Effects of nitrogen fertilizer on photosynthetic light energy transfer and use in hybrid fescue under drought stress

The aim of this study was to investigate the response of chlorophyll a fluorescence parameters of hybrid fescue (× Festulolium loliaceum (Huds.) P. Fourn.) under partly regulated environment and drought stress effect. The results showed that the increasing nitrogen content increased the values of the studied indicators. Meanwhile drought stress reduced them. At the highest fertilization level N90, the photosynthetic performance (PItotal) index increased by 89 % compared to N0, the effect of drought reduced this indicator by 50 %, but remained higher than PItotal of plants of N0 level. After the recovery period, these differences became even more pronounced. Similar regularities were found for other investigated parameters such as quantum yield of electron transport (phi(Eo)) and quantum yield for the reduction of end acceptors of PSI per photon absorbed (phi(Ro)). Total electron carriers per reaction center (Sm) also increased with increasing nitrogen content in the soil. The higher nitrogen content significantly increased the values of the mentioned indicators after the recovery period. These aforementioned changes in photosynthetic energy transfer also lead to higher plant biomass and lower losses due to drought stress.