Plant Development

Question 1

• in order to survive, plants require light and water for photosynthesis
• they have developed tropisms to help ensure they grow towards adequate light and water

POSITIVE TROPISM- grows towards stimulus

NEGATIVE TROPISM- grows away from stimulus

Answer 1

PHOTOTROPISM- growth of plant shoot towards the light

• in a plant stem= positive phototropism
• in a plant root= negative phototropism

Question 2

AUXINS
•family of plant hormone e.g. IAA
•produced in the tips of growing stems + roots
•unequal distribution of auxin causes unequal growth rates in plants

•it controls the growth of stems and roots

Answer 2

AUXIN AND PHOTOTROPISM:

• in a stem the shaded side contains more auxin causing it to grow more so the plant bends towards the light
• if the tips of a plant were removed, the stems wouldn’t grow

Question 3

AUXIN AND GEOTROPISM:

• negative geotropism- stem grows against gravity
• positive geotropism- stem grows towards gravity
• root horizontal= bottom side contains more auxin + grows less (+ geotropism)
• stem horizontal= bottom side contains more auxin +grows more (- geotropism)

Answer 3

GIBBERELLINS:

•group of plant hormones responsible for growth and development

•important for initiating seed development + germination
-end seed dormancy
-promote flowering
-increase fruit size
•seed dormancy must be broke for them to germinate

Question 4

• gibberellins are used in the production of seedless fruit to increase the size
• gibberellins are also involved with auxin in controlling internode length

Answer 4

CYTOKININS:

• they stop the plant aging and dying
• auxin and cytokinins together promote cell division

Question 5

ABA:

•regulates seed development (prevents premature germination and is synthesised during desication of seed)

•regulates water loss by cloning stomata
-roots sense H2O deficiency
(ABA synthesis + release, transport ABA to leaves)
-stomata cells close
(guard cells are ABA target cells)
•plant regains turgor

Answer 5

ETHYLENE:

• causes fruit to ripen
• is a hydrocarbon has
• synthesis prompted by auxin

SALICYLIC ACID(SA):

•regulates plant growth + development aswell as resistance to abiotic stress