Effects of Extracts from Paecilomyces Variotii on Chlorophyll Fluorescence Transient in Leaves of Maize under Waterlogging Stress

Abstract

【Background and objective】 Waterlogging is an abiotic stress occurring frequently during maize growth season, especially in its initial seedling stage. The crude extract of endophyte Paecilomyces variotii is a bio-stimulant widely used in China to promote plant growth and improve its resistance against waterlogging. We extracted Paecilomyces variotii (PVE) from the endophytic fungus in a wild sea buckthorn, which is not only able to protect crops from pathogens but also promotes crop growth. However, the underlying mechanisms of how PVE enhances the tolerance of maize against waterlogging is obscure. The aim of this paper is to fill this knowledge gap. 【Method】 We used maize as the model plant and conducted the experiment in laboratory. Maize seedings treated with PVE were subjected to waterlogging, with seedlings not treated with PVE taken as control. For each treatment, we measured the change in chlorophyll fluorescence transient curve (OJIP) of the seedings. 【Result】 Waterlogging hindered growth of the maize seedling and reduced its net photosynthetic rate (Pn) as a result. Waterlogging lasting more than four days changed the OJIP curve by reducing the active reaction centre per unit area, and altered the ability of electronic transmission from QA to QB (Ψo and δRo). Treating the seedlings with PVE alleviated the waterlogging-induced decrease in specific energy fluxes per unit area for absorption (AB/CSm), trapping (TRo/CSm), and electron transport (ETo/CSm), while in the meantime maintaining a relatively high heat dissipation capacity (DIo/CSm). 【Conclusion】 Spraying PVE over maize seedings enhanced their tolerance to waterlogging stress and helped their quick recovery after the waterlogging receded.

Keywords

• maize
• waterlogging stress
• extracts from paecilomyces variotii
• chlorophyll fluorescence transient