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Titanium dioxide nanoparticles impaired both photochemical and non-photochemical phases of photosynthesis in wheat


Titanium dioxide nanoparticles (TiO2-NP) are increasingly being proposed for nanoagriculture but their effect on photosynthesis is limited and contradictory, mostly regarding putative chronical effects associated to the exposure to the commercial P25 formulation (anatase:rutile). This research aims at evaluating how chronical exposure to P25-NP affect photosynthetic processes in Triticum aestivum. Wheat plants were exposed (from the germination stage) to 0, 5, 50, and 150 mg L−1 P25-NP for 20 days. P25-NP impaired both light-dependent and -independent phases of photosynthesis, decreased chlorophyll a content, maximal and effective efficiency of PSII, net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentration, and starch content. On the other hand, no effects were observed in photochemical and in non-photochemical quenching values, on total soluble sugar (TSS) content or in RuBisCO activity. Our results support that the induced decay in chlorophyll a content compromised the electron transport through PSII and that stomatal limitations impaired CO2 assimilation. The decline of starch content seems to be a consequence of its degradation as a mechanism to maintain the TSS levels. Consequently, we propose that photosynthetic related endpoints are sensitive and valuable biomarkers to assess TiO2-NP toxicity.

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Fig. 5


Chl a(b):

Chlorophyll a(b)



C i :

Intercellular CO2 concentration

E :

Transpiration rate

Fm :

Maximal fluorescence yield of dark-adapted state

F m′:

Maximal fluorescence yield of light-adapted state

F v/F m :

Photosystem II (PSII) maximum efficiency

F 0 :

Minimal fluorescence yield of dark-adapted state

g s :

Stomatal conductance


Non-photochemical quenching

P N :

Net photosynthetic rate


Photochemical quenching


PSII effective photochemical efficiency


Relative water content


Total soluble sugars


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The Fundação para a Ciência e Tecnologia (FCT/MCT) supported S. Silva (SFRH/BPD/74299/2010), M. C. Dias (SFRH/BPD/100865/2014), and G. Pinto (SFRH/BPD/101669/2014) grants from QREN–POPH/FSE—Tipologia 4.1—Formação Avançada. This work was financed by FCT/MEC through national founds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020, within the projects CEF (UID/BIA/04004/2013), CESAM (UID/AMB/50017), QOPNA (UID/QUI/00062/2013), and LAQV/REQUIMTE (PT2020 UID/QUI/50006/2013, POCI/01/0145/FEDER/007265).

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Correspondence to Sónia Silva.

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Dias, M.C., Santos, C., Pinto, G. et al. Titanium dioxide nanoparticles impaired both photochemical and non-photochemical phases of photosynthesis in wheat. Protoplasma 256, 69–78 (2019).

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