Elevated CO₂ concentrations can change the multi-level nutritional relationship of the ecosystem through the cascading effect of the food chain. To date, few studies have investigated the effects of elevated CO₂ concentration on the Araneae species through the tritrophic system. Hylyphantes graminicola (Araneae: Linyphiidae) is distributed widely in Asia and is a dominant predator in cotton fields. This study investigated chemical components in the food chain of cotton (Gossypium hirsutum)—cotton aphid (Aphis gossypii)—predator (H. graminicola) and compared the development, reproduction, and predation of H. graminicola under ambient (400 ppm) and elevated concentration of CO₂ (800 ppm). The results showed that the elevated CO₂ concentration increased the chemicals of cotton and cotton aphid, but it did not affect the nutrients, development, reproduction, and predation of the spider. However, the survival rate of the spider was significantly decreased in elevated CO₂. The results will further our understanding of the role of natural enemies in an environment with elevated CO₂ concentration.

With the commercialization of transgenic cotton that expresses Bt (Bacillus thuringiensis) insecticidal proteins, mirid bugs have become key pests in cotton and maize fields in China. Genetically engineered (GE) crops for controlling mirids are unavailable owing to a lack of suitable insecticidal genes. In this study, we developed and validated a dietary exposure assay for screening insecticidal compounds and for assessing the potential effects of insecticidal proteins produced by GE plants on Apolygus lucorum, one of the main mirid pests of Bt cotton and Bt maize. Diets containing potassium arsenate (PA) or the cysteine protease inhibitor E-64 were used as positive controls for validating the efficacy of the dietary exposure assay. The results showed that with increasing concentrations of PA or E-64, A. lucorum larval development time was prolonged and adult weight and fecundity were decreased, suggesting that the dietary exposure assay was useful for detecting the toxicity of insecticidal compounds to A. lucorum. This assay was then used to assess the toxicity of Cry1Ab, Cry1Ac, Cry1F, Cry2Aa, and Cry2Ab proteins, which have been transformed into several crops, against A. lucorum. The results showed that A. lucorum did not show a negative effect by feeding on an artificial diet containing any of the purified Cry proteins. No significant changes in the activities of digestive, detoxifying, or antioxidant enzymes were detected in A. lucorum that fed on a diet containing Cry proteins, but A. lucorum fitness was reduced when the insect fed on a diet containing E-64 or PA. These results demonstrate that A. lucorum is not sensitive to the tested Cry proteins and that the dietary exposure assay is useful for evaluating the toxicity of insecticidal compounds to this species.

Delayed sowing of wheat (Triticum aestivum L.) in cotton-based system reduces the productivity and profitability of the cotton-wheat cropping system. In this scenario, relay cropping of wheat in standing cotton might be a viable option to ensure the timely wheat sowing with simultaneous improvement in wheat yields and system profitability. This 2-year study (2012–2013 and 2013–2014) aimed to evaluate the influence of sowing dates and relay cropping combined with different management techniques of cotton sticks on the wheat yield, soil physical properties, and the profitability of the cotton-wheat system. The experiment consisted of five treatments viz. (S1) sowing of wheat at the 7th of November by conventional tillage (two disc harrows + one rotavator + two plankings) after the removal of cotton sticks, (S2) sowing of wheat at the 7th of November by conventional tillage (two disc harrows + two plankings) after the incorporation of cotton sticks in the field with a rotavator, (S3) sowing of wheat at the 7th of November as relay crop in standing cotton with broadcast method, (S4) sowing of wheat at the 15th of December by conventional tillage (two disc harrows + one rotavator + two plankings) after the removal of cotton sticks, and (S5) sowing of wheat at the 15th of December by conventional tillage (two disc harrows + two plankings) after the incorporation of cotton sticks in the field with a rotavator. The highest seed cotton yield was observed in the S5 treatment which was statistically similar with the S3 and S4 treatments; seed cotton yield in the S1 and S2 treatments has been the lowest in both years of experimentation. However, the S2 treatment produced substantially higher root length, biological yield, and grain yield of wheat than the other treatments. The lower soil bulk density at 0–10-cm depth was recorded in the S2 treatment which was statistically similar with the S5 treatment during both years of experimentation. The volumetric water contents, net benefit, and benefit-cost ratio were the highest in the S3 treatment during both years of experimentation. Thus, relay cropping of wheat in standing cotton might be a viable option to improve the soil physical environment and profitability of the cotton-wheat cropping system.

Crop nutrient management is an essential component of any cropping system. With increasing concerns over environmental protection, improvement in fertilizer use efficiencies has become a prime goal in global agriculture system. Phosphorus (P) is one of the most important nutrients, and strategies are required to optimize its use in important arable crops like cotton (Gossypium hirsutum L.) that has great significance. Sustainable P use in crop production could significantly avoid environmental hazards resulting from over-P fertilization. Crop growth modeling has emerged as an effective tool to assess and predict the optimal nutrient requirements for different crops. In present study, Decision Support System for Agro-technology Transfer (DSSAT) sub-model CSM-CROPGRO-Cotton-P was evaluated to estimate the observed and simulated P use in two cotton cultivars grown at three P application rates under the semi-arid climate of southern Punjab, Pakistan. The results revealed that both the cultivars performed best at medium rate of P application (57 kg ha⁻¹) in terms of days to anthesis, days to maturity, seed cotton yield, total dry matter production, and harvest index during 2013 and 2014. Cultivar FH-142 performed better than MNH-886 in terms of different yield components. There was a good agreement between observed and simulated days to anthesis (0 to 1 day), days to maturity (0 to 2 days), seed cotton yield, total dry matter, and harvest index with an error of −4.4 to 15%, 12–7.5%, and 13–9.5% in MNH-886 and for FH-142, 4–16%, 19–11%, and 16–8.3% for growing years 2013 and 2014, respectively. CROPGRO-Cotton-P would be a useful tool to forecast cotton yield under different levels of P in cotton production system of the semi-arid climate of Southern Punjab.

Silicon (Si) is as an important fertilizer element, which has been found effective in enhancing plant tolerance to variety of biotic and a-biotic stresses. This study investigates the Si potential to alleviate zinc (Zn) toxicity stress in cotton (Gossypium hirsutum L.). Cotton plants were grown in hydroponics and exposed to different Zn concentration, 0, 25, and 50 μM, alone and/or in combination with 1 mM Si. Incremental Zn concentration in growth media instigated the cellular oxidative damage that was evident from elevated levels of hydrogen peroxide (H₂O₂), electrolyte leakage, and malondialdehyde (MDA) and consequently inhibited cotton growth, biomass, chlorophyll pigments, and photosynthetic process. Application of Si significantly suppressed Zn accumulation in various plant parts, i.e., roots, stems, and leaves and thus promoted biomass, photosynthetic, growth parameters, and antioxidant enzymes activity of Zn-stressed as well unstressed plants. In addition, Si reduced the MDA and H₂O₂production and electrolyte leakage suggesting its role in protecting cotton plants from Zn toxicity-induced oxidative damage. Thus, the study indicated that exogenous Si application could improve growth and development of cotton crop experiencing Zn toxicity stress by limiting Zn bioavailability and oxidative damage.

Plants face changes in leaves under lead (Pb) toxicity. Reduced glutathione (GSH) has several functions in plant metabolism, but its role in alleviating Pb toxicity in cotton leaves is still unknown. In the present study, cotton seedlings (28 days old) were exposed to 500 μM Pb and 50 μM GSH, both alone and in combination, for a period of 10 days, in the Hoagland solution under controlled growth conditions. Results revealed Pb-induced changes in cotton’s leaf morphology, photosynthesis, and oxidative metabolism. However, exogenous application of GSH restored leaf growth. GSH triggered build up of chlorophyll a, chlorophyll b, and carotenoid contents and boosted fluorescence ratios (F ᵥ/F ₘ and F ᵥ/F ₀). Moreover, GSH reduced the malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and Pb contents in cotton leaves. Results further revealed that total soluble protein contents were decreased under Pb toxicity; however, exogenously applied GSH improved these contents in cotton leaves. Activities of antioxidant enzymes (catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), glutathione reductase (GR), and ascorbate peroxidase (APX)) were also increased by GSH application under Pb toxicity. Microscopic analysis showed that excess Pb shattered thylakoid membranes in chloroplasts. However, GSH stabilized ultrastructure of Pb-stressed cotton leaves. These findings suggested that exogenously applied GSH lessened the adverse effects of Pb and improved cotton’s tolerance to oxidative stress.

Cadmium (Cd) pollution is present in the world over especially in the industrialized parts of the world. To reduce Cd accumulation in various crops especially food crops, alleviating agents such as reduced glutathione (GSH) can be applied, which are capable either to exclude or to sequester Cd contamination. This study investigated the leaf-based spatial distribution of physiological, metabolic, and microstructural changes in two cotton cultivars (Coker 312 and TM-1) under GSH-mediated Cd stress using single levels of Cd (50 μM) and GSH (50 μM) both separately and in mix along with control. Results showed that GSH revived the morphology and physiology of both cotton cultivars alone or in mix with Cd. Cd uptake was enhanced in all segments of leaf and whole leaf upon the addition of GSH. GSH alleviated Cd-induced reduction in the photosynthetic pigment compositions and chlorophyll a fluorescence parameters. Mean data of biomarkers (2,3,5-triphenyltetrazolium (TTC), total soluble protein (TSP), malondialdehyde (MDA), hydrogen peroxide (H₂O₂)) revealed the adverse effects of Cd stress on leaf segments of both cultivars, which were revived by GSH. The oxidative metabolism induced by Cd stress was profoundly influenced by exogenous GSH application. The microstructural alterations were mainly confined to chloroplastic regions of leaves under Cd-stressed conditions, which were greatly revived upon the GSH addition. As a whole, Cd stress greatly affected TM-1 as compared to Coker 312. These results suggest a positive role of GSH in alleviating Cd-mediated changes in different leaf sections of cotton cultivars.