XYLEM AND TRANSPIRATION

Question 1

describe the movement of water in a plant

Answer 1

1. water is lost from air space via diffusion through stomata
2. water potential of air space decreases
3. water moves from cells into air space (evaporation due to heat)
4. water potential of cell decreases
5. water moves from the neighboring cells / xylem into these cells via osmosis

Question 2

adaptations of the xylem

Answer 2

thick cell walls - withstand tension
lignin in cell walls - waterproof and withstand tension
no end walls and stacked - continuous column of water
no cytoplasm - reduces resistance / continuous column

Question 3

what is cohesion

Answer 3

force from the attraction between molecules of the same substance

Question 4

what is adhesion

Answer 4

force from attraction between molecules of different substances

Question 5

tension and diameter of xylem

Answer 5

tension refers to the pull of water in the xylem
increased transpiration means higher tension
more water is pulled up due to a higher water potential gradient
the higher tension causes the diameter of the xylem to become narrower

Question 6

what is the cohesion tension theory

Answer 6

sun provides solar energy so water evaporates from leaves via transpiration
water is lost when stomata open and close for gas exchange creating a water potential gradient across the leaf
creating a transpiration pull - drawing water from xylem into leaf
tension is created in the xylem. the force causes the xylem to narrow at high rates of transpiration
cohesion between water molecules causes a continuous , unbroken column of water from xylem to cells