Rs. Boyd et Sn. Martens, NICKEL HYPERACCUMULATION BY THLASPI-MONTANUM VAR. MONTANUM (BRASSICACEAE) - A CONSTITUTIVE TRAIT, American journal of botany, 85(2), 1998, pp. 259-265
Adaptations to particular stresses may occur only in populations exper
iencing those stresses or may be widespread within a species. Nickel h
yperaccumulation is viewed as an adaptation to high-Ni (serpentine) so
ils, but few studies have determined if hyperaccumulation ability is r
estricted to populations from high-Ni soils or if it is a constitutive
trait found in populations on both high-and low-Ni soils. We compared
mineral element concentrations of Thlaspi montanum var. montanum plan
ts grown on normal and high-Ni greenhouse soils to address this questi
on. Seed sources were from four populations (two serpentine, two non-s
erpentine) in Oregon and northern California, USA. Plants from all pop
ulations were able to hyperaccumulate Ni, showing Ni hyperaccumulation
to be a constitutive trait in this species. Populations differed in t
heir ability to extract some elements (e.g., Ca, Mg, P) from greenhous
e soils. We noted a negative correlation between tissue concentrations
of Ni and Zn. We suggest that the ability to hyperaccumulate Ni has a
daptive value to populations growing on non-serpentine soil. This adap
tive value may be a consequence of metal-based plant defense against h
erbivores/pathogens, metal-based interference against neighboring plan
t species, or an efficient nutrient scavenging system. We suggest that
the Ni hyperaccumulation ability of T. montanum var. montanum may be
an inadvertent consequence of an efficient nutrient (possibly Zn or Ca
) uptake system.