Changes of dorsoventral asymmetry and anoxygenic photosynthesis in response of leaves to the SiO nanoparticle treatment.

Natural SiO nanoparticles (SiO-NPs) are widely distributed in the environment, and at the same time, synthetic SiO-NP may be applied in agriculture. Evaluations of physiological responses to SiO-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 leaves, S, by values of the CO assimilation rate (S ), dark respiration (S), maximal and operating quantum yields of photosystem II (SF/F, SF'/F'; using PAM-fluorometry), and oxygen coefficients of photosynthesis (SΨ; using photoacoustics). The results indicated that S and SΨ were significantly influenced by SiO-NPs treatment, since and Ψ were declining more markedly when the light was directed to the abaxial side of leaves compared to the adaxial side. Overall, SiO-NPs-induced stress increased 'anoxygenity' of photosynthesis.