Influence of P-fertilizers on photosynthetic pigments and phytohormones of perennial ryegrass grown on co-contaminated soils

The choice of plants dedicated to the phytomanagement of metal-contaminated soils is a crucial factor in the successful rehabilitation of polluted sites. To assess the resistance of these plants to the contaminated environment, their physiological responses may constitute good indicators of the potential toxicity effects of metals. Two agricultural soils, used for foodstuff and feedstuff production, were selected in view of their contamination level by Cd, Pb and Zn. After adding fertilizers, their effects on the (i) accumulation and translocation of metals, (ii) biomass and (iii) production of abscisic acid, photosynthetic pigments and total phenolic compounds were studied. Although no real effect of phosphates was obtained for ryegrass grown on the least contaminated soil, benefits of P-fertilizers on ryegrass were reported for plants sampled from the most contaminated agricultural soil. The concentrations of carotenoids and chlorophylls a and b increased under phosphate fertilization whereas the production of abscisic acid decreased, suggesting that metal-stress was reduced in this condition. In view of the current study, this hormone appears as an indicator, sensitive to non-stress and metal-stress conditions.