Ecophysiological responses of Calligonum polygonoides and Artemisia judaicaplants to severe desert aridity

Abstract

The present study, conducted in 2011 and 2012, deals with the response of Calligonum polygonoides and Artemisia judaica to the drought conditions in Wadi El-Assiuty and its tributary Wadi Habib in the middle part of the Eastern Desert of Egypt. Soil and plant samples were collected from 50 stands in the wet (winter) and dry (summer) seasons. In the selected plants chlorophyll (Chl a and b) contents as well as the Chl stability index tended to increase significantly during the summer season. Calcium and magnesium were accumulated in considerable amounts in the studied plants. Amounts of calcium accumulated were higher than those of magnesium. Phosphates appeared in the plants in low amounts and correlated positively with those found in the soil. The studied plants showed an increase in soluble sugars accumulation. Soluble protein content increased significantly during the winter season with a corresponding decrease in free amino acids. It is quite clear that Calligonum polygonoides plants were better adapted to drought conditions prevailing in the area under study than Artemisia judaica. This was judged by the average metabolic potentiality as soluble metabolites (soluble sugars and soluble proteins) are much higher in Calligonum than in Artemisia.

Adaptive responses of Aerva javanica Burm.f. Shult. to severe aridity in the Egyptian deserts

“…Osmoregulation is the easier way to overcome the external biotic and/or abiotic stresses where it depends on the accumulation of inorganic solutes. The absorption, excluding or extraction of the osmo-regulator inorganic ions such as potassium, sodium, calcium, magnesium and chlorides is very helpful for readjusting the osmotic gradient in stressed plants (Kamel, 2008;Sunkar, 2010;Sayed et al, 2013 andSalama et al, 2015). The second way depends on the accumulation of organic compatible solutes as soluble proteins, soluble sugars, and free amino acids.…”

“…javanica accumulated more SO 4 in summer than in winter. Plants tend to accumulate more sulfates in dry seasons or habitats to maintain their succulence and they needed for biosynthesis of amino acids that contain a thiol (-SH) group (Salama et al, 2015). Phosphates appeared in low amounts in A. javanica may be due to the rapid incorporation of phosphates into plant metabolism, or poverty of phosphates in the soil.…”

“…So, they accumulate the necessary amounts of organic solutes (SS > SP > TFAA) to maintain the cell turgidity in the live branches. On the other hand, in winter the biological activity will start again and the accumulated organic solutes will be used (Salama et al, 2015). Thus the studied species are frequently adapted against drought conditions prevailing in their habitats during summer season, by accumulation of considerable amounts of soluble sugars, soluble proteins and amino acids than in winter when the prevailing ecological conditions may be fairly more favorable for such plants.…”

Some aspects of drought resistance in Citrullus colocynthis L. in the Egyptian deserts

“…To overcome the soil water deficiency, the plants cells tend to readjust their osmotic potential to prevent water losses, that can be achieved by two adaptive strategies, the first one by accumulation of inorganic ions from the external, while the second one by synthesis of compatible solutes as soluble proteins, amino acids and soluble sugars acting as osmolytes (Serrano et al, 1999;Du Jinyou et al, 2004;Sunkar, 2010;Sayed et al, 2013 andSalama et al, 2015).…”

“…These results were consistent with what was found by Salama et al (2012) on Ochradenus baccatus in Wadi Qena. On the other hand, in winter the biological activity will start again and the accumulated organic solutes will be used (Salama et al, 2015).…”