Plant systems- gas exchange and transport systems

Question 1

where does photosynthesis occur

Answer 1

the leaf

Question 2

describe the leaf

Answer 2

broad, flat part called the lamina, which is joined to the rest of the plant by a stalk or petiole. Running through this is vascular bundles called the phloem and xylem. Stomata are usually found on the epidermis of the leaf. Guard cells as well.

Question 3

Stomata

Answer 3

Small holes that release water and exchange gas. Plants need to release oxygen back into the atmosphere as a waste product. This occurs in the stoma. Also exchange of oxygen.

Question 4

Guard cells

Answer 4

a pair of cells that surround each stoma. They help regulate the rate of transpiration by opening and closing the stomata. Guard cells tend to open the stomata during the day when there is lots of sunlight and close it at night. Guard cells contain chloroplasts.

Question 5

Movement of Carbon Dioxide

Answer 5

Much of the carbon dioxide needed for photosynthesis passes through the stomata along a diffusion gradient from the air to the cells.
In the daytime, photosynthesis proceeds at a faster rate than cellular respiration and all of the carbon dioxide released in cellular respiration is used up in the chloroplasts.

Question 6

Xylem

Answer 6

Xylem is the complex, dead and permanent tissue responsible for carrying nutrients and water,

Question 7

Phloem

Answer 7

phloem is the soft and permanent tissue play its role in transporting the food and other organic material produced by the green parts especially leaves by the process of photosynthesis.

Question 8

When is a leaf well adapted for gas exchange

Answer 8

if the SA is large, gas exchange between the environment and leaf tissues is only through the stomata, and the leaf epidermis protects the internal exchange surfaces.

Question 9

Spongy Mesophyll

Answer 9

Gas exchange happens in the spongy mesophyll tissue of the leaf. Spongy mesophyll cells are covered by a thin layer of water and loosely packed. When the plant is photosynthesising during the day, these features allow carbon dioxide to diffuse into the spongy mesophyll cells, and oxygen to diffuse out of it.

Question 10

Palisade Mesophyll

Answer 10

Light absorption happens in the palisade mesophyll tissue of the leaf. Palisade cells are column shaped and packed with many chloroplasts. They are arranged closely together so that a lot of light energy can be absorbed.

Question 11

Epidermis

Answer 11

Below the cuticle is the epidermis. On the top of the leaf, this is known as the upper epidermis. This is a single layer of cells found directly below the cuticle. It helps protect the leaf by aiding in preventing water loss and providing an extra layer between the outside and inside of the leaf.

Question 12

Cuticle

Answer 12

The outermost layer is called the cuticle. It is generally waxy to protect the leaf and prevent water loss.

Question 13

Vascular bundles

Answer 13

Xylem tissue delivers water from the roots to the leaf, and phloem tissue transports glucose away from the leaf. These tissues form vascular bundles in the plant.

Question 14

sieve tubes

Answer 14

Phloem is a complex tissue composed of supporting fibres and sclereids and the living sieve tubes, companion cells and parenchyma. The sieve tubes run parallel to the long axis of the plant, from the top leaves of the plant to the roots. They are made up of elongated sieve tube elements placed end on end.

Question 15

sieve plates

Answer 15

Each sieve tube cell has a specialised end wall (sieve plate) that is perforated by numerous pores.

Question 16

companion cells

Answer 16

Specialised long companion cells are found next to each sieve tube element in most flowering plants. The walls of these two cell types are thin where they are in contact and connected by plasmodesmata.

Question 17

how does water enter plants

Answer 17

through the root hairs. direction is from roots to leaves, and this is the transpiration stream. water passes through soil to the root hairs through osmosis.

Question 18

water passes from the root hairs, across the cortex to the xylem by one of three different pathways:

Answer 18

Pathway 1: passing from one cell vacuole to the next by osmosis, through cell walls and all cell contents.
Pathway 2: moving through the plasmodesmata (fine protoplasmic connections between neighbouring cells) from one cell to the next by osmosis.
Pathway 3: moving between the cells along and through the intercellular spaces and cellulose cell walls from one cell to the next.

Question 19

Cohesion

Answer 19

the attraction of molecules within a substance to attract one another. In water, the molecules are attracted by these hydrogen bonds.

Question 20

Adhesion

Answer 20

Adhesion is the attraction between different molecules. There are forces of attraction between the water molecules and the xylem walls. These help the water to travel up through the xylem.

Question 21

factors that influence rate of transpiration

Answer 21

Light- stomata usually open in the light and close in the dark.
Temperature- an increase in temperature increases the rate of transpiration.
Humidity- increase in humidity causes a decrease in transpiration. This is due to a decreased diffusion gradient between the intercellular spaces and the atmosphere, which reduces evaporation.
Wind- increases transpiration by the removal of water vapour around the stomatal pore. This maintains a concentration gradient for all gases and water vapour.

Question 22

translocation

Answer 22

the movement of organic molecules throughout the plant. It occurs in the sieve tubes of the phloem. This movement can occur in all directions, from leaves to roots, leaves to apex and vice versa.