Plant Resposnes To Abiotic Sress

Question 1

Examples of abiotic stress to plants

Answer 1

• salinity changes
• high winds
• excess water
  -lack of water
  -Cold and head
  -changes in length of day

Question 2

Why does leaf loss occur

Answer 2

• changes in range of daylight and temperature affects photosynthesis

-glucose is required for respiration but more chemicals are produces than glucose from photosynthesis

• trees that are growing new leaves more likely to be damaged so they lose all leaves in winter and wait for longer days

Question 3

Why are plants sensitive to daylight and how do they respond

Answer 3

• they are sensitive to a lack of light- photoperiodism
• some responses- timing of flowering in plants
• sensitivity comes from light sensitive pigments which absorb different wavelengths

Question 4

Why does leaf fall (ascission) occur

Answer 4

• after Sumer, days shorten and temperature falls
• fall in light, auxin reduced so ethene increased
• ethene switches genes on for new enzyme produced
• enzymes digest and weaken cell walls in absisson zone
• vascular bundle sealed off so fatty deposits in stem side also
• fatty layer is a protective scar when leaf falls to prevent pathogens entering
• Cells in separation zone retain water and swell so leave falls

Question 5

How do plants prevent freezing

Answer 5

• cytoplasm and sap contain solutes which lower the freezing point
• some plants produce sugars and polysaccharides which act as antifreeze to prevent cytoplasm from freezing
• different genes activated and suppressed to respond to temp falls

Question 6

When does stomata closing occur

Answer 6

• depends on temperature and water availability
• under control of ABA
• ABA binds to receptors on membrane of guard cell which activates change in ionic con reducing water potential
• turbot reduced so guard cells close and water loss reduced