The influence of Rhizobium tropici produced EPM biopolymer on green bush bean root and plant growth

Abstract

A Rhizobium tropici (R. tropici) derived biopolymer has been reported as an effective, biodegradable, additive to reduce erosion. In addition to directly modifying the mechanical properties of the soil, it was postulated that indirectly it enhanced vegetation, which in turn stabilized the soil through enhanced root infrastructure. We therefore chose to study its impact directly on Green Bush Bean plants, where its effect could be measured in the early stages of plant development, starting from germination of the seeds through the initial growth of leaves and shoots. EPM derived from R. tropici bacteria ATCC (strain) grown in two laboratories were tested with similar results, indicating a high degree of reproducibility. Watering Bush Bean seeds with EPM concentrations as low as 50 and 100 mg/L produced a small increase of the germination rate, from 87% to 93% for seeds grown for ten days in a moist environment. The seeds were then transplanted into potting soil and allowed to grow for another three weeks, during which they were watered daily with tap water or the EPM solutions. Continued watering with EPM after transplantation showed enhancement in both root and stem/leaf mass three weeks after transplantation into potting soil by 45% for the two EPM biopolymers. Root density was also higher by 29% to 71% for EPM1.The mass of the leaf and shoots also showed a significant enhancement over the control, but in this case favoring EPM2, consistent with plants preferring either root or leaf production.