Toxicity effects of olive-mill wastewater on growth, photosynthesis and pollen morphology of spinach plants

Abstract

Olive mill-wastewater (OMW), a by-product of the olive oil extraction process, represents a significant environmental problem in Mediterranean areas. We studied the impact of OMW dilutions (1:10 and 1:20) on growth, photosynthesis, proline and sugar accumulation as well as on pollen morphology of spinach (Spinacia oleracea L.) plants, to evaluate the application of OMW dilutions as pretreatment technique, prior to land disposal. Biomass, height, total chlorophyll and leaf area of spinach declined progressively with decreasing OMW dilution. Since fatty acids and phenolic compounds (present in the OMW) are considered precursors in the polymerization of sporopollenin, we suggest that under OMW treatment spinach plants seem to 'direct' the excess of these substances in the production and formation of increased pollen grains. Proline did not accumulate under OMW stress, but decreased possible due to transport to pollens in response to increased demand to over-production of pollens. Both OMW dilutions resulted in a decreased efficiency of PSII functioning and an increased excitation pressure (1-q(p)). It is concluded that, higher than 1:20 OMW dilutions should be used, and/or additional treatment should be applied before use of the OMW in the environment.