Effect of field light stress on the sesquiterpene lactone content and
phytotoxicity of cultivated cardoon leaf extracts
Intensive agriculture needs new sustainable tools for weed management.
Allelopathy offered a valid alternative. Sesquiterpene lactones (STLs)
are the most important cultivated cardoon (Cynara cardunculus L. var.
altilis DC.) allelochemicals involved in weed toxicity. The present
study aims to investigate the effect of field light stress (by 60% of
plant shading) on the qualitative and quantitative composition of STLs
in cultivated cardoon leaf extracts harvested in January and April. The
phytotoxicity of leaf extracts was evaluated on the wheat coleoptile
elongation, seed germination, root and shoot length of the weeds
Amaranthus retroflexus L. and Portulaca oleracea L. Light stress
significantly increased the concentrations of total and single STLs, and
this increase was more marked if combined with harvest time (+338, 102
and 94 of cynaratriol, desacylcynaropicrin and
11,13-dihydro-deacylcynaropicrin, respectively) in April. The
concentration of STLs and the phytotoxic activity were correlated (light
stressed extracts belonging from April reduced by 91, 86 and 93% the
wheat coleoptile elongation and the root and shoot length of A.
retroflexus, respectively, at 800 ppm). Therefore, the induction of
light stress could be used to increase the concentrations of STLs in
cultivated cardoon leaves for industrial applications and to improve
their phytotoxic potential.