Structural Carbohydrates and Lignifications Associated with Submergence Tolerance in Rice (Oryza sativa L.)

Role of structural carbohydrate content and lignifications in rice shoot were studied in three indica rice (Oryza sativa L.) cultivars namely FR13A (tolerant to submergence), IR42 (susceptible to submergence) and Sabita (adapted to medium depth, 0-50 cm stagnant flooding), varying degrees of tolerance to submergence under control and 8 days after submergence conditions. During submergence, Sabita and IR 42 accelerated the rate of stem and leaf elongation more than that of FR 13A. Submergence significantly reduces the cellulose and hemicelluloses content. The decrease was more pronounced in susceptible rice cultivar than that of tolerant rice cultivar. Lignifications’ was monitored by measuring the content of lignin and the activities of two enzymes of the lignin biosynthetic pathway, coniferyl alcohol dehydrogenase (CAD) and phenylalanine ammonia-lyase (PAL) in rice shoots. Lignin content and PAL and CAD activity was more in susceptible cv. both under control and 8d after submergence. In conclusion submergence induced elongation of rice shoot might decreased the structural carbohydrate level as our experiment showed a significant negative correlation of cellulose and hemicelluloses with plant height but also positively associated with plant survival under submergence. The content of lignin and activities of CAD and PAL showed negative association with shoot elongation, yet the association of these parameters with survival was non-significant.