Some observations on the ecology, metal uptake and nickel tolerance of Alyssum serpyllifolium subspecies from the Iberian peninsula
✍ Scribed by Brooks, R. R. ;Shaw, S. ;Marfil, A. Asensi
- Publisher
- Springer-Verlag
- Year
- 1981
- Tongue
- English
- Weight
- 454 KB
- Volume
- 45
- Category
- Article
- ISSN
- 1573-5052
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✦ Synopsis
Experiments were carried out on the tolerance to, and uptake of, nickel by three Iberian subspecies of Alyssum serpylliforium Desf. Two of these subspecies, the serpentine-endemic ssp. lusitanicum from Braganga, Portugal and ssp. malacitanum from Mfilaga, Spain, are hyperaccumulators (> 1000 #g/g in dried material) of nickel. Their possible ancestor, ssp. serpytlifolium (from Granada, Spain) was a nonaccumulator of this element. Seeds of the two serpentine-endemics germinated extensively in nickel co ncentrations up to 12 000 #g/g (1.2%) whereas ssp. serpyllifolium only germinated in nickel concentrations below 60/~g/ml. Tolerance tests involving measurement of new root lengths of excised seedlings placed in varying nickel concentrations, again showed much greater tolerance of the two serpentinophytes. In both series of experiments, the order of tolerance was: ssp. lusitanicum > ssp. malacitanum > ssp. serpyllifolium. In pot trials involving seedlings of ssp. malacitanum grown in mixtures containing varying amounts of calcium, magnesium, and nickel, the most important finding was that plants will tolerate higher nickel contents in the soil when excess calcium is added. This is achieved by lowering the uptake of nickel. There appeared to be some concomitant reduction in calcium uptake in the presence of nickel, and some increase in uptake of magnesium. The resultant lower calcium/magnesium ratio in the plant, though not symptomatic of a favourable condition for colonization of serpentine soils, probably results from a mechanism which renders nickel innocuous to the plant at the expense of calcium uptake. It is suggested that the physiological characters of ssp. lusitanieum and ssp malacitanum are sufficiently different to support arguments for promoting the latter to full specific rank as has now been done for ssp. lusitanicum.