Pistil and Style Elongations Beyond the Anthers: Results From 2005 Field Experimentation

Abstract

A rapid heat increase from the high 80s-low 90s to high temperatures of 110o F on May 21 and 22, 2005, was recorded in the Blythe, CA, area, resulting in abnormal cotton flowers in mid-June, being especially characterized by elongated styles and stigmas being beyond the anthers. Two different cotton variety trials conducted in the Palo Verde Valley allowed data to be collected semi-weekly beginning June 17-20, with 100+ flowers per plot examined in each plot (four replications) of each of the 14 cotton variety entries. Every cotton variety had an average of 90+% of flowers expressing heat stress abnormalities (elongated styles) at the beginning of data collection even though the trials varied by planting date and location. Abnormal flowers were noted for several weeks, with some stigmas 21 mm beyond the anthers. Varieties differed in their responses to heat stress as measured by elongation later in the summer. Limited data were also collected for fruit retention and correlated with length of stigma extension beyond anthers. Retention percentages decreased as distance between anthers/stigmas increased, however boll size increased with less retention, possibly through nutrient partitioning. Various foliar fertilizers containing calcium were also evaluated for their effect on stigma elongations of DPL 449BR cotton. Significant differences existed for stigma elongations, with 2.5 qts./acre of CalMax resulting in statistical reduction of elongation when compared with the untreated check at 3 weeks after application. Statistical differences did not exist at four weeks although statistical differences did exist at this date for the percentage of flowers affected, with the highest percentage (81.7%) noted in untreated cotton.