VARIETAL DIFFERENCES AND GEOGRAPHICAL DIS TRIBUTIONS IN THE GROWTH OFMESOCOTYL AND INTERNODES OF RICE (ORYZA-SATIVA L) SEEDLINGS

The characteristics of internode elongation were investigated using 26 2 rice cultivars including 260 from IRRI's core collection and two rec ommended Japanese cultivars, Sasanishiki and Koshihikari. Sterilized b rown rice grains were planted on 0.8% agar medium under aseptic condit ion, and incubated in a growth chamber at 30 degrees C under total dar kness for 14 days. The lengths of mesocotyl (ML), first intermode (1IN ), second internode (2IN), third internode (3IN) and total length of i nternodes (ML + 1IN-2IN, TLI) were recorded. The frequency distributio n of the final length of ML and 1IN was nonsymmetric whereas that of t he 2IN and TLI was a nearly normal distribution. The mean length of ML , 1IN, 2IN, TLI, was 12.3 +/- 0.8 mm, 11.1 +/- 0.6 mm, 35.1 +/- 1.0 mm , 58.5 +/- 1.8 mm, respectively. Of all the cultivars, the LIN did not elongate in 22 and the 3IN did not elongate in 88. Cultivars having l onger TLI were hard to grow 3IN. The geographical distribution showed that there was wide variation in the length of the internodes of South west Asian cultivars:however, narrow variation was observed for East A sian cultivars. Correlation coefficients for ML vs 2IN, ML vs TLI, 1IN vs 2IN, 1IN vs TLI, 2IN vs TLI were positive and highly significant.