Physiological studies on the foehn tolerance of rice (Oryza sativa L.)

In this paper we investigated water status and chlorophyll content of tolerant and sensitive rice varieties after being subjected to dry wind treatment using a wind tunnel. Two rice varieties, Naepung-byeo (NP) as the tolerant variety and Ilabong (IB) as the sensitive variety, were grown in 1/1250a pots containing paddy soil. The water potential of the leaves and panicles, relative water content, and chlorophyll content were measured in each plant exposed to 3 hours of dry wind treatment 4 days after the emergence of panicles. The water potential of the panicles sharply decreased after the wind treatment. The water potential of the panicles in NP fell to -0.75 MPa at the end of the treatment as compared to -0.25 MPa before wind treatment, whereas, IB showed more severe change, from -0.34 MPa to -1.53 MPa, when treated by dry wind. The decrease in water potential of the panicles in NP was smaller than that of IB 2 hours after the treatment, and the recovery of panicle water potential was observed 6 hours after treatment. There was no significant difference in leaf water potential between NP and IB in this experiment. A similar trend was also observed in the relative water content. The relative water content of panicles under dry wind treatment decreased over time. The water content in the panicle was higher in NP than IB 2 hours after wind treatment. Six hours after treatment, the relative water content of IB panicles was only 22% with a nearly white panicle. Chlorophyll content also showed similar results as water potential and relative water content. These results indicate that the changes in the susceptibility to dry wind treatment reflect only on the panicle, as white panicle, and the NP variety has some tolerance mechanism in the panicle; therefore, damaged panicles recover over time.