Photoprotective Role of Photosynthetic and Non-Photosynthetic Pigments in Phillyrea latifolia: Is Their “Antioxidant” Function Prominent in Leaves Exposed to Severe Summer Drought?

Carotenoids and phenylpropanoids play a dual role of limiting and countering photooxidative stress. We hypothesize that their “antioxidant” function is prominent in plants exposed to summer drought, when climatic conditions exacerbate the light stress. To test this, we conducted a field study on Phillyrea latifolia, a Mediterranean evergreen shrub, carrying out daily physiological and biochemical analyses in spring and summer. We also investigated the functional role of the major phenylpropanoids in different leaf tissues. Summer leaves underwent the most severe drought stress concomitantly with a reduction in radiation use efficiency upon being exposed to intense photooxidative stress, particularly during the central hours of the day. In parallel, a significant daily variation in both carotenoids and phenylpropanoids was observed. Our data suggest that the morning-to-midday increase in zeaxanthin derived from the hydroxylation of ß-carotene to sustain non-photochemical quenching and limit lipid peroxidation in thylakoid membranes. We observed substantial spring-to-summer and morning-to-midday increases in quercetin and luteolin derivatives, mostly in the leaf mesophyll. These findings highlight their importance as antioxidants, countering the drought-induced photooxidative stress. We concluded that seasonal and daily changes in photosynthetic and non-photosynthetic pigments may allow P. latifolia leaves to avoid irreversible photodamage and to cope successfully with the Mediterranean harsh climate.

Wood vs. Canopy Allocation of Aboveground Net Primary Productivity in a Mediterranean Forest during 21 Years of Experimental Rainfall Exclusion

A Mediterranean holm oak forest was subjected to experimental partial rainfall exclusion during 21 consecutive years to study the effects of the expected decrease in water availability for Mediterranean vegetation in the coming decades. Allocation in woody structures and total aboveground allocation were correlated with annual rainfall, whereas canopy allocation and the ratio of wood/canopy allocation were not dependent on rainfall. Fruit productivity was also correlated with annual rainfall, but only in Quercus ilex. In the studied site, there were two types of forest structure: high canopy stand clearly dominated by Quercus ilex, and low canopy stand with more abundance of a tall shrub species, Phillyrea latifolia. In the tall canopy stand, the allocation to woody structures decreased in the experimental rainfall exclusion, but not the allocation to canopy. In the low canopy stand, wood allocation in Quercus ilex was very small in both control and plots with rainfall exclusion, but wood allocation in Phillyrea latifolia was even higher than that obtained in tall canopy plots, especially in the plots receiving the experimental rainfall exclusion. These results highlight likely future changes in the structure and functioning of this ecosystem induced by the decrease in water availability. A serious drop in the capacity to mitigate climate change for this Mediterranean forest can be expected, and the ability of Phillyrea latifolia to take advantage of the limited capacity to cope with drought conditions detected in Quercus ilex makes likely a forthcoming change in species dominance, especially in the low canopy stands.

Seasonal ecophysiological responses and behavior of phillyrea latifoliaspecie to climate change in Tunisia

Background As part of global climate change, variation in precipitation in arid ecosystems is leading to plant adaptation in water-use strategies; significant interspecific differences in ecophysiological response will change the plant behavior. The mainaim of this study was to investigate the ecophysiological responses of Phillyrea latifolia species to seasonal drought stress. Measurements were conducted between March and December 2018. The parameters studied were the Leaf Water Potential (ψ leaf ), Net photosynthesis (Pn), stomatal conductance (gs) and leaf transpiration (Tr), maximum efficiency of PSII photochemistry (Fv/ Fm), and Hydraulic conductivity. Main results The results showed that all measured parameters varied significantly with the season(P <.0001). The results of ψ leaf showed the highest average in summer (−2.99±0.08 MPa). Likewise, the highest values of the maximal photochemical efficiency of PSII (Fv/Fm) were observed in summer (0.83±0.06). However, the highest values of Pn (3.62±0.41 µmol m -2 s -1 )and Tr (0.3±0.028 µmol m -2 s -1 ) were noted in autumn. The Initial Hydraulic Conductivity ( K in ) value was in spring (1.34 -04 ±110 -5 mmol s -1 m -2 MPa -1 ) and autumn (1.1810 -04 ±2.3010 -6 mmol s -1 m -2 MPa -1 ) and the Maximal Hydraulic Conductivity ( K max ) was the highest during the spring season (3.4510 -04 ±2.7010 -11 mmol s -1 m -2 MPa -1 ). The results of the Stomatal Conductance (gs)were showed that the lowest values were recorded in summer (0.19±0.04 MPa). The percentage of loss conductivity (PLC) reached 66%. During the spring season, the soil had a decreasing moisture profile as it moved to the depths and varied from 15.23±5.48% at 20cm to 6.26±2.46% at 80 cm. Conclusions The best physiological performances of Phillyrea latifolia reported in spring and autumn may be attributed to favorable environmental conditions. The answers depend not only on the specie but also on the climates in which they grow.

Φυτοκοινωνιολογική έρευνα των μεσογειακών οικοσυστημάτων με Erica manipuliflora Salisb. στο Νομό Χαλκιδικής

Η Erica manipuliflora Salisb. (σουσούρα) αποτελεί κυρίαρχο είδος θαμνωδών εκτάσεων σε πολλές περιοχές της Ελλάδας. Αναπτύσσεται σε περιοχές με μεσογειακό κλίμα, οι οποίες χαρακτηρίζονται από την έντονη παρουσία ξηρής και θερμής περιόδου. Η Erica manipuliflora είναι ελάχιστα απαιτητικό είδος και μπορεί να εγκατασταθεί σε περιβάλλοντα με ακραίες συνθήκες. Η Χαλκιδική αποτελεί μία περιοχή που το συγκεκριμένο είδος βρίσκει καλή ανάπτυξη και παρόλο που καταλαμβάνει μεγάλες εκτάσεις δεν υπάρχουν πολλές πληροφορίες διαθέσιμες (μόνο αποσπασματικά από εργασίες που επικεντρώνονται στη μελέτη άλλων ειδών π.χ. Pinus halepensis) για τις φυτοκοινωνίες και τη συνοικολογία. Οι εκτάσεις του Νομού Χαλκιδικής με τη συμμετοχή του είδους Erica manipuliflora, το οποίο συμμετέχει σε αυτές είτε ως κυρίαρχο, είτε ως συγκυρίαρχο, μελετήθηκαν φυτοκοινωνιολογικά με τη μέθοδο του Braun-Blanquet (1951, 1964) με σκοπό τον καθορισμό και την περιγραφή των μονάδων βλάστησής τους. Συνολικά διενεργήθηκαν 250 φυτοληψίες [170 της παρούσας έρευνας και 80 προερχόμενες από το Δαμιανίδη (2011), για την ίδια περιοχή]. Έπειτα από αριθμητική επεξεργασία (μέθοδοι αριθμητικής ταξινόμησης και κατάταξης), διακρίθηκαν φυτοκοινωνικές μονάδες, διάφορης ιεραρχικής διαβάθμισης. Κατά την επεξεργασία του φυτοπίνακα διακρίθηκαν 5 ομάδες φυτοληψιών, οι οποίες διαφοροποιούνταν χλωριδικά και οικολογικά. Μετά την τελική επεξεργασία και συνταξινόμηση, οι φυτοκοινωνικές μονάδες που προέκυψαν, είναι δύο κλάσεις, τρεις τάξεις, δύο συνενώσεις, δύο ενώσεις, τρεις κοινότητες, δύο υποενώσεις, δώδεκα παραλλαγές και τέσσερις όψεις. Από τις παραπάνω μονάδες, η Erica manipuliflora-Pinus halepensis κοινότητα δίνεται για πρώτη φορά, με την παρούσα έρευνα. Η συνταξινόμηση των μονάδων βλάστησης δίνεται παρακάτω: ΚΛΑΣΗ: Cisto-Lavanduletea stoechadis Br.-Bl. in Br.-Bl. et al. 1940. TAΞΗ: Lavandulo stoechadis-Hypericetalia olympici Mucina in Mucina et al. 2016. ΣΥΝΕΝΩΣΗ: Hyperico olympici-Cistion cretici (Oberd. 1954) R. Jahn et Bergmeier in Mucina et al. 2009. ΕΝΩΣΗ: Ericetum verticillatae (=manipuliflorae) Oberd. 1954. ΚΛΑΣΗ: Quercetea ilicis Br.-Bl. ex A. Bolòs et O. de Bolòs in A. Bolòs y Vayreda 1950. ΤΑΞΗ: Pinetalia halepensis Biondi, Blasi, Galdenzi, Pesaresi et Vagge in Biondi et al. 2014. ΚΟΙΝΟΤΗΤΑ: Erica manipuliflora-Pinus halepensis. TAΞΗ: Pistacio lentisci-Rhamnetalia alaterni Rivas-Mart. 1975. ΣΥΝΕΝΩΣΗ: Ceratonio-Pistacion lentisci Zohary et Orshan 1959. ΕΝΩΣΗ: Oleo-lentiscetum aegaeicum Krause, Ludwig & Siedel 1963. Παραλλαγή: τυπική Παραλλαγή: υποβαθμισμένη. ΥΠΟΕΝΩΣΗ: Οleο-lentiscetum, quercetοsum cocciferae Barbero et Quézel 1976. Παραλλαγή: τυπική. Παραλλαγή: με Cistus monspeliensisΌψη: με Calicotome villosa. ΥΠΟΕΝΩΣΗ: Oleο-lentiscetum, pinetosum halepensis Barbero & Quézel 1976. Παραλλαγή: τυπική. Παραλλαγή: με Erica arborea. ΚΟΙΝΟΤΗΤΑ: Arbutus unedo-Erica arborea κοινότητα. Παραλλαγή: με Dorycnium graecum-Teucrium chamaedrys subsp. chamaedrys. Παραλλαγή: με Scleranthus perennis subsp. dichotomus-Micropyrum tenellum. ΚΟΙΝΟΤΗΤΑ: Quercus coccifera-Phillyrea latifolia κοινότητα. Παραλλαγή: με Juniperus oxycedrus subsp. deltoides. Όψη: τυπική Όψη: με Quercus pubescens. Όψη: με Linum elegans. Παραλλαγή: με Pinus nigra subsp. nigra. Παραλλαγή: τυπική. Παραλλαγή: με Cistus monspeliensis. Πέρα από τη φυτοκοινωνιολογική έρευνα, για την οικολογική ερμηνεία των φυτοκοινωνικών μονάδων, διεξήχθη εδαφολογική έρευνα μέσω 46 εδαφοτομών. Στα εδαφολογικά δείγματα που συλλέχθηκαν από τις εδαφοτομές πραγματοποιήθηκαν εργαστηριακές αναλύσεις τόσο στο δασικό τάπητα, όσο και στο έδαφος. Για την ενίσχυση της οικολογικής ερμηνείας, εκτός των αποτελεσμάτων της εδαφολογικής και της φυτοκοινωνιολογικής έρευνας, χρησιμοποιήθηκαν και τα δεδομένα του κλίματος της περιοχής έρευνας, καθώς και τα φυσιογραφικά στοιχείων των φυτοληψιών.

Sites and Time of Oviposition of Euphyllura phillyreae Foerster on Olive Trees and οon Phillyrea latifolia

The distribution of eggs of Euphyllura phillyreae Foerster (Homoptera: Aphalaridae) was recorded on twigs of olive trees and of Phillyrea latifolia L. in various locations of the Thessaloniki and Halkidiki prefectures of coastal northern Greece. On olive, the first eggs were observed in the last ten days of March and oviposition was intensified and became abundant only when the apical bud and the axillary leaf and flower buds started to swell. Eggs were laid mostly on swollen buds and on developing inflorescences. Oviposition preference was related to the stage of development of a bud and not to its location on the olive twig. On swollen leaf buds, most eggs were laid on the inner (upper) surface of the middle (second) pair of developing leaves, and fewer on the inner surface of the outer (first) pair and on the innermost (third) pair of leaves. On Phillyrea, eggs were deposited much earlier than on olive, on developing inflorescences. In choice and no-choice laboratory experiments, more eggs were laid on olive twigs bearing developing inflorescences, fewer eggs on twigs bearing only swollen terminal or axillary buds, and no eggs at all on twigs with only fully developed leaves of the previous year.