Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/18/2004
Publication Date: 6/30/2004
Citation: Pettigrew, W.T. 2004. Physiological consequences of moisture deficit stress in cotton. Crop Science. 44:1265-1272. Interpretive Summary: Cotton lint yields in the midsouthern United States have not improved much in recent years. One of the things limiting yield in cotton is the impact of drought stress, not enough water for the plant to grow. Understanding how drought stress limits cotton growth will help determine what is needed to consistently produce higher yields. This four year study investigated how drought stress affected cotton growth and yield for eight different types of cotton. Drought stress was found to stunt overall plant growth and reduce both the number and size of the leaves produced, which in turn, reduced the amount of sunlight intercepted by the leaves. Although drought stressed plants intercepted less sunlight, these leaves were more efficient in using sunlight to make food during the morning than the plants with plenty of water. By the afternoon, however, the plants with plenty of water were more efficient in making food from sunlight than the drought stressed cotton plants. This difference in how plants suffering from drought stress make food from sunlight in the morning verses the afternoon may help explain some of the reasons why cotton farmers in the midsouthern United States don't always get consistent yield increases when they apply extra water to the cotton plants through irrigation systems.
Technical Abstract: Moisture deficit stress can depress cotton (Gossypium hirsutum L.) lint production in all cotton production regions. However, most cotton physiological drought stress research has been conducted in either arid production regions or in artificial growth conditions of growth chambers or greenhouses. The objective of this research was to document the effects moisture deficit stress has on various physiological processes for cotton grown in the humid southeastern US. Field studies were conducted under dryland and irrigated conditions from 1998 through 2001 utilizing eight genotypes of diverse backgrounds, including an okra-normal leaftype near-isoline pair and transgenic lines paired with their recurrent parents. Dry matter partitioning, light interception, canopy temperature, leaf water potential, gas exchange, chlorophyll (Chl) fluorescence, and leaf Chl concentration data were collected at various times in the plots. Genotypes responded similarly to the two soil moisture regimes for virtually all of the parameters evaluated. Moisture deficit stress reduced overall plant stature with a 35% leaf area index (LAI) reduction, prompting an 8% reduction in solar radiation interception. Dryland plant leaves had 6% greater CO2-exchanges rates (CER) and 9% higher light adapted photosystem II (PS II) quantum efficiency than irrigated leaves during the morning. However, as leaf water potential of the dryland plants became more depressed during the afternoon, the CER and light adapted PS II quantum efficiency of the dryland plants became inhibited and was 6% and 10% lower, respectively, than irrigated leaves. A 19% greater leaf Chl concentration for the dryland plants may have contributed to the higher dryland CER during the morning. This polarity of photosynthetic performance throughout the day of the dryland plants relative to irrigated plants may help explain some of the irrigation yield response inconsistencies in the humid southeastern US.