Plant growth stage influences heavy metal accumulation in leafy vegetables of garden cress and sweet basil

Abstract

Background: Contamination of vegetable crops with heavy metals is a great threat to human health. On the other hand, monitoring plant tissue content of heavy metals at different growth stages could have important implications. In this study, shoot and root samples of garden cress and sweet basil were collected from five farms, from heavy metal polluted fields located in Shahre Rey, south of Tehran, Iran, in either young (3 weeks old) or mature (7 weeks old) plants. The concentrations of cadmium (Cd), lead (Pb), nickel (Ni), arsenic (As), chromium (Cr), cobalt (Co), copper (Cu), manganese (Mn) and zinc (Zn) in plant tissues were determined using atomic absorption spectroscopy. In another study, 2 weeks (young) or 6 weeks old (mature) plants of garden cress were subjected to three concentrations of Cd and Pb (0, 5, 10 mg L −1 ) under hydroponic sand culture for 5 days, in which Hoagland formula was used for nutrient solution preparation. Results:The results showed that root concentration of various heavy metals, particularly Cd, As, Ni, Co, Cu, Mn and Zn but not Pb were significantly higher than their shoot concentration in either crop under field sampling. The leaf concentration of some heavy metals was significantly different in seedling and older (mature) plant samples of either crop. Young plant leaves of sweet basil had significantly less Cd, Pb, As and higher Cu than mature plants, whereas young garden cress plants had similar Cd, Pb and higher As and Zn concentrations than mature plants. The Cr, Co, Mn and Zn concentrations were similar in young and mature plants of sweet basil. The Mn, Co, Cr and Ni concentration of young and mature plants of either crop was also similar. The result of hydroponic study showed that young plants of garden cress had higher potential to accumulate lead in shoot and root, particularly in lower (5 mg L −1 ) than higher (10 mg L −1 ) lead concentration; however, root Pb concentration at 10 mg L −1 Pb of nutrient solution showed no difference between young and mature plants. Regarding cadmium, young garden cress plants accumulated higher Cd than mature plants in their shoot, particularly under higher Cd levels (10 rather than 5 mg L −1 ) of nutrient solution; however, a wide difference in root Cd concentration was observed under low (5 mg L −1 ) than higher (10 mg L −1 ) cadmium concentration of nutrient solution. Conclusion:The results of these two studies indicate that despite that young plants have a higher potential for heavy metal uptake and accumulation, the low difference in young and mature plants in the polluted fields may be due to the longer period of plant growth of mature plants that may increase the risk of exposure to polluted air and dust deposition containing high levels of heavy metals.

Uptake and accumulation of Cr in edible parts of Eruca sativa from irrigation water. Effects on polyphenol profile and antioxidant capacity

“…Vegetables are considered essential diet components ( Wang et al., 2019 ), and can accumulate metals in concentrations higher than the maximum allowed levels, and due to fresh consumption, their contamination with heavy metals is very important in human health ( Souri et al., 2018 , 2019 ). In particular, the accumulation of Cr in edible parts of plants can cause numerous health risks for consumers.…”

“…Owing to the toxicity of Cr, this element can promote molecular, biochemical and ultrastructural changes in plant tissues ( do Nascimento et al., 2018 ). Plants can undergo chloroplast pigment degradation, reductions in photosynthetic activity, cell membrane damage and production of reactive oxygen species (ROS) under heavy metal contamination ( Hatamian et al., 2020 ; Souri et al., 2019 ; Tang et al., 2020 ). To protect against oxidative stress, plants affected by heavy metal induces enzymatic and non-enzymatic ROS scavenging systems, having the latter a crucial role in the cell defense, since they act as cofactors of antioxidant enzymes ( Gupta et al., 2019 ; Hu et al., 2020 ).…”

Aluminum toxicity reduces the nutritional efficiency of macronutrients and micronutrients in sugarcane seedlings

“…Likewise, the reduction of K content in the shoot with increased aluminum levels occurs due to the competition of cations (Al and K + ) for absorption sites in the transporters or influx channels of monovalent and divalent cations, reducing both its translocation to the shoot or its energy supply for energy-dependent transportation systems (Kochian, 1995). It has been shown that heavy metals can significantly damage conducting vessels of plants including the transportation pathways from the roots to the stems and shoots (Hatamian, et al, 2020b;Souri;Tesfamariam, 2019), that probably Al with a similar effect can damper transportation vessels of plants.…”

Different Sources of Irrigation Water Affect Heavy Metals Accumulation in Soils and Subsequently on Physiological Determinants and Physico-Chemical Properties of Guava Fruits

“…The tolerance towards heavy metal stresses varies from specie to specie, stages of growth, and plant parts (Souri et al 2019). The performance of cultivars may vary because of different genetic makeups.…”