engleski

Effect of high irradiation on chlorophyll a fluorescence in young and mature fig leaves

Combination of high irradiation and elevated temperature most often causes inactivation of oxygen evolving centre (OEC) of photosystem II (PSII). In this work we aimed to investigate influence of high irradiation on PSII photochemistry in young (YL) and mature leaves (ML) of common fig (Ficus carica L.) exposed to elevated temperature. Both leaf types were detached from the tree, acclimated at room temperature in dark for 12h and then exposed to 35±1°C combined with low (LI, ~50 µmolm-2s-1) or high irradiation (HI, ~800 µmolm-2m-1) for 4h. To evaluate PSII photochemistry, normalizations and subtractions of polyphasic fluorescence transients (OJIP) were used. While YL revealed negative L-band after HI treatment, indicating high energetic connectivity of PSII, positive L-band shown in ML suggested light induced antenna dissociation and lower PSII stability. Inflection in K-band in YL after exposure to HI treatment suggested slightly destabilization of OEC activity, while positive K-band detected in ML reflected complete inactivation of OEC. Although both leaf types showed significant reduction of maximum quantum yield of PSII (Fv/Fm) and performance index (PIABS), stronger decline was observed in ML. In conclusion, exposure of ML to HI resulted with impaired electron donation due to inactivated OEC accompanied with severe decline of PSII efficiency and overall performance. Combination of HI and increased temperature in YL increased thermostability of PSII, associated with the resistance of OEC and enhanced energy connectivity between PSII units what was also reflected by a lower decrease in Fv/Fm and PIABS compared to ML.

chlorophyll a fluorescence; OJIP; Ficus carica L.; PSII thermostability

nije evidentirano