PSII photochemistry responses to drought stress in autochthonous and modern sweet cherry cultivars

Abstract

Abbreviations: ABS/RC -absorption flux (of PSII antenna Chl) per RC; Chl -chlorophyll; DAS -days after stress (drought application); ET0/ABS (φE0) -quantum yield of electron transport from QAto PQ; DI0/RC -dissipation flux per RC; DM -dry mass; ET0/RC -electron transport flux per RC; ET0/TR0 (ψE0) -probability that a trapped exciton moves an electron into the electron transport chain beyond QA; F0 -minimum fluorescence, when all PSII RCs are open; FM -fresh mass; Fm -maximum fluorescence, when all PSII RCs are closed; Fv -maximal variable fluorescence; Fv/F0 -the ratio between the trapping flux and energy dissipation flux of PSII; Fv/Fm -maximum quantum yield of PSII photochemistry; M0 -approximated initial slope of the fluorescence transient; MDA -malondialdehyde content; OEC -oxygen-evolving complex; PIABS -performance index for energy conservation from photons absorbed by PSII until the reduction of intersystem electron acceptors; PItotal -performance index for energy conservation from photons absorbed by PSII until the reduction of PSI end acceptors; PQ -plastoquinone; PQH2 -plastoquinol; RC -reaction centre; RE0/ABS (φR0) -quantum yield of electron transport from QAto final PSI acceptors; RE0/ET0 (δR0) -efficiency with which an electron can move from the reduced intersystem electron acceptors to the PSI end electron acceptors; RE0/RC -electron flux reducing end electron acceptors at the PSI acceptor side per reaction centre; ROS -reactive oxygen species; Sm -normalized total complementary area above the OJIP transient (reflecting single-turnover QA reduction events); TR0/RC -trapping flux per PSII RC; VI -relative variable fluorescence at 30 ms (I-step); VJ -relative variable fluorescence at 2 ms (J-step); VOP -relative variable fluorescence between O-and P-steps; WC -water content; WOJ -relative variable fluorescence between O-and J-steps; WOK -relative variable fluorescence between O-and K-steps.

Photosynthetic Variability of Oblačinska Sour Cherry Ecotypes under Drought

“…ϕP 0 , PI ABS , and PI total have widely used JIP parameters in the detection of plant response to drought and therefore declared as indicators of drought [3,7,13,[16][17][18]48,49]. A very high correlation of ϕP 0 , PI ABS , and PI total with control treatment, immanent from 6 DAS onward, obtained by PCA analysis in our research confirmed that the specified parameters could be used as drought-stress indicators within sour cherry genotypes.…”

“…In the drought-exposed leaves of ecotypes D6 and BOR, a significant decrease in PI ABS was found at 4 DAS, a decrease in ψE 0 in both ecotypes and an increase in TR 0 /RC, V L , and V K only in the leaves of ecotype BOR. Those alterations are in accordance with the decrease of PI ABS and ψE 0 as well as the occurrence of positive ∆K and ∆L in the drought exposed leaves of sensitive sweet cherry cultivar [16]. PI total in the drought exposed leaves of ecotype D6 remained unchanged until 6 DAS, when its decrease was caused by changes in the parameters describing the electron transport chain, suggesting that it is the weakest part of the photosynthetic process.…”

“…This suggests impaired energetic connectivity between PSII units and impaired electron flow between the oxygen evolving complex (OEC) and the acceptor side of the RC [42]. A similar response to drought was found in the apple leaves under severe drought conditions [15] and in the leaves of modern apple and sweet cherry cultivars, suggesting higher drought tolerance of some autochthonous cultivars [3,16]. A similar pattern in OJIP curves was found in all investigated ecotypes, but it was revealed at 6 DAS in OS and D6 and 8 DAS in the leaves of ecotype 18.…”

“…According to our results, ϕP 0 is a less sensitive indicator of drought stress in sour cherry seedlings than PIs, which corroborates previous research on the bean, apple, sweet cherry, etc. [3,16,48]. Besides ϕP 0 and PIs, ψE 0 was a very sensitive indicator of drought stress from the 4 DAS onward, implying that electron transport is the most sensitive part of the photosynthetic process in this type of stress.…”

“…JIP parameters detect changes in photosynthetic efficiency at the cellular level even before the appearance of visible symptoms of stress [12]. The studies based on ChlF analysis on leaves have proven the impact of drought on plant photosynthetic efficiency in the passion fruit [13], the Amur Grape [14], apple [3,15], and sweet cherry [16], etc. Under drought stress, photosynthesis is limited by damage at the chloroplast level as the concentrations of chloroplast pigments, especially chlorophyll a and chlorophyll b, significantly decline [17][18][19][20][21].…”