Principles of Nutrient Uptake from Fertilizer Bands. VII. P32 Uptake by Brace Roots of Maize and Its Distribution Within the Leaves1
- J. A. Robertson,
- B. T. Kang,
- F. Ramirez-Paz,
- C. H. E. Werkhoven and
- A. J. Ohlrogge2
The influence on phosphorus uptake of area of roots in the fertilized soil and the rate of fertilization was investigated using aerial brace roots of maize. Either 1 or 2 brace roots were directed into soil containing 0.62 or 3.10 g of phosphorus labeled with P32. The radioactivity of the tip and/or basal portions of all leaves was measured by wrapping one thickness of leaf around a long G–M tube. The distribution of P32 in several leaves was mapped with an end window G–M tube.
The P32 accumulation measured by the in-situ technique was highly correlated with that of the standard briquet method. Phosphorus uptake varied with the rate of fertilization and the number of fed brace roots. The proportion of total phosphorus derived from the fertilizer ranged from 1–37%.
The P32 distribution in the leaves depended upon their position relative to the fertilized brace roots. The leaves on the brace root side had higher P32 activity in their tip portions than in their basal portions. This distribution is explained by limited connections between vascular bundles of the stem and the diverging of the leaf veins from the midrib.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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