Capacitance Influences on the Water Relations of Desert Perennials

电容对沙漠多年生植物水关系的影响

• 批准号: 8802237
• 负责人: Park Nobel
• 金额: $ 12.14万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-09-01 至 1991-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8802237&HistoricalAwards=false
• 关键词: Capacitance; Influences; Water; Relations; Desert

Water is the key to the growth and survival of desert plants. It can be stored in the shoots, which is especially apparent for succulent plants such as Agave deserti (the common desert agave) and Ferocactus acanthodes (a barrel cactus). Internal redistribution of such stored water can influence water flow in the transpiration stream, the pathway from the soil to the root, stem, and leaves, and lead to non-steady state (transient) effects. Such transient effects. which can be considered by incorporating capacitors in electrical circuit analogs of the transpiration stream, have received little attention for plants, although the non-steady state is actually the rule, not the exception, for plants under natural conditions. Succulent plants such as A. deserti and F. acanthodes employ Crassulacean acid metabolism, where CO2 uptake occurs predominantly at night when temperatures are lower and hence water loss from the plant to the air is less. The CO2 taken up at night leads to the formation of malate, with a consequent large increase in osmotic pressure. This increase in osmotic pressure influences water movement by osmosis, a complication that has previously not been included in electrical circuit analogs for plant water relations. A new method will be employed that allows incorporation of this non-linear factor. New imaging methods developed in medical research will also be used to observe root location in the soil. Using an electric circuit analog, water movement and water potential will be simulated at various locations with computer programs developed to solve electrical circuits. Each component (such as a leaf) in the transpiration stream will be assigned a capacitance, which will be connected through a storage resistance to the main axial flow of the vascular tissue. Field measurements of desert succulents will also be made to interpret further the key adaptations of desert succulents to water stress and water use. Synthesizing the data into a dynamic model should enhance our quantitative understanding of the cellular properties of plants and the importance of capacitance and osmotic pressure in maintaining water potentials favorable for plant survival in the field, especially when they are exposed to natural or man- made changes in environmental conditions.

水是沙漠植物生长和生存的关键。它可以储存在芽中，这对于多肉植物，如龙舌兰（常见的沙漠龙舌兰）和铁仙人掌（桶形仙人掌）尤其明显。这种储水的内部再分配会影响从土壤到根、茎和叶的蒸腾流中的水流，并导致非稳态（瞬态）效应。这种短暂的影响。这可以通过在蒸腾流的电路类似物中加入电容器来考虑，但对于植物来说却很少受到关注，尽管非稳态实际上是植物在自然条件下的规则，而不是例外。多肉植物，如荒漠草和棘棘草，利用天冬酸代谢，其中二氧化碳的吸收主要发生在夜间，此时温度较低，因此植物向空气中的水分损失较少。夜间吸收的二氧化碳导致苹果酸盐的形成，随之而来的是渗透压的大幅增加。渗透压的增加通过渗透影响水的运动，这是一个以前没有包括在植物水关系的电路类似物中的复杂问题。将采用一种新的方法来考虑这个非线性因素。医学研究中开发的新成像方法也将用于观察土壤中的根位置。利用电路模拟，水的运动和水势将在不同的位置模拟与计算机程序开发，以解决电路。蒸腾流中的每个成分（如叶片）将被分配一个电容，该电容将通过维管组织的主要轴流的存储电阻连接。沙漠多肉植物的野外测量也将进一步解释沙漠多肉植物对水分胁迫和水分利用的关键适应。将这些数据综合到一个动态模型中，可以增强我们对植物细胞特性的定量理解，以及电容和渗透压在维持有利于植物在野外生存的水势方面的重要性，特别是当它们暴露于自然或人为的环境条件变化时。