Changes of dorsoventral asymmetry and anoxygenic photosynthesis in response of Chelidonium majus leaves to the SiO2 nanoparticle treatment.

Natural SiO₂ nanoparticles (SiO₂-NPs) are widely distributed in the environment, and at the same time, synthetic SiO₂-NP may be applied in agriculture. Evaluations of physiological responses to SiO₂-NPs treatment of plants are controversial. They are often performed at adaxial leaf sides whereas NPs permeate leaf tissues through stomata located at the abaxial leaf side in the majority of bifacial plants. We measured coefficients of the functional dorsoventral asymmetry of NPs-stressed Chelidonium majus leaves, S, by values of the CO₂ assimilation rate (SP _N), dark respiration (SR), maximal and operating quantum yields of photosystem II (SF_v/F_m, SF_v'/F_m'; using PAM-fluorometry), and oxygen coefficients of photosynthesis (SΨ_O2; using photoacoustics). The results indicated that SP _N and SΨ_O2 were significantly influenced by SiO₂-NPs treatment, since P _N and Ψ_O2 were declining more markedly when the light was directed to the abaxial side of leaves compared to the adaxial side. Overall, SiO₂-NPs-induced stress increased 'anoxygenity' of photosynthesis.