Catalase Activity in Leaves and Cotyledons During Plant Development and Senescence1)1) Part X of the series "Studies on Leaf Senescence". Supported in part by a Grant from the Council of Scientific and Industrial Research, Government of India to D.M.

Catalase activity was studied as a function of the level of leaf insertion in eight monocotyledonous and eight dicotyledonous plants. Catalase activity was higher in the mature leaves than in the immature and/or senescent leaves. In the primary leaves of rice catalase activity decreased from the 5th day of sowing till the leaves were fully senescent and dried out. In Cucurbita cotyledons catalase activity increased till the 6th day after sowing and then decreased till the cotyledons were shrivelled and dried out. When senescence was delayed in the cotyledons by detopping the seedling, the catalase activity was increased. Catalase activity was decreased during the senescence of detached leaves of several species. The decrease in the catalase activity during senescense has some functional significance and the drift in the catalase activity can be taken as a reliable indicator of senescence.