Effect of growth substances on the growth, rhizome yield and diosgenin content in Costus speciosus

Abstract

An experiment was conducted at the College of Horticulture, Vellanikkara to study the influence of ethrel (100, 200 and 300 ppm), 2, 4-D (10, 20 and 30 ppm) and MH (50, 100 and 150 ppm) on the growth, rhizome yield and diosgenin content in Costus speciosus. Plant height was significantly reduced by the three levels of ethrel (100, 200 and 300 ppm) and MH (50, 100 and 150 ppm) more evidently on the 110th and 140th day after planting. Ethrel 100 and 200 ppm and MH 50 ppm significantly increased the number of tillers per plant on the 110th and 140th day. Leaf production per tiller was significantly increased by 2, 4-D 10 ppm on the 80th day and was significantly reduced by ethrel 100 and 200 ppm on the 140th day after planting. The length, width and area of the leaves and the intermodal length of shoot was significantly reduced by ethrel treatments. Individual and total leaf area in general was significantly higher in plants treated with the two lower levels of 2, 4-D (10 and 20 ppm), on the stages observed. Ethrel, at the three levels tried, significantly increased the dry matter content of shoots. The shoot/rhizome ratio was reduced significantly by ethrel and MH. The girth of main rhizome was increased significantly by ethrel 100 and 200 ppm. The number of primary fingers was significantly increased by ethrel 100 and 200 ppm and 2, 4-D 10 and 20 ppm and its length was significantly increased by ethrel 200 ppm. The number of secondary finger was significantly higher in ethrel 100 and 200 ppm and MH 150 ppm treatments. Ethrel 200 ppm recorded the maximum yield of green and dry rhizomes. Significant increase in the yield of green rhizome was also given by ethrel 100 ppm and 2, 4-D 10 and 20 ppm. The diosgenin content of the rhizomes was maximum in 2, 4-D 10 ppm (1.83 per cent), but the yield of diosgenin per ha was maximum in ethrel 200 ppm. Significant increase in diosgenin yield was also obtained in ethrel 100 ppm, 2, 4-D 20 ppm and MH 50 ppm. The greatest return per ha was given by ethrel 200 ppm, followed by ethrel 100 ppm and 2, 4-D 10 ppm.