Photosynthetic pathways (C3, C4, and CAM) and morphological functional types (e.g. shrubs, high perennial grasses, short perennial graminaceous plants, annual grasses, annual forbs, perennial forbs, halophytes, and hydrophytes) were identified for the species from salinity grasslands in Northeastern China, using the data from both stable carbon isotope ratios (δ13C) and from the references published between 1993 and 2002. 150 species, in 99 genera and 37 families, were found with C3 photosynthesis, and most of these species are dominants [e.g. Leymus chinensis (Trin.) Tzvel., Calamagrostis epigeios (L.), Suaeda corniculata (C.A. Mey.) Bunge]. 40 species in 25 genera and 8 families were identified with C4 photosynthesis [e.g. Chloris virgata Sw., Aeluropus littoralis (Gouan) Parlat] and 1 species with CAM photosynthesis. Gramineae is the leading family with C4 photosynthesis (27 species), Chenopodiaceae ranks the second (5 species). The significant increase of C4 proportions with intense salinity suggested this type plant is remarkable response to the grassland salinization in the region. 191 species were classified into eight morphological functional types and the changes of most of these types (e.g. PEF, HAL, and HPG) were consistent with habitats and vegetation dynamics in the saline grassland. My findings suggest that the photosynthetic pathways, combined with morphological functional types, are efficient means for studying the linkage between species and ecosystems in this type of saline grassland in Northeastern China.
Formation of the photosynthetic apparatus in dark-grown 2-day-old beán (Phaseolus vulgaris L.) leaves was studied. The photosystem 2 (PS 2) reaction centres started íunctioning 1 h after the beginning of irradiation. Electron transport between the two photosystems started after 4 h of irradiation. The PS 2 units were able to transfer the excitation energy to each other after 10 h of greening. The photosynthetic activity appeared a long time before the typical 77 K fluorescence bands of green leaves appeared.
In individual leaves, the photon-saturated photosynthetic activity (Psat, expressed on a dry mass basis) was closely related to the nitrogen content (Nc) as follows: Psat = Cf Nc + Psat0, where Cf and Psat0 are constants. On a whole plant basis, the relative growth rate (RGR) was closely related to Nc in canopy leaf as follows: RGR = DMf Nc + RGR0, where DMf and RGR0 are constants. However, the coefficients Cf and DMf were markedly different among plant species. To explain these differences, it is suggested that carbon assimilation (or dry matter production) is controlled by both the Nc in a leaf (or leaves) and by the net N translocation from leaves. This is supported by the finding that Psat is related to the rate of 35S-methionine translocation from leaves. We propose another estimation method for the net N translocation rate (NFR) from leaves: Nc, after full leafing, is expressed as a function of time: Nc = (Nc0 - Ncd) exp(-Nft) + Ncd, where Nf is a coefficient, t is the number of days after leaf emergence, Nc0 is the initial value of Nc, and Ncd is the Nc of the dead leaf. The NFR is then calculated as NFR = ΔNc/Δt = -Nf (Nc - Ncd). Thus Nf is the coefficient for the NFR per unit Nc. NFR is a good indicator of net N translocation from leaves because NFR is closely related to the rate of 35S-methionine translocation from leaves. Since Psat is related to the 14C-photosynthate translocation rate, Cf (or DMf) corresponds to the coefficient of saccharide translocation rate per unit amount of Nc. Cf (or DMf) is closely related to the Nf of individual leaves (or the Nf of canopy leaf). This indicates that C assimilation and C translocation from leaves are related to Nc and N translocation from leaves (net translocation of N). Cf and Nf are negatively correlated with leaf longevity, which is important because a high or low CO2 assimilation rate in leaves is accompanied by a correspondingly high or low N translocation in leaf, and the degree of N translocation in leaves decreases or increases leaf longevity. Thus, since a relatively high Psat (or RGR) is accompanied by a rapid Nc decrease in leaves, it is difficult to maintain a high Psat (or RGR) for a sustained time period. and M. Osaki, T. Shinano.
In this historical review we summarize discoveries related to the flowering genes in controlling leaf area index (LAI, the leaf area per unit ground area) in sorghum, soybean, or pea crop stands. We also analyze similar work on Arabidopsis and dwarf and intermediate stem height genes in wheat and rice. and G. B. Begonia, M. T. Begonia.
At the whole plant level, the effect of stress is usually perceived as a decrease in photosynthesis and growth. That is why this review is focused mainly on the effect of drought on photosynthesis, its injury, and mechanisms of adaptation. The analysed literature shows that plants have evolved a number of adaptive mechanisms that allow the photochemical and biochemical systems to cope with negative changes in environment, including increased water deficit. In addition, the acquisition of tolerance to drought includes both phenotypic and genotypic changes. The approaches were made to identify those metabolic steps that are most sensitive to drought. Some studies also examined the mechanisms controlling gene expression and putative regulatory pathways. and I. Yordanov, V. Velikova, T. Tsonev.
Plants of spring wheat (Triticum aestivum L. cv. Saxana) were grown during the autumn. Over the growth phase of three leaves (37 d after sowing), some of the plants were shaded and the plants were grown at 100 (control without shading), 70, and 40 % photosynthetically active radiation. Over 12 d, chlorophyll (Chl) and total protein (TP) contents, rate of CO2 assimilation (PN), maximal efficiency of photosystem 2 photochemistry (FV/FP), level of lipid peroxidation, and activities of antioxidative enzymes ascorbate peroxidase (APX) and glutathione reductase (GR) were followed in the 1st, 2nd, and 3rd leaves (counted according to their emergence). In un-shaded plants, the Chl and TP contents, PN, and FV/FP decreased during plant ageing. Further, lipid peroxidation increased, while the APX and GR activities related to the fresh mass (FM) decreased. The APX activity related to the TP content increased in the 3rd leaves. The plant shading accelerated senescence including the increase in lipid peroxidation especially in the 1st leaves and intensified the changes in APX and GR activities. We suggest that in the 2nd and 3rd leaves a degradation of APX was slowed down, which could reflect a tendency to maintain the antioxidant protection in chloroplasts of these leaves. and M. Špundová ... [et al.].
In a controlled experiment, Salix matsudana cuttings were subjected to three atmospheric temperatures (i.e. control, 0.5 and 1.0 °C above the control, respectively) to explore their short-term plastic responses to simulated atmospheric temperature rise. Warming affected significantly net photosynthetic and transpiration rates, but had no significant impacts on water use efficiency, ratio of sub-stomatal to atmospheric CO2 concentration, maximum quantum yield, water saturation deficit, tissue density, and water loss. Leaf natality and leaf mortality were affected significantly by increasing atmospheric temperature. Total plant biomass, leaf mass ratio, root mass ratio, and canopy productivity index exhibited significant responses to the warming treatments, but obvious differences in the changing details did appear among the four traits. Hence: (1) S. matsudana cuttings were sensitive to small-range atmospheric temperature increases such as 0.5-1.0 °C, which can alter growth and allocation through modifying photosynthetic rate and leaf turnover. (2) Short-term physiological acclimation did not occur in young individuals of S. matsudana. (3) The warming depressed growth of young individuals of S. matsudana to various extents. and W. M. He, M. Dong.
Permanent plastid-nuclear complexes (PNCs) exist in tobacco cells from their mitosis up to programmed cell death (PCD). PNCs in senescing cells of tobacco leaves were typical by enclosure of peroxisomes and mitochondria among chloroplasts which were in contact with nucleus. Such a complex position provides simultaneous interaction of these organelles and direct regulation of metabolism and PCD avoiding the cytosol. and T. Selga, M. Selga, A. Ozoliņa.