A field experiment was conducted to investigate the effect of GA3 and NAA on growth, biochemical function, yield attributes and yield of six boro rice varieties during February-May, 2013. The tested rice varieties were BR-2, Poshusail, Jirasail, BRRI dhan28, Lafaya and Nerica-4 and the treatments were Gibberelic acid (GA3)-H1 and Napthelene acetic acid (NAA)-H2 used as plant growth regulators (@100 ppm) sprayed at two times especially vegetative and pre-flowering stages, as well as water was applied as control (H0). Morphological parameters were significant due to application of NAA, maximum plant height (136 cm) at Lafaya and the number of tillers plant-1 (17.67) was found in BRRI dhan28 applied through 100 ppm NAA. The phyto-chemicals, on which grain yield mostly depends on it, particularly protein, proline and chlorophyll content in flag leaves were greatly affected by the application of NAA in comparison to GA3. Yield attributes viz. number of panicles hill-1, percentage of filled grains, 1000-grain weight, grain length and width, grain yield, straw yield, biological yield and harvest index were increased in all the selected rice varieties in both 100 ppm GA3 and NAA. Maximum yield was found in BRRI dhan28 (7.61 tha-1) through application of 100 ppm NAA. Finally it may be concluded that the stimulation rate of NAA was significantly better than the GA3 in response to growth, phyto-chemical function and yield contributing traits.
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