L27 - Colour in Plant Cells

Functions of plant colour

1. photosynthesis

2. pollen/seed dispersal - by animals attracted to colour

3. protection

4. a mutant appearance preferred by ppl

Plant Pigments

= small organic molecules

• absorb certain light wavelengths

• use subtractive mixing ( more colour = darker)

Types:

1. Chlorophylls (green)

• in chloroplasts for photosynthesis

2. Carotenoids (orange/red)

• in chromoplasts for colour

• in chloroplast for photosynthesis

3. Anthocyanins (red/purple/blue)

• in central vacuole for colour & UV protection (bc UV makes reactive oxygen species that are dangerous)

note: can also be for camoflage

Photoautotroph vs. chemoheterotroph

Photoautotroph = does photosynthesis

ex. green leaves

ex. venus fly traps

Chemoautotroph = feeds on other plants

ex. white leaves

Leaves

= for photosynthesis + gas exchange

• structure: broad leaves or needles

colour meaning:

1. green = chloroplasts for photosynthesis

2. green + white = defective chloroplasts

3. green + purple = anthocyanins for UV protection

4. combos = for 4 leaf colours

5. white = no chloroplasts → feed on other plants

6. changing colour = trees in temperate climates shed broad leaves

   1. green → orange & yellow = removal of chlorophylls from chloroplast to reveal carotenoids ( bc chlorophylls contain valuable nitrogen, THUS only drop leaves containing carotenoids (yellow/red))

   

   1. green → red = synthesis of new anthocyanins for protection during chlorophyll removal

Flowers

= for pollen dispersal using hungry animals (gives animals nectar)

• structure: single flowers or flower clusters

colour meaning:

1. orange & yellow = carotenoids in chromoplasts

2. red, purple & blue = anthocyanins in CV

3. bright colours = to attract birds & bees

4. no colour = attract beetles or nocturnal animals using scent

Fruits

= for seed dispersal using hungry animals

→ fruit changing colour:

• immature fruit is green to synthesize sugars

• mature fruit is red/orange/yellow/purple to attract animals

colour meaning:

1. green → red, orange & yellow = chloroplasts change into chromoplasts

(ex. tomatoes turn red, citrus fruits turn orange, bananas turn yellow)

2. green → blue & purple = synthesis of anthocyanins

(ex. blueberries, blackberries)

Roots

= anchor plant in ground + obtain water and nutrients + storage

• usually unpigmented

BUT, mutant strains of potatoes & carrots make carotenoids & anthocyanins

Examinable Content