Zhihao Zhang1, Akash Tariq2, Fanjiang Zeng3, Corina Graciano4, Bo Zhang5. 1. Xinjiang Key Laboratory of Desert Plant Roots Ecology and Vegetation Restoration, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, 830011, China; State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, 830011, China; Cele National Station of Observation and Research for Desert-Grassland Ecosystems, Cele, 848300, China; University of Chinese Academy of Sciences, Beijing, 10049, China. 2. Xinjiang Key Laboratory of Desert Plant Roots Ecology and Vegetation Restoration, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, 830011, China; State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, 830011, China; Cele National Station of Observation and Research for Desert-Grassland Ecosystems, Cele, 848300, China. Electronic address: akash.malik786@mails.ucas.ac.cn. 3. Xinjiang Key Laboratory of Desert Plant Roots Ecology and Vegetation Restoration, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, 830011, China; State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, 830011, China; Cele National Station of Observation and Research for Desert-Grassland Ecosystems, Cele, 848300, China. Electronic address: zengfj@ms.xjb.ac.cn. 4. Instituto de Fisiología Vegetal, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de La Plata, Buenos Aires, Argentina. 5. Xinjiang Key Laboratory of Desert Plant Roots Ecology and Vegetation Restoration, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, 830011, China; State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, 830011, China; Cele National Station of Observation and Research for Desert-Grassland Ecosystems, Cele, 848300, China.
Abstract
Groundwater and its associated nutrients sustain the establishment and persistence of phreatophytes. Rapid root elongation immediately after germination is vital for desert species to access deep water sources to avoid water-deficit stress. However, the growth strategy and responses to nutrients and water of young phreatophyte seedlings before their roots reach the water table are poorly understood, especially in the scenarios of nitrogen (N) deposition and drought. We investigated how simulated N deposition and drought affect the plasticity of Alhagi sparsifolia seedlings by multiple eco-physiological mechanisms. Seedlings were planted under drought-stressed or well-watered conditions and subjected to various levels of N addition (0, 3.0, 6.0, or 9.0 gN·m-2 yr-1). The amounts of N and water independently or interactively affected the photosynthetic traits, drought tolerance characteristics, morphological traits, biomass allocation strategy, and nutrient distribution patterns among the plant organs. Moreover, changes mediated by N addition at the leaf level reflected the drought acclimation of the seedlings, which may be related to biomass and nutrient partitioning between organs. The roots were found to be more sensitive to variation of the N:phosphorus (P) ratio, and greater proportions of biomass, N, and P were allocated to resource-acquiring organs (i.e., leaves and fine roots) than to other tissues. A. sparsifolia adopts numerous strategies to tolerate drought, and additional N input was crucial to enhance the growth of drought-stressed A. sparsifolia, which was mainly attributable to its positive impact on the N and P uptake capacity mediated by increased biomass allocation to the roots.
Groundpan class="Chemical">water and its associated nutrients sustain the establishment and persistence of phreatophytes. Rapn>id root elongation immediately after germination is vital for desert species to access deepn> pan class="Chemical">water sources to avoid water-deficit stress. However, the growth strategy and responses to nutrients and water of young phreatophyte seedlings before their roots reach the water table are poorly understood, especially in the scenarios of nitrogen (N) deposition and drought. We investigated how simulated N deposition and drought affect the plasticity of Alhagi sparsifolia seedlings by multiple eco-physiological mechanisms. Seedlings were planted under drought-stressed or well-watered conditions and subjected to various levels of N addition (0, 3.0, 6.0, or 9.0 gN·m-2 yr-1). The amounts of N and water independently or interactively affected the photosynthetic traits, drought tolerance characteristics, morphological traits, biomass allocation strategy, and nutrient distribution patterns among the plant organs. Moreover, changes mediated by N addition at the leaf level reflected the drought acclimation of the seedlings, which may be related to biomass and nutrient partitioning between organs. The roots were found to be more sensitive to variation of the N:phosphorus (P) ratio, and greater proportions of biomass, N, and P were allocated to resource-acquiring organs (i.e., leaves and fine roots) than to other tissues. A. sparsifolia adopts numerous strategies to tolerate drought, and additional N input was crucial to enhance the growth of drought-stressed A. sparsifolia, which was mainly attributable to its positive impact on the N and P uptake capacity mediated by increased biomass allocation to the roots.