Lolium multiflorumdensity responses under ozone and herbicide stress

Abstract

Adaptations to overcrowding of individual plants result in density dependant control of growth and development. There is little information on how anthropogenic stresses modify these responses. We investigated whether combinations of diclofop-methyl herbicide and tropospheric ozone alter the pattern of expected growth compensation with density changes resulting from intraspecific competition in Lolium multiforum Lam (Poacea) plants. Individual plant vegetative parameters and total seed production were assessed for plants growing under various densities and different herbicide rates and ozone treatments.The stressors differently changed the frequency distribution for average individual plant weight resulting from increasing densities. Only herbicide affected seedling mortality. Plants were able to compensate during grain filling maintaining similar seed production -density relationships in all treatments. Our findings contribute to the understanding of the impact of stress factors on the demographic changes in plant populations. Important ecological implications arise: (i) contrasting responses to ozone and herbicide, alone and in combination of individual plants resulted in different biomass -density relationships; (ii) stress effects on plant populations could not be predicted from individual responses; and (iii) changes in competitive outcome by single or combined stress factors may alter the expected genotype frequency in a crowded population with few dominant individuals.

Daño, producción de semillas y persistencia del hongo endófito Epichloë occultans en plantas de Lolium multiflorum bajo un ataque de herbívoros lepidópteros y contaminación por ozono

“…Ozone can alter the interaction of plants with herbivores directly if both, plants and animals, are exposed to the contaminant or indirectly when herbivores land on plants previously exposed to the gas (Holopainen 2002). Ozone can affect plant structure and growth (Heagle et al 1999;Martínez-Ghersa and Radosevich 2009), modifying chemical composition and activating (Sandermann et at. 1998) or deactivating (e.g., Ueno et al 2016) defense mechanisms.…”