AT4 STOMATES

Question 1

Snow Gum

Answer 1

Tree native to eastern Australia. Widespread and locally common in woodland and cold sites above 700m altitude.

Question 2

Longicorn Beetle Larvae

Answer 2

Also known as longhorn beetles characterised by long antennae. Larvae live and pupate in the stems and branched of trees.

Question 3

Longicorn Larvae as pathogen for Snow Gums

Answer 3

Larvae causes Dieback - tree begins to die from the tip of its leaves down to its trunk. They thrive in dry wood, and since the gum is prone to drought pressure from climate change, there is an increase in transpiration from the leaves as the stomata open, causing decrease in water within the tree, making them more susceptible.

Question 4

Physical Barriers to Dieback

Answer 4

• Bark as barrier, stops pathogen from entering (like skin)
• Complex carbohydrates, pectin and lignin, difficult to eat and digest - present in the cell walls of the tree to make them more difficult for the larvae to bore into.
• Meristematic tissue in lignotubers, the woody tissues in the base of the plant, can shoot up to anew tree from the protected base in case the original tree dies.

Question 5

Chemical Responses to Dieback

Answer 5

• secretory cells, glands and ducts produce defensive chemicals such as hydrogen peroxide which is toxic to pathogens.
• hydrogen peroxide also acts as a signalling molecule for other chemical defence mechanisms.

Question 6

How do plants balance water?

Answer 6

Plants regulate their water/salt balance, as water is necessary to photosynthesise. Plants can maintain osmotic balance by closing or opening the stomate.

Question 7

Plant response to lack of water

Answer 7

• cells produce abscisic acid which stimulates guard cells
• guard cells move potassium out of vacuoles
• water exits guard cells in osmosis
• guard cells close, reducing evaporative loss

Question 8

Plant response to too much water

Answer 8

• potassium ions into vacuole, which water follows due to osmosis
• guard cells expand and swell, causing them to open
• opened guard cell allows water to evaporate from the plant through opening the stomate

Question 9

Orientation of Leaves as an adaption

Answer 9

Positioning leaves away from sunlight or vertically hanging/curling of leaves to reduce sun exposure, which leads to less water loss. (Stomata on inner side of the curl increase humidity around stomata, reducing rate of water evaporation)

Question 10

Reduced Leaf size as an Adaption

Answer 10

Reduces the amount of water lost through transpiration, fleshy stems and leaves swell to store more water, waxy cuticles