Morpho-physiological and phytochemical responses of basil (Ocimum basilicum L.) to toxic heavy metal cadmium

Abstract

Cadmium (Cd) is a particularly noteworthy metal that may change the secondary metabolism efficacy of pharmaceutical valuable plants. This study aimed to explore the influence of Cd (0, 25, 75, 100, and 150 µM) on the morpho-physiological traits, mineral contents, essential oil composition, and morphology of secretory glands in basil (Ocimum basilicum L.). The exposure to Cd reduced significantly shoot and root dry weight, shoot and root lengths, total chlorophyll, number, and length of secretory gland compared to control plants, while increased peroxidase activity, proline content, and number of stomata. Essential oil compositions were varied in the Cd-treated plants in a dose-dependent manner. The main compounds of the essential oil were Estragole followed by Linalool and Geranial which the highest percentages were observed in the plants treated with Cd 150 µM. The Cd-treated plants exhibited reductions in calcium (Ca) and iron (Fe) concentrations in both leaves and roots. Cd contents in roots and shoots progressively enhanced with increasing Cd concentrations In general, basil showed good tolerance to Cd stress, so that 50% reduction in shoot dry weight occurred in above 100 μm treatments, which can be related to physiological reactions such as increased antioxidant activity, proline content, number of leaves stomata, and changes in other morpho-physiological factors.