4.2.3 Plant tissues, organs and systems

Question 1

how are root hair hair cells adapted for taking up water and mineral ions ?

Answer 1

• have a large surface area to increase the rate of absorption
• contain lots of mitochondria, which release energy from glucose during respiration in order to provide the energy needed for active transport

Question 2

what is the function of phloem tubes?

Answer 2

they transport food ( sugars e.g sucrose) made in the leaves during photosynthesis to the rest of the plant for immediate use or storage

Question 3

what structure do phloem tubes have ?
(detailed structure not necessary)

Answer 3

-made of elongated living cells , with small pores in the end walls to allow cell sap to flow through
-transport goes in both directions
-process called translocation

Question 4

what is the function of xylem tubes?

Answer 4

Xylem tissue transports water and mineral ions from the roots to the
stems and leaves. It is composed of hollow tubes strengthened by
lignin adapted for the transport of water in the transpiration stream.

Question 5

what structure do xylem have?

Answer 5

-very thick walls containing lignin (provides support to the plant)
-contain no cytoplasm as they are hollow and are impermeable to water
- no internal structures makes it easier for water and minerals to flow
- made of dead cells joined end to end with no end walls between them and a hole down the middle
-end walls between the cells broken down means cells now form a long tube so water and dissolved minerals can flow easily

Question 6

what is transpiration?what is it caused by ? where does it mainly happen?

Answer 6

when stomata are open , plants lose water vapour through them as well.The water evaporates from the cells lining and air spaces and then passes out of the leaf through the stomata by diffusion . This loss of water known as transpiration .
-its caused by evaporation and diffusion of water from a plant’s surface
-most transpiration happens at the leaves

Question 7

list 4 environmental factors that effect the rate of transpiration

Answer 7

light intensity
humidity
temperature
wind

Question 8

light intensity

Answer 8

-increase in light intensity will increase the rate of transpiration
-anything that increases rate of photosynthesis or increase the rate of stomatal opening will increase rate of transpiration

Question 9

humidity

Answer 9

-the drier the air around the leaf , the faster transpiration happens because evaporation takes place more quickly under dry conditions

Question 10

temperature

Answer 10

• the warmer it is , the faster transpiration happens as molecules move faster as the temperature increases so diffusion occurs more rapidly
  -rate of photosynthesis also increases as the temp goes up , so more stomata will be open for gas exchange to take place

Question 11

wind

Answer 11

-plant in windy condition means that there will be an increase in the rate of evaporation from the surface of the leaf as water molecules will be taken away more easily : this will increase the rate of transpiration

Question 12

what are root hair cells adapted for?

Answer 12

the efficient uptake of water by
osmosis, and mineral ions by active transport

Question 13

what is translocation?

Answer 13

The movement of
food molecules through phloem tissue is called translocation.

Question 14

process of translocation

Answer 14

phloem tissue

Question 15

process of transpiration (transpiration stream)

Answer 15

-water moves into the roots from the soil by osmosis : this replaces the water moving up the stem
-water moves up through the stem against gravity and into the leaves to replace water lost by evaporation . water molecules are cohesive which allows water to move in one direction and create a transpiration stream .
-water is lost from the leaf by evaporation , through open stomata

Question 16

structure and function of stomata

Answer 16

-The stomata control gas exchange in the leaf. Each stoma can be open or closed, depending on how turgid its guard cells are.
The stomata can open and close to:
control water lost by transpiration
allow gas exchange
Stomata are found mainly on the lower surface of the leaf to reduce water loss by transpiration

Question 17

function of guard cells

Answer 17

Guard cells control gas exchange and water loss from the leaf by opening and closing pores on the underside of the leaf called stomata.
When there is lots of water in the plant, the guard cells fill with water and become turgid. This opens the stomata, allows gases to be exchanged with the atmosphere and water to escape.
When there is little water in the plant, the guard cells lose water and become flaccid. This closes the stomata and prevents too much water escaping.

Question 18

explain one way the removal of dissolved sugars from the stem of the plant causes stunted growth

Answer 18

less (sugars for) respiration
(so) less energy released

Question 19

suggest one way the gardener could reduce spread of rose black spot

Answer 19

-* remove any infected parts of the plant
-use a fungicide

Question 20

describe how the movement of potassium ions into the guard cells causes the stomata to open

Answer 20

(potassium) ions increase the concentration of the solution (inside guard cells)
water moves into the (guard) cell by osmosis
cell swells unevenly (so stoma opens)
as inner wall is less flexible than outer wa

Question 21

explain why the mean rate of water uptake is higher on a hot day than on a cold day

Answer 21

(on hot day) more water lost
more transpiration
so more water taken up (by roots) to replace (water) loss (from leaves)

Question 22

explain why root hair cells contain mitochondria

Answer 22

(aerobic) respiration occurs in mitochondria
(mitochondria / respiration) release energy
(energy used for) active transport

Question 23

describe how ions,water and sugar are obtained and transported through plants (6)
(ions)

Answer 23

examples of points made in the response Ions:
(P) taken up by diffusion or active transport
* from an area of high to low concentration (diffusion) or an area of low to
high concentration (active transport)
(V) travels in the xylem
(M) to the leaves or from the roots / soil

Question 24

describe how ions,water and sugar are obtained and transported through plants (6)
(water)

Answer 24

(P) taken up by osmosis
* from an area of low to high concentration
(V) travels in the xylem
(M) to the leaves or from the roots / soil
(P) transpiration stream
* movement replaces water as it evaporates from leaves
(V) in the xylem

Question 25

sugar

Answer 25

Sugar:
(P) made during photosynthesis
(V) travels in the phloem
(M) to other parts of the plant or to storage organs or travels up and down