Effects of water-deficit stress and putrescine on performances, photosynthetic gas exchange, and chlorophyll fluorescence parameters of Salvia officinalis in two cutting times

A 2-year (2017-2018) field experiment was performed to specify if the foliar application of putrescine (PUT) under optimum and water-deficit stress (WDS) conditions would favorably affect leaf gas exchange, greenness, chlorophyll fluorescence parameters, pigments, sodium (Na), potassium (K), as well as yield and content of the essential oil (EO) relationships in Salvia officinatis L. (sage) in spring (cutting 1) and summer (cutting 2). Based on the results analysis of variance, the effects of WDS, PUT, and cutting time were significant for the dry weight, leaf area index (LAI), EO content, EO yield, chlorophyll (Chl) t, carotenoid, Na, and K of sage. According to regression results, the response of EO content, EO yield, non-photochemical quenching (NPQ), spad, Chl a, Chl t, K, and K/Na to WDS can be expressed by a quadratic model, indicating that they would attain their maximum in 75,5%, 34.86%, 38.33%, 84.13% 60%, 70%, 50.40%, and 40.28% available soil water depletion (ASWD), respectively. The response of dry weight, LAI, EO content, EO yield, Fv/Fm, spad, Phi psII, Chl a, Chl b, Chl t, carotenoid, K, and K/Na to PUT can be expressed by a quadratic model, showing that they would attain their most under 0.98, 1.14, 1.34, 1.16, 1.27, 1.18, 1.17, 1.25, 1.17, 1.27, 1.31, 1.21, and 1.19 mM of PUT, respectively. These findings suggest that, probably, the functions and structures of the photosynthetic system were further enhanced with PUT, thereby they can be promoting primary electron transfer in PSII. Also, stomatal and photosynthetic activity improved with increasing K levels with PUT.

Automated summary

The foliar application of putrescine has a positive effect on the growth and essential oil production of Salvia officinatis under optimum and water-deficit stress conditions. Water-deficit stress and the concentration of putrescine have significant effects on the physiological and yield parameters of Salvia officinatis.