Effect of plant growth regulators (PGRs) on fruits: An overview

Introduction

Phytohormones or plant growth regulators (PGRs) are organic compounds produced in a plant which supports many physiological functions and growth. The term 'phytohormone' was given by Thimmann (Suman et al., 2017) [26] . Different types of plant growth regulators include auxins, gibberellins, cytokinins, abscissic acid and ethylene (Small et al., 2018) [25] . Auxins, gibberellins and cytokinins come under plant growth promoter while abscissic acid comes under plant growth inhibitor (Khan et al., 2020) [13] . Auxin is one of the first plant hormone to be discovered (Kumari et al., 2018) [17] . PGRs play an important role in improving the quality and yield of fruits. It also serves as an aid in time of propagation. The hormones have their own specific functions (Naqvi, 2001) [20] . The categorized plant growth promoters support cell division, cell enlargement, flowering, fruiting and seed formation. Plant growth inhibitor or bioinhibitors are involved in dormancy and abscission (Chaudhary et al., 2006) [5] . Exogenous application of PGRs is done to different agricultural responses (Gaba, 2005) [10] .

Gibberelin

Kurosawa a Japanese farmer observed some rice plants were larger in size, pale, with long and narrow leaves and fruitless. After investigating, gibberellin was discovered. Gibberellins help in the regulation of fruit development. A study conducted by Garner et al., (2011) [33] showed that, foliar application of GA3 in 'Hass' variety of avocado increased yield and fruit size.

Cytokinin

Dating back to Folke Skoog's laboratory cytokinin was discovered in the 1940s. It mainly encourages cell division. Term 'cytokinin' was given by Letham in 1963 (Letham, 1963) [18] . Cytokinin regulates a variety of physiological and biochemical processes like axillary shoot branches, root meristematic cell, apical dominance and lateral roots formation (Koprna et al., 2016) [15] . A study conducted by Huang et al., (2014) [12] showed inhibition of ripening in bananas at 10 mg/L CPPU.

Abscissic acid (ABA)

Abscissic acid is found in many plant organs and tissues. Due to the presence of ABA a lot of leaves and fruits are forced to abscise in different plant species. Buds of woody plants of temperate regions are affected by ABA that causes dormancy. Exogenous applications of ABA have effect on endogenous ABA causing ripening in certain fruits like raspberry, kiwi, strawberry etc (Zaharah et al., 2012) [30] .

Ethylene

Ethylene is a natural hormone which affects the storage stability of various fruits and vegetables. The effectiveness of ethylene is influenced by both endogenous and exogenous sources (Suman et al., 2017) [26] . Another use of ethylene besides ripening is the use of ethephon treatment for flower bud development in pineapple (Onaha et al., 2001) [21] . [24] Guava Cuttings IBA, NAA 1000 ppm, 1000 ppm Debnath and Maiti, 1990 [8]

Grapes

Shoot apical meistem IBA 1000 ppm Aazami, 2010 [1]

Citrus

Nodal explants IBA 100 ppm Fadli et al., 2017 [9] Litchi Air layers IBA 5000 ppm Das and Prasad, 2014 [7] Apricot Cuttings IBA 2000 ppm Suriyapananont, 1987 [27] Apple Rootstocks IBA 1.5 mgL-1 Ghanbari, 2014 [11] Peach Cuttings IBA 50 ppm Chauhan and Maheshwari, 1970 [6] Dragon fruit Cuttings IBA 7000 ppm Ayesha and Thippesha, 2018 [3]

Jackfruit

Air layers IBA 1.5 mgL-1 Mukherjee and Chatterjee, 1978 [19] Almond Apical shoot tips IAA 0.5 mgL-1 Akbas et al., 2009 [2]

Walnut

Applied during stooling IAA NAA 100 ppm 500 ppm Rashid, 1978 [22]

Strawberry

Runners development GA3 80 ppm Kumar et al., 2012 [16]

Sweet cherry

Fruit size CPPU 100 mg/L Zhang et al., 2011 [31]

Mango

Fruit size Ethrel 200 ppm Karuna et al., 2007 [32]

Conclusion

In conclusion, phytohormones or plant growth regulators (PGRs) are essential for regulating plant growth and development. These organic compounds, including auxins, gibberellins, cytokinins, abscisic acid, and ethylene, each play distinct roles in promoting or inhibiting various physiological processes. Auxins, such as naphthaleneacetic acid, facilitate cell expansion and propagation. Gibberellins, discovered from rice anomalies, are pivotal in fruit development and yield enhancement. Cytokinins are crucial for cell division and plant growth regulation, while abscisic acid manages dormancy and abscission. Ethylene, influential in fruit ripening and storage, also aids in flower bud development. Understanding and applying these PGRs can significantly enhance agricultural practices, optimizing plant growth, fruit quality, and overall yield.

References

1. Aazami MA. Effect of some growth regulators on "in vitro" culture of two Vitis vinifera L. cultivars. Rom Biotechnol Lett. 2010;15(3):5229-5232.
2. Akbas F, Isikalan C, Namli S, Ak BE. Effect of plant growth regulators on in vitro shoot multiplication of Amygdalus communis L. cv. Yaltsinki. Afr J Biotechnol. 2009;8(22):4692-4697.
3. Ayesha S, Thippesha D. Influence of plant growth regulators on rooting of stem cuttings in dragon fruit [Hylocereus undatus (Haworth) Britton & Rose]. Int J Chem Stud. 2018;6(5):1834-1839.
4. Bons HK, Kaur M. Role of plant growth regulators in improving fruit set, quality, and yield of fruit crops: a review. J Hortic Sci Biotechnol. 2020;95(2):137-146.
5. Chaudhary BR, Sharma MD, Shakya SM, Gautam DM. Effect of plant growth regulators on growth, yield, and quality of chilli (Capsicum annuum L.) at Rampur, Chitwan. J Inst Agric Anim Sci. 2006;27:65-68.
6. Chauhan KS, Maheshwari LD. Effect of certain plant growth regulators, seasons, and types of cutting on root initiation and vegetative growth in stem cuttings of peach variety Sharbati. Indian J Hortic. 1970;27(3, 4):136-140.
7. Das AK, Prasad B. Effect of plant growth regulators on rooting survival of air layering in litchi. Adv Res J Crop Improv. 2014;5(2):126-130.
8. Debnath GC, Maiti SC. Effect of growth regulators on rooting of softwood cuttings of guava (Psidium guajava L.) under mist. Haryana J Hortic Sci. 1990;19(1, 2):7985.
9. Gaba VP. Plant growth regulators in plant tissue culture and development. Plant Dev Biotechnol. 2005;87-99.
10. Ghanbari A. Impacts of plant growth regulators and culture media on in vitro propagation of three apple (Malus domestica Borkh.) rootstocks. Iran J Genet Plant Breed. 2014;3(1):20-11.
11. Huang H, Jing G, Wang H, Duan X, Qu H, Jiang Y. The combined effects of phenyl urea and gibberellins on quality maintenance and shelf-life extension of banana fruit during storage. Sci Hortic. 2014;167:36-42.
12. Khan N, Bano AM, Babar A. Impacts of plant growth promoters and plant growth regulators on rainfed agriculture. PLoS One. 2020;15(4).
13. Kogl F, Haagen-Smit AJ. Mitteilung über pflanzliche wachstumsstoffe. Über die chemie des euchsstoffs. Proc Koninkl Ned Akad Wet. 1931;34:1411-1416.
14. Koprna R, De Diego N, Dundálková L, Spíchal L. Use of cytokinins as agrochemicals. Bioorg Med Chem. 2016;24:484-492.
15. Kumar R, Bakshi M, Singh DB. Influence of plant growth regulators on growth, yield, and quality of strawberry under U.P. sub-tropics. Asian J Hort. 2012;7(2):434-436.
16. Kumari S, Bakshi P, Sharma A, Wali VK, Jasrotia A, Kour S. Use of plant growth regulators for improving fruit production in sub-tropical crops. Int J Curr Microbiol Appl Sci. 2018;7(3):659-668.
17. Letham D. Zeatin, a fraction inducing cell division from Zea mays. Life Sci. 1963;2:569-573.
18. Mukherjee SK, Chatterjee BK. Effect of etiolation and growth regulators on air-layering of jackfruit (Artocarpus heterophyllus Lam.). Indian J Hortic. 1978;35(1):1-4.
19. Naqvi SS. Plant growth hormones: growth promoters and inhibitors. In: Pessarakli M, editor. Handbook of plant and crop physiology. CRC Press; 2001. p. 523548.
20. Onaha A, Higa M, Naksone F, Ikemiya H. Effect of ambient temperature and defoliation on flower bud induction with chemical in pineapple plants. JPN J Trop Agric. 2001;45(1):1-7.
21. Rashid A. Effect of plant growth regulators on stooling in walnuts. Indian J Hortic. 1978;35(3):202-206.
22. Roberts JA. Plant growth regulators. Springer Science & Business Media; 2012.
23. Sharma N, Anand R, Kumar D. Standardization of pomegranate (Punica granatum L.) propagation through cuttings. Biol Forum-An Int J. 2009;1(1):7580.
24. Small CC, Degenhardt D. Plant growth regulators for enhancing revegetation success in reclamation: a review. Ecol Eng. 2018;118:43-51.
25. Suman M, Sangma PD, Meghawal DR, Sahu OP. Effect of plant growth regulators on fruit crops. J Pharmacogn Phytochem. 2017;6(2):331-337.
26. Suriyapananont V. Stem cuttings of Japanese apricot as related to growth regulators, rooting media, and seasonal changes. In: III International Workshop on Temperate Zone Fruits in the Tropics and Subtropics; 1987. p. 475-480.
27. Ughareja A, Saxena D, Kaur N. Use of plant growth regulators on vegetative propagation of fruit crop. Int J Bot Stud. 2022;7(4):5-10.
28. Yang Z, Ludders P. Effect of growth regulator and media on in vitro shoot tip culture of different cultivars of mango (Mangifera indica L.) rootstocks. In: IV International Mango Symposium; 1992. p. 240-247.
29. Zaharah SS, Singh Z, Symons GM, Reid JB. Role of brassinosteroids, ethylene, abscisic acid, and indole-3acetic acid in mango fruit ripening. J Plant Growth Regul. 2012;31(3):363-372.
30. Zhang C, Whiting MD. Improving 'Bing' sweet cherry fruit quality with plant growth regulators. Sci Hortic. 2011;127:341-346.
31. Karuna C. Industry product market competition and managerial incentives. Journal of accounting and economics. 2007 Jul 1;43(2-3):275-297.