AP BIOLOGY

Detailed explanation-1: -Water and solutes are transported by the xylem from the roots to the leaves, and food is transported from the leaves to the rest of the plant by the phloem. The process by which water evaporates from the leaves and draws more water from the roots is called ‘transpiration’.

Detailed explanation-2: -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-3: -The xylem is also composed of elongated cells. Once the cells are formed, they die. But the cell walls still remain intact, and serve as an excellent pipeline to transport water from the roots to the leaves. A single tree will have many xylem tissues, or elements, extending up through the tree.

Detailed explanation-4: -After traveling from the roots to stems through the xylem, water enters leaves via petiole (i.e., the leaf stalk) xylem that branches off from that in the stem.

Detailed explanation-5: -The water either goes through the cortex cells (between the root cells and the xylem vessels) or it bypasses them – going through their cell walls. After this, the water moves up the xylem vessels to the leaves through diffusion: A pressure change between the top and bottom of the vessel.