Diversity, use and management of household-located fruit trees in two rapidly developing towns in Southeastern D.R. Congo

Recently, the growing need to complement rural and foreign sources of food and woodfuel is driving interest in urban forestry management in medium cities. The present study was designed to characterize the diversity of fruit trees in households of two rapidly developing cities in southeastern DR Congo (Lubumbashi and Kolwezi), and shed light on the sociological aspects of their management. Analyses of data collected through surveys carried out in planned and unplanned neighborhoods revealed noticeable botanical differences between the two neighborhoods within cities. In Lubumbashi, a greater number of fruit trees (6.5) and species (5.7) per 1000 m2 was recorded in the unplanned neighborhood compared to the planned neighborhood (3.4 trees and 2.0 species). A similar trend was noted in Kolwezi, although with significantly reduced values (by more than half). Across the two cities, a total of 36 fruit trees species were listed, of which 8 were exclusively identified in unplanned neighborhoods of Lubumbashi, showing a comparatively greater species richness of the city. Coincidentally, the 8 specific species are characteristic of Miombo woodland, suggesting preexistence of Miombo vegetation in these areas. Overall, the listed flora of studied neighborhoods in the two cities is dominated by exotic species, with Rutaceae the most represented family. Straightforward differences in the use of fruit trees were noted between the two cities; medicinal uses stand out in Lubumbashi, whereas uses such as shading and properties boundary predominate in Kolwezi. As common trend in the two cities, however, fruit trees scarcely receive arboricultural care, partly explained by limited knowledge on the ecological requirements of fruit trees. Current results have provided important insights into the botanical richness of fruit trees and related sociological aspects of their management at household-scale, which may help in formulating guidelines and technical tools to assessing and monitoring urban forestry in Southeastern DR Congo

Insights on the responses of Brassica napus cultivars against the cobalt-stress as revealed by carbon assimilation, anatomical changes and secondary metabolites

Cobalt (Co) is a toxin environmental pollutant, and its elevated concentrations in agricultural soils can negatively impact the crop productivity. In the current study, we evaluated the toxic effects of Co levels (0, 100, 400 μM) on the hydroponically grown seedlings of four different cultivars of Brassica napus L. cvs. ZS 758, ZY 50, Zheda 619 and Zheda 622. Results showed that lower Co dose (100 μM) executed significant but less toxic effects as compared to 400 μM Co among all studied cultivars. Excessive Co (400 μM) level had significantly declined the plant growth, biomass, chlorophyll contents, nutrients uptake, activities and transcript levels of antioxidant enzymes in leaf and root tissues of all tested cultivars.The decline in physiochemical traits was more prominent in Zheda 622, and ZS 758 performed better under Co toxicity as compared with other cultivars. Co-induced root impairment led to greater ROS and MDA accumulation and inhibit nutrients uptake. Ultimately, the lower translocation to leaves causes damages in carbon assimilation process.These results were confirmed by root staining with nitro-blue tetrazolium (NBT) and 3,3-diaminobenzidine (DAB) and damages in leaf mesophyll and root tip cells by electron microscopic analysis. More anatomical damages were noted in Zheda 622 and least in ZS 758. A significant induction of stress-related proteins (HSP90-1 and MT-1) and secondary metabolites (PAL, PPO, and CAD) under higher Co level (400 μM) indicated the greater plant-defense system against Co-induced oxidative stress and Co-homeostasis that helps in toleraance to Co-phytotoxicity. The comparison of sensitive (Zheda 622) and tolerant (ZS 758) genotypes showed that root tissues were the major target of Co toxicity. Overall, higher Co-accumulation in leaf and root tissues cause cellular toxicity and overall carbon assimilation process. This phytotoxicity was more pronounced in Zheda 622 and least in ZS 758 as compared with other cultivars

Determination of levels of trace metals in soils of kitchen gardens in the mining town of Lubumbashi and the risk of contamination of vegetable crops

Objectives: in the city of Lubumbashi, the mining activity expansion has caused the contamination of the soils of the region with metallic trace elements (MTE) and the agricultural soils have not been spared. The vegetable crops sold in different markets have high levels of MTE. Methodology and results: This study was done in order to assess the level of contamination in the MTE cultivated garden soil and its impact on growth and bioaccumulation in vegetable crops. Thirty nine (39) composite soil sample were collected from 39 sites in the vegetable mining town of Lubumbashi and a trial was set up following a completely randomized experimental design with 4 replicates of 39 treatments (soil) using amaranth and spinach as test culture. Soil samples (before test) and plants (at harvest) were analyzed for Cu, Co, Pb, Cd and Zn. The results showed, first, that the garden soil had high levels of MTE and these high levels of MTE and lead to slower growth of vegetable crops and a high degree of bioaccumulation. Conclusion and potential application of the research: There is a risk of contamination of the food chain through the consumption of vegetable harvested in different sites of the mining town of Lubumbashi vegetables. The use of efficient and effective techniques of bioremediation of contaminated soils is important to reduce the risk of acute and / or chronic toxicity among consumers. Keywords: contaminated soil, MTE, vegetable gardening, bioaccumulation, mining town of Lubumbashi J. Appl. Biosci. 201