AP BIOLOGY

Detailed explanation-1: -In plants, the transpiration stream is the uninterrupted stream of water and solutes which is taken up by the roots and transported via the xylem to the leaves where it evaporates into the air/apoplast-interface of the substomatal cavity. It is driven by capillary action and in some plants by root pressure.

Detailed explanation-2: -Water moves into the roots from the soil by osmosis, due to the low solute potential in the roots (lower s in roots than in soil). This intake o f water in the roots increases p in the root xylem, driving water up.

Detailed explanation-3: -Transpiration is the loss of water from the plant through evaporation at the leaf surface. It is the main driver of water movement in the xylem. Transpiration is caused by the evaporation of water at the leaf, or atmosphere interface; it creates negative pressure (tension) equivalent to –2 MPa at the leaf surface.

Detailed explanation-4: -Movement of water into roots Water can get into xylem vessels by two routes-the symplast pathway and the apoplast pathway. If water travels via the symplast pathway then it travels from cell to cell through the cytoplasm. Neighbouring cells are connected by small channels in the cell walls called plasmodesmata.

Detailed explanation-5: -The vascular system is comprised of two main types of tissue: the xylem and the phloem. The xylem distributes water and dissolved minerals upward through the plant, from the roots to the leaves. The phloem carries food downward from the leaves to the roots.