Does Azospirillum protect wheat plants against cd toxicity?

VAZQUEZ A; CABRERA A.; RECALDE L.; ZAWOZNIK M.S.; BENAVIDES M.P.; GROPPA M.D.

Congreso; LVI Reunión Anual de SAIB Congreso Conjunto SAIB-SAMIGE 2020; 2020

DOES AZOSPIRILLUM PROTECT WHEAT PLANTS AGAINST Cd TOXICITY?WHEAT PLANTS INOCULATED WITH AZOSPIRILLUM ARE PARTIALLY PROTECTED AGAINST Cd TOXICITYAnalía Vázquez*, Andrea V. Cabrera* , Laura Recalde *, Myriam Zawoznik*, María Patricia Benavides*#, María Daniela Groppa*#*Departamento de Química Biológica-Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires# IQUIFIB-CONICET- andreacab86@gmail.comDue to industrial activities, fertilizers application and mining, cadmium (Cd) became a major threat to the health of humans and animals that consume plants grown on contaminated soils. This metal can easily enter the food chain through edible plants, so is necessary to find out effective ways to reduce Cd entrance and accumulation in the food chain. In this work, the PGPR Azospirillum brasilense was used to inoculate wheat plants as a strategy to reduce Cd toxicity. Wheat seeds were sown in vermiculite and after 7d, they were inoculated and irrigated with Hoagland solution, with or without 150 µM CdCl2. Treatments were: Control (C), C+ CdCl2 (C-Cd); Inoculated (C-I), Inoculated + CdCl2 (I-Cd). Plants were grown in a controlled environment chamber (22 °C, 10-h-light/14-h-dark, 120 μmol m−2 s−1 light intensity). Inoculation reduced by 50% cadmium content in roots compared to C-Cd, without differences in the shoots. I-Cd plants contained 3.8 times more iron in roots and 2.4 times in leaves compared to non-inoculated Cd-treated plants. The metal reduced root length significantly, but this reduction was less pronounced when plants were inoculated compared to C-Cd (51% and 61%, respectively). Moreover, inoculation induced lateral roots development in plants treated or not with Cd. The decrease in leaves dry weight caused by cadmium (60%) was less pronounced when plants were inoculated (20%). Both, cadmium and inoculation increased nitric oxide content in roots 3.6 and 1.6 times respect to C plants, respectively. In this sense, the increase caused by Cd in inoculated plants was lower than in non-inoculated ones. Nitrate reductase (NR) activity was significantly reduced by Cd in leaves, both in I-Cd or in C-Cd plants whereas in roots, NR activity was reduced 43% and 36%, in C-Cd or I-Cd, respectively, compared to the respective controls. Inoculation could not avoid the drop in chlorophyll content in Cd-treated (I-Cd) plants while total N was scarcely diminished in Cd-treated leaves, independently of the presence of Azospirillum. Lipid damage was not detected in neither of Cd-treated plants, and electrolyte leakage increased only in Cd-treated roots, both in inoculated or non-inoculated plants. Catalase activity increased greatly after inoculation only in leaves of C-I plants, and the metal decreased the enzyme activity only in roots of C-Cd plants. In addition, guaiacol peroxidase was markedly increased in leaves of C-Cd or I-Cd plants while in roots, inoculation raised the activity of the enzyme in C-I and I-Cd plants. The results obtained suggest that Azospirillum could have a double positive role associated to wheat plants, by increasing Fe uptake and decreasing Cd entry, also favouring root elongation. This positive effect should be benefiting the establishment of wheat plants in the soil, further improving plant growth by partially protecting plants against Cd toxicity.