Stefano Gomarasca

Water quality and diversity of the Recent ostracod fauna in lowland springs from Lombardy (northern Italy)

The Po river plain (northern Italy) is delimited to two mountain ridges, the Alps and the Apennines. It hosts peculiar lowland man-modified springs, locally known as “fontanili”, which originate from natural resurgences occurring along the alluvial fans of the main watercourses, namely in the transition zone from the higher to lower plain which is characterized by changes in slope profile and sediment granulometry. These habitats usually show low variation in hydrological, hydrochemical and thermal conditions throughout the year. Twenty-eight springs, located in the provinces of Lodi and Cremona (Lombardy) in the alpine sub-catchment of the Po river were sampled in summer and autumn of 2004. Twenty-three of them were typical alluvial-fan springs, while the remaining five were terrace springs. The two groups of springs showed marked differences in their hydrochemical and hydrological characteristics. Sixteen ostracod species in three families (Candonidae, Ilyocyprididae, and Cyprididae) were identified. The most frequent species were Cypria ophtalmica (19 sites), Herpetocypris reptans (16), and Prionocypris zenkeri (13). Five species were found only once: Chlamydotheca incisa, Scottia pseudobrowniana, Pseudocandona compressa and Candona neglecta. Up to 6 taxa were recorded from a single site and the average number of taxa for each site was c. 3. The associations among ostracod taxa and their occurrence in relation to environmental factors were examined. Finally, the results of this survey were compared with a similar study previously conducted in 31 alluvial fan springs of the apennine sub-catchment of the Po river.

A mutant of Arabidopsis thaliana with a reduced response to fusicoccin. I

Because fusicoccin (FC) has the the capacity to promote solute uptake, a selective procedure for isolating mutants of Arabidopsis thaliana with a reduced response to the toxin has been developed. The procedure is based on the incubation of A. thaliana seedlings in a solution containing the cation Paraquat (Pq) at a concentration that per se does not produce bleaching of the leaves upon illumination but does in the presence of FC because of the increased uptake of the toxic cation. Using this procedure, we identified, among the progenies of 2010 M1 ethyl methanesulfonate-mutagenized plants, two mutants that stay green after exposure to FC and Pq. Some properties and inheritance of one of the two mutants (5–2) are described. Morphology of mutant plants is almost indistinguishable from that of the wild type. However, 5–2 seeds germinate and produce viable seedlings in the presence of FC plus the aminoglycoside antibiotic hygromycin B: plants of the mutant do not wilt when exposed to FC and stomata do not open or open only partially. In the presence of FC, the mutant appears less responsive than the wild type as far as the increment in fresh weight, the enlargement of leaf disc area, or the stimulation of H+ extrusion is concerned. Inheritance of the trait is monogenic dominant or semidominant, depending on the test used.

A pleiotropic Arabidopsis thaliana mutant with inverted root chirality

Abstract. Circumnutation is an oscillating movement of a growing plant organ that is believed to result from an endogenous rhythmic process intrinsic to growth. Circumnutating organs, as they extend, describe a helical trace. In Arabidopsis thaliana (L.) Heynh. circumnutation is particularly evident in primary roots and occurs, as in most plants, in a right-handed direction when viewed from above in the direction of the growing tips. We have discovered a pleiotropic mutant of Arabidopsis with left-handed root circumnutation. Major abnormalities of the mutant are: (i) a reduced size of all organs, mainly due to a defect in cell elongation or expansion; (ii) a zigzagging pattern of stem pith cells, reminiscent of the “erectoides” phenotype of the lk mutant of Pisum; (iii) roots of the mutant are gravitropic but as they grow, they form tight, left-handed coils. Genetically, the mutant depends on the presence of two independent monogenic recessive factors acting additively. The mutant alleles of both factors alter the growth of the aerial organs in a similar manner but differ at the root level: one mainly produces non-circumnutating roots, the other changes the direction of circumnutation from right to left hand.