Effect of light intensity and ascorbic acid on some morphological and physiological characteristics of Zinnia elegans L.

The aim of this study was to investigate the effect of different light intensity and ascorbic acid on the growth and flowering of Zinnia elegans L. The experiment was laid out as split plot based on a completely randomized design with three replications. The main factor was light intensity with three levels (600, 1200 and 1800 μmol m-2 s-1) using shade net and sub-plot was weeky foliar spray of ascorbic acid with three concentrations (0, 1, 2 mM). Results showed that as light intensity decreased, plant height, leaf area and spatial leaf area and flower diameter were increased and root length and volume, fresh and dry weight of leaf, stem and root, stem diameter, leaf number, electrolyte leakage and malondialdehyde increased. Flower diameter and flower fresh and dry weight, were higher in plants grown under 1200 μmol m-2 s-1 light intensity compared with those in 600 and 1800 μmol m-2 s-1. Also, with decreasing light intensity, flowering delayed, while, flower longevity increased. Moreover application of AsA increased plant height, root length, leaf fresh and dry weight and electrolyte leakage and reduced leaf area, root volume, stem fresh and dry weight, root dry weight, time of full flower opening and flower diameter. Overall, the results of this study showed that Z. elegans could be grown under full sunlight conditions, however, its growth and flowering quality were higher under 1200 μmol m-2 s-1. Therefore, it is possible to grow it under semi-shading conditions.