Oil Blue Na as A Stain for Rubber in Sectioned or Ground Plant Tissues

Oil blue NA (Calco), a stain which colors rubber bright blue, has been used effectively in studying the distribution of rubber in several plant species. Fresh or fixed sections are cut, bleached with Javelle water or NaOCl solution, treated with 9% KOH in 95% ethanol, washed with several changes of water and finally with 95% ethanol, and stained with 0.05% oil blue NA in 70% ethanol. Sections are rinsed in 50%' ethanol, placed in 40% glycerin, and mounted in glycerin jelly.

For the detection of changes in the distribution and character of rubber in milled or ground tissues, much the same staining procedure is followed. The stained tissues usually are examined and dissected under a stereoscopic microscope, a procedure which permits rubber to be recognized by both its staining reaction and by a more specific property, elastic elongation.

A microscopic technic is presented whereby it is possible to determine approximately the relative proportion of dispersed and coagulated rubber latex in unstained tissues.