Effect of Drought Stress on Cotton Fiber Quality

E. L. Vigil, O. Hinojosa and D. P. Thibodeaux


The impact of drought stress on cotton fiber and seed maturity is a major problem to the cotton industry, resulting in dyeing problems such as white specks in fabric due to immature fiber, loss in fineness and strength, altered micronaire, and high fatty acid and low protein (meal) in the seed. We have previously hypothesized that there is a temporal window of development, beginning at about 15 days post anthesis (DPA) and lasting approximately 10 days to 25 DPA, that is most sensitive to drought stress. This represents a period when cellulose is beginning to be deposited along the primary wall of fibers that are ending their elongation phase and lipid and protein are accumulating within the embryo.

We tested this hypothesis on a widely grown cotton variety, Delta Pine 50 (DP50) grown under greenhouse conditions. Seeds were sown in early May in 12 inch clay pots containing a modified sandy loam soil. Gypsum soil moisture blocks were place in a middle position between young seedling and edge of the pot. Flowers were tagged daily from first flower (June 9, 1993) up to cut out (approximately August 1st). Experiment was started on July 14, 1993. Physiological measurements of photosynthesis, stomatal conductance, transpiration and internal carbon dioxide were made with a Licor meter at weekly intervals from the beginning of the experiment. There were 28 replicate groups of control, moderate and severe drought stressed plants. Moderate drought conditions at a evapotranspiration, soil water level of 70% that of control was maintained daily by gravimetric replacement of evaporated water. Fiber quality measurements were made on samples from open bolls using the Advanced Fiber Instrument System (AFIS). Seed and fiber weights were made for samples from open bolls from the first fruiting position on reproductive branches 1-4 or 5-8, depending on age of boll, for all treatments. The ages of bolls at the start of the experiment were 15, 20, 25, and 30 DPA. The amount of stress that seeds in these different aged bolls had experienced at boll opening at 45 DPA ranged from 30 to 15 days. The seeds from severe drought bolls at 15 and 20 DPA at the start of the experiment did not appear fully mature and may be referred to as motes, even though fibers appeared fully elongated.

Vigil 2

Analysis of per cent germination for seeds from each treatment provided data that seeds at 15 and 20 DPA at the start of the experiment had 42 and 44% germination for severe drought seeds compared to 96 and 100 % for controls and 100 and 79 % for moderate drought samples. A dramatic change occurred in per cent germination for severe drought stress samples at 25 days when the per cent germination was comparable to controls and moderate drought seeds, 83% vs 95% and 92%, respectively.

Comparative analysis of fiber and seed weight revealed that seeds receiving 22 or 30 days of severe drought stress weighed approximately 30% less for both fiber and seed. The fiber from these samples had from 40 to 50% lower value for micron AFIS than fiber from either moderate drought or control seeds.

These results indicate that there is a critical window of seed ripening, namely from approximately 15 to 25 DPA, when cotton seed and fiber are most sensitive to drought stress, especially severe drought. Once seeds pass this 10 day window, they appear not to be adversely affected by severe drought. The implication of these findings is that cotton bolls have a unique capability to sustain seed and fiber maturation even under conditions of severe drought stress once the seeds have passed through the early stage of cellulose secondary wall deposition and lipid and protein storage in the embryo. Additional field and greenhouse tests will help to clarify that this phenomenon is true and provide critical new information and recommendations for irrigation or water use to assist producers in obtaining a crop of more uniform fiber quality. Supported in part by grants from Cotton Incorporated and Cotton Foundation.

Reprinted from Proceedings of the 1994 Beltwide Cotton Conferences pg. 1487
©National Cotton Council, Memphis TN

[Main TOC] | [TOC] | [TOC by Section] | [Search] | [Help]
Previous Page [Previous] [Next] Next Page
Document last modified Sunday, Dec 6 1998