Effect of long day and its interactions with gibberellic acid, sperimidine and CPPU on true potato seed (TPS) production

Abstract

Field experiments were conducted in Experimental farm, Faculty of Agriculture, Ain Shams university at Kalubia Governorate during the two successive seasons of 2005 and 2006 to investigate the influence of photoperiod, Long day (LD) and its interaction with bioregulators; 50 ppm gibberellic acid (GA3), 20 ppm (N-(2-chloro-4-pyridyl)-N’-phenylurea; common name = forchlorfenuron) (CPPU), 20 ppm spermidine (Spd) and their different combinations. Bioregulators were applied as foliar spray at 30, 50, and 70 days after planting. Three samples were taken at 40, 60 and 80 days after planting in addition to fruits and tubers yield. Plants exposed to LD (continuous light) showed an improvement in plant growth in the first and third samples as indicated by plant height, leaves number, fresh and dry weights as compared with control plants (exposed to nature day length). LD also increased inflorescences and flowers number. The interaction of LD with bioregulators showed higher values of plant growth, inflorescences and flowers production comparing with control and LD treated plants. LD did not significantly affect fruit and seed parameters. Application of GA3, CPPU, Spd, GA3+CPPU and GA3+Spd under LD significantly increase fruits number/plant. An increase in seeds number/plant and 100 seed weight were noticed by all bioregulators treatments except CPPU+Spd+LD. The best results in this regard were obtained by GA3 +Spd+LD. LD resulted in suppression of tubers yield as well as its interactions with GA3,GA3+Spd and GA3+CPPU+Spd. Total soluble carbohydrates and endogenous GA3 level were determined in relation to flower induction under different treatments. An enhancement in total soluble carbohydrates and the levels of endogenous GA3 were observed under LD treatments. These effects were more obvious by bioregulators. Maximum value of GA3 levels was obtained by GA3+Spd+LD.