Physiologia Plantarum

KLEIN, UWE; BETZ, AUGUSTIN

doi: 10.1111/j.1399-3054.1978.tb01529.xpmid: N/A

Gas production by Chlamydomonas moewusii in the light has been followed by manometric techniques during the adaptation to anaerobiosis. The only detectable gases produced are CO2 and H2 CO2 is produced at a rather constant rate whereas H2 evolution increase with time. This increase of H2 evolution during the adaptation period can be inhibited by cycloheximide and by chloral hydrate, two inhibitors of protein synthesis. If the inhibitors are added to already adapted cells there is no effect on H2 evolution. Adapted cell suspensions are sensitive to oxygen. Incubation under O2 for 10 min inhibits the H2 evolution to 100%. After removal of oxygen the capability to evolve H2 can be restored only by a new adaptation period. This second adaptation to H2 evolution can also be inhibited by cycloheximide.

HANSEN, G. K.

doi: 10.1111/j.1399-3054.1978.tb01530.xpmid: N/A

Lolium multiflorum L. was grown in pots in controlled environments. CO2‐exchange rates were continuously measured on two pots during 46 and 52 days, respectively, separating between tops and roots. After 20 days, the plants were entirely defoliated and the plants were then followed during the regrowth period. During the experiment, alternating 2–3 day periods of high and low irradiance were applied. Analogously treated plants were frequently harvested to obtain the distribution of assimilates between tops and roots. From integration of CO2‐exchange rates, diurnal photosynthesis and respiration were obtained, and utilization of assimilates was analysed. The respiration associated with the synthesis of new structural material (growth respiration) was dependent on assimilates originating from both the current and the preceding 24 h diurnal cycles. The amount of new structural material synthesized during the current 24 h diurnal cycle was estimated from the relative contribution of assimilates accumulated from the preceding and the current 24 h and diurnal cycles to growth respiration of the current 24 h. From this approximation, the respiratory components connected to synthesis of new structural material and to maintenance of already established material were found. Growth and maintenance respirations of the tops were alike during the predefoliation and the regrowth periods. For the roots, however, growth respiration was higher and maintenance respiration lower in the regrowth period. The difference between daily integrated CO2‐exchange and the amount converted into new structural material was assumed to be the daily change in assimilates stored. On the first day of a period of high irradiance, the assimilation per unit leaf weight was higher than on the following day of high irradiance, and an accumulation of storage material took place. On the first day of a period of low irradiance, the assimilation per unit leaf weight was lower than on the following day of low irradiance, and there was a depletion of assimilates stored. These effects were most pronounced during the regrowth period, indicating a change in the metabolic sink demand. This indicates a strong feedback mechanism between sources and sinks, in the sense that accumulation of products will inhibit assimilation.

PENOT, M.; BERAUD, JACKY

doi: 10.1111/j.1399-3054.1978.tb01531.xpmid: N/A

Directed Transport and Hormones — Value of Isolated Leaf as Experimental Material. Local application of aqueous phytohormonal solution (0.1 ml of various concentrations, from 50 to 0.025 mg‐l−1, of IAA, 2,4‐D, NAA, BAP, GA3) on isolated leaves influences the direction of ion transport. All tested hormones are efficient but the action depends upon the ionic species (positive action with 32P, 35S, 36Rb (K), but null with 45Ca or 46Cl). The movement of ions occurs through the phloem tissue and is not a cell‐to‐cell transfer. Competition between different parts of the leaf is demonstrated (a) between petiole which appears to be an important attractive centre and other parts of the leaf; (b) in a depetioloted leaf, between different centres induced by different phytohormones. In this respect, GA3 appears to be the most efficient hormone in the tested material — leaves of Pelargonium zonale (L.) Aiton. The effects on directional transport are discussed in relation to other processes controlled by hormones, for instance growth, senescence, protein synthesis. A direct relation of directional transport with growth or delay of senescence may be discarded. The value of isolated leaves as simplified experimental systems is underlined by the fact that weak hormonal doses are efficient (0.025 mg.l for GA3 and 0.5 mg.1 for 2,4‐D) as compared to the higher doses used in other plant systems.

TAKEUCHI, YUICHI; KOMAMINE, ATSUSHI

doi: 10.1111/j.1399-3054.1978.tb01532.xpmid: N/A

In a suspension culture of Vinca rosea L. three distinct growth phases were distinguished: a cell division phase, a cell expansion phase, and a stationary phase. At various stages of the growth cycle, extra‐cellular polysaccharides (ECP) and cell wall were isolated and their compositions were investigated. ECP are mainly composed of xyloglucan, 3,6‐linked arabinogalactan, and polyuronide. From the results of gas chromatographic analyses of sugars and partially methylated sugars in each fraction of cell wall polysaccharides, the following changes were observed in the composition of cell wall polysaccharides during culture: (1) a decrease in polyuronide content, (2) a decrease in non‐cellulosic glucan content, (3) an increase in xyloglucan content, and (4) an increase in a‐cellulose content. The significance of the changes is discussed in relation to the growth of cells.

BASIOUNY, FOUAD M.; VAN, T. K.; BIGGS, R. H.

doi: 10.1111/j.1399-3054.1978.tb01533.xpmid: N/A

Four C3 and two C4 plants were subjected for 350 h to an enhanced UV‐B radiation (280 to 310 nm) regime simulating a 0.18 atm. cm ozone level (solar angle 55°) in growth chamber. Different degrees of response among plant species were observed. UV‐B radiation reduced plant height, fresh and dry weight, protein content, total chlorophyll, inhibited net CO2 uptake and the Hill reaction activity. Some broad‐leaved species with C3 type of carbon assimilation were more susceptible to UV‐B alterations of morphological and biochemical characteristics than the narrowleaved species with C4 type photosynthesis.

BEN‐BASSAT, D.; MAYER, A. M.

doi: 10.1111/j.1399-3054.1978.tb01534.xpmid: N/A

The rate of volatilization of Hg2+ as metallic Hg is accelerated by illumination of Chlorella cells. In the presence of the uncoupler methylamine the rate of volatilization in the light is greatly but transiently increased. DCMU (3‐(3,4‐dichlorophenyl)‐1,1‐dimethyl urea) prevented the light response. In the presence of Hg2+, O2 evolution by the cells was not completely inhibited by DCMU. Hg2+ appears to prevent DCMU reaching its binding site. Light seems to increase the amount of or leakage from the cells of a metabolite capable of reducing Hg2+ to Hg°.

KATO, YUKIO

doi: 10.1111/j.1399-3054.1978.tb01535.xpmid: N/A

Adventitious buds were induced on intact, undetached leaves, isolated leaves, and both green and etiolated leaf fragments excised from young plants of Heloniopsis orientalis (Thunb.) C. Tanaka (Liliaceae) in darkness. Morphactin promoted bud initiation on undetached leaves. The regeneration loci on excised leaves were different in darkness and in light, and they were also modified by etiolation and by morphactin or benzyladenine. Experiments with pre‐incubation in darkness, with successive treatments by sorbitol and sucrose, and with DCMU‐treatment in light, led to the conclusion that bud formation on isolated leaves and leaf fragments is controlled by a photosynthetic system as well as the hormonal level.

SINHA, S. K.; KHANNA‐CHOPRA, RENU; CHATTERJEE, S. R.; ABROL, Y. P.

doi: 10.1111/j.1399-3054.1978.tb01536.xpmid: N/A

Bleeding sap and nodules from Vigna radiata were analysed for their free amino nitrogen content and amino acid composition at different stages of growth and development. The bleeding sap contained mostly basic amino acids, whereas the nodules contained both acidic and basic amino acids. The amino nitrogen content of the bleeding sap increased during growth and then declined appreciably during fruit development. In contrast, nodule amino nitrogen declined from seedling stage onwards till flowering, increased during fruit development and then declined again. Nitrate reductase activity in the leaves examined at different stages of development increased from seedling stage onwards and was maximum during early fruit‐development stage. It declined during pod‐filling stage. The study suggests that the amount of nitrogen fixed from the atmosphere is insufficient, so that the plant has to draw upon soil nitrogen as well. This may be necessary due to the high demand of nitrogen during pod filling.

HILTON, GARY M.; NESIUS, KNEELAND K.

doi: 10.1111/j.1399-3054.1978.tb01537.xpmid: N/A

Electron micrographs of Pisum sativum L. hypocotyl tips treated to localize adenyl cyclase revealed discrete deposits on the internal membranes of cytoplasmic vacuoles which correspond to previously localized enzymes described as acid phosphatases. It remains to be determined whether the specificity of the substrate, adenylyl‐imidodiphosphate, used in the present study is such as to exclude all phosphatase activity other than adenyl cyclase. The acid phosphatase localized in earlier studies by other investigators may be an adenyl cyclase. In the differentiated cells of the root cap, lead precipitate was localized in distinct areas bound to the smooth endoplasmic reticulum.

BRETELER, HANS; CATE, CHARLOTTE H. HÄNISCH TEN

doi: 10.1111/j.1399-3054.1978.tb01538.xpmid: N/A

The Dijkshoorn‐Ben Zioni model about potassium recycling in higher plants proposes a stoichiometric coupling between the upward transport of nitrate and potassium, and therefore a 1:1 ratio of these ions in the xylem sap. Phaseolus vulgaris grown in media with different NO3: K+ ratios, however, only rarely showed equimolar concentrations of the two ions in the bleeding sap. Ratios between 0.2 and 11 were observed and the ratios between concentrations of the ions in the exudate and in the external solution were positively correlated. An analysis of the major inorganic constituents of the exudate revealed an ionic balance that requires negligible amounts of charges from organic molecules.