Enhancing Cotton Yield and Quality: Understanding the Role of Plant Growth Regulators >>

Cotton, often referred to as “white gold,” is a vital cash crop globally, serving as a fundamental raw material for the textile industry. To optimize its yield and quality, growers employ various strategies, among which the application of plant growth regulators (PGRs) holds significant importance. PGRs, such as mepiquat chloride and mepiquat pentaborate, play a crucial role in regulating plant growth and development, ultimately enhancing cotton productivity. In this article, we delve into the reasons behind the utilization of PGRs on cotton, their mechanisms of action, best practices for application, and additional considerations for growers.

Plant Growth Regulators & Their Physiological Mechanisms:

Plant growth regulators are synthetic or naturally occurring compounds that influence plant growth and development processes. In cotton cultivation, two primary types of PGRs, mepiquat chloride and mepiquat pentaborate, are commonly used. These PGRs exert their effects by regulating the plant’s hormonal balance, particularly auxins and gibberellins, which are essential for cell elongation and division.

Mepiquat Chloride

Mepiquat chloride is widely used in crops like cotton to regulate vegetative growth and enhance fruiting. Mepiquat chloride primarily acts by inhibiting the biosynthesis of gibberellins, a class of plant hormones that promote stem elongation. By reducing gibberellin levels, mepiquat chloride effectively controls excessive vegetative growth, resulting in more compact plants with shorter internodes. Mepiquat chloride also influences other growth processes such as cell division and expansion. It can alter the balance of auxin and cytokinin hormones, which are critical for regulating cell growth and differentiation in plants. This application leads to improved fruit retention, manageable canopy structure, and ultimately, enhanced yield and fiber quality in cotton cultivation.

Mepiquat Pentaborate

Mepiquat pentaborate, which also contains mepiquat, is a PGR that regulates plant growth by inhibiting gibberellin biosynthesis. In addition to mepiquat, this formulation includes pentaborate ions. Pentaborate ions, specifically in the form of boron, play several crucial roles such as enhancing absorption and increasing rainfastness. The combination of mepiquat with pentaborate ions creates a synergistic effect where the boron ions not only aid in absorption but also contribute to the overall effectiveness of mepiquat as a growth regulator. This synergy enhances the regulation of plant growth processes, leading to desired physiological changes such as reduced plant height and improved plant structure.

Other “In-Can” Combinations of PGRs

There is other “in-can” combinations of the above listed plant growth regulators that control growth with synthetic cytokinin, a class of plant hormones that regulate plant growth by promoting cell division and delaying senescence in plants. Suppling exogenous cytokinin has been shown to enhance cell division and proliferation, leading to increased vegetative growth, improved flowering, and fruit set. For cotton these impacts could lead to increased branching, leaf expansion, and overall plant biomass, ultimately contributing to higher yield potential and crop productivity.

Best Practices and Timings for PGR Applications:

The timing of plant growth regulators application is crucial for maximizing their effectiveness and minimizing adverse effects on cotton plants. Typically, PGRs are applied during specific growth stages to target critical physiological processes and achieve desired outcomes.

For mepiquat chloride, the first application is often recommended around the third to fifth true leaf stage, followed by subsequent applications at intervals of two to three weeks, depending on environmental conditions and plant growth rates. This timing helps to manage vegetative growth, promote fruit retention, and enhance boll development. 

Similarly, mepiquat pentaborate applications are typically initiated during the early squaring stage and continued throughout the flowering and boll development stages. This ensures optimal regulation of plant growth and development, leading to improved yield and fiber quality.

Other Considerations for Growers:

In addition to timing, several other factors must be considered when making PGR applications in cotton cultivation:

1. Fertility Levels: Adequate nutrient availability is essential for maximizing the effectiveness of PGRs. Growers should ensure proper soil fertility through soil testing and balanced fertilization practices to support healthy plant growth and development.
2. Environmental Conditions: Environmental factors such as temperature, humidity, and moisture levels can influence the efficacy of PGRs. Ideal application conditions include moderate temperatures and sufficient soil moisture to facilitate uptake and translocation of the PGR within the plant.
3. Variety Selection: Different cotton varieties exhibit varying responses to PGRs. Growers should consider the genetic characteristics of their chosen variety and consult with agronomic experts or extension services to determine the most suitable PGR management strategies.

Ultimately, there are many excellent resources available to help cotton growers best utilize PGRs to manage plant growth and improve yield. After all, this is a “tree” that we manage for annual production. If you are a grower and have questions on PGR usage, feel free to reach out to us on our website or social media. We will work toward getting you in touch with a local expert.

Our next blog post will be focused on foliar fertilizers and biostimulants, and ultimately how these products can further the idea of “manage plant growth and improve yield” in cotton.

Author:

Meredith McGlamory

Regional Agronomy Manager – Georgia

 Sources

Chen, Y., Liu, Z., Heng, L., Leila, I. M., Zhang, X., Chen, Y., & Chen, D. (2021). Effects of  plant density and mepiquat chloride application on Cotton Boll setting in wheat–Cotton double cropping system. Journal of Integrative Agriculture, 20(9), 2372–2381. https://doi.org/10.1016/s2095-3119(20)63286-5

Pettigrew, W. T. (2010). Effects of foliar fertilizer and Mepiquat pentaborate on early planted cotton growth and lint production. Crop Management, 9(1), 1–9. https://doi.org/10.1094/cm-2010-0215-01-rs

Rate and timing of N-p-K applications on cotton in the Southeast. (2021). Grow: Plant Health Exchange. https://doi.org/10.1094/grow-cot-02-21-289

The effects of Mepiquat chloride applied to cotton at early … (n.d.). https://www.cotton.org/journal/2017-21/3/upload/JCS21-183.pdf

Guy D. Collins, Keith L. Edmisten, Randy Wells, & Jared R. Whitaker, (2017). The Effects of Mepiquat Chloride Applied to Cotton at Early Bloom and Physiological Cutout. The Journal of Cotton Science 21:183–189 (2017) 183 http://journal.cotton.org