Biochemical responses of Camellia sinensis (L.) O. Kuntze to heavy metal stress.

Three heavy metals-mercury (II), copper (II) and nickel (II), each at a con centration of 10 and 100 mug/ml, were tested for their effects on various b iochemical constituents of tea leaves. Both NI (II) and HS (II) decreased t he phenolic contents, while Cu (II) increased it to some extent. The metal treatments enhanced the activity of phenyl alanine ammonia lyase (PAL), whi le the activity of poly phenol oxidase (PPO) showed a decline. Heavy metal stress also decreased the chlorophyll content of the leaves, along with a s ignificant reduction in Hill activity. Proline content increased significan tly in all treatments.