Crop Protection & Environmental Biology
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Item Exogenous proline and hormone in combination with compost improves growth and tolerance of maize under heavy metal stress(Plants and Environmental Research Institute (PERI), Kanpur, India, 2020) Adejumo, S. A.; Awoyemi, V.; Togun, A. O.Abiotic stress such as heavy metal contamination of agricultural soil limits crop production by disrupting plant’s physiological activities and seed germination. Exogenous proline, hormone and compost have been used to induce growth and stress tolerance in crop but little is known about their interactive and anti-oxidative roles in crop exposed to heavy metal stress. This study assessed the effects of pre-sowing seed soaking with exogenous proline (P) and hormones (Gibberellic acid; GA and Indole-acetic acid; IAA) on the Pb accumulation, osmolytes (P, phenolics; PH and Glycine betaine; GB), Photosynthetic pigments (chlorophyll and carotenoids) and stress indexes (H2O2 and malonialdehyde; MDA) of maize grown on compost amended Pb (23,959 mg kg-1 Pb) contaminated soil. Compost was applied at 20 t ha-1 and 40 t ha-1, P, GA and IAA were applied at 10 mM and 5 mM solely and in combinations to give a total of 34 treatments including control (Distilled water only) and replicated 3 times. Except in IAA treatment, seed pre-treatments with exogenous P and GA and soil amendment with compost generally enhanced chlorophyll production in maize and reduced GB, carotenoids, H2O2 and MDA in treated seeds compared to control. With regards to stress indexes G2+C1 gave the lowest values. Sole application of P1, P2, C2, G1 and I2 enhanced the production of proline in treated plants compared to combined application. Combination with compost was better than hormonal combination. A combination of P2 with C (40 t ha-1) (P2C2) gave the maximum chlorophyll content and reduced the endogenous GB and P. Treatment with P2C2 also reduced Pb accumulation in plant. In conclusion, exogenous application of hormones and proline in combination with organic amendment induces heavy metal tolerance in maize and increased protection against oxidative stress compared to contaminated control. The technique that can enhance crop growth on contaminated soil, reduce metal uptake and provide osmo-protection could be a promising approach.Item Anatomical changes, osmolytes accumulation and distribution in the native plants growing on Pb-contaminated sites(Springer, 2020) Adejumo, S. A.; |Oniosun, B.; Akpoilih, O. A.; Adeseko, A.; Arowo, D. O.Native plants growing on heavy-metalcontaminated sites are the potential candidates for phytoremediation of contaminated sites due to their tolerance and adaptation to toxic environment. For better application of the technology, in-depth knowledge and understanding of the anatomy and physiology of these plant species are essential. In this study, anatomical changes in roots and leaves of various plant species growing on Pb-contaminated sites as well as osmolytes (proline, PR; glycine betaine, GB; and phenolics, PH) production and distribution in different plant parts were investigated. The soil and plant samples were collected in triplicates from two different Pb-contaminated sites, while control plants were collected from the University of Ibadan. The plants were washed and partitioned into different parts for anatomical and biochemical studies, and soil adhering to the roots of different plant species was collected for the determination of Pb contents. Sporobolus pyramidalis, Cynodon dactylon, Imperata cylindrica, Eleusine indica, Gomphrena celosioides, Rhinconspora corymbosa and Echinochloa colona are the plant species common to these contaminated sites. Though with variations based on the site, thick epidermis and sclerenchyma, pronounced and numerous vascular bundles as well as trichomes were some of the anatomical characteristics of these metallophytes from contaminated sites compared to their counterparts from uncontaminated site. These plants also produced PR, GB and PH, with PH being the highest followed by PR and GB. Accumulation in different parts of the plants also varied depending on the plant species and the osmolyte. They were more in the leaf than other plant parts. Among the plant species, Sporobolus pyramidalis had the highest value of proline (3.26 and 2.63 lg/g FW) and glycine betaine (3.44 and 2.23 lg/FW) in the leaf and stem, respectively, followed by Cynodon dactylon having 2.20 and 0.89 lg/g FW proline and 2.02 and 0.94 lg/g FW glycine betaine. On the Pb accumulation in plant, more lead (Pb) was found in the roots than other plant parts. Gomphrena celosioides accumulated the highest Pb (4537.50 and 1081.50 mg/kg) in the root and shoot, respectively, followed by Eleusine indica (3988 and 699.00 mg/kg), while the lowest values were recorded for Echinochloa colona (36.87 and 5.97 mg/kg). In rhizospheric soils, G. celosioides had the highest Pb content (34,405.00 mg/kg) which was higher than other rhizospheric soils. In conclusion, phenolics were produced more in these metallophytes and all the osmolytes were more in leaf than root. Anatomical modifications in response to heavy metal exposure differed between plant species and level of contamination. Lead accumulation in plant also varied depending on plant species.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.Item Seed germination and growth of maize (Zea mays L.) on lead contaminated soil in response to compost, exogenous proline and plant growth promoters in Ibadan, Nigeria(Ecological Society of Nigeria, 2018) Awoyemi, V.; Adejumo, S. A.Soil contamination with heavy metal poses serious threat to agricultural productivity. It induces oxidative stress on crop and causes reduction in crop yield. To enhance crop production and safety, strategies must be developed to increase crop tolerance to heavy metal toxicity and enhance crop productivity on contaminated sites. Study was carried out to determine the ability of exogenous application of proline, hormones and compost in ameliorating the effect of lead (Pb) stress on maize crop grown on lead-acid battery wastes contaminated soil. The experiment was laid out in a Completely Randomized Design (CRD) and replicated three times. The treatments were proline (P), indole acetic acid (IAA), gibberellic acid (GA), and compost. Proline and hormones were applied at 0, 5 and 10 mM as seed soaking while compost was applied to the soil two weeks before planting using 0, 20 and 40 t/ha application rates. These were applied individually and in combination to give a total of 34 treatments including, control and replicated 3 times. Un-amended contaminated and uncontaminated soil served as checks. The experiment was terminated eight weeks after planting. Data were collected on maize percentage germination, duration of survival of maize seedlings, growth parameters and dry matter yield. Maize seeds pre-treated with P at 10 mM and C (40 t/ha) and those treated with GA (5 mM) + C (20 t/ha) gave 100% germination on contaminated soil. Compared to contaminated control, duration of survival, maize growth and dry matter yield were enhanced when seeds were pre-treated with exogenous proline and hormone and gown on contaminated soil amended with compost. Seed treatment with 10 mM P + 20 t/ha compost generally increased plant height, number of leaves, stem girth and leaf area relative to control and IAA treatments. Pre-sowing seed treatment with 10 mM P and soil amendment with 40 t/ha compost increased the maize dry matter yield better than other treatments, including control. Maize growth and yield on lead-contaminated soil were enhanced with seed pre-treatment with 10 mM proline and 40 t/ha compost. Exogenous application of proline and gibberellic acid in combination with compost enhanced maize germination, growth and yield in Pb contaminated soil and alleviate Pb toxicity.Item Heavy metal (Pb) accumulation in metallophytes as influenced by the variations in rhizospheric and non- rhizospheric Soils physico-chemical characteristics.(Taylor & Francis., 2018) Adejumo, S. A.; Tiwari, S.; Shinde, V.; Sarangi, B. K.Activities at root-soil interface determine the solubility and uptake of metals by plants. Metal accumulation in plant species (Imperata cylindrical, Cynodon dactylon, Eleucine indica, Gomphrena celosoides, Sporobolus pyramidalis, Chromolaena odorata and Rhynchospora corymbosa) growing on Pb contaminated site as influenced by variations in physico-chemical characteristics, dissolved organic matter (DOM), Pb fractionation and different functional groups (using Fourier Transmittance Infra-red) of rhizospheric and non-rhizospheric soils was assessed. The electrical conductivity (2660–5520 ms) and Pb concentrations (51390.0–64080.0 mg/kg) were more in non-rhizospheric than rhizospheric soils having 276 ms to 3160 ms EC and 3289.0 to 44850.0 mg/kg Pb. More nutrients, DOM and carbohydrates functional groups (C-O; 1100 -1000 and O-H; 3700–3600) were found in rhizospheric compared to non-rhizospheric soils. The pH was slightly acidic (5.0–5.54) and E. indica with the lowest pH (5.0) accumulated highest Pb concentrations in shoot (8030 mg/kg) and root (16380 mg/kg) while C. odorata with highest values of pH, P, Ca and Mg in rhizospheric soil accumulated the least (root; 331.6 and shoot: 209.0 mg/kg). Pb was more in organic and residual fractions of rhizospheric and non-rhizospheric soils respectively. Reduction in pH, EC coupled with nutrients and DOM availability increased Pb uptake by plants.