Response of Plant growth regulators on leaf photosynthetic pigments of pot marigold

Effect of gibberellic acid on marigold (Calendula Officinalis L.) was evaluated in a pot culture experiment. A factorial experiment based on completely randomized design including 12 treatments and four replications was carried out. Main factor was foliar application stages (first,second and third) and sub factor included different concentrations of GA3 (0, 50, 150 and 250mg L-1). Results showed that foliar application of GA3had positive effect on photosynthetic pigments. Effect of different concentrations of GA3on chlorophyll a was significant (p<0.01). Chlorophyll a content was enhanced by increase in GA3concentration up to 250 mg L-1 treatment of 250mg L-1 resulted in the production of 7.78µg/L-1 chlorophyll a, the index which was to some extent dropped in other concentrations. Different concentrations of GA3 had significant effect on chlorophyll b (p<0.01). Chlorophyll b was increased by increase in GA3concentration up to 250mgL-1. the highest rate of total chlorophyll content and total pigment in three times of application and one application of 250 mg L-1 was 14.6 and 15.4 µg/L-1 respectively; whereas the lowest chlorophyll and pigment content was observed in one foliar application of control treatment with mean value as 4.67 and 5.5 µg/L-1.