Effect of Cadmium Ions on Photosynthetic Structure and Its Functions of Tea Leaves

Tea plant was cultivated in Hoagland nutrient solution containing 0.5 mmol/L Cd2+ for 8 days. Tea leaves lost their green color gradually with the change in the ultrastructure of the chloroplast . At the early stage, there was a slight decrease in the number of granum thylakoids. Then, the thylakoids piled up loosely, and chloroplasts rounded off to different extents. At the late stage , the structure of the chloroplast related to thylakoid became unclear, while the thylakoid system was disintegrated abnormally with a few single bent and swell thylakoids, and some ruptured envelope of chloroplast. Cadmium ions significantly inhibited the photosynthesis activity and led to the decline in the chlorophyll content and chlorophyll a/b ratio. Further more the photochemical efficiency of PSII(Fv/Fm)and the potential activity of PSII(Fv/Fo)decreased in different degrees with increasing Cd2+ stress . The pollution duration resulted in the damage of photosynthetic structure in tea leaf cells.