Seasonal changes in nitrogen metabolites and Na+/K+ratio in some desert species

Abstract

Seasonal changes of nitrogen metabolites and Na + /K + ratio were detected in some wild species inhabiting the western desert of Egypt. Seasons, species and their interactions were important factors affecting the total free amino acids and soluble proteins at Dakhla oasis; however, species diversity is more effective variable in regulating such metabolites at Kharga region. Such plants may respond to their environment either by increasing their water binding molecules or by preventing the formation of amino acids into proteins. Some halophytes and xerophytes may adjust osmotically to stress by the contribution of nitrogen metabolites. On the other hand, Zygophyllum coccineum , the succulent plant, may adapt to environmental conditions through the accumulation of free amino acids. The correlation analysis between Na + /K + ratio with free amino acids, soluble proteins and water content in Balanites aegyptiaca, Salsola imbericata, Tamarix aphylla, Trichodesma africanum and Z. coccineum (Kharga) indicated such changes in ionic fraction or accumulating soluble organic compounds that presumably were osmotically active and contribute to osmotic adjustment. Positive correlation was also found between chlorophyll content with ionic and nitrogen metabolites. It is likely to suggest that Acacia nilotica, Suaeda monoica and Z. coccineum at Dakhla may have changed their soluble proteins or ionic ratio as a consequence of chlorophyll response to stress, while S. imbericata and T. aphylla may control cellular protein contents. On the other hand, the interaction of both nitrogen metabolites and ionic fraction may play an important role of osmoregulation in S. imbericata, Citrullus colocynthis and Z. coccineum at Kharga region.