harvestable yields and quality of the edible plant parts [44]. According to Marschner [45], 15 to 30% of the total
magnesium in plants is associated with chlorophyll molecule. Magnesium is an essential element in biological
systems. Magnesium occurs typically as the Mg2+ ion. It is an essential mineral nutrient for life. The result shows in
Table 2 that by using Elan 9000, magnesium in leaves Stevia rebaudiana was 189.56 mg/kg-1. Meanwhile, the result
of magnesium in stems was 1760 mg/kg-1 and in flowers was 481.2 mg/kg-1. Then, the result as shown in Table 2 by
using Agilent 7500a, magnesium in leaves of Stevia rebaudiana was 1.701 mg/kg-1. Meanwhile, the result of
magnesium in stems was 1034.2 mg/kg-1 and in flowers was 1.76 mg/kg-1.
Some plants are tolerant to selenium, showing a high capability to accumulate this element without symptoms of
toxicity. They are also capable of translocating and/or transforming selenium into bioactive compounds, which play
an important role in both, human nutrition and phytoremediation [46]. The results of selenium in leaves, stems, and
flowers of the Stevia rebaudiana plant were extremely lower, as shown in Table 2.
Zinc is an essential element for plant nutrition. It plays structural and/or catalytic roles in many enzymes such as
Cu–Zn superoxide dismutase, alcohol dehydrogenase, RNA polymerase and DNA-binding proteins and is associated
with the carbohydrate metabolism [47,48]. The normal heavy metal contents of terrestrial plants growing in
uncontaminated soils were found to be in the range of 1–160 mg kg-1 for Zn [16].
Generally, for most plant species and especially crop species, aluminium tolerance is interpreted as the ability to
exclude aluminium. The exudation of organic acids from the roots is considered one of the most important strategies
by which aluminium is excluded [49]. Aluminium accumulator species are distributed in acid soils, particularly in
the tropics. More than half a century ago, Chenery [22,23] determined the aluminium concentrations in the leaves of
thousands of plant species and classified them as aluminium accumulators (≥1000 mg Al kg-1) or Al nonaccumulators
(<1000 mg Al kg-1). He reported that 1779 of 2859 species in dicots, 33 of 269 species in monocots
and gymnosperms, and 615 of 1401 species in cryptogams were aluminium accumulators. The accumulation of
aluminium in leaves, stems, and flowers of Stevia rebaudiana shown in Table 2 were an aluminium non-accumulator.
Silver is a non-essential heavy metal for any living organism, which enters the aquatic environment from natural
and anthropogenic sources (photographic processing effluents, sewage sludge, biocidal and other applications). It is
known that Ag ions interact metabolically with Cu and Se and replace H2 from the sulfhydryl groups of the
photosynthetic enzymes (such as Rubisco), changing their structure and inactivating them. Ag also forms complexes
with amino acids, pyrimidines, purines and nucleotides, as well as with their corresponding macromolecular forms,
suggesting its potential to be either highly toxic or easily inactivated by the plant [50]. However, there are very few
toxicological data of silver in plants. Silver content in plant tissue is usually less than 0.01 mg kg−1 [24]. The result
shows in Table 2 that silver in leaves of Stevia rebaudiana was 0.0676 mg/kg-1. Meanwhile, the result of silver in
stems was 0.0317 mg/kg-1 and in flowers was 0.035 mg/kg-1.
While it has been known for many years that Cobalt is an essential element for humans, animals and prokaryotes,
a physiological function of this element in higher plants has not been identified. The Co-containing vitamin B12
does not occur in plants. Whereas normal Cobalt concentrations in plants are cited to be as low as 0.1–10 mg kg-1
dry weight, its beneficial role as a trace element has been described [25]. Calcium is an essential plant nutrient,
whose role has been well documented [51]. Calcium has an important role in plant physiology, including
involvement in the responses to stress, and controls numerous processes [52]. The result shows in Table 2 that
calcium in leaves of Stevia rebaudiana was 259.44 mg/kg-1. Meanwhile, the result of calcium in stems was 558
mg/kg-1and in flowers was 450 mg/kg-1.
Manganese is an essential element in plant growth, but excessively high levels of Mn in soil can also hamper
plant growth tremendously [53]. The result as shows in Table 2 that manganese in leaves of Stevia rebaudiana was
6.0358 mg/kg-1. Meanwhile, the result of manganese in stems was 6.336 mg/kg-1 and in flowers was 12.48 mg/kg-1.
Nickel is also a non-essential metal like Cr but it may be attributed that hyper accumulators of Ni metal can store
it into vacuoles of leaves to protect the plants from Ni toxicity [54]. The normal heavy metal contents of terrestrial
plants growing in uncontaminated soils were found to be in the range 0.1 to 3.7 mg kg-1 for Ni [16]. The result shows
in Table 2 that nickel in leaves of Stevia rebaudiana was 1.6737 mg/kg-1. Meanwhile, the result of nickel in stems
was 1.53 mg/kg-1 and in flowers was 2.4 mg/kg-1.
In general, the results have shown that accumulation of heavy metals in leaves, stems and flowers of Stevia
rebaudiana carried out by using ICP-MS instruments Elan 9000 and Agilent 7500a did not reach phytotoxic
concentrations or toxic levels, see Table 1 for reference values. Thus, the results have shown that they can be used as
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