A plant growth regulator is a man-made compound that is used in today's agriculture industry for regulating various aspects of plant growth and enhancing crop yield. Many farmers and growers have questioned whether using a PGR will yield larger crops, and the answer to this question can be found by understanding how these types of products function within the plant.
PGRs are designed to alter growth patterns (including flowering and fruiting) and overall plant form (size, shape, etc.), and to regulate a plant's hormonal balance, utilization of nutrients from the soil, and ability to withstand environmental stressors. As a result, managing these characteristics can enhance crop yield through improved root development, increased similarity in terms of flowering, reduced excess vegetative growth and improved fruit set when applied appropriately and at a proper time in relation to the plant being grown.
The amount of yield benefits derived from the use of PGRs will vary from crop to crop based on plant type; the time of application; dosage; and environmental conditions. For example, if PGRs are used on fruit crops to induce flowering earlier in comparison to plants that do not receive PGRs, this may result in an increased crude protein and/or yield. However, if a PGR is applied too late after flowering to a fruit crop, or if improperly applied at any point during the growing cycle, this may not enhance fruit size and/or yield compared to an untreated plant.
To determine whether or not PGRs will increase crop yields requires a comprehensive examination of the PGR relative to proper agronomic practices, as well as evaluating all possible benefits of using PGR versus the possible agronomic implications of applying the product incorrectly.
Understanding Plant Growth Regulators (PGRs): What Are They?
There are many things farmers can do to improve productivity, such as providing fertilizers and irrigation, but some of these methods will have limited impact on the productivity of crops (yield). The use of plant growth regulators (PGR) is a very effective method for increasing crop productivity through increasing the efficiency of physiological processes, including growth, flowering, fruiting, and stress tolerance. When farmers ask if PGR will increase yield, they must first understand what PGR is and how it functions within their plants.
Agricultural chemicals that regulate plant growth are not fertilizers; they don’t include nutrients or minerals in their composition. These materials are more naturally occurring than synthetically produced, and they can either mimic the effects of hormones or modify their role, which creates an effect similar in nature to what would be experienced if a hormone had been produced by the plant itself.
Definition and Types of Plant Growth Regulators
PGR is defined as a chemical compound either naturally occurring or artificially produced that affects plant growth and development by acting in a similar way to, or modifying, plant hormones.
PGR can be divided into the following groups:
- Auxins: Auxins are plant hormones that encourage root development and elongation of cells
- Gibberellins: Gibberellins are plant hormones that stimulate the elongation of stems and the development of fruit.
- Cytokinins: Cytokinins are plant hormones that stimulate the division of cells and delay senescence (aging).
- Ethylene regulation: Ethylene is a gas that stimulates or promotes the ripening of some fruit.
- Growth inhibitors/retardants: Inhibitors or retardants slow down the vegetative growth rate of plants.
How PGR Works in Crops
Plant growth regulators or PGR, change the balance of hormones in plants; thus influencing specific physiological processes through defined growth stages.
In the following ways, PGR function in crops:
- Regulating Plant Vegetative and Reproductive Development
- Developing Adequate Root System
- Improving Flower Initiation and Fruit Setting
- Preventing Incomplete Flower and Fruit Drop
- Enhancing Stress Resistance (drought, heat, salt)
Farmers often evaluate the value of PGR through the growth of additional flower and fruit retention as well as maintaining stronger plant structures leading to increased production.
Why Farmers Use PGR in Modern Agriculture
Farmers implement the use of PGR technology to enhance the performance of their crops, ultimately improving their productivity.
The main reasons why farmers incorporate PGRs into their crop management systems include:
- Improve crop uniformity
- Improve the quality and size of fruit produced
- Minimize lodging issues in cereal crops
- Synchronize flowering
- Enhance stress resilience
For high-value crops, such as fruits, vegetables and cash crops, PGRs assist in managing the plant architecture and reproductive efficiency of plants. Although PGR will not replace proper agronomic practices, they are a valuable tool used strategically to maximize crop production.
The Science Behind Yield Improvement: How Does PGR Influence Crop Production?
Inquiring of a farmer as to how PGRs improve crop yields typically means using plant physiology and hormonal regulation as a means for determining this. PGRs do not provide nutrients like fertilizers but instead work internally through plant processes (cell division, flowering, fruit set, stress tolerance, etc.) by re-adjusting the internal plant hormone balance. By re-adjusting plant hormones, PGRs enhance plant physiological processes that lead to optimal production of crops and reproductive success thereby raising the potential yield of crops.
To understand the scientific basis of PGR use you will be able to better understand how and when to utilize PGR to positively impact the productivity of your crops.
Mechanism of Action in Yield Enhancement
The PGRs will act as mimics or alter naturally occurring plant hormones thereby producing a physiological response within the plant at each stage of growth.
How PGRs Will Increase Yield Potential
- Continued enhanced root system for nutrient uptake
- Promotes more uniform flower development
- Improves fruit set through reduced fruit loss after flowering
- Controls excessive vegetative growth
- Improves ability of crops to withstand abiotic stressors like drought.
Plant Hormones and Productivity Connection
Plant productivity is dependent on the hormonal balance of plants. Plant hormones are natural hormones that control the rate of growth within a plant. Plant Growth Regulators (PGR) are products that modify the natural plant hormones of a plant and adjust their level to ensure a plant is performing at its best.
The main hormones that are impacted by PGR:
- Auxins - Based on plant type, they can promote root development and fruit set.
- Gibberellins - They can promote stem elongation and increase fruit size.
- Cytokinins - They delay the aging of leaves and promote the division of cells.
- Ethylene Regulators - They control the ripening and flowering of plants.
Using PGR to affect these hormones will ultimately affect how a plant allocates resources and should improve a plant's productivity when used properly.
Crop-Specific Response to PGR
Not all crops will react the same way to PGR applications. The effectiveness of PGR will vary by crop type, variety, time of application, and location.
Examples of how specific crops may respond:
- Fruits (mango, grapes, apple): Larger number and size of
- Vegetables: Improved flowering and more uniform growth.
- Cereal Grains: Less lodging (blown over) of the crop and better grain fill.
- Cash Crops: Increased branching and yield Components Stats.
Research & Field Evidence: Does PGR Increase Yield?
Increased yield due to the use of PGR is a well-known aspect of the horticulture industry; both farmers and agricultural scientists are concerned about the effects that they may cause. There has been a great deal of research and empirical observations to show that PGRs can increase yield under specific conditions. Nevertheless, continuous success with yield increases due to the use of PGRs is reliant upon many factors, including type of crop, how and when PGRs were applied, how much was applied, and good management practices.
PGRs have been shown to increase yield, but that does not necessarily mean that there will be yield increases from every application of PGRs in the field. The yield benefit of using PGR's is dependent upon the product being used with appropriate timing, the proper application rates, and the environmental circumstances present at the time of application.
Results from Scientific Studies
Controlled studies have evaluated the effects of plant growth regulators on flowering and fruit set, biomass accumulation, and grain fill rates.
Summary of common research findings:
- Increased ability of fruit crops to retain flowers.
- Increase in size and uniformity of fruits
- Decreased lodging of cereals.
- Increased root development and ability to absorb nutrients.
- Increased ability of plants to tolerate drought and/or excessive heat.
Real-World Case Studies from Farmers
Farmers also provide valuable data regarding the effectiveness (or lack thereof) of using PGRs in the field and they demonstrate how these products work under real-world conditions.
Benefits observed by farmers using PGRs in the field include:
- Increased number of mango and grape fruit
- Improved pod set in leguminous crops
- More uniform flowering of vegetables;
- Fewer crop losses in cereals due to increased stem strength.
Many farmers indicate that with the use of PGRs there are improvements in crop uniformity and increased marketable yield rather than just an increase in total biomass. Many high-value horticultural crops utilize plant growth regulators for increased productivity.
When PGR Does NOT Increase Yield
While PGRs do provide positive results under many conditions, there are instances when the use of a PGR will not improve yield and, in some cases, will reduce yield.
Some common reasons that PGR may not improve yield include:
- Over-application thus suppressing growth;
- An incorrect timing of application;
- Improper nutrient management;
- Weather events that negatively affect the plant;
- Using a non-suitable variety of the crop.
Factors Affecting the Effectiveness of PGR in Yield Improvement
Many growers have inquired about whether the use of PGR will lead to yield increases; the definitive answer will ultimately depend on both how and when you utilize PGR. PGRs are powerful tools used to modify plant hormone activity, but the efficacy of PGRs will differ significantly based on how you manage them. Key components of properly using PGRs to improve yields include proper application timing, accurate application rates, and the proper environmental conditions.
When timing, application rate, and environmental conditions are all optimized and applied correctly, you can expect the PGR to provide benefits during flowering ease of fruit set and improve the plant's ability to tolerate stress. On the other hand, if mismanaged, the benefits associated with using PGR may be minimal or, in some instances, detrimental.
Timing of Application
The timing of the application of PGR is one of the most significant factors contributing to their success. Because plants grow in different ways from one growth stage to another, the application of PGR to an inappropriate growth stage will reduce the usefulness of PGR on that crop.
Reasons Why Timing Is Important:.
- The plant hormone that is predominant in a particular growth stage
- PGR applied early in the crop's life cycle may reduce the amount of vegetative growth
- Application of PGR during the flowering stage will affect fruit set
- Application of PGR during the final growth stages generally will not have much effect on yield components.
Dosage and Concentration
Plant Growth Regulators are highly sensitive to concentration. More is not necessarily a better application amount compared to fertilizers as this can negatively affect plant growth by disrupting hormonal balance through overdosing.
Effects that result from applying at an incorrect rate:
- Too much vegetative suppression
- Flower drop
- Fruit is produced smaller
- Mature later
Best Management Practices:
- Follow label recommendations.
- Modify application according to crop type.
- Avoid mixing different chemical products that do not work together.
Environmental and Soil Conditions
Environmental conditions play a large part in how PGRs perform. Even if applied correctly PGR efficiency may be limited by adverse environmental conditions such as: poor soil conditions or adverse weather conditions.
Key factors:
- Temperature extremes.
- Drought/waterlogged soil.
- Deficiency in soil nutrients.
- Humidity/wind conditions.
Healthy soils with adequate water supply create conditions for plants to physiologically adjust their responses to changing hormonal states therefore increasing their ability to adapt to the PGR's effect.
Potential Risks and Considerations When Using PGR
Many farmers use PGR to increase their crop yields, but it is just as important to consider the potential risks and limitations of using PGR. Like any agricultural input, PGR should be used responsibly and strategically. If applied improperly, misused environmentally, or made into a crutch (relied on too heavily), PGR can have unintended consequences that affect crop quality, soil health, and profitability.
Using a balanced approach to PGR will help you keep PGR as an effective tool instead of using it as a risky shortcut.
Crop Quality and Residue Concerns
When people use PGR there are concerns about how the PGR impacts the quality of the crop and the potential for chemical residues left on the crop.
Key considerations:
- Overusing PGR may impact the size/shape of fruit.
- Improper timing of application of PGR may impact quality of marketable produce.
- Use of PGR must comply with applicable regulations for residue levels.
- When producing crops that will be exported, there may be additional requirements for residue testing/monitoring.
Environmental Impact
In small amounts compared with fertilizers, PGRs may have an impact on the environment.
Environmental impacts may result from:
- Hormonal changes in plants nearby the plant growth regulator
- Runoff water pollution from the plant growth regulator
- Deterioration of beneficial microorganisms residing in the soil
- Improper use or misuse of the plant growth regulator can create an imbalance in the environment
To limit the environmental impact of using PGRs, doses need to be correct, and safe handling and recommended practices should be followed.
Economic Cost vs Yield Benefit
Farmers need to consider if the cost of applying a PGR justifies the increase in yield they received as a result.
Economic factors to evaluate regarding cost are:
- The cost of the product and the application
- The value of the crop in the marketplace
- The percentage increase in yield from using the PGR
- Return on investment (ROI)
FAQs
Q1.Does PGR increase yield in all crops?
No, PGR does not increase yield in all crops; its effectiveness depends on crop type, growth stage, dosage, and environmental conditions.
Q2.How much yield improvement can PGR provide?
Yield improvement varies by crop and management, but under proper use, PGR may enhance specific yield components like fruit set or grain filling.
Q3.Is PGR safe for food crops?
Yes, plant growth regulators are safe for food crops when used according to recommended guidelines and approved regulatory standards.
Q4.Can incorrect PGR use reduce yield?
Yes, over-application or incorrect timing of PGR can disrupt plant growth and potentially reduce yield.
Q5.Should PGR replace fertilizers?
No, PGR should not replace fertilizers; plant growth regulators regulate hormones, while fertilizers supply essential nutrients.
Conclusion: Should You Use PGR to Increase Yield?
The answer to the question of whether PGRs (plant growth regulators) increase yield isn't a simple "yes" or "no." PGR can be beneficial for increasing certain components of yield, such as flowering, fruit retention, root development, and tolerance to stress when applied at the correct time, in the proper amount, and with adequate overall agronomic management; however, application (type, time, amount and agronomic practices) has a significant effect on the yield benefits achieved with the application of PGR.
Therefore, view PGR as a precision tool, not as a shortcut to achieving higher production. PGR does not replace fertilizer, irrigation, or sound crop practices but, instead, it works in conjunction with them to assist in optimizing hormonal balance in plants at critical periods during the growth of the plant. PGRs can be valuable to the grower by improving yield, uniformity of crops, and value of crops when grown in high-value crops and/or under controlled conditions.
The decision to use PGRs therefore should be made based on the needs of the crop being produced, an assessment of the economics of using PGR, and consulting with a professional. If PGRs are used according to guidelines established for their use and are used as part of integrated crop management (ICM), they can be a valuable tool in modern agriculture; however, if they are used improperly or irresponsibly, they can be detrimental to the grower and to agriculture as a whole.
