Plant morphology, vegetative biomass composition and energy content of three different Silybum marianum accessions

Abstract

Silybum marianum (L.) Gaertn. (milk thistle) is plant species that has been utilized principally for medicinal purposes for more than 2000 years. Recently it was proposed for biomass production in marginal environments, but vegetative biomass compositional analyses had not been available so far. The study of plant morphology and biomass composition was conducted on three different S. marianum accessions grown under open field conditions. The results indicate that plant morphological traits show major differences between accessions: this suggests that the available natural variability can be further utilized in order to develop improved S. marianum cultivars. Biomass compositional analysis shows that extractives, ash, lignin and cellulose content are comparable to other herbaceous bioenergy crops and that these traits display only limited variability in the studied accessions. Hemicellulose fraction is composed only by xylans and its content appears averagely lower in comparison to other herbaceous biomasses. Interestingly, in S. marianum biomass total nitrogen content is lower if compared to other herbaceous species. The possible involvement of this specific biomass trait in S. marianum nitrogen utilization efficiency has to be further investigated.