Abstract
In the present study two species were selected based on their highest presence values to study the response to the severe drought
conditions in desert: these were Zilla spinosa and Leptadenia pyrotechnica. The results showed that soil water content and organic matter of
Wadi El-Assiuty were very low over the study period. The estimated pH values in the soil solution at the different studied stands tended to
be slight alkaline. Total soluble salts were generally higher during summer versus winter. The water content in the studied plants increased
significantly during summer. The selected species increased their content of chlorophyll a and b in summer. The stability index of
chlorophyll a and b was significantly higher in summer than that estimated in winter. Calcium and magnesium were accumulated in
considerable amounts. Ca+2 was the main accumulated cation whereas its concentration were higher than magnesium. Z. spinosa
accumulated more sulphates in summer than in winter. Phosphates appeared in low amounts in all the investigated plants. In L. pyrotechnica
tissue, Na+ concentration correlated negatively with those found in soil during summer. In winter Na+ and SO4 correlated positively and K+
correlated negatively in Z. spinosa. The studied species showed slightly increase in soluble sugars accumulation. Soluble protein content in Z.
spinosa and L. pyrotechnica decreased significantly during winter season. Amino acids content was low and varied between the two
investigated species. It seemed that the Z. spinosa is better adapted than L. pyrotechnica to drought conditions, prevailing in the area under
study. This judgement can be concluded by the average metabolic potentiality in the species, whereas soluble metabolites (soluble sugars
and soluble proteins) were relatively much higher than in the case of L. pyrotechnica.