Direct seeding has some advantages compared to transplanting system in rice, however there are some constraints need to be addressed. One constraint generally faced in the wet seeded rice is poor stand establishment. The experiment was conducted to improve seedling establishment by using selected growth regulators. Seeds of four rice cultivars, i.e. Memberamo, Widas, MR 84, and MR 219 were treated with GA3 of 25, 50, and 100 mg 1-1, and IBA (indole-3 butyric acid) of 10, 20, and 40 mg l-1.
Results showed that cultivar response to was similar in all parameters observed, however the GA3 response of cultivars to IBA was different at the initial stage. In Indonesian cultivars (Memberamo and Widas), shoot length of IBA treated seedlings was comparable to the control, but the IBA treated seedlings of Malaysian cultivars (MR 84 and MR 219) had slightly shorter shoots compared to the control. GA3 as seed treatment induced favorable early emergence and shoot growth in the initial stage, but the shoots were etiolated and resulted in susceptible to lodging even in the vegetative stage.
In comparison, exogenous application of IBA resulted in high number of adventitious roots contributing towards better establishment of seedling with broader and greener leaves. The growth regulator was lost its effect by 2 or 3 weeks after sowing. All IBA concentrations also did not show any sig- nificant differences on growth parameters or have any detrimental effect on grain yield in all cultivar tested. IBA 10 mg l-1 was sufficient in providing the required improvement in the rice seedlings.