Morphological and physiological responses of rice seedlings to complete submergence (flash flooding)

Abstract

Enhancement of shoot elongation during submergence in water that is too deep to permit re-emergence by small seedlings represents a futile escape strategy that takes place at the expense of existing dry matter in circumstances where underwater photosynthetic carbon fixation is negligible. Consequently, it compromises survival or recovery growth once flood water levels recede and plants are re-exposed to the aerial environment. Tolerance is greater in cultivars where acceleration of elongation caused by submergence is minimal.

Growth responses and accumulation of soluble sugars in Inga marginata Wild. (Fabaceae) subjected to flooding under contrasting light conditions

“…However, another important adaptation in flood conditions is the storage of nonstructural carbohydrates (soluble sugars and starch) in different regions of the plant (Vartapetian and Jackson, 1997;Kawano et al, 2009). The flooding response in shade plants at five and 15 days might be associated with the temporal pattern of shoot and root accumulation of soluble sugars compared to that for plants at time zero (p = 0.05) ( Figure 1A and 1B).…”

Submergence Tolerance of Rice Species, Oryza glaberrima Steudel

“…However, failure to regain contact with air and the oxygen, carbon dioxide, and light it supplies invariably gives rise to severe carbohydrate depletion. Therefore, this escape strategy carries a high risk for young rice plants (Kawano et al, 2009 photosynthesis and survival rate through shoot elongation ability. Enhancement of shoot elongation during submergence in water that is too deep to permit re-emergence by small seedlings represents a futile escape strategy that is used at the expense of existing dry matter in circumstances where underwater photosynthetic carbon fixation is negligible.…”

Examination of two lowland rice cultivars reveals that gibberellin-dependent early response to submergence is not necessarily mediated by ethylene

“…3 subjected to occasional and temporal flooding, that do not grow fast enough to escape from flooding, may benefit from shoot elongation restriction under these conditions because this allows saving energy reserves until resuming development following eventual de-submergence. [5][6][7] This kind of rice tolerance to submergence is conferred by an ethylene responsive factor (encoded by the gene Sub1A), that reduces GA-inducible expression under submergence by increasing the levels of the GA signaling repressors SLR1 and SLRL1. 8,9 Lowland rice is germinated in the field under a layer of water in many countries (e.g., in most Mediterranean regions), but at later developmental stages only the basal part of the plant is maintained under water.…”