Impact of Water Stress on Water Relationships, Photosynthetic Pigments and Adaptability of Haloxylon persicum Bunge (Alghada) Growing at Alghada Sanctuary in Uniza,Kingdom of Saudi Arabia

摘要

Water is one of the most important environmental factors that limits plant growth, but there are many desert plant species can withstand the extreme desert conditions prevailing in KSA. One of these plants is Alghada (Haloxylon persicum Bunge) trees,which is growing in Khobeeba desert that is designed as a sanctuary for Alghada in Uniza where lots of alghada trees are growing. This study was conducted to study the effect of drought on water relations and photosynthetic pigments of Alghada plant thatgrown in two sites, sand plains and sand dunes. The obtained results showed significant differences between soil water contents in both locations. The soil humidity values of sand plains were extremely higher than that of sand dunes. These differences may be due to decline in the dunes water flow and availability. There were significant differences in the mineral contents within soil in both sites. This difference may be due to the impact of different terrains. As shown by chemical analysis of both locations, soil in both locations was alkaline and was poor in organic matter content. There were significant difference in the average of the annual moisture content and succulence of plant samples in both sites. In sand dunes, plants were developing morethan other species that are developing on the plains desert. The results indicate also that there were significant differences between plants grown in both locations concerning their content of chlorophyll a. Chlorophyll a content in those plants grown on sand dunes was higher than plants grown on plain desert. On the other hand, there were no significant differences in chlorophyll b content between plants grown on both locations. In both locations, chlorophyll concentration increased in the rainy seasons and decreased in the dry season. There were no significant differences in the annual average content of carotenoids between plants grown in both locations, while significant differences between the average of the content of carotenoids were found in both rainy and dry seasons. The maximum values were recorded in rainy seasons, while the minimum values were recorded in dry seasons.