The cohesion-tension theory describes water transport in xylem as resulting from water loss via transpiration from leaves, which lowers mesophyll cell water potential, pulling water up the xylem in cohesive columns maintained by hydrogen bonds and adhesion to xylem walls.
A teoria da coesão-tensão descreve o transporte de água no xilema como resultado da perda de água por transpiração das folhas, o que diminui o potencial hídrico das células do mesofilo, puxando a água para cima no xilema através de colunas de água coesivas, mantidas por ligações de hidrogénio e adesão às paredes do xilema.
| Front | Describe the cohesion-tension theory of water transport in the xylem. [5 marks] |
|---|---|
| Back | 1. Water lost from leaf because of transpiration / evaporation of water (molecules) / diffusion from mesophyll / leaf cells; OR Transpiration / evaporation / diffusion of water (molecules) through stomata / from leaves; 2. Lowers water potential of mesophyll / leaf cells; 3. Water pulled up xylem (creating tension); 4. Water molecules cohere / 'stick' together by hydrogen bonds; 5. (forming continuous) water column; 6. Adhesion of water (molecules) to walls of xylem; |
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