Adil GÜNER, Vehbi ESER - optima

EDAPHIC INFLUENCE ON THE MORPHOLOGICAL VARIABILITY
OF THLASPI ROTUNDIFOLIUM
Sergio E. FAVERO-LONGO 1 , Annalisa INGARAMO 1 , Consolata SINISCALCO 1
1 Dipartimento di Biologia Vegetale, University of Torino, Torino, Italy
consolata.siniscalco@unito.it
High intraspecific variability is a well known feature of Thlaspi rotundifolium
(Brassicaceae), which led to recognize variously ranked subspecific taxa, based on
morphology and differently related to geographical or geological distribution, till supporting
taxonomic uncertainties. We showed that three contiguous populations of T. rotundifolium
growing on adjacent debris differing in lithology, i.e. calcschist, metabasite and serpentinite,
displayed morphological variability. The style length, repeatedly considered as the main
diagnostic trait of the subspecific units, was shorter on calcschist debris with respect to the
siliceous substrates and did not follow the overall growth of the plants (biomass, leaf area),
but was related with their Mg/Ca content ratio.
This research aims to establish if edaphic factors influence the morphological variability of T.
rotundifolium s.l., i.e. the style length, by affecting enzymatic processes driving plant growth.
In laboratory, different Mg/Ca ratios, mimicking the concentrations in populations grown on
the different substrates, affect the activity of glyoxalase I, an enzyme, which is responsible of
tolerance of salt, water and heavy metal stress in plants, but also supports cell division
processes. Previous works showed that its highest concentration and activity in Brassicaceae
is in the pistils. In this work, glyoxalase I activity is quantified in leaves and pistils of T.
rotundifolium (15 �kat/mg protein using a standard assay mixture with Mg and no Ca) .
Enzymatic assays carried on with the purified, commercial glyoxalase I show that its activity
is reduced by a 1:12 Mg/Ca ratio mimicking that of plants growing on calcschists, with
respect to the activity recorded with the 1:3-1:4 Mg/Ca ratios of metabasites and serpentinites.
These differences in enzyme activity likely support the differences in style length. Edaphic
factors seem to influence the intraspecific variability of T. rotundifolium through the activity
of the anti-stress protein glyoxalase I.
Keywords: Hyperaccumulator - Magnesium/calcium ratio - Serpentine vegetation - Stress
tolerance - Style length
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