مطالعه اثر تنش خشکی بر صفات فیزیولوژیک و عملکردی همیشه بهار (Calendula officinalis L.)

چکیده مقاله

As an important medicinal plant in some industries such as pharmaceutical industry, the antioxidant capacity of pot marigold (Calendula officinalis L.) in conferring drought stress, as well as physiological and yield-related traits were studied. A complete randomized block design with three replications was carried out in the research greenhouse of Birjand University during 2014, 2015. Four levels of drought stress (including 80, 60, 40 and 20 percent of the available soil water content) and two plant types (medicinal and ornamental) were considered in this study. According to the results, with increasing drought severity, APX activity decreased and SOD and CAT activity initially increased and then decreased. Over accumulation of reactive oxygen species along with inefficiency of the antioxidant system had possibly resulted in the impaired enzymatic antioxidant efficiency in the highest level of drought stress. Proline content increased along with increasing drought intensity, so that it was up to fourfold in the highest level of drought stress, compared to non-stressed control. Although proline is an antioxidant compound, no relationship was found between proline accumulation with antioxidant enzymes. Carotenoids, chlorophyll content and chlorophyll index all decrease, and MDA content increased with increasing drought intensity, as a result of damages to chloroplast membranes. Reduced photochemical efficiency of photosystem II was another consequence of intensified water deficit. Drought stress also negatively affected yield related traits, so that dry weight (27%), height (32%), number of lateral branches (33%) and flowers (50%) and flower yield (60%) decreased. We also found that medicinal pot marigold (824.3 kg.ha^-1) produced more flower than ornamental one (654.9 kg.ha^-1).  In conclusion, we found that enzymatic antioxidant system of pot marigold conferred a suitable ability to reduce adverse effects of drought-induced oxidative stress. Hence, increasing pot marigold’s antioxidant activity could result in increasing its physiological resistant to drought stress and consequently improves its yield components performance.