Abstract
The aim of the study was to investigate the growth responses of African yam bean (Sphenostylis sternocarpa (Hochst. ex A. Rich.) Harms (AYB) to cadmium pollution. Top garden soil (0 – 10 cm) was obtained as pooled and polluted with cadmium (as CdCl2) at the rate of 12 mg kg-1, which is equivalent to 3 times the ecotoxicological screening value of Cd. The polluted soils were made ready for use 3 days later. Nine selected AYB accessions (TSs-87, TSs-89, TSs-90, TSs-91, TSs-92, TSs-93, TSs-94, TSs-95, and TSs-96) were pre-soaked for 30 minutes and then sown in the polluted and unpolluted soils. Data collected were subjected to ANOVA, and means were separated at 95 % confidence interval. Results showed that incidence of cadmium pollution significantly delayed seedling emergence in all tested AYB accessions by at least one day (p < 0.05). Despite exposure to Cd, TSs-96 attained 50 % emergence faster than other accessions. Although there were general reductions in yield due to exposure to Cd, TSs-92 showed the least percentage yield reduction (50 %), compared to 74 % yield reduction in TSs-93, thereby suggesting a comparatively better yield capacity compared to the other test accessions. Overall, decrease in total chlorophyll content seems to be the major reason of injury in Cd-exposed plants.
Highlights
Anthropogenic activities, including increased rate of industrialization, concentrated agriculture, and allembracing mining accompanied by escalating population and rapid civilization, have inflicted damaging effect on the accessibility of natural endowments and resulted in extensive and severe contamination of fundamental constituents of life worldwide (Abolghassem et al, 2015)
Cd concentration in the experimental site was negligible at a concentration less than 0.001 mg kg-1The description of African yam bean (AYB) collected from Institute of Tropical Agriculture (IITA) seed bank showed that the accessions originated in Nigeria
Emergence was noticed in Cd-unexposed TSs-87 and TSs-89 at 2 days of sowing, but delayed by 1 day in their Cd-exposed counterparts (p < 0.05).Observably, it took an average difference of 1 day between the Cdexposed and unexposed AYB accessions for half of the seeds to emerge irrespective of prior exposure to cadmium pollution
Summary
Anthropogenic activities, including increased rate of industrialization, concentrated agriculture, and allembracing mining accompanied by escalating population and rapid civilization, have inflicted damaging effect on the accessibility of natural endowments and resulted in extensive and severe contamination of fundamental constituents of life worldwide (Abolghassem et al, 2015). Aside from having atomic mass of over 20 and density higher than 5 g cm−3, HMs can trigger mutagenic, cytotoxic and genotoxic repercussions on plants, animals, and higher beings via the food chains, irrigation, aquifers, and surrounding atmosphere (Rascio & Navari-Izzo, 2011). Even so, they are not biodegradable and are extremely persistent in water and soil. The disproportionate uptake of the element from the soil creates two fold problems; first is the contamination of harvested crops, which become the entry route of heavy metal in human diet, and secondly the inhibition of metabolic processes and, in severe cases, death of plants results in heavy decline in crop yield as well as potential threat to food security (Singh & Aggarwal, 2006). Zong et al (2007) have reported that plant species and genotypes within the species differ greatly in their tolerance to Cd stress
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