Browsing Cotton Report 1991 by Subjects
Now showing items 1-4 of 4
Basic Cotton Crop Development PatternsSummaries of cotton crop phenology, as a function of heat units (HU, 86/55°F limits) have been developed across a wide range of production conditions in Arizona. Optimum ranges in HU accumulations since January 1 are used to describe planting dates to maintain optimum yield potentials with full season varieties. Basic events such as the occurrence of pinhead squares, squares that are susceptible to pink bollworm, and first bloom are described in terms of HU accumulations since planting. Also, the expected ranges of HU's accumulated since planting that are required to accomplish crop cut -out are shown for three general maturity types of Upland cotton.
Cotton Response to Mutiple Applications of PIX, 1990Three field experiments were conducted in 1990 in Arizona to evaluate cotton crop response to several treatment regimes of multiple applications of PIX (an anti-gibberellic acid plant growth regulator). Treatment regimes used in 1990 employed higher rates of PIX/acre/application and extended times of applications later into the fruiting cycle than earlier experiments in 1988 and 1989. Similar to earlier experiments, results in 1990 demonstrated the ability of some PIX treatments to significantly reduce plant height, relative to the untreated check treatments. The 1990 cotton production season in Arizona consisted of conditions which led to excessive rates of fruit loss and abortion, and somewhat vegetative plants. Final fruit retention levels of 30 to 50% were realized in the three 1990 experiments after a period of fruit loss through July and August. Lint yield results revealed significant differences (P ≤ 0.05) between several selected treatments at only one of the locations in 1990.
Photosynthetic Rate and Stomatal Conductance are Related to Heat Tolerance in Pima CottonBreeding for high yield in hot environments (heat tolerance) has tripled the yield of Pirna cotton since 1949. We compared six strains (one primitive non-cultivated line, four cultivars representing advancing stages in the breeding process, and one unreleased advanced line) for their gas exchange properties in the greenhouse. Both photosynthetic rate and stomatal conductance increased with improving genetic yield potential. Photosynthetic rate was enhanced more in the morning than in the afternoon. Stomatal conductance did not limit photosynthesis; rather, the changes resulted from alterations of characteristics of the green mesophyll cells. There is no evidence that increased yield results from the enhanced photosynthetic rates of single leaves. However, the increased stomatal conductance in modem lines was also expressed in the field in 1990, allowing increased transpiration rate and evaporative cooling of leaves. Heat tolerance in Pima cotton may be related to the ability of plants to cool themselves by transpiration.
Uptake and Reside of 3, 4-Dichloro-5-Isothiazole Carboxylic Acid in Cotton Plants and Soils Under Field ConditionsDICA (3, 4-dichloro-5-isothiazole carboxylic acid) is being used as a chemical hybridizing agent in the cotton breeding program of Chembred Seed Company. This compound produces male sterile flowers. Registration of this compound by EPA requires that a plant residue study be conducted to provide data on the quantitative amounts of residues in F₁ plants and seeds, F₂ seeds and in the soil. This study was carried out in Arizona because the hybrid F₂ cotton seeds will be grown in Arizona.