Alkalies are important agricultural contaminants complexly affecting plant metabolism. In this study, rice seedlings were subjected to alkaline stress (NaHCO3:Na2CO3 = 9:1; pH 8.9) for 30 days. The results showed that stress mightily reduced net photosynthetic rate (PN), but slightly decreased transpiration rate and stomatal conductance. This indicated that decline of PN might be a result of nonstomatal factors. Alkaline stress caused a large accumulation of Na+ in leaves up to toxic concentration, which possibly affected chloroplast ultrastructure and photosynthesis. We found that alkaline stress reduced chlorophyll fluorescence parameters, such as ratios of Fv′/Fm′, Fv/Fm, photosystem (PS) II efficiency, and electron transport rates in rice plants, i.e. it influenced the efficiencies of photon capture and electron transport by PSII. This might be a main reason for the decrease of PN under such conditions. Deficiency of minerals could be another reason for the decline of PN. Alkaline stress lowered contents of N, K, Cu, Zn, P, and Fe in rice plants. In addition, the stress strongly affected metabolism of amino acids. This might be caused by imbalance in carbon metabolism as a result of photosynthesis reduction., Z.-H. Wu, C.-W. Yang, M.-Y. Yang., and Obsahuje bibliografii
Peanut plants were adapted to drought. Due to parahelionastic leaf movements under water stress they decreased heat load and transpiring area, Folding of leaflets minimised damage to photosynthetic apparatus by high temperatoe. A positive correlation between transpiration rate (E) and leaf water potential indicated the dependence of the latter on E. Phosphoenolpyruvate carboxylase (PEPC) activity progressively increased with increased period of stress, whereas activities of ribulose-l,5-bisphosphate carboxylase (RuBPC) and NADP-glyceraldehyde-3- phosphate dehydrogenase (NADP-G-3-PDH) decreased gradually.
In this article we present study of proper motions of the flare active reglons NOAA/USAF 3885 and NOAA/USAF 3886. The 30 flare of 3 - 4 September 1982 (NOAA 3886) appeared to have a close relation
to the relatlve motlon of unconnected sunspot pairs of opposite polarity, During the regressive stage of region NOAA 3885 a considerable rotation was observed In the main leader umbra.
By taking some evolutionary models of an initially 60 M⊙-star, their radial vibrational stabilities have been investigated. These models, evolving with mass loss, are in the advanced stages of their evolution, and burn He in their cores. Calculations have been performed for the first and second harmonics as well as for the fundemental mode; and some of these models were found to be vibrationally unstable in the fundemental mode.
In the temperate haptophyceaen Pavlova luíheri (Droop) Green and Pavlova sp. (not yet estimated) the dominant pigments were chlorophyll (Chl) a (57 %), fucoxanthin (17 %) and diadinoxanthin (13 %); other estimated pigments were p-carotene, Chl c, cA-fucoxanthin and diatoxanthin. UV-A of 1.7 W m-2 had no effect on pigmentation of P. luíheri, but led to a reduction of the pigment contents of Pavlova sp. The damaging effect of a high UV-A dose (11.0 W m'^) was more pronounced than that of UV-B irradiance. The strongest reduction of pigment concentrations of both Pavlova species was observed after an exposure to UV-A (11.0 W m'^) plus UV-B (1.2 W m-2). Under this combined irradiation an increase of the diatoxanthin content and a decrease of the diadinoxanthin content was found.