Cadmium (Cd) has no known role in plant biology and is toxic to plants and animals. The Cd mainly accumulated in agricultural soils through anthropogenic activities, such as sewage water irrigation and phosphorus fertilization. Biochar (BC) has been proposed as an amendment to reduce metal toxicity in plants. The objective of this study was to evaluate the role of BC (cotton stick at a rate of 0, 3, and 5 %) on Cd uptake and the photosynthetic, physiological, and biochemical responses of spinach (Spinacia oleracea) grown in Cd-spiked soil (0, 25, 50, 75, and 100 mg Cd kg soil). The results showed that Cd toxicity decreased growth, photosynthetic pigments, gas exchange characteristics, and amino acid and protein contents in 52-day-old spinach seedlings. The Cd treatments increased the concentrations of Cd, sugar, ascorbic acid, and malondialdehyde (MDA) in plants. The application of BC ameliorated the harmful effects of Cd in spinach plants. Under Cd stress, BC application increased the growth, photosynthesis, and protein contents and decreased Cd concentrations and MDA contents in plants. The maximum BC-mediated increase in dry biomass was about 25 % with 5 % BC application in control plants. It is concluded that BC could ameliorate Cd toxic effects in spinach through changing the physiological and biochemical attributes under Cd stress.
Chromium (Cr) toxicity is becoming one of a major issue for the cultivation of crops. Toxicity of Cr directly affects synthesis of chlorophyll and restricts Fe intake, which decreases crop growth. It is well documented that the reduction of Cr toxicity through the application of biochar. However, current experiment was carried out to investigate any positive effect of, banana peel waste biochar (BC) and foliar application of Fe (FFe) on growth and chlorophyll content of Spinacia oleracea L. under different levels of Cr toxicity. Seeds of Spinacia oleracea L. were grown under three levels of Cr i.e. control (Cr0), Cr35 (35 mg Cr kg−1 soil) and Cr70 (70 mg Cr kg-1 soil). Analyzed data confirmed that Spinacia oleracea L. seeds grown in 1% BC amended soils and 1000mM FFe, showed significantly better growth, Fe uptake and chlorophyll content as compared to control at Cr35 and Cr70. A significant improvement in shoot length (16.9 and 26.9%), root length (16.3 and 20.9%), plant fresh (15.5 and 28.3%) and dry weight (70.3 and 77.8%) as compared to control under Cr35 and Cr70, respectively, validated the efficacious functioning of 1% BC and FFe to mitigate Cr toxicity in Spinacia oleracea L. It is concluded that both 1% banana peel waste BC and 1000mM FFe have potential but sole application of FFe is more effective to alleviate Cr toxicity in Spinacia oleracea L. Fortification of Fe by foliar application is more effective comparative to banana peel waste biochar for improvement in growth, chlorophyll content and accessory pigments synthesis in spinach under chromium (IV) toxicity.
Heavy metals toxicity in the human being is creating an alarming condition in the world. Not only are these metals largely effecting the growth of many plants but also the consumer's health. In sector of agriculture for many years Pakistan is facing the reduction in availability of edible oil. The demand is fulfilled by importation by spending huge cost. Brassica campestris L. is very important oil seed crop of Pakistan that is providing 31% of total oil seed production in Pakistan. But due to toxicity of metals like Cd and Pb its growth and yield is decreasing. Keeping in view the importance of Brassica campestris L. in Pakistan an experiment was conducted using Pollutary manure biochar as a reclaiming agent for heavy metals and an amendment as drought stress reducer to check the improvement in yield of Brassica campestris L. It is found that biochar application not only gave positive correlation in immobilization of Pb and Cd but also improves the plants growth and yield. Enhancements in the Photosynthetic and Accessory pigments are observed regarding good vegetative growth. Thus biochar can be utilized in reducing the metals uptake as well as growth promoter.
Irrigation of arable land with contaminated sewage waters leads to the accumulation of trace metals in soils with subsequent phyto‐/zootoxic consequences. In this study, biochar derived from cotton sticks was used to amend an agricultural silt‐loam soil that had been previously irrigated with trace metal contaminated sewage waters. Metal accumulation and toxicity to spinach (Spinacia oleracea) and fenugreek (Trigonella corniculata) was investigated by measuring concentrations of Cd and Ni in plant tissues and various photosynthetic and biochemical activities of plants. Positive impacts of biochar on both spinach and fenugreek were observed in terms of biomass production that increased from 29% to 36% in case of spinach, while for fenugreek this increase was 32% to 36%. In the control treatment there was an increase in malondialdihyde, soluble sugar, and ascorbic acid contents, indicating heavy metal stress. Biochar applications increased soluble proteins and amino acids in plants and reduced the uptake of Cd from 5.42 mg kg−1 at control to 3.45 mg kg−1 at 5% biochar amended soil and Ni (13.8 mg kg−1 to 7.3 mg kg−1 at 5% biochar) by the spinach plants. In fenugreek, the Cd was reduced from 7.72 mg kg−1 to 3.88 mg kg−1 and reduction in Ni was from 15.45 mg kg−1 to 9.46 mg kg−1 at 5% biochar treated soil, reducing the possibility of transfer up the food chain. This study demonstrates that the use of biochar made from cotton‐sticks, as an amendment to arable soils that have received contaminated irrigation water, could improve plant growth and decrease Cd and Ni uptake to crops, alleviating some of the negative impacts of using sewage waters on arable land.
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