Used to prevent leaf and fruit drop and promote flowering.
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What is promoted in high auxin concentrations?
Fruit drop
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When is fruit drop useful?
Useful if there are too many small fruits that will be difficult to sell as the plant will produce fewer, larger fruits.
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How can auxin be used when taking cuttings?
Dipping the end of a cutting in rooting powder before planting it encourages root growth. Rooting powder contains auxins, a fungicide and talcum powder.
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Describe auxin and seedless fruit
Treating unpollinated flowers with auxin can promote growth of seedless fruit.
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How can auxins play a role in herbicide use?
Artificial auxins are used as herbicides to kill weeds. They are transported in phloem to all parts of the plant and act in the plant for longer.
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How do artificial auxins act in the plant for longer?
Because they are not a close fit to the enzymes that break them down.
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What do auxins promote?
Promote shoot growth so much that the stem cannot support itself, buckles and dies.
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What do gibberellins do?
Delay senescene in citrus fruit, extending the time fruits can be left unpicked, making them available in shops for longer.
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Describe action of gibberellins with cytokinins
Can make apples elongate to improve their shape.
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Describe the impact on grapes without gibberellins
Bunches of grapes are very compact which restricts the growth of individual grapes.
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What is the growth of grapes like with gibberellins?
The grape stalks elongate, they are less compacted and the grapes get bigger.
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What happens in brewing when barley seeds germinate?
The aleurone layer of the seed produces amylase enzymes that break down stored starch into maltose.
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What are the genes for amylase production switched on naturally by?
Switched on by naturally occurring gibberellins.
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What effect can adding gibberellins have?
Can speed up the process.
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How is malt produced?
Malt is produced by drying and grinding up the seeds.
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What stimulates growth between the nodes?
Spraying sugar cane with gibberellins stimulates growth between the nodes, making the stems elongate.
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Why is this useful?
Sugar cane storess sugar in the cells of the internodes, making more sugar available from each plant.
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Why can breeding conifers take a long time?
Because conifers spend a long time as juvenilles before becoming reproductively active.
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How can gibberellins speed up the process?
By inducing seed formation in young trees.
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What can seed companies who want to harvest seeds from biennial plants add and why?
Can add gibberellins to induce seed production in the 1st year.
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How can stopping plants making gibberellins be useful?
Spraying with gibberellins synthesis inhibitors can keep flowers short and stocky and prevent lodging.
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When does lodging happen?
In wet summers - Stems bend over due to weight of water collected on ripened seed heads making crop difficult to harvest.
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What can cytokinins be used to prevent?
Used to prevent yellowing of lettuce leaves after they have been picked.
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What process are cytokinins used in?
Tissue culture to help mass-produce plants as they promote bud and shoot growth from small pieces of tissue taken from a parent plant.
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How can ethene be put onto plants?
Converted to 2-chloroethylphosphonic acid which can be sprayed in solution and be absorbed and released by the plant.
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What are the commercial uses of ethene?
Speeding up fruit ripening, promoting fruit drop, promoting female sex expression, promoting lateral growth.
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How can restricting ethene's effects be useful?
Storing fruit in a low temperature with little oxygen and high CO2 concentration prevents ethene synthesis and fruit ripening so fruits can be stored for longer.
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What inhibitor of ethene synthesis can be used to increase the shelf life of cut flowers?
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