Movement of chloroplasts in mesophyll cells of Garcinia indica in response to UV-B radiation

Abstract

The effect of UV-B radiation (280-320 nm) alone with reference to photosynthesis was studied in Garcinia indica. One year-old glasshouse-grown plants were transferred to a growth chamber fitted with UV-B source. Plants were exposed to 1 mW/sq.cm of UV-B radiation for three days. Although photosynthesis was not completely inhibited due to UV-B treatment, it declined by nearly 74 percent compared to glasshouse-grown plants. In other words, photosynthesis was being carried out, albeit at a much lesser level. Horizontal arrangement of chloroplasts in all layers of mesophyll cells was observed in treated leaves. Spectroscopic measurements showed that plants accumulated flavone with lambda(max) at 230 nm, which was seen to be at the cost of a decrease in another flavone with lambda(max) at 215 nm. Paper chromatographic analysis also showed accumulation of flavone and anthocyanin in treated plants compared to control. It is proposed that UV-B radiation (280-320 nm) may act as a signal for chloroplast movement under in vivo conditions. Whether the flavone with lambda(max) at 230 nm has any cause and effect relationship with respect to UV-B-induced phototropic movement of chloroplasts in the mesophyll cells, remains to be investigated.