Plant production stuff
Heres my stuff on hormones, hope it helps
Plant Hormones and Growth and Development
Plant hormones are chemical messengers that are produced in actively growing parts such as roots, tips and stems. There are 3 main types of plant hormones:
- auxins
- cytokinins
- gibberellins
Auxins in stems and leaves promote:
- stem elongation eg. Stems bend towards light and away from gravity
- secondary thickening of stems and roots
- apical dominance preventing lower buds from growing
- the growth of fruit
- the prevention of fruits and leaves from falling.
Cytokinins are produced in roots, seeds, and cambium tissue. They control cell division and determine which cells will become root or leaf cells.
Gibberellins are produced by germinating seeds and young stems. They:
- cause plants to grow larger eg. stem growth
- regulate blossoming in certain plants
- cause seeds and buds to grow after dormancy.
Abscisic acid blocks plant growth and stimulates dormancy.
Ethylene is produced by young growing tissues and aging leaves and regulates the ripening of fruit.
Manipulating Plant Production
Auxins are used in commercial production to:
- produce seedless fruit eg. cucumbers and tomatoes
- prevent fruit from falling off trees before harvest eg. apple trees
- act as weed killers when sprayed in large concentrations because broadleaf weeds grow in an uncontrolled manner
Other hormonal uses include:
- thinning fruit trees so the fruit is larger
- ripening bananas eg. harvesting bananas green to reduce bruising and later ripening them using ethylene gas
- tissue culture
- propagation cuttings
- inhibiting stem elongation eg. dwarf plants.
