Cotton Growth Physiology

As the illustration shows, solar radiation is captured by leaves, bracts, stems and boll walls. The greater the intensity of solar radiation and as leaf area and fertility increase, the more energy (also called photosynthate) is available to produce carbohydrates which then flows into the reserve tank. At the bottom of the energy photosynthate reserve tank there is an outlet that is open all the time letting energy continuously leak out. That is because normal plant respiration demands energy to keep the plant alive.

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Once squaring begins, carbohydrates are used to fuel vegetative and reproductive growth at the same time. The successful cotton producer manages vegetative growth to enhance energy for boll development. The cotton supply and demand diagram has two outlets on the sides of the reserves tank which represent the consumption of energy for these types of growth. The amount of energy to flow through these outlets is dependent on the size or age of either the vegetative component or the size of the reproductive component.

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As the season progresses from first bloom, the boll load increases demands for carbohydrates. As boll demand increases, the level of photosynthate in the reserve tank decreases, and eventually falls below the outlet for vegetative growth. When this occurs there is no energy available for continued vegetative growth and cutout (cessation of vegetative growth) occurs. While this is the normal progression, there are exceptions when boll retention and development are below normal due to insect damage, weed competition, or poor weather. If boll retention is low, more carbohydrates are available for vegetative growth. This often increases the need for additional PGR management to avoid excessive vegetative growth.

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This article is from the Cotton Management Guide, a publication with year-round advice on managing high-yielding cotton. Download the Deltapine Cotton Management Guide now or sign up for new content to be delivered to your email each month.​​​

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Click here to learn about balanced cotton plant growth.​​