Even O90 at 40 ppm in 1% (v/v) lactic acid was only weakly stimulatory. Thus, these results are the opposite to that previously reported that chitosan could both increase the tiller number and dry matter of the ‘Suphanburi1’ rice cultivar and enhance the ‘LPT123’ rice cultivar growth , albeit during drought stress of LPT123 which was not evaluated here for the ‘Pathumthani1’ cultivar.