Discuss the use of plant hormones in horticulture



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Plant Growth Regulators are defined as small, simple chemicals produced naturally by plants to regulate their growth and development. Plant growth regulators PGR s are molecules that influence the development of plants and are generally active at very low concentrations. There are natural regulators, which are produced by the plant itself, and also synthetic regulators; those found naturally in plants are called phytohormones or plant hormones. Plant Growth Regulators can be of a diverse chemical composition such as gases ethylene , terpenes gibberellic acid or carotenoid derivates abscisic acid.

Content:
  • Use of cytokinins as agrochemicals
  • 30.7E: Auxins, Cytokinins, and Gibberellins
  • Understanding Plant Hormones
  • Study tests the complexity of important plant hormones
  • Powdered root hormone
  • Plant Hormones in Horticulture
  • Role of Plant Hormones in Agriculture and Horticulture
  • Improving citrus quality using gibberellic acid
  • Plant hormone
WATCH RELATED VIDEO: Major plant hormones (u0026 how to remember) - Control u0026 Coordination - Biology - Khan Academy

Use of cytokinins as agrochemicals

Chemical and Biological Technologies in Agriculture volume 8 , Article number: 1 Cite this article. Metrics details. Plant growth regulators are chemical substances which govern all the factors of development and growth within plants. The application of plant growth regulators to crops modifies hormonal balance and growth leading to increased yield, enhanced crop tolerance against abiotic stress and improved physiological trait of crops.

Paclobutrazol PBZ [ 2RS, 3RS 4-chlorophenyl - 4, 4-dimethyl 1H-1, 2, 4-trizolyl -pentanol], is one of the members of triazole family having growth regulating property. PBZ affects the isoprenoid pathway, and alters the levels of plant hormones by inhibiting gibberellin synthesis and increasing cytokinins level and consequent reduction in stem elongation. When gibberellins synthesis is inhibited, more precursors in the terpenoid pathway accumulate and that resulted in the production of abscisic acid.

PBZ is more effective when applied to the growing media and application on the growing medium would give longer absorption time and more absorption of active ingredient than foliar spray. It further reduces evapo-transpiration and decreases plant moisture stress by enhancing the relative water content of leaf area and develops resistance in the plants against biotic and abiotic stresses. In addition, it acts as highly active systemic fungicide and used against several economically important fungal diseases.

In this review, the current knowledge and possible applications of PBZ, which can be used to improve the growth, yield and quality of crops, have been reviewed and discussed. The role of PBZ to mitigate the harmful effects of environmental stresses in crops is also examined. Moreover, various biochemical and physiological processes leading to improved crop production under the effect of PBZ are discoursed in detail.

Plant growth regulators are organic substances produced naturally in higher plants, controlling growth or other physiological functions at a site remote from its place of production and active in minute amounts [ 1 ]. They play a role in affecting growth, yield and quality of crops [ 2 , 3 ]. Besides, they are important in stress protection [ 4 ].

Triazole compounds are systemic fungicides having plant growth regulating properties and are called as stress protectants, because of their innate ability to induce abiotic stress tolerance by increasing antioxidant enzymes and molecules in stress-affected plants [ 5 ]. The plant growth regulating properties of triazoles are mediated by their ability to alter the balance of important plant hormones including Gibberellic acid GA , Abscisic acid ABA and Cytokinins [ 6 ].

They induce a variety of morphological and biochemical responses in plants; inhibited shoot elongation, stimulated root growth, increased cytokinin synthesis and a transient rise in ABA, as well as conferring protection from various environmental stresses [ 7 , 8 ]. PBZ Bonzi , a triazole family having growth regulating property, is an extremely active chemical and affects almost all plant species, whether applied as a spray or a soil drench [ 9 ].

PBZ inhibits GA biosynthesis by blocking the oxidation of ent -kaurene [ 10 ]. It is applied to plants in the floricultural industry to control their size and quality [ 11 ]. When applied as a foliar spray, PBZ is absorbed by petioles and stems and is translocated through the xylem to the growing tip. When applied as a soil drench, it is taken up through the roots and then translocated through the xylem to the apical meristems [ 12 ]. Soil drenches with PBZ may be more effective than the foliar sprays due to increase activity and less probability of stunting and flowering delay, due to no direct contact with flowers or flower buds [ 11 ].

Depending on plant species, PBZ can delay or promote flowering. PBZ half-life in the soil varies between 6 and 12 months depending upon the soil type and environmental conditions [ 13 ].

Effectiveness of drenches is reduced if the crop is grown in a bark medium, because the chemical will adsorb to the bark and less will be available in the medium solution for the plant to absorb. Phytotoxicity symptoms are not common when applied to perennials, but care must be taken with those species that are known to be sensitive.

Therefore, the aim of this review is to summarize the evidence on the biochemical and physiological responses of PBZ as a growth regulator and as a stress protectant. Plant growth retardants are compounds which are used to reduce plant growth without changing developmental patterns or being phytotoxic [ 14 ].

The largest group of plant growth retardants consists of chemicals antagonistic to gibberellins GA , the hormone that is responsible for plant growth [ 7 ]. Commercially used inhibitors of GA biosynthesis are: a onium-type compounds, b compounds with a N -heterocycle triazole-type , c structural mimics of 2-oxoglutaric acid, and d 16, dihydroGAs [ 14 ].

PBZ, a member of triazole plant growth regulator group, is used widely in agriculture [ 15 ]. It is a cell elongation and internode extension inhibitor that retards plant growth by inhibition of gibberellins biosynthesis.

Gibberellins stimulate cell elongation. When gibberellin production is inhibited, cell division still occurs, but the new cells do not elongate. The result is shoots with the same numbers of leaves and internodes compressed into a shorter length. Reduced growth in the diameter of the trunk and branches has also been observed.

Another response of trees to treatment with PBZ is increased production of the hormone abscisic acid and the chlorophyll component phytol, both beneficial to tree growth and health.

PBZ may also induce morphological modifications of leaves, such as smaller stomatal pores, thicker leaves, and increased number and size of surface appendages, and increased root density that may provide improved environmental stress tolerance and disease resistance [ 16 ].

PBZ also has some fungicidal activity due to its capacity as a triazole to inhibit sterol biosynthesis [ 16 ]. It belongs to the triazole compounds that are characterized by a ring structure containing three nitrogen atoms, chlorophenyl and carbon side chains [ 17 ].

Although the precise features of the molecular structure which confer plant growth regulatory activities are not well understood, it appears to be related to the stereochemical arrangement of the substituents on the carbon chain [ 19 ]. There are indications that enantiomers having S configuration at the chiral carbon bearing the hydroxyl group are inhibitors of GA biosynthesis. One of the inhibitor of GA biosynthesis, paclobutrazol, is mainly used as growth retardant and stress protectant [ 20 ].

This retardation of growth is due to the interference of PBZ with gibberellin biosynthesis by inhibiting the oxidation of ent-kaurene to ent-kauronoic acid through inactivating cytochrome Pdependent oxygenase [ 21 , 22 ]. In addition, it tends to be much more effective than various other plant growth regulators at relatively low rate of applications [ 22 ]. PBZ is also known to affect the synthesis of the hormone abscisic acid and phytol.

Abscisic acid is also synthesized via the terpenoid pathway Fig. When gibberellins synthesis is blocked, more precursors in the terpenoid pathway are accumulated and shunted to promote the genesis of abscisic acid [ 23 ].

It has also been reported to inhibit normal catabolism of ABA [ 24 ]. One of the major roles of ABA is to cause closing of stomatal aperture and decreasing loss of water from leaves through transpiration.

Improvement of water relations in treated plants takes place because of enhancement in ABA content that decreases stomatal aperture, decreases shoot growth and causing less surface area for transpiration, more roots for uptake of water, and anatomical alterations in leaves that impart barriers to water loss.

Terpenoid pathway for biosynthesis of gibberellins, abscisic acid, phytol, and steroids, and path for degradation of abscisic acid. It was previously believed that triazoles were primarily transported acropetally in the xylem [ 25 ]. However, PBZ has been detected in xylem and phloem sap of castor bean [ 26 ] and pear [ 27 ] indicating that triazoles can be transported acropetally and basipetally.

Although the metabolic fate of applied has not been investigated in detail most of them have a high chemical stability [ 28 ] and depending on the site of application tend to be metabolized slowly [ 15 ]. Early and Martin [ 29 ] observed more rapid PBZ metabolism in apple leaves than other plant parts, while Sterrett [ 30 ] found little evidence for PBZ metabolism in apple seedlings. The most common application methods of PBZ are foliar sprays and media drench. PBZ shows good results for both methods [ 32 ]; however, drenches act longer and provide uniform control of plant height with lower doses [ 33 ].

When PBZ is applied by foliar spray, the compound is poorly soluble in water and consequently little translocated in the phloem. Thus, when applied by spray to the plant canopy, its action is restricted to the wet contact area [ 34 ]. On the other hand, the application of PBZ by drench is uniform and increases the product efficiency in lower concentrations compared to foliar spray.

Similarly, Banon et al. This effectiveness may be directly related to its high persistence in the soil drench [ 38 ] and in plant organs [ 39 , 40 ]. Gent and McAvoy [ 41 ] also indicated that PBZ persists in annuals, herbaceous perennials and, especially, woody ornamentals.

PBZ is considered a phloem immobile chemical [ 7 ], though some direct [ 26 ] and indirect [ 42 ] evidence exists that it is partially mobile in phloem. Studies indicate that PBZ and uniconazole-P move in plants acropetally via the xylem, accumulate in leaves, and have very low mobility in phloem [ 14 ].

This results in a low level of PBZ residues in seeds and fruits as they are supplied with nutrients via the phloem [ 25 ]. However, low phloem mobility of PBZ further reduces the effectiveness of foliar spraying, since PBZ action on plant growth would be restricted to the site of application. A lot has been done to identify the best application rate of PBZ in different places.

Factors like age of the trees, extent of vegetative growth and method of application should be considered when determining the rate of PBZ to be applied.

The rates also affect the different tree parameters variously. In general, the amount of PBZ required to promote flowering and fruiting in fruit crops is very low [ 27 ]. The rate of soil application is a function of tree size and cultivar. The rate is determined by multiplying the diameter of tree canopy in meters by 1—1. They indicated that other factors including soil type, irrigation system, etc. As to them, overdose may cause undesirable effects such as restricted growth, panicle malformation too compact , and shoot deformity.

They also asserted that to insure uniform flowering and reduce the detrimental side effects, the search for better application methods were investigated and one approach is to apply high volume of low PBZ concentration to improve better coverage. Optimizing PBZ dose is a prerequisite for any yield improvement programmes. He also reported that Camelina seed yield increased bySimilarly, reduced yields were recorded in peanut [ 45 ] and Jatropha [ 46 ] associated with higher PBZ concentrations.

Kamran et al. Patil and Talathi [ 48 ] also reported that application of 5 g of PBZ through soil enabled to induce early and regular fruiting with 2. Gibberellin: Gibberellins GAs are a large family of tetracyclic diterpenoid plant growth regulators.

Gibberellins GAs are plant hormones that are essential for many developmental processes in plants, including seed germination, stem elongation, leaf expansion, trichome development, pollen maturation and the induction of flowering [ 51 ]. Triazole compounds are antagonistic to gibberellins and auxins, reducing cell elongation and cell division by inhibiting GA 3 biosynthesis [ 52 ]. They exhibit varying degrees of both plant growth and fungicidal activity.

The intensity of their biological activity is dependent on their isomeric form [ 17 ]. The growth retarding property of PBZ is largely attributed to interference with gibberellins biosynthesis. Gibberellins are synthesized from mevalonic acid via the isoprenoid pathway, and the PBZ specifically inhibits the oxidation of ent-kaurene to ent-kaurenoic acid through inactivating cytochrome Pdependent oxygenases [ 18 ].

Furthermore, PBZ-induced growth inhibition can be reversed by exogenous application of gibberellins [ 53 ]. These observations support the hypothesis that growth inhibition due to PBZ is primarily due to reduced gibberellins biosynthesis. Abscisic acid: The effect of PBZ on ABA is of interest because ABA, like the gibberellins, is synthesized via the isoprenoid pathway, and the two compounds often exhibit opposing physiological activities. ABA is a natural plant growth regulator that has been implicated in plant acclimation and protection against environmental stress.

Exogenous application of ABA has been shown to increase plant resistance to salinity, ozone, heat, chilling and freezing [ 54 ]. Mackay et al. Hauser et al.


30.7E: Auxins, Cytokinins, and Gibberellins

Foliar application of phytohormones enhances growth of maize and soybean seedlings. Revista de Investigaciones Agropecuarias , vol. Abstract: Phytohormones such as gibberellins, auxins and cytokinins are plant growth promoting factors which added to foliar fertilizers can modulate plant growth and development of agricultural species. It was found that application of phytohormones resulted in a considerable increase in growth of soybean and maize plants.

It appears quite interesting to examine how the same hormone influences the two contradictory processes of growth and senescence. This review.

Understanding Plant Hormones

Includes plant anatomy and physiology, plant classification and identification, and basic plant care. Competencies Evaluate the commercial horticulture industry in the region. Outline the segments within the commercial horticulture industry. Identify career paths in the commercial horticulture industry. Discuss situations horticulture business encounter. Differentiate between plant groups, plant life cycles and growth habits. Discuss the botanical classification of plants. Identify key plant families.

Study tests the complexity of important plant hormones

Plant growth regulators PGRs can be used with some precision for thinning fruit, regulating growth and adjusting harvest periods for apples. They work by mimicking naturally occurring plant hormones or by blocking the production of natural plant hormones. This publication provides information on which plant growth regulators to use for a specific effect and gives instructions on how, when, where, and in what quantities to apply them. Ask Your Gardening Question.

Hormones are produced naturally by plants, while plant growth regulators are applied to plants by humans. Plant hormones and growth regulators are chemicals that affect:.

Powdered root hormone

There are various synthetic organic compounds which are applied to plants to give some positive responses. These are now widely used to get a better result in the field of agriculture and horticulture. Some of the uses of natural and synthetic hormones in the above areas are given below:. They are usually propagated by cutting pieces of stem. When the cut stem piece is placed in the moist stand, then adventitious roots come out from the cut end. The rooting of cutting now a day can be hastened by pre-treating the cuttings with powders or solution containing synthetic hormones like Indole acetic acid IAA , Indole butyric acid IBA , Naphthalene acetic acid NAA , etc.

Plant Hormones in Horticulture

Search Products:. Powdered root hormone. Main thing is dont rush planting, you can leave them on a shelf to callous for a month. Plants that root in water usually have nodes, like vines for example. Root hormone is a powdered substance that is applied to plants to stimulate root development. Going Greens rootex hormone powder grows plant from cuttings. Extracts of the root have been used for a wide variety of therapeutic purposes and are said to have an adaptogenic effect. The powder and gel form of IBA can be used by home gardener, while the liquid form is used by commercial grower.

With her research group at the Biotechnology of Horticultural Crops institute at the TUM, she investigates the mechanisms used by plants to.

Role of Plant Hormones in Agriculture and Horticulture

Plant hormones have been extensively studied for their roles in the regulation of various aspects of plant development. However, in the last decade important new insights have been made into their action during development and ripening, in both dry and fleshy fruits. Emerging evidence suggests that relative functions of plant hormones are not restricted to a particular stage, and a complex network of more than one plant hormone is involved in controlling various aspects of fruit development.

Improving citrus quality using gibberellic acid

RELATED VIDEO: GCSE Biology - Plant Hormones - Uses of Auxin, Gibberellin and Ethene #78

Plants cannot simply relocate to better surroundings when their environmental conditions are no longer suitable. Instead, they have developed sophisticated molecular adaptation mechanisms. Scientists at the Technical University Munich TUM in cooperation with the Helmholtz Center Munich and the University of Nottingham have been able to demonstrate that brassinosteroids, which until now have mainly been regarded as growth hormones, increase the resistance of plants against frost. With her research group at the Biotechnology of Horticultural Crops institute at the TUM, she investigates the mechanisms used by plants to adapt to external influences. Her research activities have centered on brassinosteroids for quite some time.

Application of Plant Hormones:. Agriculturists all over the world have developed certain unusual methods by which they successfully cultivate the crop plants.

Plant hormone

The effect of endogenous hormones on plant morphology and fruit quality of tomato under difference between day and night temperature. The difference between day and night temperature DIF was reported to influence plant morphology and fruit quality, but the mechanism was poorly known. Therefore, controlled-environment experiments were carried out to investigate the mechanism of DIF influenced plant morphology and fruit quality attributes of tomato during fruit stage. The results showed that gibberellin 3, indoleacetic acid and zeatin content of stem tip were enhanced significantly by positive DIF and inhibited by negative DIF, while abscisic acid was not significantly influenced by DIF. Plant height, stem diameter, fruit diameter and leaf area were enhanced significantly by positive DIF regimes and inhibited by negative DIF regimes. Both plant morphology and fruit quality of tomato were significantly related to endogenous hormones.

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