Plants (Extended Response)

Question 1

Outline how the hormone auxin controls phototropism in plant shoots. (5 marks)

Answer 1

-grows/bends towards (brightest) light/sun
-auxin moved from lighter to shadier side (of shoot/stem tip/apex)
-moved by auxin efflux pumps
-auxin promotes cell elongation/cell growth / auxin causes cell wall acidification/loosening
-more growth on shady side of stem (due to auxin concentration gradient)
-binds to auxin receptors (in target cells)
-auxin/auxin receptors promote expression of genes (for growth)/for H+ secretion into wall

Question 2

Outline the growth of plant shoot apex. (4 marks)

Answer 2

-growth in shoots is indeterminate/unlimited
-produces stem and leaves
-growth/cell growth/cell elongation controlled/affected by hormones/auxin/IAA
-new/extra cells produced by mitosis/cell division / apex is a meristem
-tropism/phototropism / grows towards the sun/light
-auxin moved away from sunny side/to shady side of shoot «apex»
-auxin efflux pumps set up concentration gradients

Question 3

The flowers of angiospermophyta are used for sexual reproduction. Outline three processes required for successful reproduction of angiospermophyta. (3 marks)

Answer 3

-meiosis / production of male and female gametes
-pollination / transfer of pollen from anther to stigma
-fertilization happens after pollination / fertilisation is joining of gametes
-seed dispersal / spread of seeds to new locations