1. Responses to the Environment: PLANTS

2. Plant responses are also controlled by hormones. Significant hormones in plants are: 1)AUXINS = an important role in coordination of growth and ‘behavioural’ processes in the plant's life, affecting both cell division and cellular expansion.

7. 2) GIBBERELLINS= a) Stimulate stem elongation by stimulating cell division and elongation. b) Stimulates flowering in response to long days. c) Breaks seed dormancy in plants which require light to induce germination. d) Can cause parthenocarpic (seedless) fruit development.

9. 3) ASCISIC ACID (ABA) = a)Stimulates the closure of stomata. b)Inhibits shoot growth. c)Induces seeds to synthesize storage proteins. d)Has some effect on induction and maintenance of dormancy.

12. Control of weeds by using plant hormones: Because they control plants being dormant, OR sprouting, you can control the growth naturally. Specific plants have specific chemicals / forms of hormones, thus weeds can be killed, plants left to grow.

13. Role of Auxin in Geotropism: Geo = indicating earth or ground / soil. Tropism = unidirectional growth behaviour. Shoots = negative geotropic (away from ground, more towards sun) Roots = positive geotropic (towards ground, more water, away from sun).

15. Role of Auxin in Phototropism: Photo= indicating light / radiant energy. Tropism = unidirectional growth behaviour. Shoots = positive phototropic (away from ground, more towards sun) Roots = negative phototropic (towards ground, more water, away from sun).

19. Plants have certain defence mechanisms to ensure survival: 1)Chemical defence: mainly to limit damage to leaves from insects.

21. 2) Physical defence (Thorns): to limit damage to the plant body. Prevents loss of water in xerophytes, specialised leaves.