Demand for Assimilates Determines the Productivity of Intensive and Extensive Rice Crops in Primorskii Krai

Intensive and extensive rice crops (Oryza sativa L.), regionally cultivated in Primorskii krai (maritime territory), were grown under full and 50% attenuated solar radiation. Plants of different varieties were used to examine the supply of newly synthesized and reutilized ¹⁴C-assimilates to caryopses and to estimate the dry weight dynamics of whole plants, vegetative organs, and grains. Cultivar-specific differences were revealed with respect to the sink capacity of caryopses, the export of photosynthates from the upper leaf and their delivery to the panicle, and the contributions of newly produced and reutilized assimilates to grain filling. In rice plants of all varieties grown under full insolation, the amount of photosynthates produced during grain filling was insufficient to satisfy the demand of caryopses; one-fourth or one-fifth of this demand was satisfied at the expense of mobilization of stored metabolites. The mobilization was accelerated by the elevated demand for assimilates and by attenuated insolation. In artificially shaded plants of intensive varieties, the pool of newly produced assimilates was lower and reutilization of previously gained assimilates started earlier than in shaded plants of extensive varieties. It is concluded that the higher grain yield of intensive rice varieties, cultivated in Primorskii krai, is determined by a higher demand for assimilates and by a higher production and accelerated supply of newly formed photosynthates to caryopses during the first half of the grain-filling stage. The potential productivity of these varieties is constrained by the deficit of assimilates during the second half of grain-filling stage. The low grain productivity of extensive varieties is caused by the insufficient number of grains in panicles and by low demand for assimilates throughout the period of grain filling.     

Dark and light green tissues of tobacco leaves systemically infected with tobacco mosaic virus

There are significant changes in the structure of the upper tobacco (Nicotiana tabacum L.) leaves systemically infected with tobacco mosaic virus (TMV) especially in the light green tissue (LGT). Dark green areas (DGI) had intermediate status between healthy tissue and LGT. DGI contained significantly less infectious TMV and viral antigen than the LGT. The DGI, LGT and healthy tissues did not differ in the permeability of cell membranes and in the set of acidic pathogenesis-related (PR) proteins but the total content of PR-proteins in the healthy plants was higher than in the infected ones with the DGI being intermediate between healthy tissue and LGT. The crude leaf extracts from DGI and LGT showed less total ribonuclease activity and ribonuclease isozymes in comparison with control.     

A Method for Calculating the Volume and Surface Area in Rice Mesophyll Cells

A method was developed for determining the surface area and volume of rice mesophyll cells of elaborate configuration. The method was employed to calculate these indices in several types of rice mesophyll cells found in seventy samples (53 species) of diverse origin coming from Japan, China, Korea, India, Nepal, Australia, France, Italy, Uzbekistan, Afghanistan, and Krasnodar and Primorskii regions. The cultivars of diverse geographic origin varied in cell shape and size due to the number, size, and arrangement of chloroplasts. When the volumes and surface areas of leaf mesophyll cells were compared using the method reported herein and a simple empirical model of the cell as a single ellipsoid, the two methods produced relatively similar data for cell volume; however, the surface area calculated by the former method was about two times larger than in the latter case. The method described in this paper allows for accurate calculations of the volume and surface area of rice mesophyll cells when data are available on the cell shape and linear dimensions and the number of chloroplasts per cell.     

Mesostructure of the ginseng photosynthetic apparatus in relation to ecological strategy of the species

Mesostructure of the photosynthetic apparatus was investigated in the wild plants of ginseng (Panax ginseng C.A. Mey, Araliaceae) taken from various habitats. The revealed features of the structure of phototrophic tissues (large cells, small number of photosynthesizing cells and chloroplasts per leaf area unit, low values of membrane indices of the cells and chloroplasts) point to stress-tolerant type of ecological strategy ginseng pursues in Nature.     

Age stages in the ontogeny of cultivated <Emphasis Type="Italic">Panax ginseng</Emphasis> C.A. Mey

The ontogeny of perennial polycarpic herb Panax ginseng C.A. Mey. (Araliaceae) under plantation conditions was described. Three periods (latent, pregenerative, and generative) and eight age stages have been identified in the ontogeny of cultivated P. ginseng. The generative period of this species is the longest ontogenetic period, which determines the timing of its cultivation in plantations.     

Seasonal Signal of Photosynthesis in the Forests of North Eurasia

Russian Journal of Plant Physiology - The seasonal course of the water potential in branch xylem reflects the dynamics of photosynthetic СО2/Н2О exchange in the forest...     

Ultra- and Mesostructural Response to Salinization in Two Populations of С3–С4 Intermediate Species Sedobassia sedoides

Russian Journal of Plant Physiology - The plants from two populations (P1 and P2) of xero-halophyte Sedobassia sedoides (Pall.) Freitag &amp; G. Kadereit (Chenopodiaceae) with...