Collaborative Research: Mechanisms and Ecological Consequences of Predawn Soil-Plant Water Potential Disequilibrium in Desert Shrubs; Subcontract to UC Davis

合作研究：沙漠灌木黎明前土壤-植物水势不平衡的机制和生态后果；

• 批准号: 9903004
• 负责人: James Richards
• 金额: $ 9万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-03-01 至 2003-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9903004&HistoricalAwards=false
• 关键词: Collaborative; Research; Mechanisms; Ecological; Consequences

Water is the primary factor limiting plant growth and distribution in many habitats. Thus, plant water status and water relations characteristics are closely related to plant performance, particularly in arid habitats. Measurements of plant water status just before sunrise, called plant predawn water potential, are used as a standard for comparing plant water availability in different habitats because of the expectation that predawn plant water potential is in equilibrium with soil water potential. The PIs have evidence from field and controlled environment studies that at least two desert shrub species show major departures from the expected soil-plant predawn water potential equilibrium, even when hydraulic continuity (soil-root contact) is not a limiting factor, and the PIs call this phenomenon "predawn disequilibrium." Predawn disequilibrium in the study species provides a focal point for investigating a suite of mechanisms that may account for departure from classical physiological expectations and for study of ecological consequences and adaptive significance of those mechanisms. The study shrubs are Chrysothamnus nauseosus ssp. consimilis (salt-excluding, non-halophytic) and Sarcobatus vermiculatus (salt-accumulating, halophytic) which are similar in life history and rooting characteristics. Mechanisms to be tested, in both greenhouse and field studies, include lack of time for overnight recovery, nighttime transpiration, nocturnal efflux of water from roots, growth-induced reduction in plant water potential, and solute accumulation in intercellular spaces. The PIs will then assess the plant carbon gain consequences of predawn disequilibrium by examining its relationship to photosynthesis, transpiration and water-use-efficiency. This project will contribute to a more accurate understanding of fundamental plant water relations in areas where classical interpretations fail. This improved understanding is essential for making valid ecological interpretations of water relations adaptations of wildland plants.

水是许多栖息地限制植物生长和分布的主要因素。 因此，植物水分状况和水关系特征与植物性能密切相关，特别是在干旱生境中。 日出前测量植物水分状况，称为植物黎明前水势，被用作比较不同生境中植物水分可用性的标准，因为预期黎明前植物水势与土壤水势处于平衡。项目负责人从实地和受控环境研究中获得的证据表明，至少有两种沙漠灌木物种与预期的土壤-植物黎明前水势平衡存在重大偏差，即使水力连续性（土壤-根部接触）不是限制因素，项目负责人将这种现象称为“黎明前不平衡”。 研究物种中的黎明前不平衡为研究一系列可能解释经典生理预期偏离的机制以及研究这些机制的生态后果和适应性意义提供了焦点。研究的灌木是 Chrysothamnus nauseosus ssp。 consimilis（不含盐，非盐生）和 Sarcobatus vermiculatus（积盐，盐生）在生活史和生根特征上相似。 在温室和田间研究中待测试的机制包括缺乏过夜恢复时间、夜间蒸腾作用、夜间水分从根部流出、生长引起的植物水势降低以及细胞间隙中溶质的积累。 然后，PI 将通过检查植物碳增益与光合作用、蒸腾作用和水分利用效率的关系来评估黎明前不平衡对植物碳增益的影响。 该项目将有助于在经典解释失败的领域更准确地理解植物与水的基本关系。这种更好的理解对于对野生植物的水关系适应做出有效的生态解释至关重要。