how to ripen green tomato?. plant hormones 12.6 understanding plant hormones
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HOW TO RIPEN GREEN TOMATO?
Plant Hormones
12.6 UNDERSTANDING PLANT HORMONES
A.k.a phytohormonesA group of naturally occurring organic compounds that influence physiological process at low concentration
Usually produced in one part of the plant
Translocated to another part of plant when they act
PLANT HORMONES
Plant need hormones to:Allow them to respond to environmental factors
Environmental factors CO2
O2
Toxins Gravity Temperature Sunlight Parasites Pathogens
Control plant growth, development and movement
Example of plant hormones:AuxinsGibbrellinsCytokininsAbscisinsEthylene or ethene
AUXIN
Greek (to grow)E.g. indoleacetic acid (IAA), zeatin
(natural) & kinetin (synthetic)Promote cell elongation & cell
enlargementProduce at stem tips, root tips (root
caps), stems & budsRequired by plants almost all the timeInvolved in phototropism & geotropism
AUXINS
POP QUIZ
AUXIN IN GEOTROPISM
Major effect is on stem elongation ; important in the regulation of height
Have little effect on rootsProduce at seeds, fruits & young leaves
Only required at certain times to induce major developmental changes (stem elongation)
GIBBERELLINS
Stimulate cytokinesis (cell division) & influence cell differentiation
Produced in all actively growing tissues (meristematic tissue)
Often act together with auxins
CYTOKININS
Promote stomatal closure, prolong seed dormancy & stimulate shedding of leaves, flowers and fruits
Mostly synthesized in mature leaves
ABSCISINS
A gas; transported by diffusionPromotes flower opening and fruit ripening
Also stimulates:Defence response to wounding/ infection of disease
Shoot growth & differentiationRoot growth & differentiationLeaf & fruit abcission
ETHYLENE OR ETHENE
THE USE OF HORMONES IN AGRICULTURE
1. Promote growth of roots
2. Stimulate parthenocarpy – formation of fruits without fertilisation
3. Herbicide4. Prevent fruit from
dropping before harvest is due
AUXINS
1. Promote fruit ripening2. Induce flowering in pineapple3. Increase latex flow – rubber
trees4. Promote female flower
production
ETHYLENE / ETHENE
1.+ auxins = stimulate the production of shoots & roots in tissue culture
2.Prolong the storage life of vegetables
CYTOKININS
1. Increase production of bigger & more uniform bunches of seedless grapes
2. Increase sugarcane yield3. Increase flower bud production
and stimulate their early flowering
GIBBERELLINS