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.