Lateral root formation in rice (Oryza sativa): promotion effect of jasmonic acid

The effect of JA on lateral root (LR) formation was tested using 2-day-old seedlings of IR8 rice (Oryza sativa L.). Results showed that JA in all concentrations (0.016-50 μmol/L) increased the number of LRs in the region of seminal root formed during and after the treatment (distal region), but had no effect (less than 2 μmol/L) or decreased (over 2 μmol/L) the number of LRs in the region already formed before treatment (basal region). On the other hand, the development of root hair in the distal region was inhibited, and even fully blocked by JA over 1 μmol/L. Both JAʹs effects on promoting LR formation and inhibiting root hair formation in the distal region could last at least 7 days subsequent to the removal of JA treatment. All these results indicated that JA might be one of the potent hormonal factors, other than auxin, involved in the regulation of LR formation.