Effects of Supplemental Sulfur on Growth and Stress Tolerance of Red Maple (Acer rubrum)
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Atmospheric sulfur dioxide emissions have become greatly reduced leading to reduced amounts of sulfate in soils. Without supplemental sulfur (S) fertilization, S may become a limiting nutrient. Sulfur is a constituent of some essential amino acids, which are needed for the production of all compounds containing reduced sulfur including coenzymes and proteins. Sulfur is also essential in reducing disease, toxicity, and other stress. Pathogen resistance and vulnerability to stress are directly linked to S incorporation because S is an essential component of metabolites such as glutathione, glucosinolates, and several defensive S-rich proteins. When S is the limiting nutrient, nitrogen utilization is affected because S is essential to produce the nitrogen-containing amino acids cystine and methionine. These compounds directly affect photosynthesis, growth, and dry mass accumulation of crops and are also incorporated in defense compounds. Ideally, nitrogen applications can be reduced if accompanied with adequate S concentrations. By improving nutrition with adequate amounts of essential nutrients, S fertilizers have repeatedly shown increased crop yield and plant size. The purpose of this experiment was to determine which supplemental concentration of S and N in substrate solution was optimal for the growth and stress tolerance of red maple trees grown in high porosity (HP) media. Our hypothesis was supplemental S would lead to an increase in N uptake, thereby improving growth and stress tolerance in maples, while minimizing N leaching.