ELONGATION RESPONSE OF IR-36 AND RD-19 RICE CULTIVARS TO VARIATION IN SITE OF NAPHTHALIC ANHYDRIDE AND THIOBENCARB APPLICATION

Abstract

The effect of differential application of naphthalic anhydride or NA (1, 8-naphthalic anhydride) and thiobencarb (S-4-chlorobenzyl diethylthiocarbamate) in IR-36 and RD-19 rice seedlings was determined in pot trials under laboratory conditions. The two cultivars responded similarly to NA or thiobencarb treatment in terms of inhibited root growth when the site of application was varied. However, IR-36 cultivar exhibited greater degree of inhibition than RD-19. The effective treatment sites were the plot and mesocotyl for NA; and the root, mesocotyl and coleoptile for thiobencarb. Regardless of the site of treatment, nearly all treatments inhibited root elongation, but not shoot growth. The main target site of NA and thiobencarb appeared to be in the root.