Shoot and Root Growth of Rice (Oryza sativa) in Response to V-100291

Greenhouse studies were initiated in 2001 to evaluate the effect of V-10029 applications on shoot and root growth of rice cultivars. V-10029 applications did not affect the shoot and root weight or shoot–root ratio of Cocodrie. Tolerance of Bengal was less than that of Cocodrie and was growth stage dependent. V-10029 treatments at the one- to two-leaf rice growth stage reduced shoot growth but had no effect on root, resulting in a lower shoot–root ratio compared with that of the nontreated 1 wk after treatment (WAT). At 2 and 3 WAT, both shoot and root growth were reduced by V-10029, with shoot–root ratio being greater than that of the nontreated, indicating a greater inhibition of roots than of shoots. V-10029 treatments at the two- to three-leaf rice growth stage reduced both shoot and root growth of Bengal across all three sampling dates. V-10029 treatments at the three- to four-leaf rice growth stage did not affect shoot growth but reduced root growth 2 and 3 WAT with no difference in shoot–root ratio. There was no difference in shoot and root weight or shoot–root ratio between the propanil comparison treatment and the nontreated. These results indicate that rice cultivars may differ in their tolerance to V-10029 and tolerance may be growth stage dependent.Nomenclature: V-10029, sodium 2,6-bis[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoate; propanil; rice, Oryza sativa L. ‘Cocodrie’, ‘Bengal’.Additional index words: Herbicide tolerance, shoot–root ratio.Abbreviations: ALS, acetolactate synthase; WAT, weeks after treatment.