Aspect of Growth
Growth does not occur any how in all parts of the plant. It takes place in certain tissue and places in a plant bodies. The tissue where growth takes place plant is called meristem or meristematic tissue. A meristem is a tissue that retains their ability to divide by mitosis and turn out new cells. Such meristematic tissues include root apex, stem or shoot apex base or internodes and vascular cambium.
Growth which occurs in the apical stem and root meristem is called apical growth while growth which occurs at meristem base of internodes is called auxiliary growth
Regulation of growth by Hormones
Hormones or chemical or biochemical substances produced in small quantity by cell of the body of plant and animal that has profound effect on other part of their body where they are needed for some form of growth
Plant hormones are produced only at the growing parts such as apical meristem of shoot or root i.e. shoot tip or root tip and transported to other part by diffusion.
Examples of plant hormones are auxin, gibberellin, cytokinin, abscissic acid and florigens. Plant hormones help plant in the following ways.
- It promotes stem elongation
- It makes plant to respond to tropism
iii. It causes root and stem apical division
- It causes fruit growth and ripening
- It causes flower bud and lateral root initiation
In animal, hormones are produced in ductless glands called endocrine system and release straight to the blood stream which transport them to the target organ. Animal hormones include the following
|Pituitary gland||base of head||Pituitrin|
|Pancreas||Loop of duodenum||Insulin|
|Adrenal gland||Top of each kidney||Adrenaline|
FUNCTION OF ANIMAL HORMONE
- It controls body metabolism
- It promotes growth of the animal
- It induces or stimulates reproduction