What is a (PGR) Plant growth Regulator? Commercial use of Bio- regulator in Vegetable crops.

What is a  (PGR) Plant growth Regulator?

A Growth regulator is
• An organic compound
• can be natural' or synthetic
• It modifies or control one or more specific physiological processes within a plant but the site of action and production are different. If the compound is produced within the plant it is called a Plant hormone (Eg : Auxin which regulates the growth of longitudinal cells involved in bending a stem of plant one way or the other).
 
    Bio- regulator are endogenous or synthetically produced substances which can control one or more specific biochemical and physiological Function of many species probably by their influence on gene and enzyme interactions.

Type of Bio - Regulator/ Plant Growth Regulator.

1) Natural bio-regulator

• Auxins
• Gibberellins
• Cytokinins
• Ethylene
• Abscisic acid.

2) Synthetic bio-regulator

•IBA,
• 2,4 -D
• NAA, 2, 4, 5-T
• Morphactins
• Cycocel
• maleic hydrazide etc.

A] Auxin

Type - Natural : Indole 3 acetic acid
            Synthetic: IBA, NAA, 2,4-D

Function

1) Apical dominance
• Apical bud dominance over the lateral bud and does not allow the lateral buds to grow.

2) Rooting
• Applied on cutting to stimulate root growth and development.

3) Parthenocarpy
• Fruit Formation without pollination and Fertilization.

4) Prevention of Abscission.
•  Natural auxin prevent the formation of abscission layer which may otherwise result in
Fall of leaves, flower and fruit.

5) Flowering
• Foliar spray of NAA, 2,4-D induce Flowering ( Eg cucumber).

6) storage
•  NAA is used to prevent the sprouting of potato tubers. Hence, increases Storage life.

7) Eradication of weeds
• 2,4-D and 2, 4,5-T are used to remove the weeds present in the crop field.

B] Gibberellins

function

1)  stem growth
cause hyper elongation of stem by stimulating of
both cell division and cell elongation, result in taller plant.
2) Induction of seed germination.
• GA actives germination of seed otherwise require cold (Stratification) or light to induce germination.

3) GA3  is used to break seed dormancy of freshly harvested vegetables.

4) Induction of maleness in Dioecious plant.

5) Bolting in long day plants.

C]Cytokinins

Function

1) cell division
Eg ÷ kinetic on plants is to induce cell division especially in carrot root tissue.

2) cell enlargement.
• like Auxins and gibberellins the kinetin induces cell
enlargement in the leaves of Phaseolus vulgaris , pumpkin.

3) Flower induction.
• Induce flowering in short day plants.

4) Dormancy or seeds.
• certain light sensitive seeds such as lettuce can also be broken by kinetin treatment.

5) Delay leaf senescence.

D]Abscisic acid

Function

• Growth inhibiters & ABA inhibits shoot growth but has less effect on root growth.
• Induce bud dormancy and seed Dormancy.
• Induce senescence of leaves, abscission of leaves. Flower and Fruit.
• Stomatal closing.

E] Ethylene

Now a Days Ethylene is being popular in the market mostly it is used to force the ripening of Banana, Tomato. Farmer used to harvest at the early stages and they used Ethylene to change the color and Faster the ripening process
1)Fruit ripening like  Banana,  apples, pears, Tomato, citrus.

2) Induction of femaleness ÷
Cucumber, squash, melon

3) It stimulate senescence and abscission of leaves.

4)  It cause inhibition of root growth

5) It stimulates the formation of adventitious roots.

Commercial use of Bio- regulator in Vegetable crops.

• Seed Germination.

-In tomato, pre sowing seed treatment with 100 ppm IAA, IBA and NAA enhanced the seed germination
-In muskmelon, soak seed in Ethephon at 480 mg/liter of water for 24 hours improves germination at low temperature (bottle gourd, squash melon and watermelon).

• seed Dormancy.

• Flowering.

• Sex Expression

-The treatment with PGR has found to change sex expression in cucurbits, okra, and pepper.

• Gametocides

• Hybrid Seed Production

• Fruit set

• Parthenocarpy

-  studies has shown that use of Growth Regulators vegetable cause Frequent increase in size with
their application. The role of plant growth regulators in Fruit developments can also be seen from the fact that with their help it is possible to stimulate fruit development without fertilization for Eg ÷
In Eggplant application of 2,4-D at 0.00025% in lanolin paste to cut end of styles or as foliar sprays to freshly opened flower cluster has been reported to induced Parthenocarpy.

•Fruit Ripening

Ethephon an ethylene releasing compound, has been reported to induce ripening in tomato and pepper.

• Fruit Yield.

Tomato ÷ soaking of seed in
NOA at 25-50 mg  have been reported to improve
fruit yield in tomato 

Eggplant ÷   soaking of seedling, roots in NAA at 0.2 mg / liter and ascorbic acid at 250. mg / liter has been reported to produce higher fruit yield.

Chillies and peppers 
Foliar spray of GA at 50 mg/ liter at fruit setting or plant plant planofix (NAA 10 mg/L) double sprays (at Flowering and 5 week later) decrease Flower Shedding and gave better fruit yield in chillies.