INCREASED NUTRIENT SOLUTION CONCENTRATION DURING EARLY FRUIT DEVELOPMENT STAGES ENHANCES PUNGENCY AND PHENYLALANINE AMMONIA-LYASE ACTIVITY IN HOT CHILI (CAPSICUM ANNUUM L.)

Abstract

The effect of increased nutrient concentration during different fruit development stages on the yield, pun-gency and PAL enzyme activity in hot chili cv. ’Super hot’ was studied during August 2009-January 2010. The seedlings were planted in plastic containers containing 20 L of coconut-coir-dust substrate placed inside a plastic-roofed net house and received Resh’s Tropical Dry Summer nutrient solution at a constant concentration (measured by Electrical Conductivity, EC) of 1.2 mS cm^-1 during the vegetative stage and 2.4 mS cm^-1 during the first week of blooming. Then, they were divided into treatments: Treatment 1 (control), plants continuously received nutrient solution at a constant concentration of 2.4 mS cm^-1 until end of harvest, while treatments 2-6 received nutrient solution with a change in concentration from EC 2.4 to 3.6 mS cm^-1 at 1, 2, 3, 4 and 5 weeks after the week of first bloom, respectively. The results showed that the increase in nutrient concentration at different fruit development stages did not significantly influence chili fruit characteristics and yield. However, the oleoresin, capsaicin, dihydrocapsaicin and capsaicinoid contents increased significantly when hot chili plants received the nutrient concentration increase at the 1st and 2nd week after first bloom. Phenylalanine ammonia lyase activity in the full-ripening fruits increased significantly when the nutrient solution concentration increase occurred at 1st and 2nd weeks after first bloom. The highest PAL activity of 827.48 mmole mg^-1 protein was recorded in full-ripened fruits, when the nutrient concentration increase occurred at the 2nd week after bloom."