No abstract

Quantitative information between water deficit and cotton (Gossypium hirsutum L.) reproductive potential and fiber quality is needed to improve cotton model predictability. An experiment was conducted by seeding Upland cotton cultivar, Texas Marker (TM)-1, in sunlit growth chambers. Four water stress treatments, 100, 80, 60, and 40% of daily evapotranspiration of the control, were imposed during flowering for plants grown at optimum temperature and nutrient supply. Soil moisture content and midday leaf water potential (LWP) were measured twice weekly during treatment period. Photosynthetic measurements taken during the stress treatments were correlated with midday LWP. New flowers and bolls were tagged daily to estimate boll maturation period (BMP). Plant-and boll-component dry weights were recorded at end of the experiment. Lint sample collected, grouped based on average LWP during BMP, were analyzed for fiber quality parameters. Declining photosynthetic rates as plants experience water deficits were mostly to stomatal limitation, but non-stomatal factors played a role as stress progressed. Seedcotton and seed weight, boll numbers, and total biomass declined significantly at severe water deficit treatments reflecting declining trends of photosynthesis. Fiber length, strength, and uniformity declined linearly with decrease in LWP, whereas fiber micronaire increased with decrease in LWP. Fiber strength was most responsive to changes in LWP followed by micronaire, length, and uniformity. Immature fiber content increased and fiber maturity ratio declined with diminishing LWP. The functional relationships between LWP and fiber properties will be useful to develop fiber sub-models under optimal temperature and nutrient, but varying moisture conditions.

Quantitative functional relationships between temperature and fiber quality are needed to improve predictive capability of cotton (Gossypium hirsutum L.) models. An experiment was conducted by varying day/night temperatures, 22/14, 26/18, 30/22, and 34/26°C, imposed at flowering. Upland cotton cultivar, TM-1, was seeded in the soil bins using fine sand as the rooting medium and allowed to grow under optimum water and nutrients. Flowers and bolls were tagged daily to estimate the boll maturation period. Plant height and node numbers were recorded from emergence to 21 d after treatment. Stem, leaf, boll dry weights, and boll numbers were recorded at maturity. Measured fiber quality parameters were regressed against temperature to develop mathematical functions for modeling. The optimum temperature for biomass was between 18.1 and 21.5°C and biomass declined by 10% at 25.5°C and 19% at 29.5°C. More bolls were produced at 25.5°C, but declined sharply at 29.5°C. Reproductive potential, boll mass per unit total weight, peaked at 25.5°C and was lower by 21% at 18.1°C and 53% at 29.5°C. Fiber micronaire and uniformity increased with temperature up to 26°C and declined at higher temperature, while fiber strength increased linearly with temperature. Fiber length increased linearly from 18 to 22°C, and declined at higher temperatures. Fiber micronaire was more responsive to changes in temperature followed by strength, length, and uniformity. The functional relationships between temperature and fiber properties will be useful to optimize management decisions such as planting dates and to develop fiber submodel under optimal water and nutrient conditions.

Potassium (K) deficiency affects cotton growth and development and fiber properties. An experiment was conducted in an outdoor pot culture facility by imposing four potassium stress treatments (100%, 40%, 20% and 0% of optimum K level) prior to flowering during 2010 and 2011 growing season. Upland cotton cultivar, TM-1, was seeded in the pots comprised of fine sand as rooting medium. Flowers and bolls were tagged daily to estimate boll maturation period (BMP). Leaf samples were collected every four days from flowering to maturity to estimate leaf K content. Plant height and node numbers were recorded from emergence to 21 days after treatment. Photosynthesis and stomatal conductance were measured weekly from day of treatment imposition to physiological maturity at an interval of seven days. Stem, leaf, and boll dry-component weights, and boll numbers were recorded at the end of the experiment in each year. From each boll, the lint samples were collected and grouped based on average leaf potassium concentration during BMP, and fiber quality parameters were recorded for each group in each treatment. At high K deficient (0 K) condition, total biomass declined by 27% and 28% in years 2010 and 2011, respectively. Significantly, lower numbers of bolls were retained per plant at 0 K stress treatment during both the years. Leaf photosynthesis (r 2 = 0.92) and stomatal conductance (r 2 = 0.80) declined with declining leaf K levels. Fiber length, strength, micronaire, and uniformity declined linearly with decrease in leaf K content. Weaker fibers with medium length were produced under K-deficient conditions with micronaire values in the discount range. Fiber uniformity, however, did not decline with decrease in leaf K. The identified leaf K status-specific relationships for fiber properties could be used to improve management practices under potassium deficiency and to develop new sub-routines of the existing cotton simulation models. New and improved models will be useful not only in management, but also in arena of policy decisions including future climate change impact assessment analysis.

Research on the effects of ultraviolet-B (UV-B) radiation on soybean seed quality is limited. The objective of this study was to quantify UV-B doses, 0, 5, 10 & 15 kJ•m −2 •d −1 , on soybean growth and seed quality. The experiment was conducted in the Soil-Plant-Atmosphere-Research (SPAR) facility. Chambers located at the R.R.