Effect of High Hydrostatic Pressure Treatment on Physiological Characteristics of Rice Plants (Oryza sativa L.)

Seeds of two rice (Oryza sativa L.) cultivars, Yuexiangzhan and Yuefengzhan, were soaked for 10 h, and then were treated by 75 MPa high hydrostatic pressure for 12 h. Germination rates decreased to 85.6% (Yuexiangzhan) and 83.4% (Yuefengzhan) relative to the untreated, and seedling rates were only 24.6% (Yuexiangzhan) and 21.9% (Yuefengzhan). Plant growth was inhibited in both treated cultivars during the early growth stage of seedling, but could exceed that of the contrast after sowing of 35 d. The seedlings of the treated and untreated were transplanted in the field after sowing of 35 d. Photosynthetic characteristics were compared between the treated and untreated during flag leaf development (55~130 d after sowing). The average values of net photosynthetic rate (Pn) and apparent quantum yield (AQY) in treated cultivars increased by 9.2% and 12.4% (Yuexiangzhan), 5.7% and 17.4% (Yuefengzhan), relative to the untreated, respectively. The total average photosynthetic pigment content was higher in both treated cultivars than their untreated during different growth stage. During leaf senescence, both Fv/Fm and pigment content decreased slowly or lately in two treated cultivars than the untreated. Consequently, the biomass and grain yield increased by 8%~27% and 7.6%~14% in both treated cultivars. Several mutated strains with different morphological and yield characteristics could be selected from treated rice plants. The results suggested that high hydrostatic pressure treatment is possible served as a new method of breeding in the future.