Biochemie und Physiologie der Pflanzen最新文献

The affinitive capacities of quinoidal chalcones towards the flower tissues were compared by examining apparent differences in the recovery rate of the pigments from dyer's saffron C. tinctorius) florets. Precarthamin is less extractable by non-polar solvents, while acetic acid and ammonia water rose its yield a little. Upon trituration of flowers, the solubility of precarthamin was increased considerably, the amounts of safflor yellows, on the other hand, were rather reduced by this treatment. The data are outlined correlating with the compartmental locality of the pigments in the floral tissues of the herbal plant.

The toxic effect of Ni²⁺ ions on photosynthetic electron transport was investigated by monitoring Hill activity, fluorescence, oxygen evolution and thermoluminescence properties in the green algae Scenedesmus obliquus 276-1. Nickel strongly inhibited 2,6-dichlorophenolindophenol (DCPIP) photoreduction in the broken cells of Scenedesmus, and the activity lost could not be restored by adding 1,5-diphenyl carbazide (DPC). Oxygen evolution both measured polarographically and under flash light conditions decreased by increasing the nickel concentration. Fluorescence intensity measured at room temperature decreased upon addition of nickel chloride, both in the presence and absence of DCMU. The maximum fluorescence could not be restored by addition of artificial electron donors. Thermoluminescence studies revealed that the S₂Q_A^- charge recombination, however, was inhibited with increasing concentrations of nickel chloride. The results suggest that Ni²⁺ does not block the electron flow between the primary and secondary quinone electron acceptor, but modify the Q_B site or interact with the non-heme iron between the Q_A and Q_B, leading to the impairment of photosystem II.

Experiments were performed to demonstrate that glucose oxidase from Aspergillus niger conduces towards the flower colour modification in the capitula of Carthamus tinctorius L. For inducing the catalytic reaction, glucose oxidase displayed the absolute requirement for precarthamin, (β-D-glucose and atmospheric oxygen. The enzyme alone could also react with precarthamin to produce carthamin, however, the magnitude is very weak. No activity appeared in the reaction medium containing heat-inactivated enzyme sample even after the addition of glucose. The evidence was further corroborated in an incubation model, in which hydrogen peroxide and precarthamin is co-existent, instead of being added the enzyme and its substrate. The experimental model system showed a quite similar reaction pattern to that of the enzymatic process, indicating that a concomitant weight of red carthamin is accumulated as a major product of the hydrogen peroxide catalysis. On the basis of these assays, it was postulated that glucose oxidase may participate indirectly in the carthamin formation via the process of generating its by-product, hydrogen peroxide, which could react directly with precarthamin. The data are discussed in relation to flower colour modification induced characteristically in C. tinctorius capitula.

The Effect Of Mild Water Stress (−0.5 Mpa Water Potential) On The Rate Of Photosynthesis And Related Parameters In Sunflower And Soybean Plants Was Studied. The Two Species Responded Very Differently: (a) soybean showed a very rapid and marked response which was accompanied by changes in all of the parameters related to photosynthesis and water balance, while the response of sunflower was much more slow; (b) both soybean and sunflower recovered slowly from the stress when rewatered, and the recovery was not complete, reaching values in the range of 50 to 65% compared to the control for CO₂ assimilation, the transpiration rate and stomatal conductance. The results when analysed in terms of the c_i/c_a ratio confirmed the hypothesis that under mild water stress, the reduction in photosynthesis seen is mainly due to the limitation by the stomata of the amount of available CO₂.

Contents of selected phenolic compounds in needles of Norway spruce trees (Picea abies) from the Black Forest were measured using a HPLC-technique elaborated for serial studies in forest decline research. Measurements on needles that were harvested on several dates during two growing seasons gave no hint of seasonal variations in the concentrations of the studied phenolic compounds. Values for picein demonstrate an average decrease in the needles of severely damaged trees compared with the still undamaged ones, but the results are impaired by strong individual variations among the single trees. p-Hydroxyacetophenone was found in only very low amounts showing no constant differences between damaged and undamaged trees. In contrast to that catechin, epicatechin, piceatannolglucoside, and two still unidentified compounds show significantly higher contents in needles of the damaged trees.

The effect of heat shock (5 min at 45 °C) on the cytoplasmic streaming in the cells of Campanula persicifolia, Zebrina pendula and Tradescantia albiflora leaves and the chloroplast phototaxis in the cells of T. albiflora has been investigated. It has been shown that heat shock not only increases the thermostability of these functions but also stimulates the cell reparatory ability. Cells preliminarily subjected to heat shock after test heating more rapidly restore heat suppressed functions than control cells that underwent test heating only, provided the degree of initial inhibition of functions was equal both in hardened and in control cells. The reparation rate of hardened cells immediately after test heating exceeds many-fold that of control cells. Moreover, heat shock widens the reparatory zone, that is a region of temperatures under which heating of definite duration suppresses a given function fully but reversibly. Thus heat shock intensifies the activity of the cell reparatory apparatus, the structure and action mechanisms of which are still unknown.

Effect of Sclerospora graminicola (Sacc.) Schroet. (the causal agent of ‘Downy mildew’/ ‘Green ear’ disease) infection on amino acids and phenols content of pearl millet were estimated colorimetrically at different stages of plant growth. Diseased leaves, stem and root with their healthy counterparts were selected for this study. Due to downy mildew infection amino acid pool was sufficiently reduced while reverse trend was noted for phenol accumulation in all the selected infection types. However, the level of these compounds significantly decreased with the age of the plant in both the healthy and diseased tissues. Phytopathological implications of these observations have been discussed.