Background and objective: The drought-tolerant crop plants, including rice, are required for fulfilling food requirements when drought occurs in Indonesia. The response to drought stress in rice cultivars could be studied based on the morphological, anatomical and physiological characteristics. This study evaluated the drought tolerance based on the physiological characteristics at the vegetative phase in six rice cultivars cultivated in North Sulawesi, Indonesia.
Materials and methods: The Completely Randomized Design experiment was conducted in the greenhouse by using six rice cultivars (cv. Superwin, Sultan, Ciherang, Serayu, Cigeulis and IR 64) grown in the soil mixture at the vegetative phase. The treatments in this experiment were water deficit (without water for up to 22 days) and well-watered (watering until field capacity). The evaluated physiological characteristics consisted of leaf water content, leaf relative water content, concentrations of chlorophylls (total, a and b) at 0, 7, 14, 17 and 22 days after treatment.
Results: Withholding water for 22 days at the vegetative phase resulted in a decrease of water content and the increase of concentration of chlorophylls (total, a and b) in leaf. There were two categories of drought tolerance in rice observed in this study, i.e. semi tolerant for Cigeulis, Superwin, Serayu, IR 64, Sultan and non-tolerant for Ciherang.
Conclusion: Rice cv. Cigeulis, Superwin, Serayu, IR 64 and Sultan were semi tolerant, whereas cv. Ciherang was non-tolerant rice cultivar. Leaf water content was a potential physiological indicator for drought tolerance in rice.
Keywords: chlorophyll; drought; relative water content; vegetative; water content.