Effect of low temperature hardening and growth hormone on growth and yield of summer rice (Oryza sativa L.)

An experiment was conducted in the farmers' field at Jorhat during the year 2004-05 (Nov. to May) with an objective to study the effect of low temperature hardening and growth regulator to overcome the cold stress effect on growth and yield attributing character of summer rice. For the experiment four summer rice cultivars viz., Jyotiprasad, Bishnuprasad, Joymoti and Kolaboro were selected. Four different treatments were given to the seedlings before transplanting. The first set was kept as control (T(1)), second set was given 4 degrees C cold hardening treatment in light for 48 h (T(2)), third set was given GA(3)-10 ppm treatment five days before transplanting (T(3)) and fourth set was given ABA-10 ppm treatment five days before transplanting (T(4)). Treatments were replicated four times in a split plot design. Forty days old seedlings of these varieties were transplanted in the field. Samples were collected during tillering and panicle initiation stage for various morphological, physiological and bio-chemical analyses. Parameters related to yield development were recorded at harvest stage of the crop. Various morphological and physiological parameters viz., plant height, tiller number, leaf number, leaf area, relative leaf water content, leaf chlorophyll, nitrogen, phosphorus and potash content of shoot at harvest were significantly influenced by the treatments. Seedlings treated with GA(3), exhibited better growth and plant vigour in comparison to control. Bio-chemical parameters viz., leaf proline content and total soluble sugar in stem also recorded significant increase due to GA(3), ABA and 4 degrees C hardening treatment. Yield attributing parameters such as panicle length, grains per panicle and sterility percentage were also found to be influenced significantly. From the above experiment it can be concluded that the adverse effect of low temperature on growth and development of summer rice can be reduced with suitable cold hardening treatments. Among the different treatments, GA(3) was found to be most suitable in terms of growth and yield in summer rice.