EFFECT OF SALICYLIC ACID APPLICATION ON THE GROWTH AND ACTIVE CONSTITUENTS OF FENNEL PLANTS UNDER SALINITY STRESS CONDITIONS

Abstract

Nowadays, Egypt faces a problem in the amount of available irrigation water because the Egyptian water quota is fixed, thus the cornerstone of the current Egyptian strategy is increasing crop productivity from unit area with the lowest possible amount of irrigation water. So, a pots experiment was carried out at the Experimental Farm, Faculty of Agriculture, Menoufia University, Shebin El-Kom, Egypt (30.52oN and 30.99oE) during two successive growth winter seasons, i.e. 2013/2014 and 2014/2015 to study the effect of different rates of salicylic acid (SA), different salinity levels of irrigation water and their interactions on growth, yield and chemical compositions of fennel plants (Foeniculum vulgare, Mill.), variety of purple-bronze foliage grown on clayey-textured soil. SA was added as foliar applications at four rates namely 50, 100, 150 and 200 (mg/l) in addition to control treatment with SA-free water. The water used for irrigation (artificial water) has EC of 3, 5 and 7 (dS m-1) for W2, W3 and W4 respectively, beside Nile water (W1) which is characterized by EC of 0.37 dSm-1. The design of the experiment is a complete randomized block with three replicates. In two growing seasons, a vegetative growth characters, i.e. plant height (cm), number of main branches/plant and fresh weight of whole plant (g) as well as yield parameters, i.e. number of umbels/plant, fresh and dry weights of umbels/plant (g), weight of 100 fruits (g/plant) and fruit yield (g/plant), chemical composition together with volatile oil percentage, oil constituents, photosynthetic pigments, N, P, K and total carbohydrate contents were estimated of fennel plants. The obtained results indicated that, all vegetative growth characters and yield parameters were significantly reduced with increasing salinity levels of irrigation water, excluding those irrigated by W2 level, in which slight increments in all of studied criteria were induced. Also, chlorophyll a and b contents followed the same order, where the highest decrease in values was observed in plants irrigated by W4 level either individually or together with SA compared to control treatment. Contents (%) of N, P and K were reduced with increasing salinity levels. While carotenoids, volatile oil and total carbohydrate contents (%) were gradually increased with increasing salinity levels, especially in those irrigated by W3 level. Foliar spraying with different SA concentrations could have alleviated the harmful effect of salinity stress and was associated with high significant values in the most traits under study. Interactions betweensalinity levels of irrigation water and SA concentrations appeared to be the most effective on growth and yield parameters especially when fennel plants irrigated with W2 level and spraying with SA at 150 mg/l. Generally, the results of this study concluded that, under-irrigation by using saline water, salicylic acid should be used as foliar application especially at rate 150 mg/l to reduce the hazardous effects of irrigation water salinity on both quantity and quality of fennel plants.