Effect of exogenously applied 20-hydroxyecdysone on the efficiency of primary photosynthetic processes substantially differs across plant species

Abstract

The effects of 20-hydroxyecdysone on the primary photosynthetic processes (PPP) were examined across twelve plant species using the OJIP chlorophyll fluorescence analysis. Our experiments brought evidence that the ecdysteroids can function not only as protective compounds in plants but participate also in the regulation of photosynthesis. Exogenously applied 20-hydroxyecdysone positively affected the PPP particularly in French bean and canola. Contrary to this, the PPP were negatively influenced by 20-hydroxyecdysone in pea, sunflower, and wheat. The performace of the oxygen-evolving complex, the excitonic connectivity among PSII units, the electron transport between PSII and PSI, the size of the pool of the end electron acceptors, and the absorption and trapping of the excitation energy in the light-harvesting antennae were differently affected in individual plant species. Additionally, the older and younger leaves did not respond to 20-hydroxyecdysone in the same way and this was also a species-specific phenomenon.