Effects of alkalinity-induced iron deficiency on physiological and growth variables of some upland rice cultivars under laboratory condition

Prevalence of iron deficiency (ID) in upland rice under alkalinity stress is capable of constraining its production. This investigation aimed to explicate the physiological basis of ID tolerance in some upland rice genotypes. Eighty upland rice genotypes were characterised for ID tolerance at seedling growth stage in a sand-culture hydroponics with varying NaHCO₃ concentrations (0, 15 and 25 mM). The treatments were arranged in completely randomised design with three replicates. Significant (P < 0.05) decrease was observed on leaf iron concentration, SPAD meter readings, leaf photosynthetic efficiency, quantum yield and growth variables with increasing concentration of NaHCO₃. Iron tolerance index was further estimated based on these parameters and used for ranking the genotypes. Significant (P < 0.05) decrease was observed on all physiological and growth variables measured with increasing concentration of NaHCO₃. Based on iron tolerance index, Caipo and NERICA 7 were identified as the most and least tolerant to iron deficiency respectively. The basis of iron deficiency tolerance is discussed in relation to the stability of photosynthetic apparatus and plant growth under alkalinity stress.