Explore the vast range of titles available.

Abscission is a process that allows plants to shed tissues or organs via cell separation, and occurs throughout the life cycle. Removal of leaves through the use of chemical defoliants is very important for mechanical harvesting of cotton (Gossypium hirsutum). However, our knowledge of the molecular mechanisms of the defoliation response involved is limited. In this study, RNA-seq was conducted in order to profile the differentially expressed genes (DEGs) between cultivars X50 (sensitive to chemical defoliants) and X33 (relatively insensitive) at different time points after treatment with thidiazuron and ethephon (TE). A total of 2434 DEGs were identified between the two cultivars across the different time-points. Functional categories according to GO and KEGG analyses revealed that plant hormone signal transduction and zeatin biosynthesis were involved in the response to TE. Cytokinin oxidase/dehydrogenase (CKX) genes and ethylene-related genes were up-regulated following TE treatment, and were associated with increased level of ethylene, especially in cultivar X50. Down-regulation of GhCKX3 resulted in delayed defoliation and a reduced ethylene response. The results show that crosstalk between cytokinin and ethylene regulates cotton defoliation, and provide new insights into the molecular mechanisms underlying the mode of action of defoliants in cotton.

Examines the domestic and international use of phenoxy herbicides by the United States in the mid-twentieth century   In The Defoliation of America: Agent Orange Chemicals, Citizens, and Protests , Amy M.

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.

Defoliant spraying is an important aspect of the mechanized processing of pepper harvesting. Complete and uniform spraying of defoliant could improve the quality of defoliation and reduce the impurity content in processing pepper. In this study, we assessed the effect of aerial spraying of adjuvants on physicochemical properties of defoliant solution and droplet deposition when using an unmanned aerial vehicle (UAV) for defoliation spraying. The results showed that Puliwang was a better aerial spray adjuvant suitable for spraying defoliants for processing pepper using UAVs, with a higher defoliation rate and better droplet deposition. Although the YS-20 adjuvant had a higher droplet deposition amount (0.72 μg/cm 2 ) in the middle layer, its performance was poor in droplet size, density, and coverage. The size and density of the droplets added with the Manniu were basically the same as the Puliwang, even the distribution uniformity was better (the CV of the upper canopy layer was only 33.6%), but the coverage rate was poor. In the treatment with AS-901N, there was no marked increase in droplet size, so evaporation and drift were not improved, eventually resulting in a lower defoliation rate. Puliwang had the highest comprehensive score, followed by AS-910N, YS-20, and Manniu.

Defoliant spraying is an important aspect of mechanized cotton harvesting. Fully and uniformly spraying defoliant could improve the quality of defoliation and reduce the impurity content in cotton. Improving the coverage of defoliant droplets in the middle and lower layers of cotton and ensuring the full and even dispersion of droplets in the cotton canopy are essentially in increasing the defoliation effect. In this study, we assessed the effect of aviation spray adjuvants on droplet deposition, defoliation, boll opening and defoliant retention in cotton leaves sprayed by an unmanned aerial vehicle (UAV). The results showed that adding aviation spray adjuvants could significantly improve the defoliant droplet deposition. Fifteen days after spraying, the defoliation rate was 80.31% and the boll opening was 90.61%. The defoliation rate increased by 3.12–34.62% and the boll opening rate increased by 6.67–29.56% after the addition of aviation spray adjuvants. Using a vegetable oil adjuvant could significantly increase the droplet coverage rate and the retention of defoliants in cotton leaves.

Cotton (Gossypium hirsutum L.) is the most widely used natural fiber worldwide in the textile industry; thus, maintaining or even improving fiber quality is essential to produce the best quality yarn and uniform fabrics. Final fiber quality properties are determined not only by genotypes or environmental conditions during crop development but can also be affected by other postmaturity factors, such as harvesting and ginning methods, and harvest time (HT). The aim of this study is to associate the different environmental factors that affect specific lint quality traits produced by a delay in HT, also assessing cultivar effect. This field study included four cotton cultivars evaluated at seven different HTs (manual harvested) for different quality parameters. Results indicate that prolonged exposure of cotton fiber to the environment affects lint percentage (LP), strength (Str), reflectance (Rd), and yellowness (+b). Str showed a decrease of 0.02 g tex−1 day−1 from defoliant application, whereas LP, Rd, and +b presented different rates according to the season. No differences were obtained neither for length nor for fineness and maturity (micronaire) traits. In addition, the analysis of the results together with the climatic data recorded during the experiments indicated a negative correlation among Str, Rd, and +b with the number of rainy days, accumulated precipitation, and frost temperatures. Overall, this study establishes specific relationships between certain fiber characteristics and environmental conditions, being an important tool for crop management with regards to climate predictions that could help to make estimates of economic losses when the harvest is delayed. Core Ideas Lint percentage presented differences among Argentine cultivars analyzed. There were variations in yield and quality parameters among seasons. A delayed harvest time affected lint percentage, fiber strength, and color parameters. Specific fiber quality parameters negatively correlated with some climatic parameters.

Cotton mechanized harvesting is the development direction of cotton production. The rapid development of mechanized cotton harvesting in Xinjiang has significantly increased the efficiency of cotton harvesting and reduced the harvesting cost. However, in the rapid development of mechanized cotton harvesting, there are also the problems of net yield, recovery rate and poor harvesting quality, which lead to the poor quality competitiveness of mechanized cotton harvesting. In order to solve the problem of mechanized cotton loss, the key is to reduce the problem of cotton miscellaneous, and breed cotton varieties suitable for mechanized harvesting. The purpose of this study was to clarify the key trait correlation of defoliation through the establishment and association analysis of foliation and deciduous phenotype indicators in cotton. In this study, the phenotypic indexes of defoliation and deciduous traits were established through the comprehensive analysis of the defoliation rate of 273 cotton germplasm resources and other 11 related phenotypic traits in the field, in order to provide guidance for the breeding and production of cotton varieties collected by breeders. In addition to peeling rate, an analysis of the association between 11 agronomic parameters and peeling rate and hanging rate revealed that the number of effective branches, chlorophyll SPAD value, fruit branch angle, and hanging rate have substantial correlation in 3 years. Hence The hanging rate, fruit branch angle, effective branch number, and chlorophyll SPAD value can be used as the evaluation indicators of varieties for peeling ability trait index.

A grape-bud-oriented genomic platform was produced for a large-scale comparative analysis of bud responses to two stimuli of grape-bud dormancy release, hydrogen cyanamide (HC) and heat shock (HS). The results suggested considerable similarity in bud response to the stimuli, both in the repertoire of responding genes and in the temporary nature of the transcriptome reprogramming. Nevertheless, the bud response to HC was delayed, more condensed and stronger, as reflected by a higher number of regulated genes and a higher intensity of regulation compared to the response to HS. Integrating the changes occurring in response to both stimuli suggested perturbation of mitochondrial activity, development of oxidative stress and establishment of a situation that resembles hypoxia, which coincides with induction of glycolysis and fermentation, as well as changes in the interplay between ABA and ethylene metabolism. The latter is known to induce various growth responses in submerged plants and the possibility of a similar mechanism operating in the bud meristem during dormancy release is raised. The new link suggested between sub lethal stress, mitochondrial activity, hypoxic conditions, ethylene metabolism and cell enlargement during bud dormancy release may be instrumental in understanding the dormancy-release mechanism. Temporary increase of acetaldehyde, ethanol and ethylene in response to dormancy release stimuli demonstrated the predictive power of the working model, and its relevance to dormancy release was demonstrated by enhancement of bud break by exogenous ethylene and its inhibition by an ethylene signal inhibitor.

Arbuscular mycorrhizal fungi (AMF) are totally dependent on a suitable host plant for their carbon resources. Here, we investigated under in vitro conditions, the impact of defoliation practices, i.e., mechanical defoliation or chemical defoliation with a contact herbicide (Reglone®, containing the active ingredient diquat) or systemic herbicide (RoundUp®, containing the active ingredient glyphosate), on the dynamics of spore production of Rhizophagus irregularis and Rhizophagus intraradices associated with Solanum tuberosum and/or Medicago truncatula. Glyphosate affected the spore production rate more rapidly and severely than diquat or mechanical defoliation. We hypothesize that this effect was related to disruption of the C metabolism in the whole plant combined with a possible direct effect of glyphosate on the fungus within the roots and/or perhaps in soil via the release of this active ingredient from decaying roots. No glyphosate could be detected in the roots due to technical constraints, while its release from the roots in the medium corresponded to 0.11% of the active ingredient applied to the leaves. The three defoliation practices strongly affected root colonization, compared to the non-defoliated plants. However, the amount of glyphosate released into the medium did not affect spore germination and germ tube growth. These results suggest that the effects of defoliation on the dynamics of spore production are mainly indirect via an impact on the plant, and that the effect is faster and more marked with the glyphosate-formulation, possibly via a direct effect on the fungus in the roots and more unlikely on spore germination.

During the cotton harvesting stage, the application of chemical harvest aids, such as thidiazuron and ethephon, facilitates cotton defoliation and boll maturation, serving as a crucial management tool in modern cotton cultivation systems. This paper reviews recent advancements in cotton defoliation and ripening research; delves into the physiological mechanisms underlying defoliation, boll maturation, and cotton fiber development; and summarizes the effects of major defoliants and herbicide-type desiccants on plants. It also explores the roles of hormones and genes that are involved in the defoliation process and identifies the key factors influencing the effectiveness of harvest aids. Additionally, this paper offers recommendations and scientific prospects for optimizing cotton defoliation and ripening technologies in the future. Through these contributions, it aims to provide valuable insights for the research and application of efficient harvesting of mature cotton, stimulate innovation in cotton defoliation and ripening technologies, enhance the quality and yield of cotton, reduce labor costs, and contribute to the sustainable development of the cotton industry.