Effect of Various Intensities of Drought Stress on δ¹³C Variation among Plant Organs in Rice: Comparison of Two Cultivars

Abstract

The δ 13 C value is widely used to assess the effects of drought on water status in plants. However, there is little information regarding the δ 13 C signature in different organs of rice. We conducted a field study to examine whether the δ 13 C among different plant parts would be affected by the intensities of drought, and to evaluate genotypic variation in δ 13 C fluctuation among plant parts affected by drought intensities. Two cultivars, “Nipponbare” ( Oryzasativa ssp. japonica ) and “Kasalath” ( O. sativa ssp. indica ), were grown in the field with a line-source sprinkler system. The δ 13 C values of panicles, flag leaves, straws, culms, and roots were measured from plant samples. The δ 13 C value increased as drought stress increased, especially in the panicles and roots. “Nipponbare” showed higher values of δ 13 C than “Kasalath” under the well-watered and mild drought stress conditions, but there was no significant difference between the genotypes in the δ 13 C value under the severe drought stress condition. The variation in δ 13 C value among different plant parts was also increased with increasing drought stress. In contrast, these variations were small under well-watered conditions. Furthermore, there was much greater variation in the δ 13 C value among different plant parts in “Kasalath” than in “Nipponbare” when the plants were grown under drought stress conditions. A significant negative relationship was observed between the δ 13 C value of panicles and shoot dry matter production, suggesting that the δ 13 C value of panicles may be the best indicator of plant water status in rice.