Cotton Leaf Photosynthesis and Carbon Metabolism

Photosynthesis is the basis of plant dry matter production and a major determination of yield in cotton (Gossypium hirsutum L.). Much of the cotton yield increases in recent years can be attributed to the improved partitioning of dry matter into reproductive growth rather than vegetative growth. However, this strategy can only be taken so far before the amount of photosynthesizing leaf area becomes the limiting factor. Therefore, improved plant photosynthesis coupled with good dry matter partitioning could lead to additional yield improvements. Research has identified both genetic and environmental variations in the rate of cotton photosynthesis. Superior leaf photosynthetic performance has been exhibited by okra and super‐okra leaf types compared to the normal leaf types. Photosynthetic variation has also been identified within the normal leaf type pool of germplasm. However, geneticists have generally not targeted this trait for genetic improvement in cotton. In addition, leaf tissue concentration of the three major plant nutrients (nitrogen, potassium, and phosphorus) need to be maintained at sufficient levels for optimum photosynthesis. Under deficient soil fertility conditions, supplemental fertilization can increase overall growth due to both increased leaf area production and increased photosynthetic rate per unit leaf area. Both excessive and deficient soil moisture conditions can depress the photosynthetic performance of the plant and its corresponding growth. Similarly, an optimum temperature range exists, above and below which the photosynthesis is negatively impacted. This knowledge of variation in both genetic and environmental influences on photosynthesis offers hope of improved photosynthetic performance through either a concerted genetic selection or modified production systems that minimize exposure to some of the rate‐limiting environmental conditions.