Biology 2601A/B Lecture Notes - Lecture 18: Plasmodesma, Potential Gradient, Endodermis
9 Dec 2015
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Water is pulled from into the roots and up to the leaves by way of the cohesion- A negative water potential is generated at the mesophyll cell wall during evapotranspiration and water is pulled up towards the site of evaporation. This is achieved by the cohesion of water molecules (hydrogen bonding) transferring tension down the water column. Stomatal openings, which let co2 in and water out, provide one layer of resistance, while the boundary layer provides the other layer of resistance. The boundary layer is a layer of unstirred air on the outside of a leaf. Due to the high water vapour content over the leaf, less water is lost from leaf tissue when the stomata are open. However, the boundary layer can experience thinning when higher wind speeds are present causing more transpiration. Root hairs & the absorption of water by plants:
