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Fluid Journal : Fluid Journal 2005-2007
12 Fluid Journal EARLY SPRING 2007 DR. W. B. GORDON Kansas study suggests superior yield response when manganese is added to glyphosate- resistant soybeans. Does Glyphosate Gene Affect Manganese Uptake in Soybeans? There is evidence to suggest that glyphosate-resistant soybean yields may still lag behind those of conventional soybeans. Many farmers have noticed that soybean yields even under optimal conditions are not as high as expected. In Kansas, average yield seldom exceeds 60 to 65 bu/A even when soybeans are grown with adequate rainfall and/or supplemental irrigation water. The addition of the gene that imparts herbicide resistance may have altered other physiological processes. Some scientists suggest that soybean root exudates have been changed and plants no longer solubilize enough soil Mn. Application of glyphosate also may retard Mn metabolism in the plant. Addition of supplemental Mn at the proper time may correct deficiency symptoms and result in greater soybean yields. In higher plants photosynthesis, in general, and photosynthetic O2 evolutions in Photosystem II (Hill Reaction), in particular, are processes that respond most sensitively to Mn deficiency. Manganese deficiency-induced changes in O2 evolution are correlated with changes in the ultra- structure of thylakoid membranes (internal chlorophyll containing membranes of the chloroplast where light absorption and chemical reactions of photosynthesis take place). When Mn deficiency becomes severe, the chlorophyll content decreases and the ultra-
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