The Effect of Ascorbic Acid Foliar Application on the Ecophysiological Characteristics of Catharanthus roseus L. Under Water Deficit Stress

Water is one of the most important environmental factors that regulate plant growth and development, and water deficit is considered the most important restricted factor for plant products, in that several chemical materials have been used to reduce the harmful effects of water deficit. One of these compounds is ascorbic acid and it has antioxidant effects in plants. For this purpose, a factorial pot experiment in the form of a completely randomized design with three replications was conducted to investigate the effect of water deficit on the morphological and physiological characteristics of Catharanthus roseus (Cape periwinkle) under ascorbic acid foliar spraying in 2019. The test factors include: Drought stress (I) at 4 levels based on field capacity (FC): 1) Control (no stress) (I1) Irrigation at 100% FC, 2) Mild stress (I2) Irrigation at 75% FC; 3) Medium stress (I3) Irrigation at 50% FC; and 4) Severe stress (I4) Irrigation at 25% FC; foliar application of ascorbic acid was at 4 levels: 0, 25, 50, 100 mM. The seeds of C. roseus were sown in a 50% field soil +30% peat + 20% perlite substrate. The obtained results showed that the concentration of chlorophyll a and carotenoids, leaf soluble sugar, proline amount and catalase enzyme activity increased with increasing severity of water deficit, but the morphological characteristics of root and shoot dry weight decreased. Application levels of ascorbic acid led to the improvement of the measured traits, and in most of the traits, the 50 mM level was significantly superior to other levels. According to the obtained results, it is recommended to use ascorbic acid to improve the growth of plants such as C. roseus under drought stress.