phloem and xylem

Question 1

purpose of the xylem

Answer 1

to transport water to the leaves

Question 2

xylem vessels structure

Answer 2

they are composed of long, skinny tubes that run from the roots to the leaves. the xylem is made up of hollow cells, lignin and pits

Question 3

two types of cells in the xylem

Answer 3

vessel elements and tracheids

Question 4

tracheids

Answer 4

long, hollow cells that conduct water and that water passes through. they have pits to allow the transfer of water as they have no end walls

Question 5

vessel elements

Answer 5

much larger and connect end to end with end walls to allow rapid water transport

Question 6

what is transpiration

Answer 6

when water moves from the roots to the leaves via the xylem, water then evaporates at the stomata of the leaf during gas exchange, this process is passive.

Question 7

how is water lifted up the plant (transpiration)

Answer 7

at water evaporates from the stomata, the air pressure in the leaf becomes lower than in the roots. as water molecules stick together (cohesion) and adhere to the xylem (adhesion) which allows water to be drawn up.

Question 8

what are guard cells

Answer 8

regulate the opening and closing of the stoma , two on either side of each stoma

Question 9

how do guard cells open/close

Answer 9

potassium ions are pumped into guard cells and water will diffuse via osmosis making the guard cells turgid, opening the stoma. when potassium ions are pumped out of the cell, osmosis will occur making the cells flaccid and stoma closed

Question 10

factors that affect transpiration

Answer 10

temperature, light, humidity, wind and water avliabilty

Question 11

what is translocation

Answer 11

is the movement of sucrose around the plant from the source to the sink (tissue of a plant where substances are stored), its an active process

Question 12

two types of cells in the phloem

Answer 12

sieve element cells and companion cells

Question 13

what are sieve element cells

Answer 13

they are long and narrow and connected to each other, they have sieve tube elements, and sieve tube plates and lateral sieve areas to transport things between cells

Question 14

what is the process of translocation

Answer 14

glucose is produced in the leaf cells, this is the source, glucose is then pumped into campanion cells where they diffuse across the phloem and are transported as sucrose

Question 15

what happens when sugar molecules diffuse into the phloem in translocation

Answer 15

due to an increased concentration of sugar molecules, water will diffuse into the sieve cells from the xylem, making the sieve cells turgid

Question 16

what happens once the sieve cells become more turgid in translocation

Answer 16

the increase in the turgor pressure forces the contents of the phloem into the required cells, fruit cells and or root cells where it is then actively transported

Question 17

what happens once the sugar has reached the required cells (sink cells) in translocation

Answer 17

once the sugar molecules are unloaded into the sink cells, the turgor pressure will return to normal and the water will diffuse back into the xylem