Garlic (Allium sativum) based interplanting alters the heavy metals absorption and bacterial diversity in neighboring plants

Abstract

Heavy metals are naturally occurring elements that have a high atomic weight and let out in the environment by agriculture, industry, mining and therapeutic expertise and thrilling amassing of these elements pollutes the environment. In this study we have investigated the potential of garlic interplanting in promoting hyper accumulation and absorption of heavy metals to provide a basis for phytoremediation of polluted land. Monoculture and inter-plantation of garlic were conducted to investigate the absorption of cadmium and lead contamination in the land. A group of experiments with single planting (monoculture) of Lolium perenne, Conyza canadensis and Pteris vittata as accumulators were used. The results have shown that garlic has a potential as a hyper accumulate and absorb heavy metals. It was found that the accumulation of Cd and Pb was much higher with inter-planting. Garlic boosts up the absorption of heavy metals in Lolium perenne of Cd 66% and Pb 44% respectively. The Inter-planting of garlic with Pteris vittata promotes the Cd 26% and Pb 15%. While the maximum accumulation of Lead 87% and Cadmium 77% occurred in Conyza canadensis herb plant. The bacterial diversity in the soil was analyzed for each experimental soil and was found that the Proteobacteria, Acidobacteria, Actinobacteria, Firmicutes, and Planctomycetes were commonly abundant in both single planting (monoculture) of ryegrass and interplanting ryegrass with garlic habitats. Variances were observed in the bacterial floral composition of single (monoculture) and intercropping (interplant) soils. Relative abundance of bacterial taxa revealed that the proportion of Proteobacteria, Acidobacteria, and Actinobacteria in the inter-planting group was slightly higher, while Firmicutes and Planctomycetes were low. This study provides the evidence to control the heavy metals contaminated soils with weed species. Growth promotion and heavy metal uptake of neighboring plants proved the specific plant-plant and plant-microbial associations with garlic plants. This inter-planting strategy can be used to improve heavy metal absorption.

Figure 1

Single planting and inter-planting treatments of Garlic with P. vitatta (a), Conyza canadensis (b) and Lolium perenne (c).

Figure 2

(a) Each branch of phylogenetic tree represents a species and the length of the branch is the evolutionary distance between the two species, that is the degree of difference in the species. (b) Relative abundance of the bacterial species in single (A) and interplant cultures (B). The vertical axis represents the species name at a certain classification level, and each bar corresponding to the species represents the average relative abundance of the species in each sample group, and the different colors indicate different group in the middle area is the difference between the abundance percentages of the two groups in the set confidence interval. The color of the dot is displayed as the group color with a large abundance of species and the type I interval on the dot is the upper and lower limits of the difference value. The rightmost side is the P value, *0.01 < P ≤ 0.05**0.001 < P ≤ 0.01***P ≤ 0.001.

Figure 3

Common phyla relative abundance of soil bacterial community shown as percentage of pooled data from single and interplant treatments.

Figure 4

Distribution of bacterial OTUs in all soil samples showing in Venn diagram for Single plant is represented by (A) and interplant by (B). Overlapping area in Venn diagram represents the shared bacterial OTUs between single plant and interplant treatments.

Figure 5

Hierarchical cluster analysis of 100 main OTUs bacterial communities were determined by genus. Scale indicates the relative abundance of each OTU read color intensity. Clustered based on complete linkage method were applied for samples communities.

Figure 6

Distance dissimilarity heatmap on Genus level of Bray–Curtis dissimilarity matrix of Single and interplant groups (T_1, T_2, T_3 represents single Treatments, while D_1, D_2 and D_3 represent interplant treatments). According to the standard protocols by Majorbio Bio Pharm Technology Co. Ltd. (Shanghai, China), using Sanger software (https://www.i-sanger.com/).