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Some techniques for the study of roots in place; with special reference to their use in the root development of four grasses and two legumes of econmic importance. Frederick, Rexingford Albert

Abstract

There are several limitations to the use of the 'direct' method for studying root systems in their natural habitats. Newer techniques are needed in understanding many characteristics of roots, which are still obscure. The growing of orchardgrass, colonial bentgrass and red clover in special containers, demonstrated a technique for optical study of root systems, and illustrated an apparent localization of individual plant roots in dense stands. Field tests on square foot plots of orchardgrass and Kentucky bluegrass with placements of a dye, acid fuchsin, at various depths, failed to replicate the preliminary laboratory findings, that the absorption by roots of this material not only stained the roots red, but was soon evident in the aerial portions. Plant injections and soil placement of the fluorescent compounds, eosin, fluorescein and esculin failed to produce fluorescence in plants growing in special containers. The strategic placements of small quantities of radioactive phosphorus (P³²) at various depths in plots of orchard grass, red fescue, Kentucky bluegrass and colonial bentgrass on Alderwood loamy sand, enabled the depth of root penetration to be assessed by measuring radioactivity in the leaves with a Geiger-Muller counter. The movement of P³² in the soil was studied on the profiles of similar plots kept bare of vegetation, and on which similar placements were made. A modified technique resulted in the localization of the radioactive phosphorus in the soil. Plants in established plots of orchardgrass, red fescue, Kentucky bluegrass and colonial bentgrass were injected with P³² near the crown. The movement to the roots was found to be very slow when radioactivity was checked in the roots from the profiles. In a four week old alfalfa clone, injected three weeks earlier, P³² was recorded to have reached the maximum depth attained by visible roots. This was not the case with the grasses. The absorption of lithium from lithium chloride placed at various depths in rows of orchardgrass and alfalfa was determined by photometric analysis of samples from aerial portions. The extent of the root penetration was determined by the relatively higher concentrations of lithium in plants located above these placements.

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