ECOLOGICAL DIVERSITY OF Ziziphus spina-christi (L.) WILLD. OF FOUR PROVENANCES IN SAUDI ARABIA: DIFFERENTIAL RESPONSES TO DROUGHT STRESS AND CHARACTERIZATION OF GROWTH, BIOMASS AND PROLINE CONTENTS

Abstract

In the present study, four provenances were studied and (i) soil parameters by localities, (ii) Morphology of fruits, seeds and leaves, (iii) Germination percentage under temperature and osmotic potential, (iv) Growth and biomass production under drought stress, (v) proline and total soluble sugars contents under drought stress were determined. The germination responses of seeds were determined over a wide range of constant temperatures (15 to 50 °C) and polyethylene glycol (PEG₆₀₀₀) solutions of different osmotic potentials (0 to −1,2 MPa). The effect of drought on several physiological parameters are studied by submitted plants to water deficit (10 and 20 days of withheld irrigation). Morphological study indicating a large-scale diversity among the provenances. Germination was inhibited by either an increase or decrease in temperature from the most suitable temperature found (40 °C). The highest germination percentages (95%) were obtained under control conditions without PEG, and increasing moisture stress progressively inhibited seed germination, which was less than 18 % at −1.2 MPa. The results showed that growth parameters and biomass production in leaves, stem and roots were not impacted under medium drought stress stress. The applied drought stresses increased the proline and soluble sugars contents of the plant. Cultivating Ziziphus spina-christi under drought or salt stresses could be a good alternative to valorize antioxidant molecules from this species in industrial applications.