A comparative study of chlorophyll (Chl) fluorescence characteristics was made between a soybean [Glycine max (L.) Merr.] Chl-deficient mutant (light green leaf, LG, Eji^ii), and a nearly isogenic Chl normál biotype (dark green leaf, DG, EnEn) of cultivar Clark, LG had a lower light-saturated net photosynthetic rate (/^n), compared with DG at early stages of growth (before pod filling), but the difference in Ejsi between LG and DG became smaller at later stages of growth. The lower of LG may result from lower Chl content (Chl a and b), lower carboxylation efficiency, and lower photochemical efficiency of photosystem 2. Both LG and DG grown at low iradiance [about 200-300 pmol(photon) m'^ s"’] in a growth cabinet had similar photochemical effíciencies. However, the efficiency was lower in LG than in DG grown in field sunlight in mid summer, especially during the aftemoon on clear days, indicating that LG is more sensitive to photoinhibition.
In the untransformed rice (WT) and transgenic rice with the PEPC and PPDK genes (CK) we determined activities of C4 photosynthetic enzymes, photosynthetic response to irradiance and temperature, the metabolic index of active oxygen, and the yield component factors. The activities of C4 photosynthetic enzymes in WT were very low, while those of corresponding enzymes in CK were highly observable. Moreover, after adenosine triphosphate (ATP) treatment, and under high irradiance and high temperature, the net photosynthetic rate of CK increased by 17 and 12 %, respectively, as compared to that achieved without ATP treatment. The resistance of CK against photo-oxidation was enhanced under these conditions, and CK yield increased by 15 %. ATP treatment enhanced the photosynthetic productivity of CK, thereby proving that ATP is the key factor in enhancing the photosynthetic capacity of transgenic rice with C4 gene. Our new technical approach can be used in breeding rice with high photosynthetic efficiency and high grain yield. and B. J. Zhang ... [et al.].
The present work showed that spider mite-infested leaves placed in the light were more attractive to predatory mites than the infested leaves placed in the dark; furthermore, an increase in the light intensity enhanced this attractiveness. However, the increase of the light intensity did not change the attractiveness of the uninfested leaves to predatory mites. The capacity of cyanide-resistant respiration and the photosynthetic rates of both the infested and uninfested leaves increased with increasing light intensities, whereas the photosystem (PS) II chlorophyll (Chl) fluorescence decreased. The increase of the capacity of cyanide-resistant respiration in the infested leaves was more dramatic than that in the uninfested leaves, whereas the values of photosynthetic rates and Chl fluorescence were lower in the infested leaves than those in the uninfested leaves. Treatment of the infested and uninfested leaves with 1 mM salicylhydroxamic acid (SHAM, an inhibitor of cyanide-resistant respiration) decreased photosynthetic rates and caused further reductions in PSII fluorescence, especially under a higher light intensity. In contrast, the effects of SHAM on PSII fluorescence parameters and photosynthetic rates of the infested leaves were more dramatic than on those of the uninfested leaves. The treatment with SHAM did not significantly change the attractiveness of the infested or uninfested leaves to the predatory mites under all of the light intensities tested. These results indicated that cyanide-resistant respiration was not directly associated with the light-induced attraction of predators to plants, but it could play a role in the protection of photosynthesis. Such role might become relatively more important when photosynthesis is impaired by herbivores infestation. and H. Q. Feng ... [et al.].