The Bases Of Gizzu Herbs Adaptation To Water limited Invironment In North Darfur

Abstract

A field survey was carried out in the Gizzu district, which lies in the Northern Darfur State, to determine species composition and distribution of Gizzu flora. The morphological characteristics of a selected group of herbs and grasses in the Gizzu area and their relation to water-limited adaptation were investigated. In addiition, laboratory and glass house experiments were conducted to determine the effect of temperature and water stress on the perfomance of two species of Blepharis, namely B .linariifolia and B. ciliaris. The morphological, physiological and anatomical bases of adaptation were discussed. The results idicated that the flora of the Gizzu district is composed of four types of vegetation namely; permanent trees and shrubs, perennial herbs and grasses, succulent and ephemeral (annual) plants. The majority of Gizzu herbs and grasses were commonly observed on light soils ( sandy soil ) compared to the relatively heavy soils ( Wadi soil ). The distribution of the vegetation types were closely associated with the amount of rainfall and soil types in the Gizzu area. The variations in morphological characteristic of Gizzu herbs and grasses were due to their adaptive fitness to defined boundaris of soil and weather. The seeds of Blepharis species germinated on a wide range of temperatures (15–45oC) and the percentages of germination were higher particularly when the seeds were soaked befor sowing. The results also indicated that, the water-stressed plants of Blepharis had significantly reduced leaf surface area, and increased the number of hairs and prickles. They also showed low stomatal conductance, transpiration rate and leaf water potential. More over, the anatomical variations were particularly evident in stressed plants specially in the thickness of the cuticular layer in leaves and the prederm in both roots and stems.