Salt tolerance enhancement in indica rice (Oryza sativa L. Spp. indica) seedlings using exogenous sucrose supplementation

Abstract

Salt-affected soil is an abiotic stress which is an acute problem, interrupting the metabolic processes of plants, resulting in reduced growth and productivity. The objective of this study was to enhance the salt tolerance ability of Pathumthani 1 (PT1) sensitive rice cultivars using exogenous sucrose. Fourteen-day-old seedlings of PT1, along with Homjan (HJ), salt-tolerant (positive control), were cultured in MS liquid medium supplemented with 0.0, 29.2, 58.4 or 116.8 mM sucrose, then exposed to 0.0 or 342.0 mM NaCl. An osmotic potential (Ys) in the leaf tissues of rice seedlings dropped significantly when subjected to 342 mM NaCl. Exogenous sugar application in the culture medium was directly absorbed and enriched in rice seedling, leading to soluble sugar accumulation and played a key role as osmoregulation of salt defense mechanism. The increase in Ys in the leaf tissues of salt stressed seedlings directly caused damage to the ultrastructure of chloroplstic organelles, as well as to photosynthetic pigments i.e. chlorophyll a, chlorophyll b and total chlorophyll. Chlorophyll content and chlorophyll fluorescence parameters were stabilised in salt-stressed rice seedlings pre-treated with 58.4 mM sucrose, resulting in enhanced growth performance. A positive correlation between photosynthetic pigment degradation and chlorophyll fluorescence diminution was demonstrated. Exogenous application of 58.4 mM sucrose to the culture medium may play a role as an alternative way to enhance salt tolerance in rice, especially in PT1, a saltsusceptible cultivar.