Effects of drought stress and superabsorbent polymer on morpho-physiological and biochemical traits of Caper (Capparis spinosa L.)

Capparis spinosa, commonly known as caper bush, is native to certain hostile growing conditions including sandy or gravelly soils, rocky hillsides, cliffs, stone walls and rock crevices in Mediterranean coastal regions. Caper plant is used for the prevention of soil erosion in sloppy areas. Synthetic superabsorbent polymer was developed as a soil conditioner to heighten plant establishment and growth in drought-prone growing area. During growing seasons of 2016-2017, the effects of soil amendment with the superabsorbent Polymer A200 in four levels (S1= 0, S2= 75, S3= 150 and S4= 225 g) were investigated for each caper plant, considering three levels of irrigation (I1=0, I2= One irrigation per month and I3= one irrigation every two months) on the physical properties of the soil as well as their physiological parameters (chlorophyll a, b and total chlorophyll, carotenoid, Tss, electrolyte leakage) and plant height, yield per hectare, WUE, Soil moister, RWC and leaf area of an established caper plant under drying conditions. Analyses of variance showed that the interaction effects of treatments were significant (p<0.01) in all the studied traits. The results showed that water stress significantly decreased the height of a plant, yield per hectare, WUE, Soil moister, RWC, leaf area, total Chlorophylla, Carotenoid and electrolyte leakage, whereas the application of superabsorbent polymer compensated for the negative effect of drought stress, especially in high rates of polymer application (150 g), where the maximum effect was attained for all the studied traits. These findings strongly suggested that the irrigation intervals of caper can lead to an increase in the application of the superabsorbent polymer.