Interaction between engineered nanoparticles and plants is still a widely unexplored area. While there is a growing body of research on the toxicity of nanoparticles to plants, their stress-inducing capabilities are less known. Determination of chlorophyll content in plant leaves is a relatively easy way of real-time assessment of the physiological state of the plant. Cauliflower (Brassica oleracea convar. Botrytis) seedlings were subjected to the TiO2 nanoparticles either by being planted in the nano-TiO2 enriched soil (1g/kg) or by exposure of its leaves to nano-TiO2 suspension (1g/L). Chlorophyll content in the shoots (mmol/m2) was measured both before and following the exposure in set interval; shoots were then harvested and prepared for Ti content analysis. While no significant decrease of chlorophyll content was observed in the unexposed plants, chlorophyll content significantly decreased after four days in the seedlings growing in the nanoparticle-enriched soil and after twelve days in the seedlings subjected to the suspension. All the seedlings appeared vital, yet the decrease in chlorophyll content indicates nanoparticle-induced stress that may seriously affect the yield from cultivated crops when these are exposed to nano-metal oxides or their composites as well as raise health concerns due to their bioaccumulation in the plant tissues.Keywords: nano metal oxides, chlorophyll, exposure, stress
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