Volume No. 9 Issue No.: 3A Page No.: 733-743 January-March 2015




Shanthi N.*1 and Nithia Jannita S.*2

1. Department of Botany ,Pachaiyappa College, Chennai,Tamilnadu (INDIA) 2. Department of Botany, American College, Madurai, Tamilnadu (INDIA)


Received on : October 10, 2014




Thinning of ozone layer increased the level of UV-B radiation fluxuation on the earths surface. The level varies with full sunlight condition and shaded condition (50% reduce). We analysed the response of some naturally grown medicinal plants like Achyranthus, Acalypha, Tridax and Ruellia to UV-B radiation at full sunlight and shaded condition. The plants were selected from Madurai Kamaraj University, Botanical garden, Tamilnadu, India. Typical morphological and physiological changes were observed in these four plants. When compared to plants grown in full sunlight condition, the plants grown in shaded condition having broad lamina and long internodes. The leaf area also two fold higher in shade grown plant than full sunlight grown plant. The natural UV-B radiation also affected of total chlorophyll, carotenoid biosynthesis, electron transport and PSII activity. The impact was high in full sunlight grown plant than shade grown plant. But it increases the secondary pigment like anthocyanin and flavanoid level in various extend. Such increase was higher in full sunlight grown plants. Among four species in Acalypha and Achyranthes were only marginal changes were observed. This is confirmed by in vitro experiment, whereas the isolated chloroplast of two species exposed to artificial UV-B radiation in different time interval. There is no sudden loss of PS(II) activity instead of that they try to stabilize or restore PSII activity in one hour period


Keywords : UV-B radiation, Chlorophyll, Photosystem II, Flavaniods, Anthocyanin