13.5 Plant Growth and Developement

Question 1

Factors affecting plant growth

Answer 1

• Light
• Nutrients
• Temperature
• Soil

Question 2

Light

Answer 2

• The type of light reaching a plant can determine its
  growth!
• Different types of light and different wavelengths
• Plants have photoreceptors (molecules that can detect different wavelengths of light)
  Why would this be necessary?
• Seasonal changes to light
• Daily changes to light

Question 3

Nutrients

Answer 3

Two types of nutrients are needed:
1. Macronutrients: nutrients needed in large quantities (more than 1000mg per 1kg of plant mass)
- Ex: nitrogen, phosphorus, potassium
2. Micronutrients: nutrients needed in small
quantities (less than 100 mg per 1kg of plant mass)
- Main 8: boron, chlorine, copper, iron, manganese,
molybdenum, nickel, zinc

Question 4

Temperature

Answer 4

• All cellular processes are effected by temperature
• There is a range that plants have for optimal growth (this depends on the plant)
• The temperature is chosen to favour reproductive success (ex: angiosperms will pollinate based on conditions favourable for the seed)
  Issues? Climate Change
• Every increase in 1oC, flowering occurred 5 days earlier
• Flowering has been occurring 2.2-12.7 days earlier
• Issues for pollinators and competition!

Question 5

Soil

Answer 5

• Soil plays 3 roles in growth
  1. Provides a medium for plants to anchor
  2. Retains water and dissolved nutrients (these
  nutrients are found in the humus layer of soil)
  3. Provides root with air (aerenchyma is a spongy
  tissue in plants that promotes gas exchanges)
• Soil pH is also crucial (scale of acidity)

Question 6

Growth regulator

Answer 6

• Plant growth regulator: a chemical produced by plants that regulates growth and differentiation
• These signal a plant to undergo changes, but why?
• Tropism: a directional change in growth or movement in response to a stimulus
• Stimulus is an external change for the plant

Question 7

Types of tropism

Answer 7

• Phototropism: change in direction of plant growth
  in response to light
• Gravitropism: change in growth pattern due to
  response in gravity
• Thigmotropism: change in growth pattern in
  response to touch

Question 8

Phototropism

Answer 8

• Response to phototropism is a compound called
  auxin
• This elongate the shoot system to maximize sunlight

Question 9

Gibberellins

Answer 9

• A family of compounds that share a similar
  chemical structure and act in similar ways in plant
  cells:
• Have some of the following functions:
• Promote cell division
• Promote plant elongation (and therefore growth)
• Flowering and production of fruit