THE MOVEMENT OF INJECTED P32 THROUGHOUT THE WHEAT PLANT

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Abstract
Specific activity (counts per minute per gram dry matter) measurements, autoradiographs, and densitometer tracings on the autoradiographs indicated that P32, injected into the stem of wheat plants, moved rapidly into the root system and was distributed uniformly throughout it. Although root weights varied with depth, the specific activity of the washed root material remained relatively constant.The stage of plant growth markedly influenced the translocation of the P32 into the roots. Quantitative measurements indicated that approximately five times as much activity moved into the root systems of 40-day-old compared with 60-day-old plants. A soil moisture stress increased the specific activity of the roots.A linear increase in the specific activity of the root material was obtained by-increasing the number of tillers injected per wheat plant (amount injected constant). The addition of indoleacetic acid, NH4H2PO4, or H3PO4 to the carrier-free P32 reduced, rather than increased, movement to the roots.