Interactive effects of biotic stressors and provenance on chemical defence induction by holm oak (Quercus ilex)

Key Message The patterns of induced chemical defences in Quercus ilex leaves are specific to the biotic stress factor that causes them. Interactive effects between stressors depend on provenance. Abstract Quercus forests are suffering serious decline worldwide, closely linked to the consequences of climate change. The increase of biotic stressors threatens the survival of the holm oak (Quercus ilex), a dominant tree species in the Mediterranean Basin. A better understanding of its resistance mechanisms is urgently required to enable a better control of its decline. In this work, the ability of holm oaks from six Iberian provenances to respond to multiple biotic damage is studied through an analysis of their induced chemical defence patterns. Using 2016 seedlings established in a common garden trial (6 regions × 12 families/region × 7 seedlings/family × 4 treatments), biotic damage was induced at the root level (by infection with the widespread pathogen Phytophthora cinnamomi) and at the above-ground level (by mechanical defoliation). The levels of constitutive and induced total phenols, total tannins and condensed tannins were measured. Results showed that (1) the defensive chemical patterns present significant local and geographical variation, (2) survival to stress is more related to constitutive defences than induced ones, (3) the induced response is stressor-specific, and (4) there is an interactive effect amongst stressors whose sign (induction/inhibition) depends on the provenance. These findings on biotic stressor effects on the chemical defences and survival of holm oak can contribute to the development of genetic material selection programs in the integrated control of the widespread decline of Quercus.

Funkcionalna diferencijacija provenijencija hrasta crnike na istočnoj obali Jadranskoga mora

Hrast crnika (Quercus ilex L.) je sredozemna vazdazelena vrsta drveća, koja na svom području pridolaska pokazuje veliku morfološku i funkcionalnu varijabilnost. Cilj ovoga rada bio je utvrditi postoji li diferencijacija hrasta crnike na klimatskom gradijentu istočne obale Jadranskoga mora (opisanom s prosječnom godišnjom količinom oborina, prosječnom količinom oborina tijekom ljetnog perioda i klimatskim deficitom vlage) s obzirom na funkcionalne značajke lišća (opisane sa specifičnom lisnom površinom, indeksom relativnog sadržaja ukupnih klorofila u lišću i stopom neto fotosinteze mjerene u lišću). Specifična lisna površina mjerena je na lišću uzorkovanom u tri provenijencije na prirodnom staništu te lišću uzorkovanom u pokusnom nasadu na mladim biljkama porijeklom iz tih istih provenijencija. U pokusnom nasadu mjeren je i indeks relativnog sadržaja ukupnih klorofila i stopa neto fotosinteze. Provenijencija Pula u odnosu na provenijencije Zadar i Bar ima veću specifičnu lisnu površinu te manji indeks relativnog sadržaja ukupnih klorofila i stopu neto fotosinteze. To potvrđuje prilagodbu provenijencije Pula na vlažnije stanište, a provenijencija Zadar i Bar na suše stanište te ujedno ukazuje na funkcionalnu diferencijaciju provenijencija hrasta crnike na istočnoj obali Jadranskoga mora s obzirom na klimatske prilike. Isti obrazac diferencijacije prema specifičnoj lisnoj površini u prirodnim sastojinama i pokusnom nasadu ukazuje na ekotipsku diferencijaciju istraživanih provenijencija. Prema tomu, hrast crnika mogao bi imati značajnu mogućnost funkcionalne prilagodbe na promijenjene klimatske uvjete.

Thinning decreased soil respiration differently in two dryland Mediterranean forests with contrasted soil temperature and humidity regimes

The effects of a thinning treatment on soil respiration (Rs) were analysed in two dryland forest types with a Mediterranean climate in east Spain: a dry subhumid holm oak forest (Quercus ilex subsp. ballota) in La Hunde; a semiarid postfire regenerated Aleppo pine (Pinus halepensis) forest in Sierra Calderona. Two twin plots were established at each site: one was thinned and the other was the control. Rs, soil humidity and temperature were measured regularly in the field at nine points per plot distributed into three blocks along the slope for 3 years at HU and for 2 years at CA after forest treatment. Soil heterotrophic activity was measured in laboratory on soil samples obtained bimonthly from December 2012 to June 2013 at the HU site. Seasonal Rs distribution gave low values in winter, began to increase in spring before lowering as soil dried in summer. This scenario indicates that with a semiarid climate, soil respiration is controlled by both soil humidity and soil temperature. Throughout the study period, the mean Rs value in the HU C plot was 13% higher than at HU T, and was 26% higher at CA C than the corresponding CA T plot value, being the differences significantly higher in control plots during active growing periods. Soil microclimatic variables explain the biggest proportion of variability for Rs: soil temperature explained 24.1% of total variability for Rs in the dry subhumid forest; soil humidity accounted for 24.6% of total variability for Rs in the semiarid forest. As Mediterranean climates are characterised by wide interannual variability, Rs showed considerable variability over the years, which can mask the effect caused by thinning treatment.

Effect and Response of Quercus ilex subsp. ballota [Desf.] Samp. Seedlings From Three Contrasting Andalusian Populations to Individual and Combined Phytophthora cinnamomi and Drought Stresses

Quercus ilex L. is the dominant species in the Mediterranean forest and agrosilvopastoral ecosystem “dehesa.” Currently, this forest species is threatened by natural and anthropogenic agents, especially by the decline syndrome, which is caused by Phytophthora cinnamomi and drought periods. Although the morphological and physiological responses of Q. ilex to combined stress (P. cinnamomi and drought) have been examined already, little is known at the molecular level. In this study, we studied the effect and response of 8-month seedlings from three contrasting Andalusian populations (Seville [Se], Granada [Gr], and Almeria [Al]) to the individual and combined stresses of P. cinnamomi and drought from morphological, physiological, biochemical, and proteomics data. Whereas, seedling damage (leaf chlorosis and necrosis) and mortality were greater under the combined stresses in the three populations, the effect of each individual stress was population-dependent. Resilient individuals were found in all the populations at different percentages. The decrease in leaf chlorophyll fluorescence, photosynthetic activity, and stomatal conductance observed in undamaged seedlings was greater in the presence of both stresses, the three populations responding similarly to drought and P. cinnamomi. Biochemical and proteomic analyses of undamaged seedlings from the two most markedly contrasting populations (Se and Al) revealed the absence of significant differences in the contents in photosynthetic pigments, amino acids, and phenolics among treatments. The Se and Al populations exhibited changes in protein profile in response to the different treatments, with 83 variable proteins in the former population and 223 in the latter. Variable proteins belonged to 16 different functional groups, the best represented among which were protein folding, sorting and degradation, carbohydrate, amino acid, and secondary metabolism, photosynthesis, and ROS scavenging. While photosynthetic proteins were mainly downaccumulated, those of stress-responsive were upaccumulated. Although no treatment-specific response was observed in any functional group, differences in abundance were especially marked under the combined stresses. The following variable proteins are proposed as putative markers for resilience in Q. ilex, namely, aldehyde dehydrogenase, glucose-6-phosphate isomerase, 50S ribosomal protein L5, and α-1,4-glucan-protein synthase [UDP-forming].

Evaluation of Nutritional, Phytochemical, and Mineral Composition of Selected Medicinal Plants for Therapeutic Uses from Cold Desert of Western Himalaya

The aim of this study was to determine the elemental and nutritive values of leaf parts of 10 selected wild medicinal plants, Acer pictum, Acer caecium, Betula utilis, Oxalis corniculata, Euphorbia pilosa, Heracleum lanatum, Urtica dioica, Berberis lycium, Berberis asiaticaand, and Quercus ilex, collected from the high hills of the Chitkul range in district Kinnaur, Western Himalaya. The nutritional characteristics of medicinal plant species were analyzed by using muffle furnace and micro-Kjeldahl methods, and the mineral content in plants was analyzed through atomic absorption spectrometry. The highest percentage of used value was reported in Betula utilis (0.42) and the lowest in Quercus ilex (0.17). In this study, it was found that new generations are not much interested in traditional knowledge of ethnomedicinal plants due to modernization in society. Therefore, there is an urgent need to document ethnomedicinal plants along with their phytochemical and minerals analysis in study sites. It was found that rural people in western Himalaya are dependent on wild medicinal plants, and certain steps must be taken to conserve these plants from extinction in the cold desert of Himalayan region. They are an alternative source of medicine because they contain saponin, alkaloid, and flavonoid etc. as well as minerals. The leaves used for analysis possesses good mineral content, such as Na, N, K, P, Zn, Fe, Cu, Mn, Ca, Mg, and S. Hence, in the current study it was observed that medicinal plants are not only used for therapeutic purposes, but they can also be used as nutritional supplements.

Antioxidant and Antibacterial Effects of Pollen Extracts on Human Multidrug-Resistant Pathogenic Bacteria

The present work was designed to search the possible antibacterial effect of the ethanolic extract of pollens from six botanical origins, Punica granatum, Quercus ilex, Centaurium erythraea, Coriandrum sativum, Ruta graveolens, and Citrus aurantium, against multidrug pathogenic bacteria, Escherichia coli, Pseudomonas aeruginosa, Enterobacter cloacae, Acinetobacter baumannii, Klebsiella pneumoniae, and Staphylococcus aureus. The content of phenolic compounds, flavones, and flavonols was measured. The antioxidant activities were evaluated using four assays: total antioxidant capacity, DPPH, ABTS, and reducing power. Antibacterial activity was studied using the agar disk diffusion method, and the MIC and MBC were determined. Results obtained showed a positive correlation between the antioxidant content of pollen extracts and the antibacterial capacity, Punica granatum and Quercus ilex pollen extracts were the most efficient against Gram-positive and Gram-negative bacteria, and Centaurium erythraea, Coriandrum sativum, and Ruta graveolens had a moderate effect, while Citrus aurantium had no antibacterial effect. It is concluded that pollens can be a good source of bioactive molecules that exhibit potent antioxidant effects and strong antibacterial activities.