THE SOURCE AND PHOSPHATASE ACTIVITY OF EXOENZYME SYSTEMS OF CORN AND TOMATO ROOTS

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Abstract
The source of the exoenzyme systems of roots was shown to be the sloughed-off cellular material which was a release of root cap and epidermal cells to the rhizosphere during normal root development. Microscopic examination of this cellular material from solution cultures showed it to be composed largely of well-nucleated, intact cells which underwent considerable swelling and elongation soon after being released from the root. Employing commercial preparations of yeast nucleic acid and Ca glycerophosphate some of the properties of these "extra-root" enzymes were studied. The previous level of P nutrition of corn and tomato plants had no measurable effect on the nuclease activity of their roots. The roots of P-starved plants exhibited a slightly higher glycerophosphatase activity than those of plants which had been given ample P for 8 days prior to the tests. The glycerophosphatase system of corn roots had an opt. reaction of pH 4 at a temp. of 27[degree]C in 12-hr. tests. Maximum activity of the same system was obtained at 45[degree]C (pH 4) in 9-hr. tests. Optimum pH for the nuclease system of corn roots at 27[degree]C for 12 hrs. was approx. 6.3. Maximum activity of this system was obtained at 60[degree]C when a pH of 7 was maintained for 12 hrs.

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