Control Of Growth And Development

Question 1

Tropism

Answer 1

Directional growth in response to a stimulus “+” towards stimulus “-“ away

Question 2

3 types of Tropism

Answer 2

1. Phototropism- stimulus is light ( above ground, grows towards sunlight)
2. Gravitropism- stimulus is gravity ( roots grow with gravity)
3. Thigmotropism- stimulus is touch/ grow around something (ie- vines)

Question 3

Nastic movement

Answer 3

Non- growth and non- directional response to a stimulus, ( e.g. touch for mimosa or Venus flytrap)

Question 4

Define AUXINS and the GROWER USE

Answer 4

• Promote cell elongation (mostly at tip of shoots). Stimulates formation of roots and vascular differentiation
• in herbicides to make weeds elongate too fast, synchronize fruit ripening, prevent apical dominance

Question 5

Define Gibberellins and growers use

Answer 5

• Cause stem elongation, flowering, and stimulate seed germination
• fruit production, increase length of fruit stems and and size of fruit, stimulate gloating for seed production

Question 6

Define cytokinins and it growers use

Answer 6

• promote cell division and differentiation and slow cell aging in leaves
• promote growth and delay, aging of tissue

Question 7

Define Ethylene and it’s growers use

Answer 7

• cause leaf to drop in fall or when damaged, and stimulate the ripening of fruit ( breaks down complex carbs into simpler sugars)
• control levels of gaseous hormone to control ripening
• low levels to deleye ripening
• high levels to stimulate ripening by exposing to ethylene

Question 8

Abiscisic acid and growers use

Answer 8

Inhibits growth (e.g- maintains dormancy in buds and seeds) p, controls the closing of stomata 
-protects plants during shipment to nurseries