Crop Protection & Environmental Biology
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Item Low light intensity and compost modified biochar enhanced maize growth on contaminated soil and minimized Pb induced oxidative stress(Elsevier, 2021) Adejumo, S. A.; Owoseni, O.; Mur, L.A.J.Heavy metal uptake by agricultural crops poses great danger to human health. Application of compost and biochar has been used extensively for metal immobilization in soil and to reduce metal uptake by crop plant. Their efficiency is however, limited by other environmental factors like water and light intensity. In this study, the effects of organic amendments (Mexican Sunflower Compost and Rice Husk (RH) biochar) in combination with varying light intensities on growth and Pb uptake by maize crop grown on industrially contaminated soil containing 53,752 mg/kg Pb was investigated. Compost and biochar were applied singly and in combination at 0, 2.5, 5 and 7.5 t ha1 while different layers of net were used to vary light intensity (one layer =60: 386 lx, two layers =53:340 lx, three layers =27 %: 177 lx and zero layer with 100 % light intensity of 634 lx served as control). Soil Pb concentration and stress metabolites (Proline and cysteine) production before and after the experiment were also determined. Results showed that, higher rates of organic amendments and reduced light intensity increased the vegetative growth and yield of maize on contaminated soil compared to 100 % light intensity. Combination of biochar and compost performed better than sole application. It reduced post-cropping soil Pb concentration and Pb uptake by maize, especially under low light intensity. The stress metabolites were more in the leaves of maize crop grown in un-amended soil and under 100 % light intensity. Addition of organic amendment coupled with reduction in light intensity therefore, enhanced maize growth on contaminated soil, reduced Pb uptake and oxidative stress, while, heavy metal accumulation and stress metabolites production were more in maize grown in un-amended soil and exposed to high light intensity.Item Ameliorative roles of compost on okra (Abelmoschus esculentus L.) exposed to drought stress at vegetative and reproductive growth stages(Society of Land Measurements and Cadastre from Transylvania - SMTCT, 2020) Ezeh, O. S.; Adejumo, S. A.Okra growth and yield are adversely affected by drought at different growth stages. This is aggravated by poor soil fertility. In this study, the roles of compost applied at 0, 5 and 10 t/ha on the tolerance and morphophysiological response of okra (NHAe 47-4) exposed to varying levels of water stress (25%, 50%, 75% and 100% field capacity, FC), at different growth stages (vegetative, reproductive and vegetative-reproductive stages) for ten days duration were assessed. Data were collected on okra growth and yield, leaf relative water content (LRWC), leaf photosynthetic pigments (LPG) and proline accumulation. Results showed that drought stress reduced LRWC, LPG, growth and yield of Okra. This reduction was more evident in okra plants exposed to severe stress for 10 days and at the reproductive stage. Soil amendment with compost however, had cushioning effect on drought stressed okra. Compared to control, it increased the LRWC, LPG, growth and yield of okra. The ameliorative roles of compost were however, dependent on stress intensity, compost dosage, okra growth stage and stress duration. Though, okra plants stressed at 25% FC were more affected by drought stress, but compared to the un-amended soil, those grown on amended soil were more tolerant. Higher compost rate was superior to lower rates. Whereas, higher proline accumulation was recorded in plant exposed to 25% field capacity without amendment, proline accumulation was reduced in the plants grown on compost amended soil and exposed to drought which was an indication of stress reduction. Generally, okra stressed at vegetative growth stage only was able to recover rapidly and had better yield compared to those stressed at reproductive growth stage. It is concluded that addition of compost to soil could reduce the drought stress effect on okra.Item "Biochar in combination with compost reduced Pb uptake and enhanced the growth of maize in lead (Pb)‑contaminated soil exposed to drought stress "(Springer, 2010) Adejumo, S. A.; Arowo, D. O.; Ogundiran, M. B.; Srivastava, P.Crops are constantly faced with the challenges of different abiotic stresses on the field. Development of sustainable approach for stress amelioration on crop is pertinent. This study investigated the ameliorative roles of biochar and compost on maize crop simultaneously subjected to drought and heavy metal (Pb) stresses. Metal stress was imposed by growing maize on Pb-contaminated soil while drought stress was imposed by reducing the soil field capacity to 25 and 50%. Four levels (0, 5, 10 and 15 t/ha) of biochar and compost replicated three times as well as their combinations were used. Pb uptake, translocation factors, photosynthetic pigments, osmolytes (proline and cysteine), biomass accumulation in stressed maize crop, and post-cropping soil Pb concentration were determined. Combination of stresses reduced biomass accumulation in maize. Biochar in combination with compost, however, enhanced biomass production in stressed maize crop by 50–75% compared to unamended soil (control). Proline accumulation was more under the single stress of heavy metal (100% FC) compared to combined stresses. Unlike proline, combined stresses of Pb and 50% FC enhanced chlorophyll and cysteine accumulation more than single stress. Their concentrations were further increased with amendments compared to control. Pb accumulation in maize crop was more under combined stresses than single stress (100% FC). Compared to other soil amendments, application of biochar alone at 10 t/ha, generally reduced Pb uptake by maize and post-cropping soil Pb concentration. Biochar and compost reduced Pb uptake, and enhanced biomass and osmolyte production in stressed maize crop.Item Mechanisms of lead and chromium hyperaccumulation and tolerance in plant(Enproct Consultants Ltd., 2019) Adejumo, S. A.Heavy metal contamination of agricultural lands poses serious threat to food security. Lead (Pb) and Chromium (Cr) are among the most toxic heavy metals reported but least studied. Their presence in soils has detrimental effects on crop productivity. Among different ways of remediating contaminated sites, phytoremediation technology like phytoextraction is now receiving greater attention. It involves the use of plants for cleaning heavy metal polluted media. It is environment-friendly, aesthetically appealing, cost-effective and can be applied in-situ. The plant species that are used for this process are metal tolerant and some of them called hyperaccumulators possess the ability of accumulating high concentrations of specific metals in the above-ground tissue. They have developed several mechanisms both at the genetic and molecular levels for their adaptability and efficiency. The molecular mechanisms could either be enzymatic or non-enzymatic. The enzymatic mechanism involves the participation of different antioxidant enzymes while the non-enzymatic strategies are based on the production of different antioxidant compounds for scavenging reactive oxygen species which are produced in heavy-metal stressed plants. For tolerance and metal accumulation in the above-ground parts of an hyperaccumulator, metal homoestasis through over-expression of different genes have also been reported. In this review, heavy metal toxicity, phytoremediation options and mechanisms of hyperaccumulation and tolerance in plants are discussed with focus on Pb and Cr.