Definition and Function of Hormones

Is a collection of organic compounds instead of nutrient ( nutrients ) , both naturally occurring and man-made , which in very small levels to encourage , inhibit , or alter the growth , development , and movement ( taksis ) plants . " Small levels " is meant to be in the range of millimoles per liter to one micromol per liter . The use of the term " hormone " himself used the analogy of hormone function in animals . However, the plant hormone is not produced from a special form of glandular tissue appendix ( endocrine ) as animals , but it resulted from non - specific tissue ( usually meristematic ) that produce this substance when get stimulated . Spread of plant hormones do not have to go through the vascular system of plants because the hormone can be translocated through the cytoplasm or space between cells .

Plant hormone produced by the individual concerned ( " endogenous " ) . Hormone from outside the individual systems can also be done ( " exogenous " ) . Exogenous administration may also involve non - natural chemicals ( synthetic , not made from plant extract ) that give rise to similar stimuli with natural phytohormones . Therefore , to accommodate the differences of animal hormones , is also used istilahzat plant growth regulators (English : plant growth regulator / substances) for plant hormones . There are hundreds of plant hormones or growth regulators ( PGR ) which is known to man , whether produced naturally by the plants themselves ( endogenous ) and the resulting non - plant olehorganisme synthetic or man-made ( exogenous ) . Grouping is done for easy identification , and are based primarily based on a similar physiological effects , not based on mere similarity of chemical structure .

Following the agreement of many experts , there are five major groups of plant hormones , namely auxin ( AUX ) , cytokinin ( CK ) , gibberellins ( or gibberellic acid , GA ) , ethylene ( ethene , ETH ) , and abscisic acid ( abscisic acid , ABA ) . The first three groups tended to be positive for growth at physiological concentrations , ethylene can support or inhibit growth , and abscisic acid primarily an inhibitor ( inhibitor ) growth . In addition to the five factions , known also other groups that serve similar but plant hormone known to work for some groups of plants alone or an exogenous hormone , namely brasinosteroid , jasmonate acid , salicylic acid , polyamines , and karrikin . Some synthetic compounds act as inhibitors ( inhibiting progression ) .

There are nine auxin , cytokinins 14 , 52 gibberellins , three abscisic acid , and the ethylene produced naturally and have extracted the [ 1 ] . No synthetic plant growth regulator that has a function similar to natural plant growth regulator , although it has a different chemical structure . In practice , often PGR synthetic ( man-made ) is more effective or less expensive when applied to kepentinganusaha farmer rather than the extraction of natural PGR .

TYPES OF HORMONES AND FUNCTIONS

A. auxin

Auxin term was first used by Frits Went found that a compound that causes the bending of the coleoptile toward light . Coleoptile bending caused by cell elongation terpacunya plastered on the side of the piece of agar containing auxin . Went auxin found now known as indole acetic acid ( IAA ) . Besides IAA , plants contain three other compounds which are considered as the hormone auxin , yaitu4 - chloro indolasetat ( 4 chloro IAA ) found in young IJI b type nuts , phenyl acetic acid ( PAA ) are found in many plant species , and acid indolbutirat ( IBA ) which is found in the leaves of corn and a variety of dicotyledonous plant species . Auxin plays a role in a wide variety of plant activities include :

Fruit Development

At the time ripe seed growing , seed auxin issued to the sections of interest thereby stimulating the fruit formation . Thus , the provision of auxin in the pollinated flowers are not going to stimulate the development of seedless fruits . It is called partenokarpi .

Apical Dominance

Apical dominance is growing tip of the bud of a plant that inhibits the development of lateral buds on the stem side down . Apical dominance is a result of the downward transport of auxin is made ​​in the apical meristem . Young leaves and fruit abscission young form of auxin , in order to remain strong both attached to the trunk . However , if the reduced auxin formation , a layer of specialized cells are formed at the base of the petiole and fruit so that the leaves and fruit fall Formation of auxin stimulates the formation of adventitious roots that grow wild roots from stems or leaves in many species .

B. gibberellins

Gibberellins were first discovered in Japan in 1930 from the study of diseased rice plants . Rice with the fungus Gibberella fujikuroi is growing too high . Japanese scientists isolated a substance from the fungus culture . These substances called gibberellins . Forms such as gibberellins GA3 , GA1 , GA4 , GA5 , GA19 , GA20 , GA37 , and GA38 . Gibberellins produced by fungi and higher plants . Gibberellin synthesized in almost all parts of the plant , such as seeds , young leaves , and roots . Gibberellins have several roles , among others :

• Encourage the extension of the abnormal stem intact .
• Seed germination and mobilization of food reserves of the endosperm to embryo growth .
• The development of flowers and fruit .
• Eliminate the nature of genetically dwarf plants .
• Stimulates cell division and elongation .

C. Kinetin is the first synthetic cytokinin discovered by Carlos Miller on dried fish . After it was found that other cytokinin compounds in the liquid endosperm of corn , namely zeatin .

D. Another synthetic cytokinin BAP ( 6 - benzilaminopurin ) and 2 - ip . Cytokinins have several functions , among others : Stimulates cell division in meristematic tissue .

1. Stimulate differentiation of the cells produced in the meristem .
2. Encourage the growth of side shoots and leaf expansion .
3. Delaying the aging leaves .
4. Stimulate the formation of buds and seeds capable of breaking the rest period ( dormancy breaking ) .

E. Ethylene gas that fruits especially older releases a gas called ethylene . Ethylene is synthesized by plants and led to more rapid ripening process . In addition to ethylene produced by plants , there is a synthetic ethylene , which etepon ( 2 - kloroetifosfonat acid ) . This synthetic ethylene traders often used to speed up the ripening of fruit . In addition to spurring ripening , ethylene also stimulate seed germination , stem thickening , encourage leaf drop , stem elongation and inhibit germination . In addition , ethylene delay flowering , reduce apical dominance and root initiation , and inhibit seedling stem elongation .

F. Abscisic acid ( ABA ) , abscisic acid ( ABA ) is an inhibitor ( inhibitor ) in plant activities . This hormone is formed in daundaun adults . Have a physiological role of abscisic acid are:

1. Accelerate abscission aging plant parts , such as leaves , fruit and bud dormancy .
2. Induces transport photosynthesis to grain growing and promotes the synthesis of protein deposits .
3. Organize the closing and opening of stomata especially during water stress 

F. Traumalin acid. Traumalin acid is referred to as hormone wound / cambium because this hormone plays a role when the plant tissue is damaged. If injured, plants will stimulate the cells in the injured area to be longer so as to hold meristem cell division to close the wound. You need to know besides hormones, vitamins can affect the growth and development, such as vitamin B12, vitamin B1, vitamin B6, vitamin C (ascorbic acid). These vitamins function in the formation of hormones and serves as a coenzyme.

G. Kalin. Did you know Kalin is a hormone that functions to stimulate the growth of plant organs, including:

• rhizokalin, can stimulate root growth;
• kaulokalin, can spur the growth of the stem;
• fitokalin, can spur the growth of the leaves;
• anthokalin, can spur the growth of flowers.