Silicon Actuates Poplar Calli Tolerance after Longer Exposure to Antimony

The presence of antimony (Sb) in high concentrations in the environment is recognized as an emerging problem worldwide. The toxicity of Sb in plant tissues is known; however, new methods of plant tolerance improvement must be addressed. Here, poplar callus (Populus alba L. var. pyramidallis) exposed to Sb(III) in 0.2 mM concentration and/or to silicon (Si) in 5 mM concentration was cultivated in vitro to determine the impact of Sb/Si interaction in the tissue. The Sb and Si uptake, growth, the activity of superoxide dismutase (SOD), catalase (CAT), guaiacol-peroxidase (G-POX), nutrient concentrations, and the concentrations of photosynthetic pigments were investigated. To elucidate the action of Si during the Sb-induced stress, the impact of short and long cultivations was determined. Silicon decreased the accumulation of Sb in the calli, regardless of the length of the cultivation (by approx. 34%). Antimony lowered the callus biomass (by approx. 37%) and decreased the concentrations of photosynthetic pigments (up to 78.5%) and nutrients in the tissue (up to 21.7%). Silicon supported the plant tolerance to Sb via the modification of antioxidant enzyme activity, which resulted in higher biomass production (increased by approx. 35%) and a higher uptake of nutrients from the media (increased by approx. 10%). Silicon aided the development of Sb-tolerance over the longer cultivation period. These results are key in understanding the action of Si-developed tolerance against metalloids

Effects of Exogenous Application of Indole-3-Butyric Acid on Maize Plants Cultivated in the Presence or Absence of Cadmium

Auxins are plant hormones that affect plant growth, development, and improve a plant’s tolerance to stress. In this study, we found that the application of indole-3-butyric acid (IBA) had diverse effects on the growth of maize (Zea mays L.) roots treated without/with Cd. IBA caused changes in the growth and morphology of the roots under non-stress conditions; hence, we were able to select two concentrations of IBA (10−11 M as stimulatory and 10−7 M as inhibitory). IBA in stimulatory concentration did not affect the concentration of H2O2 or the activity of antioxidant enzymes while IBA in inhibitory concentration increased only the concentration of H2O2 (40.6%). The application of IBA also affected the concentrations of mineral nutrients. IBA in stimulatory concentration increased the concentration of N, K, Ca, S, and Zn (5.8–14.8%) and in inhibitory concentration decreased concentration of P, K, Ca, S, Fe, Mn, Zn, and Cu (5.5–36.6%). Moreover, IBA in the concentration 10−9 M had the most positive effects on the plants cultivated with Cd. It decreased the concentration of H2O2 (34.3%), the activity of antioxidant enzymes (23.7–36.4%), and increased the concentration of all followed elements, except Mg (5.5–34.1%), when compared to the Cd