We analyzed several approaches dealing with the components of non-photochemical energy dissipation and introduced improved versions of the equations used to calculate this parameter. The usage of these formulae depends on the conditions of the sample (acclimation to dark or irradiation, presence or absence of the "actinic light"). The parameter known as "excess" cannot be used as a component of energy partitioning. In reality, this parameter reflects the differences between potential and actual quantum yields of photochemistry. and D. Kornyeyev, A. S. Holaday.
Leaf-root interaction is a critical factor for plant growth during maturation and activity of roots is maintained by a sufficient supply of photosynthates. To explain photosynthate distribution among organs in field crops, the node unit hypothesis is proposed. One node unit consists of a leaf and an upper adventitous root, as well as the axillary organs and the lower adventitious root, which is adjacent to one node. Using 14C as tracer, the carbon distribution system has been clarified using spring wheat, soybean, tomato, and potato. The interrelationship among organs from the strongest to the weakest is in the following order: (1) within the node unit > (2) between the node unit in the same or adjacent phyllotaxy > (3) in the main root or apical organs, which are adjacent to the node unit. Within the node unit, 14C assimilated in the leaf on the main stem tended to distribute to axillary organs in the same node unit. The 14C assimilated in the leaf of axillary organs tended to distribute within the axillary organs, including adventitious roots in the axillary organ and then translocated to the leaf on the main leaf of the same node unit. In different organs of the node unit in the same or adjacent phyllotaxy, 14C assimilated in the leaf on the main stem was also distributed to the organs (node unit) belonging to the same phyllotaxy in dicotyledons, while in monocotyledons, the effect of phyllotaxy on 14C distribution was not clear. Among roots/apical organs and node unit, 14C assimilated in the upper node unit was distributed to apical organs and 14C assimilated in the lower node unit was distributed to roots. Thus the node unit hypothesis of photosynthate distribution among organs is very important for understanding the high productivity of field crops. and M. Osaki ... [et al.].
Over-expression of chloroplastic glycerol-3-phosphate acyltransferase gene (LeGPAT) increased unsaturated fatty acid contents in phosphatidylglycerol (PG) of thylakoid membrane in tomato. The effect of this increase on the xanthophyll cycle and chloroplast antioxidant enzymes was examined by comparing wild type (WT) tomato with the transgenic (TG) lines at chilling temperature (4 °C) under low irradiance (100 µmol m-2 s-1). Net photosynthetic rate and the maximal photochemical efficiency of photosystem (PS) 2 (Fv/Fm) in TG plants decreased more slowly during chilling stress and Fv/Fm recovered faster than that in WT plants under optimal conditions. The oxidizable P700 in both WT and TG plants decreased during chilling stress under low irradiance, but recovered faster in TG plants than in the WT ones. During chilling stress, non-photochemical quenching (NPQ) and the de-epoxidized ratio of xanthophyll cycle in WT plants were lower than those of TG tomatoes. The higher activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) in TG plants resulted in the reduction of O2-. and H2O2 contents during chilling stress. Hence the increase in content of unsaturated fatty acids in PG by the over-expression of LeGPAT could alleviate photoinhibition of PS2 and PS1 by improving the de-epoxidized ratio of xanthophyll cycle and activities of SOD and APX in chloroplast. and N. Sui ... [et al.].