Effect of salicylic acid on bioproductivity and drought tolerance potential of Marigold (Tagetes erecta)

Abstract

Marigold (Tagetes erecta L.) is famous for its medicinal and aesthetic values which put it among the top floriculture crops in the world. Drought stress negatively affects various physiological and biochemical mechanisms taking place in the marigold which leads to irreparable damage to cell organelles and consequently results in significant loss of flower yield. Various plant growth regulators are reported to have positive roles in the drought stress amelioration. However, there is a lack of work done focusing on the effect of salicylic acid (SA) application on marigold plant growth and drought tolerance. A series of rain-out shelter and a field experiments were conducted for this study. A local marigold variety Desi gainda/Gutta was used for all experiments. In the dose optimization experiment for SA seed priming, five treatments including no priming, hydro-priming, priming with SA @ 50, 100 and 150 mg L-1 were applied to marigold in the normal as well as drought stress conditions. From the above study, 100 mg L-1 proved optimum rate of SA for seed priming. In the same way, for the dose optimization of SA foliar application, the experimentation was repeated according to Experiment 1. There were two drought stress levels i.e. normal irrigation and drought. No spray, water spray, SA @ 50, 100 and 150 mg L-1 were the treatments used. Salicylic acid applied with 100 mg L-1 concentration performed the best and found optimum rate for foliar spray. In the next experiment, optimum method of SA application was determined. Six treatments including, no treatment, hydro-priming, priming with SA (optimum dose), water spray, SA foliar spray (optimum dose), SA priming plus SA foliar spray (optimized doses). Foliar spray of SA was found more viable method and suggested optimum method of SA application. In next experiment, the best time to apply SA was determined. Plants were grown till maturity and drought stress was imposed by skipping every alternate irrigation in pots. The treatments used included no spray, SA foliar spray (100 mg L-1) at vegetative, SA foliar spray (100 mg L-1) at reproductive growth stages of marigold and SA foliar spray (100 mg L-1) at both vegetative plus reproductive growth stages. Reproductive growth stage was found more responsive towards SA foliar spray using 100 mg L-1 rate. After that the results obtained from above mentioned studies were verified in the field. In the field conditions, drought stress was imposed by skipping every alternate irrigations to crop in experiment 5 and SA was sprayed by optimized dose, method and time, as from above indicated experiments, to marigold plants. Results suggested that drought stress seriously damaged the growth of marigold plant and SA foliar application improved growth and helped plants in increasing their yield during and without drought stress. Further, it was concluded that exogenous application of SA, not only increased bioproductivity of marigold plants but also ameliorated the negative impacts of drought stress by enhancing drought tolerance potential in plants.