Chemical Control In Plants Flashcards
Which stimuli affects plants?
External environmental cues that have direct impact on the well being of the plant
Sensitive to light, intensity of light and direction of the light.
Also sensitive to gravity. Water, temperatures and some chemicals.
What is growth
Permanent increase in the size of an organism
How is growth brought about
Cell division and the assimilation of new material within the cells that result from the division, followed by ell expansion
Where are the main areas of cell division in a plant
Meristems, occurs just behind the top of a root or a shoot. Particularly sensitive just behind the tip of W root or shoot
What number of ways can chemical messages act?
Easier for cellulose walls to be stretched, and in turn makes it easier for cells to explain and grow
What is division?
When the cell divided into more cells
What is auxin
For example. IAA, powerful growth stimulants that are effective in very LOW concentrations.
Where are auxins produced
In young shoots and always move down the plant from shoots to roots
What does the movement of auxin involve
Active transport and calcium ions
What are auxins involved in
Apical dominance. Where they suppress the growth of lateral shoots so the one main stem grows fastest
Also involved in tropical responses of plant shoots to unilateral lift. Depends on both the concentration of the hormone and region of the plants
What do you use auxin in in garden
Taking cuttings: applying rooting powder containing different auxins.
Weed killers: synthetic auxins mimic the effects of natural plant hormones.
How does IAA affect the plant
Made in the tip of the shoot and diffuses back towards the done of elongation. Bonds to specific receptor sites on the cell surface membranes, activating the active pumping of hydrogen ions into the cell wall spaces. Changes h concentration, providing optimum temp of 5 for enzymes that break bonds between adjacent microfibrils to slide past. Cells absorb water by osmosis and result in turgor pressure. Eventually IAA is destroyed by enzymes and ph of cell wall rises , the enzyme is inhibited and bonds form between the cellulose microfibrils and then the cell wall becomes more rigid
What is gibberellin
Growth regulators
What does gibberellin affect?
Affect the internodes of the stem, stimulating elongation of growing cells, also promote the growth of fruit. Involved in breaking dormancy in seeds and in germination, as they stimiate the formation of enzymes in seeds. Eg, stimulate the production of amylase which breaks down starch stores in cereal plants. Makes glucose available for respiration in the embryo plant as it develops as the seed germinates. Also stimulates bolting- period of sudden rapid growth.
What are cytokinins
Growth regulators
