Optimal regulation mechanisms of leafphotosynthesis and respiration across its longevity

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1. Sucrose fed to the roots of Phaseolus vulgaris plants caused an increase in the carabohydrate content and accelerated senescence in mature source leaves. Neither of these was the case in young sink leaves.2. When environment of the first leaves of Phaseolus vulgaris plants differed from that for other plant parts, photosynthetic properties of young leaves were affected not only by their environment but also by the environment of the first leaves. This implied involvement of systemic regulation of photosynthetic properties. One of such regulation mechanism was shown to relate to redox regulation.3. Acclimation of leaf photosynthetic properties to the growth temperature was analyzed and found to be involve all the changes in temperature dependences of Rubisco kinetics, Rubisoo activation, electron transport activity, and of internal conductance for CO2 diffusion from the intercellular spaces to chloroplast stroma.4. CO2 leak of the CO2 concentration mechanism of C4 plants was analyzed based on measurement of carbon isotope discrimination. The leakiness (ratio of CO2 leaked per CO2 fixed by PEPCase) increased with the decrease in irradiance. This would relate to the inferior performance of C4 in low light.5. In response to strong light, N deficiency and low temperature, the alternative oxidase which is responsible for the cyanide resistant respiration was upregulated and played important roles in resisting such stresses.6. Methods for respiratory cost evaluations were revised and applied to analyses of temperature effects on respiration.7. Sensitivity of the abaxial stomata to light, in particular green light, was shown to be greater that that of the adaxial stomata in Helianthus annuus leaves.8. Petiole curvature of Chenopodium album was analyzed photobiologically. At least three light sensors were shown to engage.