Increasing Rice Seedling Growth under Induced Water-Deficient Conditions Using Indole-3-Acetic Acid Produced from Enterobacter sp. Bacteria

Purpose: Water deficiency stress affects rice growth and productivity around the world while reducing indole-3-acetic acid (IAA) levels within plants. This study aims to determine the effects of IAA, produced from the endophytic bacteria Enterobacter sp. (RD4-1-1), on the germination and seedling growth of two lowland rice varieties, namely, RD31 and RD41, under water deficiency stress. Research Method: Water deficiency was simulated in culture medium [using the percentage of polyethylene glycol 6000 (PEG)] and soil cultivation (using different watering frequencies). The effects of RD4-1-1 IAA at various concentrations on rice under water deficiency stress were assessed by measuring a variety of characteristics related to germination and seedling growth. Findings: The effects of RD4-1-1 IAA supplementation in rice depended on the availability of water and the rice variety. RD4-1-1 IAA promoted the germination and growth of rice seedlings according to most measured characteristics, but the effective concentration levels differed with water deficiency in RD31 and RD41 varieties. In particular, the appropriate concentration of bacterial IAA was lower and was in a narrower range when applied to plants in soil compared with that required when IAA was used in plants cultured on medium. Originality/ Value: This study is one of few studies to report the effects of appropriate concentrations of microorganism-produced plant hormones on rice growth under water-deficient conditions.