inducible defense

glucanhydrolases

metalloid toxicity

PR-proteins

trade-off

Pollution

Plants

Toxic substances

Heavy metals

Heavy metals contamination of plants

Nitrogenous nutrition influences the availability of other plant resources and, consequently, affects plant defense responses. Both a shortage and excess of N impact plants´ ability to accumulate and survive metals/metalloids, but available data are still fragmented and often contradictory. A series of 8 different NH₄NO₃ concentrations, ranging from zero to excessive nitrogen (35 mM N), was applied in growth media to hydroponically grown wheat (Triticum aestivum). The plants were grown at a sublethal concentration of arsenic (5 mM As³⁺) for 10 days and foliar accumulation of As, N and P was determined. In addition, induction of defense-related chitinase and β-1,3-glucanase enzyme isoforms was quantified upon the separation of plant protein extracts in polyacrylamide gels. As³⁺ interfered with N and P accumulation in shoots and strongly activated several enzyme isoforms. These responses varied with the N supply and indicated a low rate of As accumulation at low N concentrations. On the other hand, limited As transfer to shoots was a clear benefit at high N concentrations. Nevertheless, both extreme N concentrations restricted the growth. Several enzyme isoforms of both chitinases and β-1,3-glucanases exerted sensitivity to As³⁺, N supply or both. Their individual responses, however, contradict the generally accepted view on positive correlation between these defense molecules and N nutrition. Impacts of interplay between As³⁺ toxicity and nutritional stress on wheat responses are discussed. The results might contribute to knowledge applicable in efficient fertilization and food safety strategies.