Effect of high light intensity on the recovery of rice seedlings from submergence
2000
Ella, E.S. | Kawano, N. | Ito, D. (International Rice Research Inst., P.O. Box 3127, 1271 Makati City (Philippines))
The damage of submergence may be partly caused by O2 species (AOS) such as H2O2 produced during the change in environment from low light intensity and low O2 supply during submergence to higher light intensity and higher O2 supply after desubmergence. Light stress results not from high light intensity per se but from the absorbed light in excess of that used during photosynthesis. This research identifies the involvement of an AOS-scavenging system, such as ascorbate antioxidant, in the alleviation of the damage (lipid peroxidation) after desubmergence and during recovery in high light intensity. After 24 h of light treatment, the submergence-tolerant IR42 had more H2O2 and greater lipid peroxidation than the submergence-tolerant FR13A. In IR42, H2O2 production is more in high light than in low light, while it remained the same in FR13A. High light increased lipid peroxidation in both cultivars. Relative to the nonsubmerged seedlings, IR42 had reduced chlorophyll content earlier (just after 1 d of treatment cf, 3d for FR13A) and in greater extent than FR13A in both light treatments. After 2 d of light treatment, FR13A had more ascorbate than IR42 and gave higher value in low light than in high light. Results suggest that more H2O2 may be produced during high light recovery which causes more damage, and that ascorbate may be involved in alleviating such damage. A study on AOS- scavenging enzyme and further characterization of the photosynthetic capacity of the submerged seedlings during recovery will be done to confirm these results
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