Plant Stress Physiology and Photosynthesis

The objective of this laboratory is to understand the physiological responses and adaptation of plant to various environmental stresses. Chlorella is one of the major targets. Recultivation after a mild heat stress results in loss of photosynthetic activity and all chlorophylls in Chlorella cells within one day. We found that DNA in nucleus and chloroplasts were also degraded along with chlorophylls, but the cell membrane remained intact. In addition, there was no massive protein degradation, but a novel nuclease activity was detected. We are trying to clarify whether this process is due to photo-oxidation and/or programmed cell death.

We also study the response of photosynthesis to environmental stresses, using chlorophyll fluorescence as a tool to monitor the operation of the whole photosynthetic system. The measurement of chlorophyll fluorescence is easy, fast and non-invasive. We are detecting the variations of chlorophyll fluorescence under various stresses, to find out what kinds of damages could be brought about by these stresses. We are also trying to construct a chlorophyll fluorescence ‘image’ system, hoping this simple and rapid measurement can be developed into an early warning system that can tell the plants are under stress. It might find an application in agricultural production.