Congeneric Serpentine and Nonserpentine Shrubs Differ More in Leaf Ca:Mg than in Tolerance of Low N, Low P, or Heavy Metals |
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Authors: | Ryan E O’Dell Jeremy J James James H Richards |
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Institution: | (1) Department of Land, Air and Water Resources, University of California, One Shields Avenue, Davis, CA 95616-8627, USA;(2) Present address: USDA, Agricultural Research Service, 67826-A Hwy 205, 97720-9394 Burns, OR, USA |
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Abstract: | Serpentine soils limit plant growth by NPK deficiencies, low Ca availability, excess Mg, and high heavy metal levels. In this
study, three congeneric serpentine and nonserpentine evergreen shrub species pairs were grown in metalliferous serpentine
soil with or without NPKCa fertilizer to test which soil factors most limit biomass production and mineral nutrition responses.
Fertilization increased biomass production and allocation to leaves while decreasing allocation to roots in both serpentine
and nonserpentine species. Simultaneous increases in biomass and leaf N:P ratios in fertilized plants of all six species suggest
that N is more limiting than P in this serpentine soil. Neither N nor P concentrations, however, nor root to shoot translocation
of these nutrients, differed significantly between serpentine and nonserpentine congeners. All six species growing in unfertilized
serpentine soil translocated proportionately more P to leaves compared to fertilized plants, thus maintaining foliar P. Leaf
Ca:Mg molar ratios of the nonserpentine species were generally equal to that of the soil. The serpentine species, however,
maintained significantly higher leaf Ca:Mg than both their nonserpentine counterparts and the soil. Elevated leaf Ca:Mg in
the serpentine species was achieved by selective Ca transport and/or Mg exclusion operating at the root-to-shoot translocation
level, as root Ca and Mg concentrations did not differ between serpentine and nonserpentine congeners. All six species avoided
shoot toxicity of heavy metals by root sequestration. The comparative data on nutrient deficiencies, leaf Ca:Mg, and heavy
metal sequestration suggest that the ability to maintain high leaf Ca:Mg is a key evolutionary change needed for survival
on serpentine soil and represents the physiological feature distinguishing the serpentine shrub species from their nonserpentine
congeners. The results also suggest that high leaf Ca:Mg is achieved in these serpentine species by selective translocation
of Ca and/or inhibited transport of Mg from roots, rather than by uptake/exclusion at root surfaces. |
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Keywords: | calcium chaparral macronutrients magnesium nickel serpentine shrubs |
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