Effects of potassium on plant development, physiological characteristics and flower quality in zinnia

Zinnia is an ornamental plant used outdoors as a bedding flower, increasing in importance in the world and our country. This study aimed to determine the optimum potassium concentration to obtain high-quality plants in zinnia. For this purpose, the effects of potassium concentrations on the morphological, quality and physiological properties of zinnia plants were investigated in the study. In the study, five different potassium (K2SO4) concentrations (0, 100, 200, 300 and 400 mg l-1) were applied to two different zinnia (Zinnia elegans L.) cultivars (Zesty Fuchsia and Dreamland Red). During the experimental period, changes in plant height, stem length, number of branches, number of leaf pairs and leaf colours were determined at 10-day intervals. In detailed examinations at the end of the experiment, shoot and root biomass (fresh and dry weights), root/shoot ratio, root length, stem diameter, leaf dimensions (width, length and width/length ratio), capitulum characteristics (diameter, height and number) and the duration for the first flowering were identified. Besides, within the scope of physiological evaluations made at the end of the experiment, leaf pigment concentrations (chlorophyll-a, chlorophyll-b and total chlorophyll and carotenoids), leaf relative water content and ion leakage were determined. The zinnia varieties in the study presented a range of performance spectra with differences against high and low doses of potassium applications. While potassium treatments generally supported plant development, increasing the potassium dose to 400 mg l-1 negatively affected plant height, stem length, shoot biomass, leaf sizes and physiological parameters. At the end of the study, 200-300 mg l-1 K were determined as the effective doses for zinnia plants. As a result, with the study, with the optimum level of potassium treatment, some outputs were provided to obtain zinnia plants with high yield, quality and superior appearance for environmental designs.