## 1 Introduction
Cu is also an essential component of various proteins such as plastocyanin, of the photosynthetic system and of cytochrome oxidase of the respiratory electron transport chain [14], but an excess of Cu in soil plays a cytotoxic role, induces stress and causes injury to plants. This leads to plant growth retardation and leaf chlorosis. Exposure of plants to excess Cu generates oxidative stress and ROS [15]. Oxidative stress causes disturbance of metabolic pathways and damage to macromolecules [16]. The beneficial phytoremediative potential of plant growth-promoting rhizobacteria (PGPR) has been proven in studies conducted on cereal (rice, maize and wheat) crops by [PERSON] et al. [17], [PERSON] et al. [18] and [PERSON] et al. [19]. PGPR in the roots and rhizosphere greatly reduce heavy metal stress in plants by secreting organic acids, subsequent production of siderophores, 1-aminocyclopropane-1-carboxylic (ACC)-deaminase, phytohormones, chelation, immobilization, and enzymatic transformation [13; 20]. [PERSON] et al. [21] have recommended the cultivation of certain plant germplasm possessing the ability to accumulate HMs. Generating awareness among farmers (the primary stakeholders in this regard) will be a sine qua non to incorporate and popularize this phytoremediation technology. Leguminous crops belonging to the Fabaceae group, such as _Vicia faba_ (broad beans), _Pisum sativum_ (garden peas), _Plusiolus vulgaris_ (common beans), and _Lens culinaris_ (lentilswhite, green, red and yellow), are key components of human diets globally, as they are sources of carbohydrates, proteins, vitamins and minerals [22]. It must not be forgotten that they were among the first outputs from poor and degraded soils. The adaptability of crops from the Fabaceae group and their ability to tolerate high salinity, temperatures and even droughs, yielded different varieties in different environments (pedo-climatic), and enabled the restoration of arid ecosystems, as noted by [PERSON] et al. [23]. Legumes are noteworthy for their ability to capture and fix atmospheric nitrogen in the soil, through a mutualistic symbiotic relationship with soil-dwelling rhizobia bacteria. They also tend to absorb excessive amounts of HMs and accumulate them in their edible and non-edible parts [24], thus posing a clear risk to animals and humans downstream in the trophic chain [25]. Ironically, by virtue of this ability, legumes are looked upon as agents of soil-phytoremediation, when the pollutants of concern are HMs [16; 26; 27]. It goes without saying that whenever they are called upon to fulfill this function, they cease to be food-crops. It has been reported that the bioaccumulation of heavy metals in vegetables, especially in leafy vegetable [28], is influenced by many factors, including climate, atmospheric deposition, soil HM concentrations, soil-type, and the degree of maturity of plants when they are harvested [29]. The concentrations of heavy metals in the plant vary according to the type of plant [30]. The ability of legumes to grow in marginal soils is often attributed to the symbiotic associations they have established with nitrogen-fixing rhizobia, and some of them tolerate extreme environmental conditions such as salinity, drought, or high temperatures. [PERSON] et al. [31] reported that cobalt (Co), lead (Pb) and chromium (Cr) are accumulated in faba bean leaves, Fe in pods, while Zn and Cu tend to be accumulated in the seeds. While a handful of studies have been carried out on the accumulation of Pb, Cd and Cu in legumes, it is worthwhile to pose new research questions and try to answer them in this study. Therefore, the authors have decided to investigate the locations and the degrees of accumulation (bifurcated as 'accumulators' and 'hyper-accumulators') of the three HMs selected for the analysis. Such an approach may considerably upgrade all procedures aimed at selecting heavy metal-tolerant varieties to be exploited for cultivation in contaminated soil.