Effects of Supplemental Sulfur on Growth and Stress Tolerance of Red Maple (Acer rubrum)
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Sulfur (S) is an essential macronutrient for the growth and development of plants, but S deposits are in decline throughout the Eastern U.S. It has been shown that supplemental S increases, crop yield, plant size, and is also essential in reducing disease, toxicity, and other stress. Previous studies have found that an average optimal S concentration for greenhouse plants is 16 mg·L-1 , while studies conducted on woody plants have shown that dry weights reached near maximum levels when S concentrations were 30 mg·L-I . For this study, red maple (Acer rubrum Linneaus) trees were planted in high porosity (HP) media and given a half-strength Hoagland's solution with 0, 10, 20, 30 and 40 mg·L-1 of S at two levels of nitrogen (N), either 300 or 500 mg·L-I. The hypothesis was that increased [S] would increase N uptake leading to improved growth and stress tolerance. Measurements of various growth parameters, photosynthesis, and SPAD did not show any positive relationship to [S]. Also, trees given increased S did not show improved drought tolerance. We concluded that supplemental S did not significantly benefit red maple trees grown in HP media. This does not indicate that S has no beneficial effects on maple trees, as it is possible that initial 8 content was adequate for the nourishment of the trees. Future studies are recommended to test the hypothesis in a nutrient-free medium.