Plant Hormones. Types of hormones Like animals, plants use hormones to produce functional and...
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Transcript of Plant Hormones. Types of hormones Like animals, plants use hormones to produce functional and...
Types of hormonesLike animals, plants use hormones to produce functional and structural changes. Types of hormones includeAuxinsGibberellinsCytokininsEthylene
AuxinAuxins are a type of hormone that produces cell elongation and allows the plant to grow in length and to develop.
The natural Auxin is a compound called indoleacetic acid or IAA
Auxin associated with phototropism - early experimentsdemonstrate tip as receptor.
Auxin continuedAuxin is made at the apical meristem of a shoot and moves down at a rate of 10 mm per hour to the region of elongation and stimulates cell growth.
Question????At this speed, how do you think it is transported through the cell?
Auxin moves down the plantAnswer Too slow for phloem transportationIt is carried by the parenchyma tissue from one cell to the next.
Auxins do two things to help with cell elongation: Soften the cell walls so the plant can expandIncrease the rate of cell division
Demonstration of transported chemical
Loosening of cell wall
Lateral growth Auxins produced in the meristem inhibits growth of side branches (lateral stems)
Cytokinins You will remember from Mor 4 that cytology is the study of cells.
The hormone, Cytokinins stimulate cell division (mitosis and cytokinesis)
Cytokinins are produced by actively growing tissue and can move throughout the plant in the xylem, phloem and parenchyma cells.
Function of cytokininsPromotes cell division.Lateral bud development.Delay of senescence (AGING).Stomata opening.Rapid transport in xylem stream.
Cytokinins are used with Auxins to help plants to grow and develop
Effects of GibberellinsGeneral cell elongation.Breaking of dormancy.Promotion of flowering.
GibberellinsGibberellins are growth hormones that allow the plant to grow in length.Gibberellins were discover in Asia when some farmers noticed that rice would grow too fast and tall which was caused by a fungus called Gibberella. Gibberellins are usually produced in roots and young leaves and stimulate a growth in leaves and stems but not in roots. Gibberellins are also found to increase seed germination and flower development
Discovered in association with Foolish disease of rice (Gibberella fujikuroi)infecteduninfected
Gibberellins and plant growth
EthyleneH H \ / C = C / \ H H
Functions of ethyleneGaseous in form.Rapid diffusion.Affects adjacent individuals.Senescence (aging) and abscission (the natural process by which leaves or other parts are shed from a plant).Interference with auxin transport.Initiation of stem elongation and bud development.
Ethylene gasYears ago, farmers use to heat fruit in a kerosene oven to make them ripen faster. Scientist learnt that it was not the heat but the ethylene gas byproduct that made it ripenWe now know that plants develop their own ethylene as a hormone that makes fruit ripen
EthyleneScientist also discovered that ethylene is the opposite to Auxin and inhibits cell growth
Thanks ClassHave a great day!!!