Glyphosate and nickel differently affect photosynthesis and ethylene in glyphosate-resistant soybean plants infected by Phakopsora pachyrhizi

Nickel (Ni) and glyphosate (Gl) are able to reduce the symptoms of Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, in soybean. However, their combined effects on the energy balance and ethylene metabolism of soybean plants infected with this fungus has not been elucidated. Therefore, the effects of Ni, Gl, and the combination of Ni + Gl on ASR development, photosynthetic capacity, sugar concentrations, and ethylene concentrations in plants of a Gl-resistant cultivar, uninfected or infected with P. pachyrhizi, were investigated. Inoculated plants supplied with Ni had the highest foliar Ni concentration in all the treatments. Gl had a negative effect on the foliar Ni concentration in Ni-sprayed plants. The ASR severity was reduced in plants sprayed with Ni and Gl. Carotenoid and chlorophyll concentrations were higher in inoculated Ni, Gl, and Ni + Gl plants than in control plants. Based on the chlorophyll a fluorescence parameters, the photosynthetic apparatus of the control inoculated plants was damaged, and the least amount of energy was directed to the photochemistry process in these plants. The reduced capacity of the photosynthetic mechanism to capture light and use the energy absorbed by photosystem II in inoculated plants was reflected in their reduced capacity to process CO₂, as indicated by the high internal CO₂ concentrations and low rates of net carbon assimilation. The low sugar concentrations in inoculated plants from the control treatment were linked to their reduced photosynthetic capacity due to the high ASR severity. In uninfected plants, the ethylene concentration was not affected by Ni or Gl, while the ethylene concentration decreased in inoculated plants; this decrease was more pronounced in plants from the control treatment than in treated inoculated plants. In conclusion, this study sheds light on the role played by both Ni and Gl in ASR control from a physiological perspective. Soybean plants exposed to Ni and Gl were able to maintain high ethylene concentrations and photosynthetic capacity during the P. pachyrhizi infection process; as a result, these plants consumed less of their reserves than inoculated plants not treated with Ni or Gl.     

Rheological properties of cross-linked hyaluronan-gelatin hydrogels for tissue engineering

Hydrogels that mimic the natural extracellular matrix (ECM) are used in three-dimensional cell culture, cell therapy, and tissue engineering. A semi-synthetic ECM based on cross-linked hyaluronana offers experimental control of both composition and gel stiffness. The mechanical properties of the ECM in part determine the ultimate cell phenotype. We now describe a rheological study of synthetic ECM hydrogels with storage shear moduli that span three orders of magnitude, from 11 to 3 500 Pa, a range important for engineering of soft tissues. The concentration of the chemically modified HA and the cross-linking density were the main determinants of gel stiffness. Increase in the ratio of thiol-modified gelatin reduced gel stiffness by diluting the effective concentration of the HA component.