PLANT GROWTH REGULATORS - Plant growth regulator is also called as Phytohormone - Thimann (1948) gave the term Phytohormone - Organic substances which are produced naturally in plants - synthesized in one part and usually translocated to other part - every small quantity influence the growth and other physiological functions of the plants. Classes of Plant Growth Regulators Auxins- IAA, NAA, IBA, 2,4-D Gibberellins- GA3 Cytokinins- Kinetin, Zeatin Ethylene- Ethrel Abscisic acid- Dormins, Phaseic Acid Flowering hormones - Florigin, Anthesin, Vernalin Synthetic substances - Synthetic Auxins, Synthetic Cytokinins Growth inhibitors - AMO-1618, Phosphon-D, Cycosel, B-999.

1. Use of Growth regulators in propagation,
flower induction and retention
By
Mr. Sanjay Chetry
Ph.D. Scholar
Dept. of Fruit Science
TNAU, Coimbatore
ID: 2020632001

2. PLANT GROWTH REGULATORS
 Plant growth regulator is also called as Phytohormone
 Thimann (1948) gave the term Phytohormone
 organic substances which are produced naturally in plants
 synthesized in one part and usually translocated to other part
 every small quantity influence the growth and other physiological functions of
the plants.
Classes of Plant Growth Regulators
Auxins
IAA, NAA,
IBA, 2,4-D
Gibberellins
GA3
Cytokinins
Kinetin,
Zeatin
Ethylene
Ethrel
Abscisic acid
Dormins,
Phaseic Acid
Flowering hormones
Florigin, Anthesin,
Vernalin
Synthetic substances
Synthetic Auxins,
Synthetic Cytokinins
Growth inhibitors
AMO-1618, Phosphon-D,
Cycosel, B-999.

3. Role of Growth Regulators in propagation, flower induction and retention
1. Propagation: Multiplication of plant is known as propagation.
Auxin plays an important role in inducing rooting in cuttings.
NAA is a synthetic auxin that is routinely used for vegetative propagation of
plants from stem and cuttings.
Low conc. of auxin promotes the growth of intact roots and high conc.
inhibits.
GA3 is very useful in seed germination as it required for activation of
vegetative growth of the embryo.
Gibberellin application also activates the alpha amylase synthesis in the
aleurone layer where it converts starch to sugar which translocated to growing
embryo to provide energy source

4. Effect of pre-sowing seed treatment with bio-regulators

5. Gibberellins Proteases Protein Tryptophan Auxin
Effect of growth regulators on rooting in cuttings/ stooling

6. 2. Flower Induction:
It is the process of transformation of vegetative apex to flowering depends upon
the intensity of stimulus.
Application of growth regulators at different stages of growth helps in
inducing flowering
Paclobutrazol, SADH are anti-gibberellin and are used to promote
flowering in Pear and Mango
PBZ restricts vegetative growth and increase reproductive phase in
Mango
Ethylene is very effective in inducing flowering in Pineapple
Ethephon @ 25ppm brings early flowering in Pineapple.
NAA has also been found to promote flowering by synthesizing ethylene

7. Soil app. of PCB@1g a.i./m2 tree canopy
HDP/UHDP in Mango

8. Effect of bioregulators on flowering in Mango

9. 3. Flower/Fruit Retention
Flower/Fruit retention percentage is what determines the yield of the crop.
Apple
Early drop
June drop
Pre-harvest drop
Fruit drop
 Among these, pre-harvest causes serious economic losses.
 Due to reduction in level of auxin or increase in ethylene levels in fruit
 NAA @ 10 ppm 20-25 days before harvesting check the pre-harvest drop
effectively

10. Mango
Pin head drop
Pea size
Pre-harvest drop
Fruit drop
 It occurs because tree cannot provide enough nutrition to all the fruits
 Triple spray of NAA @ 5ppm (full bloom, pea stage and marble stage)
(Singh et al., 1986)
 NAA@ 20-40 ppm is also found effective.
(Singh et al., 1959; Chadha & Singh, 1963 and Pal et al., 1976)
 Spray of Urea (4%), KNO3 (3%) and NAA (40 ppm) increased no. of
fruits/plant. (Sharma et al., 1990)
 Spray of 3% Urea increased 11.35% fruit retention when sprayed at pea stage.
(Singh et al., 1991)

11.  In Citrus, major flower drop occurs from early flowering stages until 2-3 weeks
after full bloom.
 Ovule fertilization usually plays a major role in subsequent retention.
 2.5 to 3 months after full bloom a major fruitlet drop
 Often occurred when carbohydrate competition limited fruitlet retention
In Acid lime var. PKM 1, the highest fruit retention (57.09%) was recorded in
Paclobutrazol @ 1.5 g a.i /m2 + NAA 200ppm, and the fruit retention was lowest
in control with (26.18%).

12. Effect of Growth retardant on fruit set and development

13. Conclusion
PGR modify or regulate physiological processes in an
appreciable manner in the plant when used in small
concentration.
They are rapidly absorbed and move rapidly through the
tissues
These chemicals are specific in their action and each hormones
has quite a great role in inducing rooting, flower and retention.
Therefore, application of various hormones should be
applied as recommended and at particular stage for
increasing its effectiveness.

14. Arunadevi, A., Kumar, S. B., Rajangam, J., & Venkatesan, K. (2019). Effect of plant
growth regulators on growth, yield and quality of acid lime (Citrus aurantifolia
Swingle.) var. PKM 1. Journal of Pharmacognosy and Phytochemistry, 8(3), 3438-
3441.
Bisht, T. S., Rawat, L., Chakraborty, B., & Yadav, V. (2018). A recent advance in use of
plant growth regulators (PGRs) in fruit crops-a review. International Journal of
Current Microbiology and Applied Sciences, 7(5), 1307-1336.
Jameel, A., Naik, R., Madhumathi, C., Reddy, S., & Venkataramana, K. (2018). Physiology
of flowering in mango. Journal of Pharmacognosy and Phytochemistry, 7(6), 2375-
2382.
Kishore Kumar Das, P. K. Yadav, S. R. Bhunia and Singh. R. S. 2020. Effect of Plant
Growth Regulators on Flowering Parameters of Ber (Zizyphus Mauritiana Lamk).
Int.J.Curr.Microbiol.App.Sci. 9(03): 2684-2690.
Kumari, S., Bakshi, P., Sharma, A., Wali, V. K., Jasrotia, A., & Kour, S. (2018). Use of
plant growth regulators for improving fruit production in sub-tropical crops. Int J Curr
Microbiol App Sci, 7(03), 659-668.
References

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