Patterns of spatio‐temporal distribution of winter chronic photoinhibition in leaves of three evergreen Mediterranean species with contrasting acclimation responses

Abstract

High irradiance and relatively low temperature, which characterize Mediterranean winters, cause chilling stress in plants. Downregulation of photosynthetic efficiency is a mechanism that allows plants to survive these conditions. This study aims to address whether this process shows a regular spatial pattern across leaf surface or not. Three species (Buxus sempervirens, Cistus albidus and Arctostaphylos uva-ursi) with contrasting responses to winter stress were studied. During 7 days, macro and micro Fv/Fm spatial patterns were monitored by the use of chlorophyll fluorescence imaging techniques. In the field, the strongest photoinhibition was found in B. sempervirens, while there was almost no chronic photoinhibition in C. albidus. In leaves of the first species, Fv/Fm decreased from base to tip while in C. albidus it was uniform over the leaf lamina. An intermediate behavior is shown by A. uva-ursi leaves. Spatial heterogeneity distribution of Fv/Fm was found inside the leaves, resulting in greater Fv/Fm values in the inner layers than in the outer ones. Neither xanthophyll-linked downregulation of Fv/Fm nor protein remobilization were the reasons for such spatial patterns since pigment composition and nitrogen content did not reveal tip-base differences. During recovery from winter, photoinhibition changes occurred in Fv/Fm, pigments and chloroplast ultrastructure. This work shows for the first time that irrespective of physiological mechanisms responsible for development of winter photoinhibition, there is an acclimation response with strong spatio-temporal variability at leaf level in some species. This observation should be taken into account when modeling or scaling up photosynthetic responses.

Unexpected Vulnerability to High Temperature in the Mediterranean Alpine Shrub Erysimum scoparium (Brouss. ex Willd.) Wettst

“…Among them, ChlaF-imaging seems a promising tool, because it enables the characterization of either acclimation or damage against temperature treatments at leaf and at plant levels [49,50]. Importantly, this method provides information on the spatio-temporal pattern of temperature effects on leaf photochemistry [51,52]. While the maximum photochemical efficiency of photosystem II (F v /F m ) has traditionally been used in the early-diagnosis of temperature-derived damage in photosynthetic tissues of mountain plants [22,53], a recent study has pinpointed the ChlaF decrease ratio, as a more sensitive parameter [33].…”

“…This socalled vitality index (R fd ), was introduced in the 1980s [54], relates to the leaf photochemical capacity under continuous irradiance, and strongly correlates with carbon assimilation [55]. To date, relatively few studies have taken advantage of the ChlaF-imaging analyses to provide spatio-temporal patterns in alpine leaf damage under temperature stress [51,52], and none of them has focused on the R fd parameter.…”

Effects of environmental factors and management practices on microclimate, winter physiology, and frost resistance in trees

“…During the leafy period, low temperatures affect the activity of photosynthetic-related enzymes. Therefore, electrons accumulate in the photosystems and generate reactive oxygen species ( Ensminger et al, 2006 ; Mai et al, 2009 ; Silva-Cancino et al, 2012 ).…”

Photosynthetic Performance in Pinus canariensis at Semiarid Treeline: Phenotype Variability to Cope with Stressful Environment

“…One of the most challenging stresses that should be closely studied is photoinhibition. Photoinhibition is a result of the overexcitation of the photosynthetic apparatus when a large amount of light energy is trapped by chlorophylls and an excess cannot be safely dissipated [2]. This overexcitation carries with it the potential to damage the photosystem II (PSII) [3].…”