transpiration and translocation

Question 1

describe the structure of the phloem

Answer 1

-columns of elongated living cells with small pores (sieves) in the end walls to allow cell sap to flow through
-contains cytoplasm
-tubular

Question 2

what is cell sap a mixture of?

Answer 2

water and sugar

Question 3

describe the structure of the xylem

Answer 3

-made of dead cells joined end to end with no end walls between them and a hole down the middle
-they are strengthened by lignin
-tubular

Question 4

function of xylem cells

Answer 4

transports water and mineral ions, from the roots to the stem and leaves (one direction), through transpiration

Question 5

function of phloem tubes

Answer 5

-transport food substances (mainly dissolved sugars) made in the leaves to the rest of the plant
-transport goes in both directions through a process called translocation

Question 6

what is transpiration caused by?

Answer 6

the evaporation and diffusion of water from a plant’s surface

Question 7

how does the plant replace the water lost?

Answer 7

The evaporation creates a shortage of water in the leaf, so water is drawn up from the rest of the plant through the xylem. This means more water is drawn from the roots so there is a constant transpiration stream.

Question 8

what is a transpiration stream?

Answer 8

the constant movement of water from the roots through the xylem and out of the leaves

Question 9

why and how does water escape from the leaves?

Answer 9

there is more water inside the plant than in the air outside so it escapes from the leaves through the stomata by diffusion

Question 10

what is translocation?

Answer 10

the movement of dissolved sugars from the leaves to other parts of the plant through phloem tissue

Question 11

what is transpiration?

Answer 11

the evaporation of water vapour from the surface of a plant