Abstract

Plants at high altitude are subject to enhanced oxidative stress due to high UV fluence (resulting from air rarefaction) compared to places at low altitude. For survival, plants have developed specific cell protective compounds viz. the flavonoids. Flavonoid derivatives (viz. flavonoid glycoside) may also serve as precursor of aroma producing compounds and are thus relevant in studies on plant quality under varying UV fluence. This study was conducted with an aim to understanding the effect of geographic location viz. altitude on aroma compounds in tea leaf, focusing on the internationally reputed Darjeeling tea. Darjeeling grown tea clones (compared with the same clones growing in Assam) are found to have higher; (a) accumulation of flavonoids and flavonoid glycosides that are known to function as UV screens and antioxidants with flavonoid glycosides, additionally serving as aroma precursors, (b) activity of phenylalanine ammonia lyase for flavonoid biosynthesis, (c) activity of β-D glucosidase that releases aroma conferring aglycons from flavonoid glycosides, (d) accumulation of aglycons viz. linalool that is known to cause aroma in tea. In all the cases, a varietal difference (manifested in respective clones) was observed. The understanding developed from the study should help not only for plant survival in the face of global climate change but also for aroma enhancement in tea plants cultivated at non-conventional sites.

Key words: UV radiation, reactive oxygen species, flavonoid glycoside, aroma, tea, high altitude.