This slide focuses on the importance of plant growth regulators in fruit production and quality improvement. As we know very well that the PGR plays an important role in growth and development of plants. Plant growth regulators are chemicals used to modify plant growth such as increasing branching suppressing shoot growth, increasing return bloom, removing excess fruit, or alternate fruit maturity. The plant hormones are extremely important agent in the integration of developmental activities. Environmental factors often exert inductive effects by evoking changes in hormones in metabolism and distribution within the plant. Apart from it, they also regulate expression of intrinsic genetic potential of plants. Control of genetic expression has been demonstrated for the phytohormones at both transcriptional and translational levels. Also, hormones receptors and binding proteins have been identified on membrane surface that are specific for some hormones. The use of growth regulators has become an important component of agro-technical procedures for most of the cultivated plants and especially for fruit plants. So far in fruit crops, excessive fruit drop can be controlled by the exogenous application of plant growth regulators. The auxin and gibberellins are widely used to control the fruit drop and to improve the quality of fruit. Ontogenic development from fruit set to fruit ripening and final reach to customer, several agents are responsible for elimination of some fruits from fruit set to final maturity. In this seminar, I will focus on the major functions of plant growth regulators in fruit production.

1. Master’s Seminar (FSC-591)
Banda University of Agriculture and Technology,
Banda (U.P)
Name- Abhishek Pratap
ID:- 2049
M.Sc. (Horticulture)
Department of Fruit Science

2. IMPORTANCE OF PGRs IN
FRUIT PRODUCTION AND
QUALITY IMPROVEMENT

3. CONTENTS
• Introduction
• History
• Commercial applications
• Future thrust
• Conclusion

4. INTRODUCTION
Definition:
Phillip (1971)
• Compounds related to auxins and gibberellins
• Inhibitors of gibberellin biosynthesis,
• Cytokinins (cell division)
• Abscisic acid (dormin) and
• Compounds affecting the ethylene status.

5. HISTORY OF GROWTH REGULATORS
• Existance of growth substances was first proposed by Charles Darwin (1880)
in his book The Power of Movements in Plants
• Auxin was the first hormone to be discovered in plant and at one time
considered to be only naturally occurring plant growth hormone.
• Prajapati et al. (2015)
• Three types of plant hormones Auxins, Gibberellins and Cytokinins were
discovered in early decades of the twentieth century, in 1930’s and in 1960’s
respectively.
• Thomas (1956)

6. AUXINS
• Auxins were the first plant hormones to be discovered. Auxins are
produced in higher concentration by growing tips of stems and roots
of plants from where they migrate to another places to induce
growth.
• Types of Auxins:
Natural Auxins: are Indole-3-Acetic Acid (IAA), Indole-3-Acetonitrile,
Indole-3-Acetaldehyde and Indole-3-Ethanol.
Synthetic auxins: are Indole Butyric Acid (IBA), Phenyl Acetic Acid,
2,4-Dichlorophenoxy Acetic Acid (2,4-D), α-Naphthalene Acetic
Acid (NAA) and 2,4,5-Trichlorophenoxy Acetic Acid (2,4,5-T)

7. GIBBERELLIN
• Gibberellins are named after the fungus Gibberella fujikuroi
which causes rice plants to grow abnormally tall.
(Kurosawa et al. 1930)
• Gibberellin produced in shoot apex mainly in leaf primordial
and root system, hence they translocate easily in the plant
in both directions.
• Now more then 135 different gibberellins are available.
• The most commonly occurring gibberellin is GA3.

8. CYTOKININ
• They were first isolated from coconut milk.
• Skoog and Miller isolated a cell division stimulating
factor. They named it Kinetin because of its amazing
power to stimulate cell division
• Letham proposed the term Cytokinin because of the
property to activate cytokinesis during cell division.
• They are synthesized in root apex, endosperm of
seeds, young fruits, where cell division takes place
continuously.

9. ETHYLENE
• It is naturally occurring gaseous growth
regulator.
• Ethylene is produced by most or all plant
organs.
• Synthesis of ethylene is inhibited by carbon
dioxide and requires oxygen.
• It stimulates the formation of adventitious roots.

10. ABSCISIC ACID
• It is also known as dormins, which acts as anti-
gibberellins.
• It is synthesized in leaves of wide variety of plants.
• Responsible for closing stomata during drought
conditions, hence acts as plant stress hormone.
• It is powerful natural growth inhibitor.

11. OTHER PGR’s
• Brassinosteroides recognized as a sixth class of plant hormones which stimulate cell elongation and
division, gravitropism, resistance to stress and xylem differentiation.
• Melatonin parthenocarpic fruit formation in pear.
• Morphactins fluorine containing compounds that tend to produce morphological changes and
suppress growth.
• Salicylic acid plant defence activation mediate host responses upon pathogen infection.
• Triacontanol enhances the physiological efficiency of the cells and, thus, exploits the genetic
potential of plant to a large extent.
• Karrikins are the group of plant growth regulators found in the smoke of burning plant material and
has the ability to stimulate the germination of seeds.

12. COMMERCIAL USE OF
PLANT GROWTH
REGULATORS IN FRUIT
CROPS

13. SEED GERMINATION
• Soaking of seeds in 500 ppm GA3 for 40 hrs. favors the appropriate
seed germination as well as the growth of the radicle and plumule
leading to better growth and survival of seedlings.
Wani et al. (2014)
• Gibberellins are used in substitution of chilling requirement which
remains essential for germination of many fruit seeds.
Apple seeds Litchi seeds Strawberry seeds

14. GROWTH
• Foliar spray of triacontanol in the form of mixtalol @ 6 ml/10 l water
improves the length of terminal shoot, number of leaves and
increase in leaf area.
Mandal and Kumar (1989)
• Application of GA3 at 150 ppm shows earliness in sprouting of new
shoot, increased shoot length and maximum number of leaves per
shoot in sapota.
Bhujbal et al. (2012)
• The application of GA3 in strawberry at 80 ppm improved
vegetative growth, runner production, ascorbic acid and acidity.
Kumar et al. (2012)
• Application of NAA in phalsa at 200 ppm resulted maximum height
of bush (177.33 cm) and length of shoot (99.17 cm).
Kacha et al. (2012)

15. Effect of gibberellin on seedling growth

16. VEGETATIVE PROPAGATION
• Application of NAA 10,000 ppm increased rooting in hard to root
rootstocks of apple MM-109, M-4 and M-9.
Tripathi et al.(2006)
• Cytokinin is important for callus and the ratio of cytokinin to auxin if
cytokinin: auxin ratio is high it promotes shoot proliferation while as
low cytokinin: auxin ratio enhances root formation.
Jain (2013)
• In grapes & banana, BA and NAA are essential for establishment of
explants. Gibberellic acid and salicylic acid are important for
proliferation of stem explants
Fry and Street (1980)

17. Rooting of cuttings in hormonal solution Air layering in guava

18. CANOPY MANAGEMENT
• Growth regulators develop a higher number of branches, higher leaf
area and better ratio between tiny roots and skeletal ones.
Vahid et al. (2016)
• Application of NAA in “Fuji” apple significantly decreased shoot
growth and re-growth rate. 2 or 3 application of NAA (60-70 days after
full flowering) at the concentration of 10 to 40 mg/l can control the
canopy size in high density orchard system.
Choi and Minsoon (2001)
• Application of NAA at 200 ppm in phalsa resulted maximum height of
bush (177.33 cm) and length of shoot (99.17 cm).
Kacha et al. (2012)

19. Ultra High Density apple orchard

20. FLOWERING
• Spray of 150 ppm NAA and 6 per cent urea in mango increases the total
number of flowers/panicle and percentage of hermaphrodite flowers.
Baghel and Tiwari (2003)
• Foliar spray of ethrel @ 200 ppm increases the number of flowers/panical
in mango.
Vijaylakshmi and Srinivasan (1998)
• Ethylene releasing agents such as ethephon are used widely to induce
flowering in pineapple.
Turn bull et al. (1999)
• Foliar application of 0.5 gm PBZ + 0.4 gm ethephon / l promotes flowering
in litchi with erratic fruiting.
Ramburn (2001)

21. • CCC @ 500 ppm induced the earliest flowering and highest
number of flowers, fruit set, retention and yield.
Brahmachari et al. (1996)

22. FRUIT SETTING
• Application of ethrel at 25 or 50 ppm in guava enhanced fruit set
percentage, weight, quality of fruit while, reduced number and weight of
seeds thereby increased pulp / seed ratio.
Brahmachari et al. (1995)
• Application of GA3 at 100 ppm increased the fruit set percentage and
increase the fruit size.
Kim et al. (2003)

23. PARTHENOCARPY & SEED LESSNESS
The application of hormones to induce parthenocarpic fruits in horticultural crops
Hormones Types Crop Species
Auxin
2,4-D Tomato, Pear, sweet chili pepper
NAA Cucumber, Strawberry, African palm
Brassinosteroids EBR Cucumber
BZR Sugar apple
Cytokinin ВАР Grapes
CPPU Cucumber, Fig, Pears, Kiwi, Pointed gourd
Gibberellic acid GA3
Citrus, Grapes, Loquat, Persimmon, Tomato
tree fruit
GA4 Pear
GA4 +7 Pear
PAC Pear
Ethylene ACC Tomato
1-MCP Tomato
Melatonin melatonin Pear
Sharif et al. (2022)

24. SEEDED
SEEDLESS
Sharif et al. (2022)

25. FRUIT THINNING
• NAA at 350 ppm at pea stage favours dropping of extra fruits and
retention of superior quality fruits in Nagpur mandarin.
Sawale et al. (2001)
• Fruit thinning is a very important practice in viticulture to develop
superior quality bunches.it is done by 50ppm GA3.

26. QUALITY IMPROVEMENT
• Application of NAA @ 20 to 60 ppm increases fruit weight,
organoleptic rating, TSS, ascorbic acid and total sugar content of
guava fruits
Yadav et al. (2001)
• Spray of NAA 300 ppm results in thinned fruit lets, increased fruit size,
decreased splitting to 30 per cent, decreased the incidence of
creasing to 28 per cent.
Greenberg et al. (2006)
• Foliar application of GA3 @ 25 ppm increases the fruit weight,
volume, TSS, ascorbic acid, peel and yield in ‘Nagpur’ mandarin.
Ingle et al. (2001)

27. • Application of 25 ppm 2,4-D plus 30 ppm NAA at the beginning of pit-
hardening in cherry increases fruit size, total yield and fruit quality.
Stern et al. (2007)

28. FRUIT RIPENING
Foliar sprays of GA3 at 20ppm in ‘Ponkan’ mandarin delays in the fruit
harvesting, which was induced by the physiological effect of GA3.
Modesto et al. (2006)
Delayed ripening in
Kinnow mandarin by foliar
application of Salicylic
Acid.
BUAT,Banda

29. COLOR DEVELOPMENT
Clusters of grapes attained marketable quality 30 days earlier on
treatment of 300ppm ABA and colored quickly than untreated grapes.
Cantin et al. (2007)
Degreening in citrus is done by application of 1-5ppm ethylene. However,
in other fruit crops ethylene is applied in higher concentrations (100-
150ppm) for ripening and breakdown of chlorophyll.

30. YIELD
• Application of NAA @ 40 ppm in pear cv. ‘Conference’ and ‘Blanquilla’ and
improved fruit retention per cent and fruit yield.
Asin et al. (2010)
• Application of NAA at pea stage and marble stage in “Costata” persimmon
significantly increased vegetative growth, fruit retention and fruit yield in both the
seasons.
Kassem et al. (2010)
• Foliar application of GA3 at 25ppm in avocado after 1 month of fruit set
increased yield and fruit size.
Garner et al. (2011)

31. FUTURE THRUST
• Most of the biological processes are governed with multiple genes
(polygenic), so gene transfer may be difficult and time consuming
hence the use of PGR’s may be beneficial for short imperatives.
• PGR’s provide an immediate impact on crop improvement
programmes and are less time consuming.
• Application of PGR’s must lead to quantifiable advantages for the
users.
Cont……

32. • Industries involved in development of PGR’s should be well informed
about the latest scientific development in production of PGR’s.
• Plant growth regulators should be recognized as more than
academic curiosities.
• They are not only interesting but profitable to use to grower,
distributor and manufacturer.
• More research is needed to develop simple, economic and
technical viable production system of PGR’s.

33. CONCLUSION
Plant growth regulators has an immense potential in fruit production to
increase the yield, quality, optimum flowering, earliness, cold and high
temperature fruit setting, sex modification, early seed germination,
seed longevity, early rooting of cuttings and layering, rapid union of
grafts, seedless fruit production, increased shelf life and resistance to
some biotic and abiotic stresses of fruit crops to meet the consumer
requirements. But more research is needed to develop simple,
economical and technically viable production system of bio-regulator.
Bio-regulators must be toxicologically and environmentally safe.