The impact of drought stress (DS) on eight Eurasian and North African genotypes of wild barley (Hordeum spontaneum) was evaluated by analysis of chlorophyll (Chl) a fluorescence fast induction curves using the JIP-test. Three-week-old, pot-grown plants were exposed to a DS treatment by withholding water for nine days. The genotype-specific impairment of the functionality of the photosynthetic electron transport chain was quantified using the relative decline of the performance indices (PIabs and PItot), two key parameters of the JIP-test. The genotypes showing the highest (HOR10164) and lowest (HOR10710) relative PIs under DS were subjected to additional experiments, including measurements of leaf gas exchange, water status, pigment content, key enzyme activity, and protein abundance. The genotypes showed a specific profile of DS-mediated inhibition of photosynthesis, associated with higher relative leaf water contents in HOR10164 at the end of the treatment. Whereas decreased photosynthetic rate in HOR10164 was mainly caused by stomatal closure, nonstomatal limitations (decreased Rubisco content and activity) were detected in HOR10710. Additional genotype specific features were the upregulation of the NADP-malate dehydrogenase in HOR10164 and a decreased fraction of QA-reducing reaction centers in HOR10710., C. Jedmowski, S. Bayramov, W. Brüggemann., and Obsahuje bibliografii
Activities of crucial enzymes involved in the Calvin cycle, glycolysis, and oxidative pentose phosphate cycle (PPC) were investigated in green calli of sugar beet {Beta vulgaris L.) during the transitíon from photoheterotrophic to photoautotrophic growth. The actívities of the Calvin cycle enzymes were increased by lowering the sucrose concentration of the medium, whereas the actívities of dissimilatíon related enzymes were either decreased or not inftuenced. The photoautotrophic culture cultívated on sucrose-free medium and 2 % CO2 grew at a rate six tímes slower than the photoheterotrophic one. Its growth continued on polyurethane pads soaked with agar-free medium and was fully inhibited by 0.5 pM DCMU.
Plants cultivated on acid soils that contain toxic levels of Al3+ usually produce low yields. A multi-factorial treatment of gypsum (G), boron (B), and limestone (Lm) was applied to such soil in order to determine the biochemical basis of the best management plan for ameliorating the soil acidity for sustainable growth of alfalfa. The alfalfa shoots were subjected to analysis for hexose, protein, nucleotide, and chlorophyll (Chl) contents, fructose 1,6-bisphosphatase (FBPase) activity, and the RNA synthetic activity of glutamate dehydrogenase (GDH). Hexose and protein contents of control alfalfa without B and G, but with Lm (672 g m-2) amendment were 0.87 and 38.30 g, respectively, per kg shoot. Increasing the G doses at fixed moderate doses of 0.15 and 0.30 g m-2 B decreased the FBPase activity by ∼53 and ∼31 %, respectively. However, increasing the B doses at higher fixed G (1 kg m-2= G1.0) increased the FBPase activity by ∼91 % thus indicating that G1 optimized the saccharide metabolism by neutralizing the soil acidity. In the absence of B, increasing the G doses also maximized the hexose and Chl contents, but minimized the nucleotide amount. In the absence of G, increasing the B doses maximized the RNA synthetic activity of GDH, but lowered the hexose and Chl contents as well as the FBPase activity without affecting the protein contents, thereby permitting the selection of B (0.45 g m-2) with Lm as the best amendment for the sustainable growth of alfalfa. Treatment with 0.45 g B and 0.5 kg G (= G0.5) induced the strongest B-Ca antagonism by maximizing the hexose and Chl contents but severely suppressing the FBPase activity and the RNA synthetic activity of GDH. Therefore, the coordinate optimization of saccharide metabolism through the G-dependent neutralization of soil acidity, and of RNA metabolism through the B-dependent detoxification of Al3+ are the biochemical options for the mitigation of the adverse effects of soil acidity for the optimization of sustainable alfalfa production. and G. O. Osuji ... [et al.].
The altitudinal effects on photosynthesis were measured on progenies of three populations of Rosa platyacantha Schrenk from altitudes of 1,170 (L); 1,580 (M); and 1,920 (H) m a. s. l. During the day, net photosynthetic rate (PN) decreased in all populations due to the high air temperature in the summer. The H population showed a significantly lower PN at noon compared to other populations. The midday depression of PN occurred in L and M populations due to stomatal limitations, while PN inhibition was associated with PSII activity decline in the H population. In order to avoid photodamage, the plants of H population triggered active antioxidant defenses with a higher enzyme activity and redox ratio of ascorbate at midday compared to the L and M populations. However, more oxidative injury still occurred in the H plants at noon due to higher lipid peroxidation. Our results indicated that the provenance significantly affected photosynthesis in R. platyacantha from northwestern China., S. H. Yang, J. J. Wei, H. Ge., and Obsahuje bibliografii