Part Seven - Flowering Plants: Form and Function 743

35. Transport in Plants 764

35.1 How Do Plants Take Up Water and Solutes? 765 Water moves through a membrane by osmosis 765 Aquaporins facilitate the movement of water across membranes 767 Uptake of mineral ions requires membrane transport proteins 767 Water and ions pass to the xylem by way of the apoplast and symplast 768 35.2 How Are Water and Minerals Transported in the Xylem? 769 Experiments ruled out xylem transport by the pumping action of living cells 769 Root pressure does not account for xylem transport 770 The transpiration–cohesion–tension mechanism accounts for xylem transport 770 A pressure chamber measures tension in the xylem sap 771 35.3 How Do Stomata Control the Loss of Water and the Uptake of CO2? 773 The guard cells control the size of the stomatal opening 773 Transpiration from crops can be decreased 774 35.4 How Are Substances Translocated in the Phloem? 775 The pressure flow model appears to account for translocation in the phloem 776 The pressure flow model has been experimentally tested 776 Plasmodesmata allow the transfer of material between cells 777