Growth and Anatomical Response of Gogo Rice ( Oryza sativa L.) var. Inpago Unsoed 1 to Paclobutrazol Application

Due to its capability of growing in a dry land, growth improvement of gogo rice plant is an alternative way to increase rice production. The plant is a 100 cm tall plant that requires long lifespan, and easily bends. Paclobutrazol, a retardant capable of inhibiting cell elongation and subapical internode elongation, can be used to control the plant height by inhibiting its growth. The substance might also increase the chlorophyll content, and trigger the plant to be resistant to bacteria and mold. Inpago Unsoed 1 was used in this research because it was highly productive, tolerant to drying and resistant to blast disease. The purposes of this research were to obtain the appropriate height of the gogo rice plant, and to understand the anatomical response of the plant to the paclobutrazol application. Experiments were performed based on Randomized Completely Design with factorial. The main factors were four paclobutrazol concentrations (0, 100, 200, and 300 ppm). The second factors were paclobutrazol application times (three, four, and five weeks after planting). The variables observed were plant height, leaf width, stomata density, stomata size, stem diameter and thickness of stem supporting tissue. Data were analyzed by Analysis of Variance continued with LSD test. The results showed a highly significant effect of the interaction between paclobutrazol concentration and time application on plant height. The treatment demonstrated optimum plant hight was the combination of 100 ppm of paclobutrazol applied at four weeks after planting. There was an interaction between paclobutrazol concentration and applied time on stem diameter, stomata number in lower epidermis of the leaf and leaf width. However, there was no significant effect of paclobutrazol observed on stomata size. The significant effect also observed on an interaction between paclobutrazol concentration and applied time on supporting tissues thickness. The greatest stem diameter was observed on 200 ppm paclobutrazol applied four weeks after planting. The number of stomata (normally 11 stomata/mm 2 leaf) increased in average to 27.7 stomata/mm 2 leaf on plant treated with 200 ppm at five weeks application of paclobutrazol. The widest leaf observed on 200 ppm applied at three weeks after planting, and reduced on the higher application of paclobutrazol. The thickest supporting tissue on the stem was observed on 200 ppm paclobutrazol applied at three weeks after planting, which was 30.83 µm. Triani Hardiyati Iman Budisantoso Siti Samiyarsih