Re: Vanadium: Nature's "Junk Food" For Plants

Tim Jenkins (timj@mainmin.co.nz)
Mon, 21 Jun 1999 12:41:54 +1200

Vanadium can take the form of vanadate (V5+) which has the same bipyramidal
structure of ligands (i.e. with oxygen and hydroxyl groups) as phosphate.
Therefore vanadium could compete with phosphate for uptake by plants but the
significance of this would depend on the relative levels of vanadate and
phosphate. Vanadium can be at high levels in some plants e.g. parsley at 30
ppm but just 10% of that in lettuce. This is much lower than the levels of
phosphorus e.g. 5000 ppm and so the uptake of phosphorus may not be a
significant problem. The inhibition of Na+-K+ ATPase seems to be to be much
more of a possibility. At very low levels, vanadate can have a significant
effect on this enzyme which mistakes the vanadate for phosphorus and becomes
locked in an unusable form.

I am going to be looking in to the significance of this and would appreciate
any more information that is out there. It could be, of course, that any
relationship between vanadium levels and phosphorus availability/uptake
could just be due to soil type difference and it just happens that the soil
types that have lower P availability also have high vanadium levels.
Vanadium is associated with ores and it is likely that high vanadium soils
may be higher in aluminium and iron than other soils (iron and aluminium as
well as potentially vanadium causing problems with P availability). I
imagine that this has already been checked out to some extent.

If it is established that vanadium is a significant problem I would be
interested in how to test for it (probably a nitric/perchloric digest to get
a total level?) and how to reduce its effects (e.g. liming?).

Dale mentioned vitamin C being oxidised by vanadate. This is likely to be a
vice versa thing in that excess vanadium levels can be controlled by vitamin
C. The trick would then be to produce plants with as high levels of vitamin
C and other antioxidants as possible - in other words produce high quality
plants and vanadium problems could be limited.

Tim

Tim Jenkins
SoilTech
P.O. Box 558
CHRISTCHURCH
NEW ZEALAND

>
>I was curious so I searched for info on vanadium toxicity. I didn't find
>anything in the literature suggesting that this is an important problem,
but
>I did find out about the mechanism of toxicity. It does mimic phosphate,
>inhibiting plasmamembrane ATPase, and so inhibits active transport of PO4
>and everything else. Vanadium (V) also oxidizes ascorbate producing free
>radicals and associated membrane damage. If you want the 8 abstracts I
>found, let me know.
>
>Dale

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