Effects of restricted oxygen, nitric oxide, and mercuric chloride on the seed germination and early elongation growth of rice.

Germination and early elongation of rice after germination were investigated in anoxic air treatment, nitric oxide gas treatment, and six concentrations of mercuric chloride solutions to determine the effects of limited oxygen environment, nitric oxide, and inhibited water flux through cell membrane in 17℃. Anoxic air treatment affected germination of tested six varieties vern little. However root elongation rates were severely inhibited while shoot growth was affected less. Reductions in shoot and root elongations demonstrated genotypic variations. Nitric oxide delayed the germination of rice even though it didn't affect the final percent germination. Elongations of root and shoot were inhibited in nitric oxide treatment. The inhibitor effect of nitric oxide on the shoot elongation of rice was less severe, while nitric oxide completely inhibited the root emergence of rice. Concentrations of HgCl₂ greater than 300 μM dramatically reduced the rate and percentage of germination when compared to distilled water treatment. The reduced percent germination showed the greatest variation among rice varieties in 500 μM solution of mercuric chloride. Ansanbyeo, Jinheung, and Odaebyeo were affected less by HgCl₂, Nonganbyeo and Sangmibyeo were intermediate, and the germination of Andabyeo was greatly reduced by HgCl₂. Root elongation of germinated rice seedlings was more sensitive to oxygen deficits, nitric oxide, and HgCl₂ treatments than germination and shoot elongation. In conclusion, poor seedling establishment of rice sown in flooded paddy soils, in which the oxygen supply to the seeds is restricted, appears to the result of limited root elongation rate.