Definition of phosphate-stress in Zea mays
Sachay, James E.
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Phosphate-stress was determined in the monocot Zea mays. Definition of phosphate-stress was investigated by growing plants with and without phosphate in defined nutrient solution and measuring a number of parameters. These parameters included (1) measurements of shoot and root, (2) weight of shoot and root, (3) phosphatase activity present in the root, and (A) total phosphate levels of shoot and root. Conclusions of this study showed that phosphate-stressed corn had increased root growth, while shoot growth decreased. Not only were phosphate-starved roots longer, but they were less massive and less branching than phosphate-rich roots. Phosphatase secretion increased A-fold in roots starved for phosphate. Threshold for phosphate-stress has been determined to occur between 5uM and 15uM phosphate. The soluble phosphatase secreted from the root surface has been partially purified by ion-exchange chromatography. An acid and an alkaline phosphatase with pH optima 5.5 and 7.5, respectively, were demonstrated.