Effect of light intensity on the age dependence of nonphotochemical fluorescence quenching in wheat leaf

Abstract

The effects of actinic light (AL) intensity on the age dependence of nonphotochemical quenching of fluorescence (q N ) and effective quantum yield in PSII ( PSII ) were studied in continuously illuminated wheat leaves of the upper tier. Regular changes were revealed in both age dependence of q N at elevated AL intensities and light curves of q N . These changes are related to alterations in strategies of redistribution and use of absorbed light energy by the photosynthetic apparatus at different stages of wheat leaf development. Unlike Ф PSII , q N as a parameter was more sensitive to the differences in the leaf age at a certain range of light intensity. At the same time, the stability of q N at moderate light intensities may serve as an indication of leaf maturity.Additional key words: chlorophyll fluorescence induction; leaf age; photosystem II.--Nonphotochemical quenching of fluorescence (q N ) is commonly used to analyze stress tolerance in plants (Baker 2008, Ashraf and Harris 2013). It is well known that nonphotochemical quenching of chlorophyll fluorescence, q N , involves at least three molecular mechanisms: ΔpH-dependent quenching, which determines energy-dependent quenching of fluorescence (q E or the fast component, q Nf ); transition of the pigment system from state 1 to state 2 (q T or the medium component, q Nm ); and photoinactivation of PSII (q l or the slow component, q Ns ) (Baker, 2008). The contribution of each component to the total nonphotochemical quenching, q N , is determined by the actinic light intensity (Bukhov 2004), and their proportions and significance change during the leaf ontogeny (Hong et al. 1999, Müller et al. 2001, which may affect age variations in the q N as a whole. Indeed, under low and medium intensities of actinic light (AL), differences in the q N between mature and aged leaves are insignificant. These differences, however, become greater as AL intensity increases (Hong et al. 1999). Mechanisms determining nonphotochemical quenching of excited states of chlorophyll are mainly studied for PSII, as this photosystem is considered to be more sensitive to photoinhibition than PSI. Although it is well known that q N is age-and light-dependent, the age dependence of q N under medium intensities of AL and the effect of an increase in the AL intensity have not been sufficiently studied. No data have been reported on light curves of q N for leaves of different ages. The actinic light intensities reported in the literature varied between 200 and 1,500 μmol m -2 s -1 PPFD (Hong et al. 1999;Lichtenthaler et al. 2005; Wang and Chen 2011), and the available experimental data are not sufficient to evaluate the effect of the AL on the age dependence of the q N in the plant leaves. Thus, the purpose of this ---Abbreviations: CFI -chlorophyll fluorescence induction; F0 -minimal fluorescence yield of the dark-adapted state; F0' -minimal fluorescence yield of the light-adapted state; Fm -maximal fluorescence yield of the dark-adapted state; Fm' -maximal fluorescence yield of the light-ad...

Relative tolerance of photosystem II in spike, leaf, and stem of bread and durum wheat under desiccation

“…In contrast to instruments routinely used for point measurements, ChlF imaging system provides additional advantage of spanning many points in a plant organ for ChlF signals (Rousseau et al 2015). Both conventional instruments and imaging systems have been used for assessing plant stress responses often with focus on leaf photosynthetic efficiency (Nesterenko et al 2015, Kalaji et al 2017, Eisvand et al 2018. To the best of our knowledge there are rare attempts made to investigate PSII photosynthetic efficiency of spike and a known example is for assessing influence of diseases (Bauriegel et al 2011), but not for responses to stresses such as desiccation.…”

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

“…(2) the parameter must remain sufficiently stable under widely varying fluorescence-exciting light -actinic light (AL) -intensity (Nesterenko et al 2012(Nesterenko et al , 2015; and (3) the parameter must be sensitive to changes in PSA activity under stress and recovery of the PSA state once the stress ceases (Li et al 2013, Shikhov et al 2016. Nesterenko et al (2014Nesterenko et al ( , 2015 studied age dependence of the main characteristics of CFI and the effect of AL intensity on their values in wheat (Triticum aestivum L.) leaves. The authors determined such para meters as quantum yield in PSII (Fv/Fm), effective quantum yield in PSII (ΦPSII); qP, qN, and NPQ -parameters of photochemical and nonphotochemical quenching of Chl fluorescence; the FP/Ft ratio; and vitality index Rfd.…”

“…An increase in AL intensity to 580 µmol(photon) m -2 s -1 and higher caused a considerable age dependence of fluorescent parameters. The FP/FS ratio and parameters of nonphotochemical quenching of fluorescence -NPQ and qN -were found to be the most sensitive to the leaf age (Hong et al 2000, Nesterenko et al 2015. These fluorescent parameters are often used to estimate PSA stress tolerance (Lichtenthaler et al 2005, Shikhov et al 2011, Ashraf 2013).…”