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BACKGROUND AND OBJECTIVE: There are scarcity scientific reports on the response of medicinal plants to zinc nutrition, despite its remarkable role in growth, cell division, photosynthesis and tryptophan formation, which is involved auxin (IAA) synthesis. Therefore, further studies are required to understand the effects of zinc on one of these important plants, marigold plant. MATERIALS AND METHODS: For this, a greenhouse experiment was conducted to evaluate the promoting impacts of zinc-nutrition (0, 50, 75, 100 mg L-1) on marigold growth, plant height, branch number, herb and root fresh mass (FM), herb and root dry mass (DM), flowering attributes, inflorescence number/plant (IN), inflorescence diameter (ID), inflorescence (IW) weight (fresh and dry), days to first bud emergence, leaf relative water content (RWC) as well as some physiological responses, pigments, total carbohydrate, N, P, K, Zn contents of marigold plants. RESULTS: The results indicated that zinc-fertilizer at 100 mg L-1 was the superior treatment in improving the previous parameters relative to the other levels and control. Supplying Zn significantly enhanced growth parameters, flower attributes, RWC as well as nutrient contents of marigold leaves. Chlorophyll, carotenoids content and carbohydrates (%) were enhanced due to suppling Zn. Zn treatments raised the contents of N, P, K and Zn in leaves relative to unfertilized ones. A comparison of the usage treatments showed that the higher dose of Zn was better than the lower one or control but insignificant differences were observed between this treatment and the intermediate one (75 mg L-1) for some studies parameters. CONCLUSION: The obtained results suggest that exogenous application of Zn could be essentially for the nutrition program of marigold plants to provide plants by the optimum dose of Zn-fertilizer for improving the growth and, quantity and quality of inflorescence parameters.
Alamer et al. (Sun,) studied this question.