Ecophysiological plasticity in broad leaf weed Rumex acetosa under allelochemical stress

Secondary metabolites such as ferulic acid (FA) and p-hydroxybenzoic acid (pHBA) have demonstrated inhibitory effects on germination and seedling growth of lettuce and perennial grasses. However, to date little is known about the physiological mechanisms of action of these natural compounds in broad-leaved weed, Rumex acetosa. The objective of this study was to determine the plasticity response of Rumex acetosa in terms of leaf carbon isotope composition and other physiological parameters to the interaction of plant secondary metabolites (PSM) (FA, pHBA) and the usefulness of carbon isotope discrimination (Δ13C) as indicative of the functional performance of intrinsic water use efficiency (iWUE) at leaf level. R. acetosa plant were grown under greenhouse condition and subjected to PSM stress (0, 0.1, 0.5, 1.0, 1.5 mM) for 06 days. Here we show that, FA and pHBA are potent inhibitors of Δ13C that varied from 21.0‰ to 22.9‰. Higher pHBA and FA supply enhanced the Nleaf and retard the Cleaf. The CO2 concentration from leaf to air (Ci/Ca) was decreased while iWUE increased. These results confirm the phytotoxicity of FA and pHBA on R. acetosa seedlings, and Δ13C, Ci/Ca and iWUE are suitable indicators of physiological plasticity