Topic 10 - Water movement through the soil-plant continuum
Essential elements from Topic 10:
Topic 10 provides an overview of the forces that move water through plants and the ways that plants influence water transport.
1.Plants lose water to the atmosphere when taking in CO2 for photosynthesis. This water must be replaced to prevent desiccation.
2.Water moves as a liquid from the soil, through a plant, to the site of evaporation by following gradients in water potential from high to low. Water in the xylem is held under tension in a metastable state.
3.The state of water is measured as water potential. The water potential is the potential energy of water on a volumetric basis relative to pure water.
4. Water potential has four components: gravitational, pressure, osmotic and matric. Water moves in different directions on the basis of total water potential, which is the sum of the four components.
5. Matric potential is due to capillary forces. In soil we find capillaries in the pores between soil particles. In plants the relevant capillaries are the pores between the cellulose microfibrils that make up cell walls.
6.Water in plants is often in a metastable state, meaning it is beyond its boiling point. Water can remain in this state, as long as it is not nucleated by an air bubble. Plants have pit membranes between xylem conduits that can prevent the entry and spread of air bubbles. However, plants differ in their abilities to exclude air bubbles, leading to different "vulnerability curves" and therefore different environments in which the plants can survive.
7.Stomata regulate water loss by opening and closing (an active process) in response to environmental stimuli such as CO2, light, and water status.
Essential elements from Topic 10:
Topic 10 provides an overview of the forces that move water through plants and the ways that plants influence water transport.
1.Plants lose water to the atmosphere when taking in CO2 for photosynthesis. This water must be replaced to prevent desiccation.
2.Water moves as a liquid from the soil, through a plant, to the site of evaporation by following gradients in water potential from high to low. Water in the xylem is held under tension in a metastable state.
3.The state of water is measured as water potential. The water potential is the potential energy of water on a volumetric basis relative to pure water.
4. Water potential has four components: gravitational, pressure, osmotic and matric. Water moves in different directions on the basis of total water potential, which is the sum of the four components.
5. Matric potential is due to capillary forces. In soil we find capillaries in the pores between soil particles. In plants the relevant capillaries are the pores between the cellulose microfibrils that make up cell walls.
6.Water in plants is often in a metastable state, meaning it is beyond its boiling point. Water can remain in this state, as long as it is not nucleated by an air bubble. Plants have pit membranes between xylem conduits that can prevent the entry and spread of air bubbles. However, plants differ in their abilities to exclude air bubbles, leading to different "vulnerability curves" and therefore different environments in which the plants can survive.
7.Stomata regulate water loss by opening and closing (an active process) in response to environmental stimuli such as CO2, light, and water status.