GREENING AND PHOTOSYNTHESIS IN ANAEROBICALLY GROWN ECHINOCHLOA CRUS-GALLI VAR ORYZICOLA AND ORYZA SATIVA AFTER EXPOSURE TO AIR.

摘要

Oryza sativa (rice) and Echinochloa crus-galli var oryzicola (oryzicola), a serious weed of rice, are able to germinate under anaerobiosis. When grown without oxygen, both plants produce a non-pigmented shoot, which then greens and develops photosynthetically upon exposure to air. In this study, the development of photosynthesis in anaerobically germinated rice, a C(,3) plant, and oryzicola, a C(,4) plant, is compared to greening of air and dark germinated seedlings.;In anaerobically germinated oryzicola, activities of PEP carboxylase, NADP-malate dehydrogenase and NADP-malic enzyme were lower than RuBP carboxylase until well after net photosynthesis was seen. The importance of high RuBP carboxylase activity was also evidenced by the initial photosynthetic product labeling pattern of anaerobically germinated oryzicola. In early stages of greening, pulse-chase experiments gave results more typical of C(,3) plants than of C(,4) plants. By 96 hours of greening, however, the anaerobically germinated seedlings showed pulse-chase kinetics typical of C(,4) photosynthesis. Oryzicola appears better adapted photosynthetically to germination in a low oxygen environment than rice, which probably contributes to the success of oryzicola as a major rice weed.;Net photosynthesis in anaerobically germinated rice was seen 76 hours after exposure to air. By comparison, in similarly treated oryzicola, net photosynthesis occurred after 40 hours. Both rice and oryzicola germinated in air/dark exhibited net photosynthesis after 6 hours of exposure to light. Chlorophyll and carotenoid content and RuBP carboxylase activity also showed similar sequences of development. However, in anaerobically germinated oryzicola seedlings, a more rapid development of pigmentation and RuBP carboxylase activity occurred. Although these seedlings had reduced photosynthesis relative to air/dark germinated seeds, photosynthetic rates were equivalent to similarly treated rice.