Influence of JA and CPPU on Growth, Yield and á- Amylase Activity in Potato Plant (Solanum tuberosum L.)

Field experiment was carried out in the Experimental Farm, Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima, Kalubia governorate, Egypt, to investigate the influences of bioregulators; Jasmonic acid (JA) at 5 and 10 ppm and N-(2-chloro-4-pyridyl)-Nʹ-phenylurea (CPPU) at 10 and 20 ppm and their combinations on potato (Solanum tuberosum L.) plant growth, yield and a- amylase activity during the two successive seasons of 2007 & 2008. Bioregulators were applied as foliar spray at 55 and 75 days after planting. Application of CPPU(10 and 20 ppm) and the combination of CPPU at 20 ppm with JA at 5 and 10 ppm showed an improvement in plant growth as indicated by plant height, leaves number, branches number, plant fresh and dry weights. Application of CPPU and its combinations with JA significantly improved tubers number, tuber size, tubers weight/ plant and yield ton/fed comparing with control plants. CPPU at 20 ppm + JA at 5 ppm and CPPU at 20 ppm gave the best results of tubers number, size and the yield. These positive effects of CPPU at 20 ppm and its combination with JA at 5 ppm were correlated with significant increase in total chlorophylls in leaves and phenols, total soluble sugars and total soluble carbohydrates in tuber tissues. An enhancement in total soluble carbohydrates and a amylase activity at harvest and 2 weeks later followed by reduction in these measurements at 4 weeks after harvest were observed by CPPU at 10 and 20 ppm. Excluding JA, all combination treatments showed positive increase in total carbohydrates and a amylase activity at harvest, 2 and 4 weeks after harvest. While plants treated with JA showed significant increase in phenols at harvest and a- amylase activity at 4 weeks after harvest