The elongation of mesocotyl and coleoptile plays important roles in the seedling emergence and stand establishment of dry direct-seeded rice. Experiments were carried out to elucidate the effects of seed-presoaking treatments of GA3 and some inorganic salts on the mesocotyl, and coleoptile elongation of rice. Seed-soaked GA3 promoted the elongation of mesocotyl, but little effect on the coleoptile elongation. The stimulation effects of GA3 were found to be enhanced by addition of CaCl2 However, the sole treatment of CaCl2 showed no stimulating effect on the mesocotyl and coleoptile elongation. Mesocotyl elongation was most prominent in the combined treatments of 50ppm GA3 with 100 mM CaCl2 . The synergistic effects of GA3 and CaCl2 on mesocotyl elongation varied with varietal groups. The stimulating effects of GA3 were enhanced significantly by the addition of CaCl2 in japonica varieties, Dongjinbyeo, Ilpumbyeo and Milyang 95, and tall indica variety, Labelle, but not in semidwarf Tongil type varieties, Tongilbyeo, Milyang 23, and Nampungbyeo, and semi-dwarf indica, Short Labelle. The promoting effects of GA3 on the mesocotyl elongation were decreased in proportion to the lowered osmotic potential by PEG 6000 on the contrary to CaCl2 This implies that the synergistic effects of CaCl2 with GA3 on mesocotyl elongation was not caused by osmotic potential lowered by CaCl2 addition but by the salt itself. Salts such as Ca(NO3 )2 , MgCl2 BaCl2 , NaCl, KCl and KNO3 showed the synergistic effects with GA3 on mesocotyl elongation as well. The degree of synergistic effects showed no differences among salts tested, implying that there is no specificity of ions constituting the salts.

• Taeg Su Nam
• Byun Woo Lee