Temperature and atmospheric carbon dioxide concentration [CO2] affect cotton (Gossypium hirsutum L.) growth and development, but the interaction of these two factors on boll and fiber properties has not been studied. An experiment was conducted in naturally lit plant growth chambers to determine the influence of temperature and atmospheric [CO2] on cotton (cv. DPL‐51) boll and fiber growth parameters. Five temperature regimes were evaluated: the 1995 temperature at Mississippi State, MS; the 1995 temperature minus 2°C; and the 1995 temperature plus 2, 5, and 7°C. Daily and seasonal variation and amplitudes were maintained. Atmospheric [CO2] treatments were 360 (ambient) and 720 μL L−1. Boll number, boll growth, and fiber properties were measured. Boll size and maturation periods decreased as temperature increased. Boll growth increased with temperature to 25°C and then declined at the highest temperature. Boll maturation period, size, and growth rates were not affected by atmospheric [CO2]. The most temperature‐sensitive aspect of cotton development is boll retention. Almost no bolls were retained to maturity at 1995 plus 5 or 7°C, but squares and bolls were continuously produced even at those high temperatures. Therefore, the upper limit for cotton boll survival is 32°C, or 5°C warmer than the 1995 U.S. Mid‐South ambient temperatures. The 720 μL L−1 atmospheric [CO2] had about 40% more squares and bolls across temperatures than the 360 μL L−1 [CO2]. Fibers were longer when bolls grew at less than optimal temperatures (25°C) for boll growth. As temperature increased, fiber length distributions were more uniform. Fiber fineness and maturity increased linearly with the increase in temperature up to 26°C, but decreased at 32°C. Short‐fiber content declined linearly from 17 to 26°C, but was higher at higher temperature. As for boll growth and developmental parameters, elevated atmospheric [CO2] did not affect any of the fiber parameters. Changes in temperature, however, had a dramatic effect on boll set and fiber properties. The relationships between temperature and boll growth and developmental rate functions and fiber properties provide the necessary functional parameters to build fiber models under optimum water and nutrient conditions.

have the highest boll set and account for the majority of the yield. A change in boll distribution was noted when Early cotton (Gossypium hirsutum L.) planting in the Texas Coastal the growing season was characterized by lower tempera-Bend has the potential for improved performance through drought ture, less solar radiation, and higher precipitation amounts avoidance. This 2-yr field study was conducted to compare the effect of boll position on fiber properties across planting dates and to determine (Jenkins et al., 1990). how flowering date, boll position, and environmental factors affect During the first week after anthesis, fiber and outer fiber quality. Cotton ('Deltapine 5409') was planted early March, late integuments receive the greatest portion of photosyn-March, and mid-April each year. In 1997, lint yield for the early plantthate. After that, the distribution of photosynthate being date (731 kg ha Ϫ1 ) was significantly higher than the middle (622 tween the remainder of the seed and fiber is about equal. kg ha Ϫ1 ) and late (533 kg ha Ϫ1 ) planting dates. No significant differ-Fiber elongation begins 2 d after anthesis and continues ences in yield were found in 1999. Boll distribution patterns for middlefor an additional 3 to 4 wk. Around 15 d after anthesis, and late-planted cotton were similar. In 1997, the drier of the 2 yr, the deposition of a mainly cellulosic secondary wall befiber length and micronafis values increased at all boll locations with gins (Stewart, 1986). The degree of secondary-wall deearliness of planting while in 1999, the longest and most mature fiber position determines fiber maturity. Micronaire is a comwas associated with a number of boll locations in the middle planting date. High temperatures before and during boll development accom-posite measure of maturity and fiber fineness since fiber panied by adequate moisture increased fiber maturity.

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from ambient levels of 360 mol mol Ϫ1 increased vegetative biomass by 40% and boll biomass by 20% (Reddy The consequences of elevated carbon dioxide concentrations et al., 1997). Open-top chamber experiments (Kimball ([CO 2 ]) and N nutrition on cotton (Gossypium hirsutum L.) growth, and Mauney, 1993) showed that elevated [CO 2 ] of 650 development, yield, and fiber quality were determined. Cotton cultivar mol mol Ϫ1 increased the aboveground biomass by 63% NuCOTN 33B was grown in sunlit controlled environment chambers at three levels of [CO 2 ] (180, 360, and 720 mol mol Ϫ1 ) and two levels and seed cotton yield by 60% compared with plants of N [continuous N throughout the plant growth period (Nϩ) and grown at ambient [CO 2 ]. Similarly, results from FACE N withheld from flowering to harvest (NϪ)]. Leaf N concentration experiments showed that CO 2 enrichment (550 mol decreased with increasing [CO 2 ] under both N treatments. These low mol Ϫ1 ) produced 35% more biomass and 60% more lint leaf N concentrations did not decrease the effect of elevated [CO 2 ] yield compared with plants grown at ambient atmoin producing higher lint yields at both N treatments, the response spheric [CO 2 ] (Mauney et al. Pinter et al., 1996). being highest for plants grown at elevated [CO 2 ] and Nϩ conditions.Generally, increasing atmospheric [CO 2 ] is shown to Fiber quality was not significantly affected by [CO 2 ], but the leaf N have a stimulatory effect on plant biomass production as concentrations, which varied with [CO 2 ], had either a positive or a a consequence of the rise in net photosynthesis (Bazzaz, negative influence on most of the fiber quality parameters. Leaf N 1990; Poorter, 1993, 1998). Although a strong response during boll maturation period had significant positive correlations of cotton yield to future CO 2 increases was observed, with mean fiber length (r 2 ϭ 0.63), fine fiber fraction (r 2 ϭ 0.67), and other environmental factors are shown to modify this immature fiber fraction (r 2 ϭ 0.65) and negative correlations with mean fiber diameter (r 2 ϭ 0.61), short fiber content (r 2 ϭ 0.50), fiber response (Poorter and Perez-Soba, 2001). cross-sectional area (r 2 ϭ 0.76), average circularity (r 2 ϭ 0.74), andThe response of agricultural crops to future climate micronafis (r 2 ϭ 0.65). It is inferred that future elevated [CO 2 ] will change also depends on management practices. One key not have any deleterious effects on fiber quality and yield if N is environmental factor is nutrient availability, which is an optimum. The developed algorithms, if incorporated into processimportant factor influencing the extent of CO 2 response level crop model, will be useful to optimize cotton production and of the plants (Poorter, 1998). Under field conditions, fiber quality.

A key cotton fiber quality property is micronaire, which acts as an indicator of the fiber's maturity and fineness. Previous studies have demonstrated the ability of Near Infrared (NIR) instrumentation to measure these cotton properties with varying degrees of success, but these studies did not provide conclusions on the capabilities of NIR spectroscopy as a general technique for these analyses. Recent advances in NIR technology could result in improved measurements of these cotton properties. A comparative investigation was implemented to determine the capabilities of modern commercial bench-top and portable NIR systems to monitor cotton fiber micronaire, maturity, and fineness in order to gain insight as to the "universality" of the NIR measurements for these fiber properties. Cotton samples were analyzed on five commercial systems and an older, custom-built system. Very good spectral agreement was observed between the portable and bench-top NIR units. The rapid and simultaneous measurement of cotton micronaire, maturity, and fineness by multiple commercial systems was demonstrated and compared favorably to the custom system, but without the delay and cost in building custom units. For the benchtop NIR systems, all end-state criteria were successfully meet. The "universal" nature of the NIR measurement of these cotton fiber properties was validated for commercial NIR systems. As expected, the NIR results for the portable NIR units were normally not as good as those for the bench-top instruments, but they were very acceptable for demonstrating the potential for the portable units to measure these cotton fiber properties.