Invasive Populations of Elephantgrass Differ in Morphological and Growth Characteristics from Clones Selected for Biomass Production

Abstract

Elephantgrass (Pennisetum purpureum Schum.) has demonstrated potential for use as a biomass crop, but in Florida, some naturalized types are invasive weeds in sugarcane (Saccharum sp.) fields, along roadsides, and in natural areas. It is not known whether elephantgrass introductions and breeding lines developed for biomass production (i.e., “selected”clones) differ from naturalized populations sufficiently that risk assessment and regulatory decisions should be made at the level of the clone instead of the species. The objective was to compare morphological and physiological traits of elephantgrass-naturalized populations and selected clones. Ten naturalized populations and six selected clones were evaluated in replicated trials at two field locations during 2 years. Selected clones were 8–14 % taller and had leaf blade length that was 48–87 % longer, and leaf blade width that was 61–89 % wider than naturalized clones. Selected types averaged 5.7 to 7.2 fewer tillers per plant than naturalized types, but tiller mass of selected types was 70 % greater than naturalized types. Leaf N concentration was 43 % greater for selected types and was associated with greater light-saturated leaf photosynthesis, stomatal conductance, leaf transpiration rate, and leaf dark respiration than naturalized types. Photosynthetic parameters indicated a greater maximum photosynthetic rate, leaf dark respiration, and light compensation point for selected versus naturalized clones. Clones selected for use as biomass crops differ widely in morphology and physiological response from naturalized populations, supporting a conclusion that risk assessment of elephantgrass should occur at the level of the clone rather than the species.