Relationship between Photosynthetic Characteristics, Anatomical Structure, and Physiological Indexes of Two Halophytes in Different Habitats

Drought and salinity are considered to be the major limiting factors for plant growth in desert areas. Halophytes can maintain their growth in extreme salt environments. However, few studies have linked the photosynthetic characteristics of halophytes with their anatomical structures and leaf water potential to jointly explain the effects of drought and salt on leaf internal water use efficiency (WUEi). For this reason, two different halophytes, Nitraria sibirica and Alhagi sparsifolia, were selected to analyze the leaf physiological traits in response to different water and salt gradients. The analysis further revealed the influence of soil water and salt content and anatomical characteristics on plant photosynthesis. The results showed that the leaf water potential, morphology, anatomical parameters, and photosynthetic parameters of the two plants in different habitats showed significant species-specific physiological responses. The value of WUEi of N. sibirica was negatively correlated with net photosynthetic rate (Pn), stomatal conductance (Gs), tightness of palisade tissue (CTR), and soil factors, while the WUEi of A. sparsifolia was positively correlated with Pn, Gs, and CTR. The indirect effects of soil salinity and soil moisture on WUEi were also found to be species-specific. This study will help to improve the understanding of the ecological adaptability of plants to water and salt stress and provide a theoretical basis for clarifying the drought tolerance and salt tolerance adaptation strategies of halophytes in arid areas.