Effects of sodium azide (NaN3) and cytokininon vegetative growth and yield of black rice plant (Oryza sativa L. ‘Cempo Ireng’)

Abstract

Oryza sativa L. ’Cempo Ireng’ is one of the black rice cultivars grown in the area of Sleman Regency, Yogyakarta, Indonesia. Black rice is known to contain a high nutrient, but has a relatively long harvest time (5-6 months) and low productivity. One effort to improve agronomic traits is by artificial induction of mutation using sodium azide (NaN3), whereas external application of cytokinin may also increase the growth and yield of black rice plant. The aims of this research were to evaluate the effect of the sodium azide on vegetative growth of black rice plant, and to determine the best concentration of cytokinin for optimizing vegetative growth of black rice plant. This research was held at the Green House, Laboratory of Plant Physiology, Biology Faculty, Universitas Gadjah Mada. This research was designed in Randomized Block Design with two factorial treatments. The first factor was sodium azide (NaN3) application which consists of three different concentrations including 0, 1.5 and 2.5 mM, and the second factor was cytokinin application which consists of three different concentrations namely 0, 25 and 50 ppm. Seeds of black rice were soaked in sodium azide for 18 hours, and cytokinin was applied twice at the age of 1 and 2 months after planting. Growth and development parameters observed were percentage of seed germination, plant height, number of leaf, leaf area, chlorophyll content, activity of nitrate reductase, stem and leaf anatomy. The data were analyzed with ANOVA at P = 5% and followed by Duncan’s Multiple Range Test (DMRT) at 95% significance level. The results showed that soaking of black rice seeds in sodium azide can slow germination, reduce the percentage of seed germination and plant height. Combination of sodium azide and cytokinin persisted the number of leaves by delaying senescence, increased chlorophyll content, nitrate reductase activity, the number of stomata, thickness of leaves and stems, but reduced the length of the stem and leaf epidermal cells. Plants treated with 2.5 mM of sodium azide combined with cytokinin of 25 ppm or 50 ppm showed a better vegetative growth and a slight increased in yield compared to the control.