Senescence behaviour of Hydrilla verticillata (L.f.) Royle, Ottelia alismoides (L.) Pers., the two submerged angiosperms having no stomata and Commelina benghalensis (L.), a terrestrial angiosperm having distinct stomata, was studied in both light and darkness with increase in incubation time, chlorophyll content decreased faster in the light than in the dark in Hydrilla and Ottelia leaves in contrast to Commelina leaves where chlorophyll was lost at a slower rate in light than in darkness. The ratio of chlorophyll a to b and total chlorophyll to carotenoid decreased more extensively in light in comparison to darkness in Hydrilla and Ottelia leaves. For Commelina leaves, such decrease was greater in the dark than in the light. Protein content gradually decreased, while α-NH2 content increased with progress of senescence in all three species. The possible similarities and differences in the senescence behaviour of these two types of plants have been discussed.
