Root response of woody phreatophyte species to drought stress (Case study: Eucalyptus camaldulensis Dehnh)

Phreatophytes are the plants that supply their water requirements directly through the development of efficient roots from surface water resources and for optimum growth, the root should be in direct contact with water or a completely moist soil. Considering the importance of roots in the process of water and nutrient uptake from soil, it is necessary to study the mechanism of root adaptation to environmental stresses, including drought stress, especially in woody phreatophyte species, which are more important in forestation. In this research, the weight and length distribution of Eucalyptus camaldulensis Dehnh roots as a pharotypophyte species was investigated. The experiment was carried out under lysimetric conditions at different irrigation regimes (irrigation at field capacity as control, 30% and 60% of deficit irrigation). The results of this study indicated that the weight and root length decreased with decreasing plant access to water or deficit irrigation. The weight and length distribution of roots at different depths depended on the amount of plant access to water, so that the root distribution in the deeper soil decreased by increased deficit irrigation stress. Therefore, it can be concluded that, in contrast to xerophyte and mesophyte plants, the root penetration of E. camaldulensis depends thoroughly on the amount of water in the deeper soil depths. In other words, the dried underlying layers of soil inhibit the root growth in the depths, and the plant manages its vegetative growth through adaptation with available water in the soil surface layers.