Light and growth temperature alter carbon isotope discrimination an estimated bundle sheath leakiness in C4 grasses and dicots

We combined measurements of short-term (during gas exchange) and long-term (from plant dry matter) carbon isotope discrimination to estimate CO2 leakiness from bundle sheath cells in six C4 species (three grasses and three dicots) as a function of leaf insertion level, growth temperature and short-term irradiance. The two methods for determining leakiness yielded similar results (P > 0.05) for all species except Setaria macrostachya, which may be explained by the leaf of this species not being accommodating to gas exchange. Leaf insertion level had no effect on leakiness. At the highest growth temperature (36°C) leakiness was lower than at the two lower growth temperatures (16°C and 26°C), between which no differences in leakiness were apparent. Higher irradiance decreased leakiness in three species, while it had no significant effect on the others (there was an opposite trend in two species). The inverse response to increasing irradiance was most marked in the two NAD-ME dicots (both Amaranthus species), which both showed almost 50% leakiness at low light (300 μmol quanta m-2 s-1) compared to about 30% at high light (1,600 μmol quanta m-2 s -1). NADP-ME subtype grasses had lower leakiness than NAD-ME dicots. Although there were exceptions, particularly in the effect of irradiance on leakiness in Sorghum and Boerhavia, we conclude that conditions favourable to C4 photosynthesis (high temperature and high light) lead to a reduction in leakiness

Corrosion behavior of fine-grained Mg-7.5Li-3Al-1Zn fabricated by extrusion with a forward-backward rotating die (KoBo)

The microstructure-dependent corrosion resistance of dual structured fine-grained Mg-7.5Li-3Al-1Zn has been investigated. The alloys were extruded using extrusion with a forward-backward rotating die (KoBo, a newly developed SPD method) at two different extrusion ratios. The fine-grained microstructures formed in the alloys were characterized, and the influence of grain refinement on corrosion resistance was analyzed. For fine-grained (α + β) Mg-Li alloys, a higher extrusion ratio led to more intensive grain refinement; however, this relationship did not improve their corrosion resistance in a chloride-containing solution. The corrosion resistance of the alloys was mainly controlled by the refinement of α(Mg) and β(Li), along with the distribution of second phases. The presence of MgLi2Al at grain boundaries facilitated their dissolution