SiO2 nanopriming protects PS I and PSII complexes in wheat under drought stress

Drought is an important abiotic stress that hampers the growth of plants by inhibiting photosynthesis resulting in major crop losses. Silicon is known for its role to alleviate impact of various abiotic stresses in plants. In the present study, drought sensitive wheat variety HI-1544 was subjected to drought stress (DS) by withholding irrigation. The aim of this study was to evaluate the impact of SiO₂ nanopriming in protecting photosynthesis, particularly photosystems (PSI and PSII), under drought condition. DS significantly reduced the quantum yield of PSII (YII) and PSI (YI) in unprimed drought stressed (UP+DS) plants but non-significant reduction was observed in NP+DS wheat plants. Likewise a severe impairment in the electron transport rate of PSII and PSI (ETRII and ETRI) in UP+DS was noticed as compared to NP+DS plants. Among energy dissipation parameters, regulated and non-regulated energy dissipation [Y(NPQ) and Y(NO) respectively] showed prominent increase in UP+DS plants when compared to NP+DS wheat plants. Decrease in YI was accompanied by significant increase in donor Y(ND) and acceptor side Y(NA) limitation of PSI in UP+DS plants. These parameters were less affected in NP+DS wheat plants. A remarkable inhibition in the oxidation reduction kinetics of P700 was observed in UP+DS plants while it were less affected in NP+DS wheat plants. The data suggests that the impact of drought stress (DS) was more prominent on PSII than PSI. SiO₂ nanopriming conferred more protection to PSII complex, thereby improving photosynthetic efficiency under DS.