BRIEF COMMUNICATIONEstimation of changes in the activity of photosynthetic apparatus of plant leaves based on half-time of fluorescence intensity decrease

Abstract

The range of variations in parameter τ0.5 - half-time of fluorescence intensity decrease during the slow phase of chlorophyll fluorescence induction (CFI) - has been studied during ontogeny of leaves of monocotyledonous and dicotyledonous plants in plant communities of different structures. Plants were grown hydroponically on expanded clay aggregate in growth chambers, under PPFD of 400 μmol(photon) m-2 s-1, under controlled conditions. Analysis of the literature data and results of experimental observations of τ0.5 behavior compared to other CFI parameters, nonphotochemical quenching coefficient, qN, in particular, leads to the conclusion that parameter τ0.5 can be effectively used for indirect estimation of variations in the activity of photosynthetic apparatus during ontogeny of plant leaves. Dramatic global climate change is a factor that increases the importance of stress tolerance of plants, on the one hand, and urges researchers to develop methods for monitoring the state of the plants, on the other. All stressors, whatever part of the plant they may affect, eventually, directly or indirectly, influence photosynthesis, which is primarily related to the activity of photosynthetic apparatus (PSA) at the leaf level. In recent years, the method of chlorophyll fluorescence induction (CFI) based on the Kautsky effect has become a widespread method for ecological monitoring of plant communities (Lichtenthaler et al. 2005, LazĂĄr 2015, Kalaji et al. 2017). Sometimes, when plants are subjected to external stresses, it is essential to determine quickly the functional state of the leaf PSA and estimate reversibility (or extent) of changes in PSA activity. A common approach is to use a set of characteristics based on measurements of amplitude parameters of the plant leaf CFI curve (Roháček 2002).