This group includes elements that are used as nutrients by only a limited number of plant species.  When high concentrations of an element, not commonly found in most plants, is seen in a particular species, it raises the possibility that the element is essential for that species.  The plants may use these for non-nutritional purposes.  It is thought that species where these elements are present may use them for protection against invading bacterii.  For example, Barium is found in brazil nuts; Aluminum in tea; Chromium, Nickel and Cobalt in gramineae; Silicon in rice and cucumbers.


NICKEL  (Ni) 58.70 Atomic Weight

(Essential Trace Element?)

Nickel in its elemental form occurs sparingly in terrestrial and meteoric deposits.  In compounds, it constitutes approximately 0.007% of the earth’s crust, twice as abundant as copper.  Its primary use is in the manufacture of metals and as a protective coating.  It has properties that are resistant to oxidation and corrosion.  The biological role of Nickel in uncertain, as it is carcinogenic or toxic, depending upon its compound form.  It is not known why certain species of plants contain higher levels of Nickel.