Stimulation of Root Growth in Several Vegetables by Wood Pulp Extract

Abstract

Effects of extract from wood pulp (wood pulp-made support for plant tissue culture) on the root growth of several vegetables, i. e., cucumber (Cucumis sativus L.), lettuce (Lactuca sativa L.), pea (Pisum sativum L.), radish (Raphanus sativus L.), tomato (Lycopersicon esculentum Mill.), and Welsh onion (Allium fistulosum L.) were examined. Roots of germinated seeds were grown in an extract diluted with water. Root growth of all vegetables except for the pea was stimulated by wood pulp extract. The most sensitive, consistent results were obtained with lettuce, thus it was chosen for further experiments. The pulp extract stimulated root growth much more than did glucose, sucrose, or an inorganic nutrient, suggesting that the root growth stimulating substance (s) are neither sugars nor inorganic ions.
When pulp extract was fractionated into ethanol soluble and insoluble fractions, the root growth stimulating activity was found in insoluble fraction, indicating that the active substance has high polarity. The ethanol insoluble fraction was further purified by gel filtration using Sephadex G -25 and Bio-Gel P -2 columns. By using Bio-Gel P -2 column, the activity was found in 3 low molecular weight fractions. These results indicate that pulp extract contains at least 3 kinds of root growth-stimulating substances which are highly polar compounds of low molecular weight.