten days aqueous vacuoles have developed. After 21 days the cell organelles are smaller and fewer, though some spherosomes are still presen

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00174.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00175.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00176.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Book reviewed in this article:C. A. Backerand R. C. Bakhuizen van denBrinkJr., Flora of JavaF. H. Perring, P. D. Selland S. M. Walters, A Flora of Cambridgeshire, with a section on Bryophyta by H. L. K. Whitehouse

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00177.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY