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John E Casida - One of the best experts on this subject based on the ideXlab platform.
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oxidative chemistry and toxicology of s s s tributyl phosphorotrithioate def Defoliant
Journal of Agricultural and Food Chemistry, 1992Co-Authors: Shao Yong Wu, John E CasidaAbstract:Treatment of (BuS) 2 P(O)SBu (DEF Defoliant) with m-chloroperoxybenzoic acid in chloroform yields products tentatively assigned as DEF sulfoxide and sulfone and in methanol gives (BuS) 2 P(O)OMe probably via the very reactive (BuS) 2 P(O)S(O)Bu. This chemical model for DEF as an oxidative phosphorylating agent is applicable to the mouse liver mixed-function oxidase (MFO) system as the oxidant and cholinesterase as the trapping agent for the reactive intermediate(s) with 1000- and 10-fold metabolic activation for inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), respectively
Meizhen Song - One of the best experts on this subject based on the ideXlab platform.
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chemical Defoliant promotes leaf abscission by altering ros metabolism and photosynthetic efficiency in gossypium hirsutum
International Journal of Molecular Sciences, 2020Co-Authors: Xiangru Wang, Yanchao Xu, Hengheng Zhang, Qiang Dong, Ripon Kumar Sikder, Guozheng Yang, Meizhen SongAbstract:Chemical defoliation is an important part of cotton mechanical harvesting, which can effectively reduce the impurity content. Thidiazuron (TDZ) is the most used chemical Defoliant on cotton. To better clarify the mechanism of TDZ promoting cotton leaf abscission, a greenhouse experiment was conducted on two cotton cultivars (CRI 12 and CRI 49) by using 100 mg L−1 TDZ at the eight-true-leaf stage. Results showed that TDZ significantly promoted the formation of leaf abscission zone and leaf abscission. Although the antioxidant enzyme activities were improved, the reactive oxygen species and malondialdehyde (MDA) contents of TDZ increased significantly compared with CK (water). The photosynthesis system was destroyed as net photosynthesis (Pn), transpiration rate (Tr), and stomatal conductance (Gs) decreased dramatically by TDZ. Furthermore, comparative RNA-seq analysis of the leaves showed that all of the photosynthetic related genes were downregulated and the oxidation-reduction process participated in leaf shedding caused by TDZ. Consequently, a hypothesis involving possible cross-talk between ROS metabolism and photosynthesis jointly regulating cotton leaf abscission is proposed. Our findings not only provide important insights into leaf shedding-associated changes induced by TDZ in cotton, but also highlight the possibility that the ROS and photosynthesis may play a critical role in the organ shedding process in other crops.
Stewart S. Higgins - One of the best experts on this subject based on the ideXlab platform.
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Abscisic Acid as a Potential Deciduous Fruit Tree Nursery Stock Defoliant
Horttechnology, 1998Co-Authors: Fenton E. Larsen, Stewart S. HigginsAbstract:Abscisic acid (ABA) was tested as a Defoliant for nursery trees of `Bartlett' pear (Pyrus communis L.) and the apple (Malus×domestica Borkh.) cultivars Imperial Gala, Gibson Golden Delicious, Scarlet Spur Delicious, Law Red Rome, Granny Smith, Braeburn, and Red Fuji. ABA was sprayed once or twice, with 1 intervening week, at 500, 1000, or 2000 ppm. Percentage defoliation was assessed at 1-week intervals for 4 weeks. For all cultivars, two applications of 2000 ppm ABA ranked among the most effective treatments for rapid defoliation; this treatment led to at least 95% defoliation for all cultivars. For many cultivars, however, other treatments caused similar defoliation percentages by digging time. All tested cultivars were effectively defoliated (>80%) by two 1000-ppm applications ABA or one 2000-ppm application. One or two 500-ppm applications effectively defoliated `Bartlett', `Gibson Golden Delicious', and `Law Red Rome'. Nursery managers, therefore, need to consider a range of ABA concentrations and alternative application protocols to obtain optimum benefit from ABA. Although ABA shows promise as a Defoliant, it lacks government approval for commercial use.
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Abscisic Acid as a Defoliant for Deciduous Fruit Tree Nursery Stock
Hortscience, 1997Co-Authors: Fenton E. Larsen, Stewart S. HigginsAbstract:Artificial defoliation of deciduous fruit tree nursery stock is often necessary so that plants can be dug early enough to escape inclement fall weather. In this research, we assessed the efficacy of abscisic acid (ABA) as a Defoliant. ABA was applied as a foliar spray at one of three concentrations—500, 1000, or 2000 ppm a.i. Trees were sprayed either once or twice for a total of six chemical treatments, plus untreated controls. The defoliation and growth responses of eight cultivars were evaluated with the cooperation of commercial nurseries in Washington State. While all treatments caused significantly greater defoliation than was observed in untreated trees, ABA at 500 ppm applied once or twice, or 1000 ppm applied only once, was generally sufficiently effective only on `Bartlett', `Gibson Golden Delicious', and `Law Red Rome', but not on `Imperial Gala', `Scarlet Spur Delicious', `Granny Smith', `Braeburn', or `Red Fuji'. Single or double applications of 2000 ppm or double applications of 1000 ppm often produced faster defoliation than double applications of 500 ppm, but defoliation was not always superior after 4 weeks. No pre-digging field damage was noted, but some treatments appeared to reduce trunk diameter increase after replanting, with no consistent trends among cultivars, except with `Bartlett' pear, which was frequently negatively affected. ABA appears to be very promising as a nursery tree Defoliant.
J. M. Nelson - One of the best experts on this subject based on the ideXlab platform.
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Effects of Combinations of Accelerate and Other Defoliants on Defoliation of Upland Cotton
1996Co-Authors: J. M. NelsonAbstract:Field studies were conducted on upland cotton at the Maricopa Agricultural Center to evaluate the effectiveness of Accelerate when used in combination with other Defoliants. In a September test, good defoliation was obtained in seven days using Ginstar or Dropp + Def + Accelerate and in 14 days using Accelerate + Prep. In October, under cooler conditions, no treatment provided acceptable defoliation in 14 days. In both tests, Ginstar used alone resulted in higher leaf drop percentages than Ginstar + Accelerate. Introduction There are many chemicals available for defoliating cotton in central Arizona. Some of these chemicals are used in combination with other Defoliants to provide improvements in leaf drop, regrowth control or boll opening. In this test, the harvest aid Accelerate was evaluated for its effectiveness when tank mixed with other Defoliants currently being used in the area. According to its label, Accelerate is to be used in combination with sodium chlorate or organic phosphate Defoliants to give a faster more dependable leaf drop. Materials and Methods Field experiments were conducted at the University of Arizona Maricopa Agricultural Center in Maricopa, Arizona. Seeds of Pima S -7 and DP5415 cotton were planted in moist soil on 11 April 1995. The plantings were furrow irrigated and received a total of 105 lbs. of N /acre during the season. Standard practices for irrigation, fertilization, and pest control were followed. The final irrigation was on 29 August 1995. Descriptions of the defoliation treatments used in the tests are shown in Table i. Defoliation treatments were applied to pima and upland cotton on 22 September 1995 and to upland cotton on 20 October 1995. In all tests, defoliation treatments were applied with a HiBoy sprayer using a 7 nozzles /row spray boom and 24 GPA application rate. Plots were 4 rows wide by 40 ft. long. Each test utilized a randomized complete block experimental design with 4 replications. Plots were rated for leaf drop by 2 -3 persons 7 -18 days after application of chemicals. Counts of unopened bolls were made for the October test on 8 November 1995 or 18 days after treatments were applied. Unopened bolls smaller than three -fourths inch in diameter were not counted as unopened bolls. hi the September tests, maximum and minimum temperatures were 100 and 68 °F, respectively, on the day Defoliants were applied. Average maximum and minimum temperatures for the 14 day period after application were 94 and 61 °F, respectively. During the 14 day period after application of Defoliants, 288 HU (86/55 °F thresholds) were accumulated and 0.75 in. of rainfall was recorded. In the October test, maximum and minimum temperatures were 95 and 50 °F, respectively, on the day Defoliants were applied. Average maximum and minimum temperatures for the 14 day period after application were 84 and 47 °F, respectively. During the 14 day period after application of Defoliants, 171 HU were accumulated and 0.35 in. of rainfall was recorded.
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Effect of Combinations of Accelerate and other Defoliants on Defoliation and Yield of Pima and Upland Cotton
1995Co-Authors: J. M. Nelson, G. L. HartAbstract:Field studies were conducted at the Maricopa Agricultural center to evaluate the effectiveness of Accelerate when used in combination with other Defoliants. In
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Effect of Plant Water Status on Defoliation and Yield of Upland Cotton for Short-Season Production
1992Co-Authors: J. M. Nelson, P. G. Bartels, G. HartAbstract:A field study was conducted at the Maricopa Agricultural Center to determine the influence of plant water status at the time of defoliation on the effectiveness of Defoliants and yield of shortseason cotton. Irrigation termination dates of 14 and 26 August and 10 September were used to achieve different levels of plant water stress at the time Defoliants were applied (19 September). Irrigation termination dates had no effect on seedcotton yield for cotton defoliated in September. As the period between the termination irrigation and the date of chemical defoliation was increased the effectiveness of Defoliants was increased. CWSI and plant water potential measurements indicated that the irrigation termination dates resulted in large differences in plant water stress at defoliation time. There was a significant increase in the defoliation percentage as CWSI values increased (from 0.32 to 0.96) and water potential decreased (from -1.5 to -3.5 MPa). Shortseason cotton (163 days) produced 4,396 lbs. seedcotton /A as compared to 5,299 lbs. /A for a full season crop (212 days). Introduction The use of a short -season production system has increased in Arizona in recent years. A problem area for growers in the management of cotton for short -season production is defoliation. For shortseason production, the crop must be defoliated in late August or September when conditions are favorable for vegetative growth and foliage is often very dense. Multiple applications of Defoliants are generally required to satisfactorily prepare the crop for harvest. Although the use of chemicals as conditioners for defoliation has been studied extensively, little research has been done on the management of water to condition the cotton plant for defoliation. In general, excessive water prior to and at the time of defoliation can result in vegetative plants with dense canopies. If the plants are very dry at the time Defoliants are applied, there may not be sufficient physiological activity in the leaves to carryout the effects of the Defoliants. In addition, if leaves are dried past a certain point, leaf weights may not be great enough to cause blades and petioles to break free of the plant at the abscission layer. However, water stress can increase defoliation because stressed plants produce fewer new leaves and existing leaves age faster. A general recommendation has been to allow one month between the fmal irrigation and the application of Defoliants. The objective of this study was to determine the effect of plant water status at the time of defoliation on the effectiveness of Defoliants and yield of short -season cotton. The use of the CWSI (Crop Water Stress Index) and plant water potential as guides to when Defoliants will be most effective was evaluated. Materials and Methods Seed of DPL 90 cotton was planted on 9 April in moist soil at the Maricopa Agricultural Center. The planting received a total of 68 lbs. of N/A preplant and during the season. Three irrigation treatments to provide
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Effect of Plant Nitrogen Status on Effectiveness of Pix and Defoliants for Short-Season Cotton Production
1990Co-Authors: J. M. Nelson, R. E. Briggs, G. HartAbstract:A field study was conducted at the Maricopa Agricultural Center to determine the effect of nitrogen fertility level on the effectiveness of PIX and Defoliants for shortseason cotton production. Increasing the nitrogen fertility level from 90 lbs N/A to 240 lbs N/A increased lint yields from 2.23 to 3.14 bales /A, respectively, in a 157 -day growing season. FIX treatments did not promote earliness, and resulted in yield reductions. Increasing the application rates of Dropp from 0.1 to 0.2 lbs a.i. /A and Def -6 from 0.75 to 1.13 lbs a.i. /A resulted in increases in leaf drop. There was a significant linear decrease in the effectiveness of Defoliants as the petiole NO3 N content increased from 850 to 2450 ppm. INTRODUCTION Recently, there has been interest in Arizona in the use of a short -seasonproduction system for cotton. The short -season system referred to here is a 135to 150 -day season with an approximate 15 August irrigation termination date. This production system has several advantages over a fullseason system such as: reduced irrigation and insecticide inputs; it can act as a method of population suppression of pink bollworm and other insects by reducing the overwintering generation and it can result in improved lint quality. The main disadvantage of the short -season system is that growers face a loss of yield from the elimination of the lateseason "top crop." To offset this, the short -season crop should be managed to maximize the production of early bolls. One method of promoting earliness is through the use of growthregulating chemicals. Growth regulators have potential as a means of manipulating growth to increase the production of early bolls as well as controlling plant growth and reducing production inputs. Another area of concern for growers in the management of cotton for short-season production is defoliation. For short -season production, the crop must be defoliated in late August or early September when conditions are favorable for vegetative growth, and foliage is often very dense. Limited information is available concerning the management of nitrogen fertility to condition the cotton plant for defoliation, particularly for early termination. The objective of this research was to determine the effect of the nitrogen fertility level on effectiveness of PIX and Defoliants for short -season cotton production. An important aspect of this work was to evaluate the use of petiole nitrate monitoring as a guide to Defoliant selection and time of application. MATERIALS AND METHODS Seeds of the cultivar DPL 90 were planted on 7 April 1989 in moist soil at the Maricopa Agricultural Center. The plot area did not receive preplant N fertilizer. A crop of sweet sudan was grown without N fertilizer in the plot area in the summer of 1988 and removed from the field at the end of the season to lower the residual N content of the soil. The N treatments used were: 1) 90 lbs N /A, 2) 150 lbs N /A, and 3) 240 lbs N /A. The N fertilizer was sidedressed on plots on 20 April, 8 June, 21 June, 11 July and 25 July. Soil samples were collected before planting and after harvest to determine the residual N present. The nitrate content of cotton
Shao Yong Wu - One of the best experts on this subject based on the ideXlab platform.
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oxidative chemistry and toxicology of s s s tributyl phosphorotrithioate def Defoliant
Journal of Agricultural and Food Chemistry, 1992Co-Authors: Shao Yong Wu, John E CasidaAbstract:Treatment of (BuS) 2 P(O)SBu (DEF Defoliant) with m-chloroperoxybenzoic acid in chloroform yields products tentatively assigned as DEF sulfoxide and sulfone and in methanol gives (BuS) 2 P(O)OMe probably via the very reactive (BuS) 2 P(O)S(O)Bu. This chemical model for DEF as an oxidative phosphorylating agent is applicable to the mouse liver mixed-function oxidase (MFO) system as the oxidant and cholinesterase as the trapping agent for the reactive intermediate(s) with 1000- and 10-fold metabolic activation for inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), respectively