Assessing effect of drought stress and ascorbic acid application on some growth and bio-chemical parameters of marigold (Calendula officinalis L)

In order to evaluate the effect of various levels of drought stress and foliar-application of ascorbic acid on some growth and biochemical parameters of marigold (Calendula officinalis L), an experiment was conducted with a factorial arrangement based on completely randomized design with three replications in Greenhouse of Bardsir Agricultural Faculty, Shahid Bahonar University in 2014. The experimental treatments were different levels of drought stress (irrigation based on: 1- filed capacity (control), 2- 75%, 3- 50% and 4- 25% of filed capacity) and foliar-application of ascorbic acid (0, 1 and 10 mM). The results showed that the growth parameters (fresh and dry weight of plant, leaf area index and plant height), proline and soluble sugars showed significant different based on simple and interaction effects of the both treatments. But, chlorophyll a and b contents were only affected by irrigation treatments. The carotenoid contents showed significant difference by any the treatments. Fresh and dry weight of plant, leaf area index and plant height were significantly decreased with increased drought stress. However, increase in drought stress caused to increasing proline, soluble sugar and chlorophyll a and b contents. The results showed that in all drought treatments, foliar-application of ascorbic acid had a positive role on improving growth parameters and increasing contents of proline and soluble sugar, particularly in 10 mM application. Therefore, it seems that ascorbic acid can be considered as an antioxidant and plant growth regulator for mitigating the drought stress impacts on marigold planting.