STRUCTURAL AND FUNCTIONAL VARIABILITY OF HOLM OAK (QUERCUS ILEX L.) IN DIFFERENT CONDITIONS OF WATER AVAILABILITY

A: Biogeography and history.- The ecological significance of sclerophyllous oak forests in the western part of the Mediterranean basin: a note on pollen analytical data.- Biogeography, ecology and history of Mediterranean Quercus ilex ecosystems.- Notes on Quercus ilex L. in Liguria (NW Italy).- B: Structure, productivity and dynamics.- Structure, biomass and production of a resprouted holm-oak (Quercus ilex L.) forest in NE Spain.- Factors affecting radial growth of Quercus ilex L. in a coppice stand in southern France.- Litterfall as a measure of primary production in Mediterranean holm-oak forest.- Growth and yield of young Quercus ilex coppice stands in the Tafferte forest (Morocco).- Comparative phenology and growth in different species of the Mediterranean maquis of central Italy.- Dynamics of holm oak (Quercus ilex L.) coppices after clearcutting in southern France Flora and life cycles changes.- Variation in the genetic structure and reproductive biology of holm oak populations.- Evidence for hybridization between sympatric holm-oak and cork-oak in Spain based on diagnostic enzyme markers.- Temperature-vegetation structure interaction: the effect on the activity of the ant Messor barbarus (L.).- What are the consequences of being a downy oak (Quercus pubescens) or a holm oak (Q. ilex) for breeding blue tits (Parus caeruleus)?.- C: Water relationships.- The influence of summer and winter stress and water relationships on the distribution of Quercus ilex L..- Quercus ilex facing water stress: a functional equilibrium hypothesis.- Morphological adaptions of Quercus ilex leaves in the Castelporziano forest.- Evaluation of actual evapotranspiration of a Quercus ilex L. stand by the Bowen Ratio-Energy Budget method.- Comparison of the hydrological characteristics of three small experimental holm oak forested catchments in NE Spain in relation to larger areas.- Comparative water relations of four Mediterranean oak species.- Daily and seasonal variation in water relations of macchia shrubs and trees in France (Montpellier) and Turkey (Antalya).- Water relations of cork-oak (Quercus suber L.) under natural conditions.- D: Nutrient cycling and budget.- Is primary production in holm oak forests nutrient limited? A correlational approach.- Organic matter distribution and fluxes within a holm oak (Quercus ilex L.) stand in the Etna volcano A synthesis.- The efficiency of nitrogen retranslocation from leaf biomass in Quercus ilex ecosystems.- Litter dynamics in post-fire successional forests of Quercus ilex.- Soil nitrogen dynamics in a holm oak forest.- Decomposition rate of Quercus rotundifolia leaves in an evergreen oak forest of the Duero Basin (Province of Zamora, Spain).- Productivity and nutrient uptake in a holm oak (Quercus ilex L.) stand and during regeneration after clearcut.- Variation in tissue element concentrations in Quercus ilex L. over a range of different soils.- Preliminary results of a fertilization-irrigation experiment in a Quercus ilex L. forest in relation to leaves and twigs characteristics.- The role of Diplopoda litter grazing activity recycling processes in a Mediterranean climate.- E: Management.- Ecological dynamics of Quercus dominated woodlands in California and southern Spain: a state-transition model.- Old holm oak coppices... new sylvopastoral practices.- Quercus ilex browse utilization by Caprini in Sierra de Cazorla and Segura (Spain).- Ecology of vegetative regeneration after coppicing in macchia stands in central Italy.- Matter transfer and land use by cattle in a dehesa ecosystem of central Spain.- Regeneration by sprouting of holm oak (Quercus ilex) stands exploited by selection thinning.- Effect of cleaning and thinning on height growth and girth increment in holm oak coppices (Quercus ilex L.).- List of Contributors.

Despite the huge biodiversity characterizing the Mediterranean environment, environmental constraints, such as high sunlight and high temperatures alongside with dry periods, make plant survival hard. In addition, high irradiance leads to increasing ozone (O3 ) concentrations in ambient air. In this era of global warming, it is necessary to understand the mechanisms that allow native species to tolerate these environmental constraints and how such mechanisms interact. Three Mediterranean oak species (Quercus ilex, Quercus pubescens and Quercus cerris) with different features (drought tolerant, evergreen or deciduous species) were selected to assess their biometrical, physiological and biochemical responses under drought and/or O3 stress (80-100 nl l(-1) of O3 for 5 h day(-1) for 77 consecutive days). Leaf visible injury appeared only under drought stress (alone or combined with O3 ) in all three species. Drought × O3 induced strong reductions in leaf dry weight in Q. pubescens and Q. cerris (-70 and -75%, respectively). Alterations in physiological (i.e. decrease in maximum carboxylation rate) and biochemical parameters (i.e. increase in proline content and build-up of malondialdehyde by-products) occurred in all the three species, although drought represented the major determinant. Quercus ilex and Q. pubescens, which co-occur in dry environments, were more tolerant to drought and drought × O3 . Quercus ilex was the species in which oxidative stress occurred only when drought was applied with O3 . High plasticity at a biochemical level (i.e. proline content) and evergreen habitus are likely on the basis of the higher tolerance of Q. ilex.

Resprout and mature plant shoot growth, leaf water status and gas exchange behavior, tissue nutrient content, flowering, and production were studied for co-occurring shallow-rooted (Arbutus unedo L.) and deeprooted (Quercus ilex L.) Mediterranean tree species at the Collserola Natural Park in Northeast Spain Resprouts showed higher growth rates than mature plant shoots. During fall, no differences in eco-physiological performance of leaves were found, but mobilization of carbohydrates from burls strongly stimulated growth of fall resprouts compared to spring resprouts, despite low exposed leaf area of the fall shoots. During summer drought, resprouts exhibited improved water status and carbon fixation compared to mature plant shoots. Shoot growth of Q. ilex was apparently extended due to deep rooting so that initial slower growth during spring and early summer as compared to A. unedo was compensated. Tissue nutrient contents varied only slightly and are postulated to be of minor importance in controlling rate of shoot growth, perhaps due to the relatively fertile soil of the site. Fall flowering appeared to inhibit fall shoot growth in A. unedo, but did not occur in Q. ilex. The results demonstrate that comparative examinations utilizing vegetation elements with differing morphological and physiological adaptations can be used to analyze relatively complex phenomena related to resprouting behavior. The studies provide an important multi-dimensional background framework for further studies of resprouting in the European Mediterranean region.

O 3 and O 3+CO 2 effects on a mediterranean evergreen broadleaf tree, holm oak ( Quercus ilex L.)

Abstract: Cork oak and holm oak share a large part of their natural range, and are known to hybridize in mixed stands. This hybridization is supposed to have played a relevant role in the past history of cork oak. Previous research has reported that F1 hybrids are produced with holm oak acting as pollen recipient, therefore carrying holm oak chloroplast. Additionally, F1 hybrids have been assumed to be pollinated mostly by cork oak. Continued backcrossing of F1 hybrids with cork oak (supported by flowering phenology) could have created the organellar introgression patterns observed nowadays in Eastern Spain and Southern France cork oak populations. On the contrary, no organellar introgression has been detected in holm oak and multiple generation backcross individuals to holm oak have not been reported so far. In this work, we examined whether hybrids preferentially backcross with cork oak or with holm oak. To reach this goal, we genotyped by using eight microsatellite loci the progeny of four cork and four holm oak trees (33 and 44 half-siblings, respectively), and of four hybrids (468 half-siblings) collected over three years from a natural mixed population. We used the STRUCTURE software to estimate the proportion of the genotype of each seedling inherited from cork oak (qs) or from holm oak (qi). The ratio of the offspring q value over the mother q value helped determine the source of pollen that originated each acorn. Our results show for the first time that hybrid trees can be effectively pollinated by both parental species. Additionally, each hybrid tree was predominantly pollinated by the most abundant oak species in its vicinity. These results confirm the occurrence of bidirectional introgression, previously suggested for adult hybrid trees in the field, and point out the pattern of introgression in the seedlings could be most affected by the abundance of the parental species.

Fire-driven oak regeneration in French Mediterranean ecosystems

SummaryClimate change and pathogen outbreaks are the two major causes of decline in Mediterranean holm oak trees (Quercus ilex L. subsp. ballota (Desf.) Samp.). Crown‐level changes in response to these stressful conditions have been widely documented but the responses of the root systems remain unexplored. The effects of environmental stress over roots and its potential role during the declining process need to be evaluated.We aimed to study how key morphological and architectural root parameters and nonstructural carbohydrates of roots are affected along a holm oak health gradient (i.e. within healthy, susceptible and declining trees).Holm oaks with different health statuses had different soil resource‐uptake strategies. While healthy and susceptible trees showed a conservative resource‐uptake strategy independently of soil nutrient availability, declining trees optimized soil resource acquisition by increasing the phenotypic plasticity of their fine root system.This increase in fine root phenotypic plasticity in declining holm oaks represents an energy‐consuming strategy promoted to cope with the stress and at the expense of foliage maintenance. Our study describes a potential feedback loop resulting from strong unprecedented belowground stress that ultimately may lead to poor adaptation and tree death in the Spanish dehesa.

Holm oak (Quercus ilex ssp. ballota (Desf.) Samp) is one of the most important species in forest communities of the western Mediterranean Basin, but is very vulnerable to environmental stress during the first years of its life. In particular, summer drought and winter frosts limit the distribution, survival, and growth of Holm oak. These two stress factors can lead to plasmolysis and/or oxidative stress. We hypothesized that autumn fertilization with nitrogen (N) can improve plant tolerance to these abiotic stress factors and improve plant quality and there- fore reforestation success. A 12-week autumn application of 30 or 60 mg N (plus 70 mg N applied to both treatments during the previous 28 weeks in the nursery, i.e. 100 and 130 mg N in total, respectively) improved overall growth, root growth capacity, frost tolerance, and nutritional status of plants relative to plants given 0.0 and 1.5 mg autumnal N, and had no negative effect on seedling response to water stress. A very small increment in N doses during the autumn (1.5 vs. 0.0 mg N) improved some morphological parameters, such as stem diameter (D) and shoot dry weight, and physiological parameters, such as total anti- oxidant activity. The highest autumnal N dose (60 mg) increased leaf nutrient content without decreasing the concentration, but had a tendency to reduce frost tolerance relative to seedlings given a lower autumnal N dose (30 mg).

Paleoecology can provide valuable insights into the ecology of species that complement observation and experiment‐based assessments of climate impact dynamics. New paleoecological records (e.g., pollen, macrofossils) from the Italian Peninsula suggest a much wider climatic niche of the important European tree species Abies alba (silver fir) than observed in its present spatial range. To explore this discrepancy between current and past distribution of the species, we analyzed climatic data (temperature, precipitation, frost, humidity, sunshine) and vegetation‐independent paleoclimatic reconstructions (e.g., lake levels, chironomids) and use global coupled carbon‐cycle climate (NCAR CSM1.4) and dynamic vegetation (LandClim) modeling. The combined evidence suggests that during the mid‐Holocene (∼6000 years ago), prior to humanization of vegetation, A. alba formed forests under conditions that exceeded the modern (1961–1990) upper temperature limit of the species by ∼5–7°C (July means). Annual precipitation during this natural period was comparable to today (>700–800 mm), with drier summers and wetter winters. In the meso‐Mediterranean to sub‐Mediterranean forests A. alba co‐occurred with thermophilous taxa such as Quercus ilex, Q. pubescens, Olea europaea, Phillyrea, Arbutus, Cistus, Tilia, Ulmus, Acer, Hedera helix, Ilex aquifolium, Taxus, and Vitis. Results from the last interglacial (ca. 130 000–115 000 BP), when human impact was negligible, corroborate the Holocene evidence. Thermophilous Mediterranean A. alba stands became extinct during the last 5000 years when land‐use pressure and specifically excessive anthropogenic fire and browsing disturbance increased. Our results imply that the ecology of this key European tree species is not yet well understood. On the basis of the reconstructed realized climatic niche of the species, we anticipate that the future geographic range of A. alba may not contract regardless of migration success, even if climate should become significantly warmer than today with summer temperatures increasing by up to 5–7°C, as long as precipitation does not fall below 700–800 mm/yr, and anthropogenic disturbance (e.g., fire, browsing) does not become excessive. Our finding contradicts recent studies that projected range contractions under global‐warming scenarios, but did not factor how millennia of human impacts reduced the realized climatic niche of A. alba.

Acorn fruit oils from two species of oak, Quercus rotundifolia L. (holm-oak) and Quercus suber L. (cork-oak), were extracted by n-hexane. The acorn fruit of Quercus rotundifolia L. was also extracted by supercritical CO 2 at 18 MPa and 313 K, a superficial velocity of 2.5 x 10 -4 ms -1 , and a particle size diameter of 2.7 x 10 -4 m. The oils were characterised in terms of fatty acids, triglycerides, sterols, tocopherols, and phospholipids. The main fatty acid in both fruit species was oleic acid (about 65%), followed by linoleic acid (about 16.5-17%) and palmitic acid (about 12.1-13.4%). The main triglyceride found in acorn oils was the 000 (oleic, oleic, oleic) triglyceride (33-38%), followed by the POO (palmitic, oleic, oleic) triglyceride (12.6-18.2%). In terms of sterols, the main component in acorn oils of both species was β-sitosterol (83.5-89%), followed by stigmasterol (about 3%). However, in Quercus suberL., acorn oil was found to consist to 10.2% of campesterol. The amount of cholesterol was low (0.27% for the Quercus rotundifolia L. oil extracted by supercritical fluid extraction, and 0.18% for the oil extracted by n-hexane). The Quercus suber L. acorn oil presented 0.1 % of cholesterol. The total amount of tocopherols in Quercus rotundifolia L. acorn oils was almost the same when the oil was extracted by n-hexane (973 mg/kg oil) or by supercritical CO 2 (1006 mg/kg oil). The Quercus suber L. acorn oil presented a high value of total tocopherols (1486 mg/kg oil). The supercritical CO 2 did not extract the phospholipids. The amount of phospholipids was very similar for both species of oak acorn oils extracted by n-hexane. Oxidative stability was also studied, by using the peroxide value and the Rancimat method, revealing that all the oils were significantly protected against oxidation. The influence of storage, under several conditions, on the oxidative stability was also studied. The Quercus rotundifolia L. oil extracted by n-hexane was better protected against oxidation after a few days of storage at 60 °C.

Aims: Drought stress may affect the Morphology, biochemistry, growth, and physiology of Brassica juncea (Indian mustard), a low-cost, oil-yielding, and economically significant plant. In this paper assessing various growth, morphological, and physiological parameters under different irrigation regimes could offer some significant information for the selection of a suitable and appropriate genotype for breeding. Study Design: Two commonly grown cultivars (RH-725 and RH-749) of mustard in Haryana under four irrigation regimes were evaluated. The applied Irrigation regimes were: control (double irrigation: once at the 50% flowering and another at the 50% fruiting stages), early irrigation (at 50% flowering only), late irrigation (at 50% fruiting only), and stress (no irrigation). The plants were exposed to short-term water shortages during the vegetative and reproductive growth stages. Drought stress in both stages had a negative effect on the morphological and physiological parameters of mustard. Place and Duration of Study: An open field experiment was performed at the Nursery of Kurukshetra University, Kurukshetra, Haryana, India, located at the latitude of 290–95° north and longitude of 760–82° east, with a height of 258.4 m above sea level. Crop sown under field conditions from October to March for two consecutive years (2018-2019, 2019-2020) at a temperature of 30-32 °C (days) and 15-25 °C (nights). Methodology: Measured adaptability using 15 morphological, 4 physiological, and 7 different growth parameters. PCA data revealed that physiological and growth parameters are more sensitive than morphological parameters in distinguishing the control and drought treatments. Alterations in physiological parameters occurred at all three levels of water stress. Growth analysis and yield parameters decreased with the severity of stress. Drought-stress treatments gradually reduced the Morphological and physiological traits of mustard. Results: The study revealed a relationship between Brassica species' adaptation to drought stress and the rapidity, severity, and duration of the drought event. This highlights the importance of considering these factors while selecting genotypes for breeding programmes aimed at improving drought tolerance in B. juncea. Overall, the research provides valuable information for selecting suitable and appropriate genotypes for breeding drought-tolerant varieties of B. juncea. By understanding the specific physiological (relative water content, leaf osmotic potential, membrane stability index, electrolytic index) and growth parameters (plant height, root length, fresh and dry weight of leaves and roots, leaf area etc.) that are more sensitive to drought stress. Furthermore, this study revealed a relationship between Brassica species' adaptation to drought stress and the rapidity, severity, and duration of the drought event. Based on PCA values, the cultivar RH-749 performed better both morphologically and physiologically under all stress conditions compared to RH-725. This suggests that RH-749 is more adapted and tolerant to drought stress, making it a potential candidate for breeding and cultivation in water-limited environments.

The retinal ganglion cells (RGCs) have diverse morphology and physiology. Although some studies show that correlations between morphological properties and physiological properties exist in cat RGCs, these properties are much less distinct and their correlations are unknown in mouse RGCs. In this study, using three-dimensional digital neuron reconstruction, we systematically analyzed twelve morphological parameters of mouse RGCs as they developed in the first four postnatal weeks. The development of these parameters fell into three different patterns and suggested that contact from bipolar cells and eye opening might play important roles in RGC morphological development. Although there has been a general impression that the morphological parameters are not independent, such as RGCs with larger dendritic fields usually have longer but sparser dendrites, there was not systematic study and statistical analysis proving it. We used Pearson's correlation coefficients to determine the relationship among these morphological parameters and demonstrated that many morphological parameters showed high statistical correlation. In the same cells we also measured seven physiological parameters using whole-cell patch-clamp recording, focusing on intrinsic excitability. We previously reported the increase in intrinsic excitability in mouse RGCs during early postnatal development. Here we showed that strong correlations also existed among many physiological parameters that measure the intrinsic excitability. However, Pearson's correlation coefficient revealed very limited correlation across morphological and physiological parameters. In addition, principle component analysis failed to separate RGCs into clusters using combined morphological and physiological parameters. Therefore, despite strong correlations within the morphological parameters and within the physiological parameters, postnatal mouse RGCs had only limited correlation between morphology and physiology. This may be due to developmental immaturity, or to selection of parameters.

Some technological and physiological aspects were analysed during seed storage of holm oak (Quercus ilex L.), a typical Mediterranean recalcitrant species. Considering the mild dormancy and desiccation sensitivity of these seeds, the influence of the storage environment on viability was examined. Acorns were maintained at low temperature and at high moisture content either inside thin polyethylene bags or mixed with peat in a bin. Storage in polyethylene bags, if compared with peat treatment, maintained optimal seed quality parameters. The effects of the two treatments on some physiological parameters were analysed during 1-year seed storage. Acorns stored in a bin with peat started to germinate early and exhibited a more rapid seed deterioration caused by metabolism-linked oxidative damage. The latter phenomenon was linked to a higher respiration and H2O2 level, induction of catalase activity, as well as lowered glutathione pool and ATP content. In addition, a more oxidized redox poise was observed. On the contrary, the plastic film of polyethylene, limiting gaseous exchanges, maintained acorn metabolic activity at low levels and allowed the accumulation of ethylene inside the storage atmosphere. These factors, inducing a dormant-like state, could have played a crucial role in prolonging seed storage.

ABSTRACTThe total antioxidant activity (TAA) and the accumulation of small heat shock proteins (sHsps) were analysed under field conditions in Quercus ilex with regard to organ ontogeny and the physiological state of the plant. The results point toward the participation of sHsps and an increase of TAA in the general adaptation syndrome (GAS) of woody Mediterranean evergreens. In leaves and stems, there was a definite TAA seasonal pattern but no effect from diurnal variations or from the current stage of organ ontogeny. TAA was about twice as large in summer as in spring and winter and the hydrophilic antioxidant content was about 16 times greater than that of lipophilic antioxidants. The accumulation of sHsps in leaves also showed a seasonal pattern, but no effect from diurnal variations or from leaf ontogeny. In summer days, the sHsps content remained invariable even during the daylight hours in which the leaves were physiologically recovered. However, the accumulation of sHsps in stems did vary in relation to organ ontogeny. Old stems had a high accumulation of sHsps throughout the year, whereas in young stems, accumulation of sHsps was detected only in summer. This is probably due to a higher quantity of lignified and suberized tissues in the older stems. Using two‐dimensional immunodetection for leaves and stems, two sets of Hs protein species (17 and 10 kDa regions) were observed. In stems, there was an increase in 10 kDa proteins from winter to summer. These results are discussed and the possible role of the two types of polypeptides in the face of environmental and endogenous oxidative stress are considered.

High water vapour pressure deficit influence on Quercus ilex and Pinus pinea field monoterpene emission in the central Iberian Peninsula (Spain)