Gas Exchange Characteristics of Leaves as Indicators of the Basic Limitations to the Rate of Photosynthesis. Second Annual Report, 1 June 1985-31 May 1986

摘要

The response of photosynthesis to light, CO sub 2 and O sub 2 is studied by measuring the exchange of gases (water vapor and CO sub 2 ) between the atmosphere and the leaf. These measurements are combined with measurements of metabolite levels and enzyme activities which can disclose the molecular events which limit or regulate the rate of photosynthesis. The purpose of this research is to identify the underlying molecular events which give rise to easily measured photosynthetic characteristics so that those processes which are most important in regulating or limiting photosynthesis in leaves can be identified. A significant result of this research has been the identification of the cause of O sub 2 insensitive photosynthesis in C sub 3 plants. It has been determined that this anomalous behavior is caused by deactivation of the primary carboxylating enzyme, RuBP carboxylase, in low O sub 2 . It is believed that this deactivation occurs because the plant is unable to use all of the products of photosynthesis that could be made if deactivation did not occur. Current efforts are directed toward understanding how this deactivation may be advantageous to the plant and how rapidly it can occur. 30 refs., 1 fig., 3 tabs. (ERA citation 11:029503)