Effect of Early Season Square Removal on Three Leaf Types of Cotton¹

Abstract

In certain environments, reduced leaf‐open canopy cottons (Gossypium hirsutum L.) allow more light penetration and air circulation within their canopies than do normal leaf types. However, too much reduction in canopy can reduce overall productivity and economic yield. Removal of floral buds (squares) early in the season has been shown to result in larger plant size. Square removal was carried out in the field (fine‐silty, mixed, thermic, Aquic Fragiudalf soil type) on normal, okra, and super okra leaf type near‐isogenic lines of a ‘Stoneville 213’ background cotton for 3 and 6 weeks to determine i) if improved yield could be obtained in one or both open canopy types by enlarging the canopy and ii) if delaying fruit set produced differential responses in these leaf types. Results would form a basis for development of a boll weevil (Anthonomus grandis Boh.) trap crop system using exogenous chemicals to effect square abscission. Removal of squares increased plant height, leaf area index (LAI) and number of sympodial branches. The super okra leaf type produced the greatest responses to square removal. Fruit set was more rapid and occurred during a shorter interval for all leaf types undergoing square removal for 3 weeks, but the greatest response was obtained from super okra. Comprehensive analysis in 1983 indicated the rapid fruit set was due primarily to more sympodia fruiting simultaneously. The 3‐week treatment was more consistent in this response than the 6‐week treatment because of the generally shorter horizontal and vertical flowering intervals. Economic yield of normal and okra leaf types was generally not improved by square removal, whereas the super okra leaf type in the 3‐week square removal treatment produced an average 23.5% greater lint yield than its control. Differences in lint percentage were significant between treatments in 1981 with significant leaf type by treatment interactions in 1983. The data indicate that the super okra leaf type had the most consistent responses to 3 weeks of manual square removal. These results imply that this leaf type would produce the best response to exogenous chemical abscission of squares and the greatest chance of recovery from early season insect pressure.

Effects of early-fruit removal on endogenous cytokinins and abscisic acid in relation to leaf senescence in cotton

“…Moderate increases in biological yield (7.1%) and seed cotton yield (8.6%) were obtained under field conditions, although no yield advantage was found for potted plants. These results are in agreement with previous findings in which early reproductive sink removal increased the vegetative growth and favored more productive fruiting from later-developed positions to compensate for earlier losses (Kletter and Wallach 1982;Kennedy et al 1986;Ungar et al 1987;Jones et al 1996;Sadras 1996;Bednarz and Roberts 2001). Most importantly, the removal of early fruiting branches delayed the main-stem leaf senescence characterized by increase of chlorophyll concentration and photosynthetic activity of leaves.…”

“…Compensation for early fruit removal in cotton has been of great interest to both agronomists and entomologists, as it will not only help in establishing the recovery potential, but also provide a good experimental condition to study association between source and sink, as well as vegetative and reproductive growth (Dong et al 2008b;Zhang et al 2008). Numerous fruit removal studies have shown that reproductive sink removal enhances vegetative growth and development (Patterson et al 1978;Kennedy et al 1986;Ungar et al 1987;Jones et al 1996). Loss of early fruiting forms has also been shown to increase root growth (Sadras 1996;Dumka et al 2004), alter spatial yield distribution (Bednarz and Roberts 2001), and improve Cry1AC expression of transgenic Bacillus thuringiensis Berliner (Bt) cotton (Zhang et al 2008).…”

Pamukta Tarak ve Çiçek Uzaklaştırmanın Etkisi : III. Çiçeklenme ve Silkme Düzeni

“…This might be caused by cumulative effects of removal of squares. The results confirm the findings of Kennedy et al (1986). Also, it is indicated that flowering rate was increased by other flower removals and increase was apparently observed throughout two weeks later when removals were ended.…”

Recovery from Terminal and Fruit Damage by Dry Season Cotton Crops in Tropical Australia

“…Therefore, mid-season fruit loss may be less likely to be replaced. To fully compensate from mid-season square loss with minimum delay requires that more bolls on higher and more distal positions develop simultaneously after damage (Kennedy et al 1986, Jones et al 1996b, Bednarz and Roberts 2001. Our study showed a lower yield ranking for mid-season than early season fruit injury, indicating that some of the squares removed were not replaced.…”