Ascertain the Effect of PEG and Exogenous ABA on Rice Growth at Germination Stage and Their Contribution to Selecting Drought Tolerant Genotypes
In this study, the effect of exogenous ABA on radicle and plumule growth at germination stage was investigated, compared with PEG osmotic stress culture condition and the consistency between genotypic variation in exogenous ABA and PEG sensitivity at germination stage and in water deficit treatment at reproductive stage in the field was evaluated. Fifteen rice ( Oryza sativa L.) cultivars with different drought resistant ability were studied, 7.8x10<sup>-6</sup> mol L<sup>-1</sup> ABA and 30% PEG1500 (-1.1 MPa) were used to culture the germinated seeds for 5 days and the length, fresh and dry weight of radicle and plumule were measured and compared with normal condition (distilled water). In the field water stress experiment, drip irrigation was served for all plots every other day and water was discontinued for 14 days when the flag leaf reached stage 0 for the main stems in the plot. In this study, both PEG and ABA applied could inhibit the growth of plumule and radicle and significant difference existed among genotypes in the reduction rate of plumule and radicle. While for most of the tested genotypes, the response to ABA was similar to PEG and water stress in the field as well, which indicated the genotypes variation and ranking for the treatment with ABA based on the reduction rate of radicle and plumule growth parameters and with PEG based on reduction rate of plumule growth were rather similar to the same genotypes in field water deficit experiment based on the yield reduction rate. So exogenous ABA at germination stage could be and even more effective compared with PEG to quantify the drought resistance among genotypes in rice.