Responses of elephantgrass to nutrient solution pH levels

Seedlings of elephantgrass (Pennisetum purpureum, Schum.), cvs. Vruckwona a nd Napier, were grown in aerated nutrient solution and exposed to pH levels of 4.0, 5.0, 6.0, or 7.0. After 30 days under controlled conditions, the e ffects on growth were evaluated. Plants exposed to pH 5.0, as compared to t hose under pH 4.0, showed increases in total leaf area, plant height, numbe r of leaves (NL), and leaf, root, and stem fresh weight. No significant dif ferences were found in stubble fresh weight, maximum individual leaf area, leaf area ratio (LAR), leaf area:plant height ratio, and leaf, root, stem, and stubble dry weight and dry matter percentage. Seedlings exposed to pH 4 .0, as compared to those under pH 5.0, exhibited higher leaf:stem ratio on a fresh weight basis (FWR) and a tendency for higher leaf: stem ratio on a dry matter basis (DWR). Cultivar Vruckwona yielded superior results than Na pier for most studied parameters, except for NL, LAR, and DWR (in which the re were no significant differences) and for stubble length and FWR (in whic h Napier performed better). The results suggest that reductions below 5.0 i n the nutrient solution pH cause growth inhibition, affecting root, stem, a nd leaf FW to a greater extent. The magnitude of such effects varies among contrasting cultivars. In turn, pH increases above 5.0 induce no significan t growth reduction or promotion.