Northern Provenances of Silver Fir Differ with Acclimation to Contrasting Light Regimes

Phenotypic differentiation of Abies alba was identified among selected provenances originating from the northern edge of this species’ natural geographic range. We posited that although the seed sources of the study populations were not geographically distant, progenies would differ with respect to growth, needle pigment concentration, and values of photochemical parameters in response to contrasting light conditions. Potted seedlings of six provenances were grown for two seasons under low light (LL, 40% of full irradiance) or high light (HL, 100% of full irradiance). The results showed that the provenances differed in diameter at root collar (DRC) and in relative growth rates of height (RGR). Seedlings grown in full light had a greater mean value of DRC than those in LL. LL increased total needle chlorophyll (Chltot) and carotenoid concentrations compared with HL, and Chltot was modified by the provenance of the seedlings. The provenance “Syców”, localized at the northern limit of the species range, showed the lowest value of maximal electron transfer rate (ETRmax) and lower values of growth parameters compared with the other study provenances. Relative growth rate, Chltot, and non-photochemical quenching of fluorescence (NPQ) were correlated with some climatic characteristics of seed stands and formed clusters indicating the local adaptation of the study populations. These results provide evidence of low intraspecific A. alba differentiation in terms of growth dynamics, photochemical capacity, and tolerance to different light regimes. The intraspecific diversity found in our study among the northern lead populations could be, however, important for the natural expansion of this species further north and for the selection of provenances to be used in the programme of the A. alba restoration in the Sudety Mountains, southern Poland, where decline of this species has been observed

A highly tunable silicone-based magnetic elastomer with nanoscale homogeneity

Magnetic elastomers have been widely pursued for sensing and actuation applications. Silicone-based magnetic elastomers have a number of advantages over other materials such as hydrogels, but aggregation of magnetic nanoparticles within silicones is difficult to prevent. Aggregation inherently limits the minimum size of fabricated structures and leads to non-uniform response from structure to structure. We have developed a novel material which is a complex of a silicone polymer (polydimethylsiloxane-co-aminopropylmethylsiloxane) adsorbed onto the surface of magnetite (γ-Fe(2)0(3)) nanoparticles 7–10 nm in diameter. The material is homogenous at very small length scales (< 100 nm) and can be crosslinked to form a flexible, magnetic material which is ideally suited for the fabrication of micro- to nanoscale magnetic actuators. The loading fraction of magnetic nanoparticles in the composite can be varied smoothly from 0 – 50% wt. without loss of homogeneity, providing a simple mechanism for tuning actuator response. We evaluate the material properties of the composite across a range of nanoparticle loading, and demonstrate a magnetic-field-induced increase in compressive modulus as high as 300%. Furthermore, we implement a strategy for predicting the optimal nanoparticle loading for magnetic actuation applications, and show that our predictions correlate well with experimental findings