5.5.4 commercial uses of plant hormones

Question 1

commercial uses of (artificial) auxin

Answer 1

1. prevent leaf & fruit ‘drop’
2. promote flowering for commercial flower production
3. taking cuttings = dip end of cutting into rooting powder to encourage root growth (contains auxins & talcum powder)
4. herbicides = auxins used to kill weeds (as they’re man-made, plants find them more difficult to break down so act in plant for longer) & promote shoot growth so much that stem cannot support itself, buckles & dies

Question 2

what are cytokinins used for

Answer 2

• delay leaf senescence = used to prevent yellowing of lettuce leaves after picking
• used in tissue culture to help mass-produce plants = promote bud/shoot growth in explants (produces short shoot with lots of side branches that can be split & grown separately)

Question 3

how are gibberellins used in fruit production

Answer 3

• delay senescence in fruit = extends time they can be left unpicked & makes them available for longer in shops
• elongate grape stalks = less compact & grapes grow bigger

Question 4

how can ethene be used

Answer 4

• scientists developed 2-chloroethylphosphonic acid = sprayed in solution, easily absorbed & slowly releases ethene within plant
• eg. speeds up ripening of apples, tomatoes & citrus fruits

Question 5

how can restricting ethene also be useful

Answer 5

• storing fruit at low temperature with little oxygen & high carbon dioxide levels prevents ethene synthesis = prevents fruit ripening
• fruits can be stored for longer