In consideration of their origin the adaptive strategies of the evergreen species of the Mediterranean maquis were analysed. Rosmarinus officinalis L., Erica arborea L., and Erica multiflora L. had the lowest net photosynthetic rate (PN) in the favourable period [7.8±0.6 μmol(CO2) m-2s-1, mean value], the highest PN decrease (on an average 86 % of the maximum) but the highest recovery capacity (>70 % of the maximum) at the first rainfall in September. Cistus incanus L. and Arbutus unedo L. had the highest PN during the favourable period [15.5±5.2 μmol(CO2) m-2s-1, mean value], 79 % decrease during drought, and a lower recovery capacity (on an average 54 %). Quercus ilex L., Phillyrea latifolia L., and Pistacia lentiscus L. had an intermediate PN in the favourable period [9.2±1.3 μmol(CO2) m-2s-1, mean value], a lower reduction during drought (on an average 63 %), and a range from 62 % (Q. ilex and P. latifolia) to 39 % (P. lentiscus) of recovery capacity. The Mediterranean species had higher decrease in PN and stomatal conductance during drought and a higher recovery capacity than the pre-Mediterranean species. Among the pre-Mediterranean species, P. latifoliahad the best adaptation to long drought periods also by its higher leaf mass per area (LMA) which lowered leaf temperature thus decreasing transpiration rate during drought. Moreover, its leaf longevity determined a more stable leaf biomass during the year. Among the Mediteranean species, R. officinalis was the best adapted species to short drought periods by its ability to rapidly recover. Nevertheless, R. officinalis had the lowest tolerance to high temperatures by its PN dropping below half its maximum value when leaf temperature was over 33.6°C. R. officinalismay be used as a bioindicator species of global change. and L. Gratani, L. Varone.
Morphological, anatomical, and physiological leaf traits of Corylus avellana plants growing in different light conditions within the natural reserve "Siro Negri" (Italy) were analyzed. The results highlighted the capability of C. avellana to grow both in sun and shade conditions throughout several adaptations at leaf level. In particular, the more than 100% higher specific leaf area in shade is associated to a 44% lower palisade to spongy parenchyma thickness ratio compared with that in sun. Moreover, the chlorophyll (Chl) a to Chl b ratio decreased in response to the 97% decrease in photosynthetic photon flux density. The results highlighted the decrease in the ratio of Chl to carotenoid content, the maximum PSII photochemical efficiency, and the actual PSII photochemical efficiency (ΦPSII) associated with the increase in the ratio of photorespiration to net photosynthesis (PN) in sun. Chl a/b ratio was the most significant variable explaining PN variations in shade. In sun, PN was most influenced by the ratio between the fraction of electron transport rate (ETR) used for CO2 assimilation and ETR used for photorespiration, by ΦPSII, nitrogen content per leaf area, and by total Chl content per leaf area. The high phenotypic plasticity of C. avellana (PI = 0.33) shows its responsiveness to light variations. In particular, a greater plasticity of morphological (PIm = 0.41) than of physiological (PIp = 0.36) and anatomical traits (PIa = 0.24) attests to the shade tolerance of the species., R. Catoni, M.U. Granata, F. Sartori, L. Varone, L. Gratani., and Obsahuje bibliografii
The relationships between dark respiration rate (RD) and net photosynthetic rate (PN) in Quercus ilex L. shrubs growing at the Botanical Garden in Rome were analysed. Correlation analysis of the data sets collected in the year 2006 confirmed the dependence among the considered leaf traits, in particular, RD was significantly (p<0.05) correlated with PN (r = 0.40). RD and PN increased from March to May [1.40±0.10 and 10.1±1.8 µmol(CO2) m-2 s-1 mean values of the period, respectively], when air temperature was in the range 14.8-25.2 °C, underlining the highest metabolic activity in the period of the maximum vegetative activity that favoured biomass accumulation. On the contrary, the highest RD [1.60±0.02 µmol(CO2) m-2 s-1], associated to the lowest PN rates (44 % of the maximum) and carbon use efficiency (CUE) in July underlined the mobilization of stored material during drought stress by a higher air temperature (32.7 °C). and L. Gratani, L. Varone, A. Bonito.
Seedlings of Bidens cernua L. emerged when mean air temperature was 17.0±1.3 °C. The highest net photosynthetic rate (PN), 13.8±0.8 µmol(CO2) m-2 s-1, was monitored during the vegetative period (May-August), decreasing on an average by 50 % during flowering (August-September) and during fruiting (September-November) phases. The senescence phase (October-November) was characterised by 79, 58, and 18 % decrease of PN, chlorophyll content, and leaf area (LA), respectively, from the maximum values. The time span from seedling emergence to the end of fruiting phase was 202 d. The total plant biomass was 1.58±0.05 g of which 81 % was aboveground plant portion. The total dry mass relative growth rate averaged over the assimilation period was 0.0804±0.0002 kg kg-1 d-1, and it was correlated to both the net assimilation rate (NAR) and the leaf area ratio (LAR). and L. Gratani ... [et al.].
Leaf gas exchange and plant water relations of three co-occurring evergreen Mediterranean shrubs species, Quercus ilex L. and Phillyrea latifolia L. (typical evergreen sclerophyllous shrubs) and Cistus incanus L. (a drought semi-deciduous shrub), were investigated in order to evaluate possible differences in their adaptive strategies, in particular with respect to drought stress. C. incanus showed the highest annual rate of net photosynthetic rate (PN) and stomatal conductance (gs) decreasing by 67 and 69 %, respectively, in summer. P. latifolia and Q. ilex showed lower annual maximum PN and gs, although PN was less lowered in summer (40 and 37 %, respectively). P. latifolia reached the lowest midday leaf water potential (Ψ1) during the drought period (-3.54±0.36 MPa), 11 % lower than in C. incanus and 19 % lower than in Q. ilex. Leaf relative water content (RWC) showed the same trend as Ψ1. C. incanus showed the lowest RWC values during the drought period (60 %) while they were never below 76 % in P. latifolia and Q. ilex; moreover C. incanus showed the lowest recovery of Ψ1 at sunset. Hence the studied species are well adapted to the prevailing environment in Mediterranean climate areas, but they show different adaptive strategies that may be useful for their co-occurrence in the same habitat. However, Q. ilex and P. latifolia by their water use strategy seem to be less sensitive to drought stress than C. incanus. and A. Bombelli, L. Gratani.
There are significant differences in leaf life-span among evergreen sclerophyllous species and drought semideciduous species growing in the Mediterranean maquis. Cistus incamus, which has a leaf life-span of four-eight months, was characterised by the highest net photosynthetic rates (PN), while Quercus ilex and Phillyrea latifolia, which maintain their leaves two-three and two-four years, respectively, had a lower PN. The longer leaf life-span of the two evergreen sclerophyllous species may be justified to cover the high production costs of leaf protective structures such as cuticle, hairs, and sclereids: cuticle and hairs screen radiation penetrating into the more sensitive tissues, and sclereids have a light-guiding function. Q. ilex and P. latifolia have the highest leaf mass/area ratio (LMA = 209 g m-2) and a mesophyll leaf density (2065 cells per mm2 of leaf cross section area) about two times higher than C. incanus. In the typical evergreen sclerophyllous species the steepest leaf inclination (α = 56°) reduces 42 % of radiation absorption, resulting in a reduced physiological stress at leaf level, particularly in summer. C. incanus, because of its low leaf life-span, requires a lower leaf investment in leaf protective structures. It exhibits a drastic reduction of winter leaves just before summer drought, replacing them with smaller folded leaves. The lower leaf inclination (α = 44°) and the lower LMA (119 g m-2) of C. incanus complement photosynthetic performance. Water use efficiency (WUE) showed the same trend in Q. ilex, P. latifolia, and C. incanus, decreasing 60 % from spring to summer, due to the combined effects of decreased CO2 uptake and increased transpirational water loss. and L. Gratani, A. Bombelli.
The morphological, anatomical and physiological variations of leaf traits were analysed during Quercus ilex L. leaf expansion. The leaf water content (LWC), leaf area relative growth rate (RGRl) and leaf dry mass relative growth rate (RGRm) were the highest (76±2 %, 0.413 cm2 cm-2 d-1, 0.709 mg mg-1 d-1, respectively) at the beginning of the leaf expansion process (7 days after bud break). Leaf expansion lasted 84±2 days when air temperature ranged from 13.3±0.8 to 27.6±0.9 °C. The net photosynthetic rate (PN), stomatal conductance (g s), and chlorophyll content per fresh mass (Chl) increased during leaf expansion, having the highest values [12.62±1.64 µmol (CO2) m-2 s-1, 0.090 mol (H2O) m-2 s-1, and 1.03±0.08 mg g-1, respectively] 56 days after bud break. Chl was directly correlated with leaf dry mass (DM) and P N. The thickness of palisade parenchyma contributed to the total leaf thickness (263.1±1.5 µm) by 47 %, spongy layer thickness 38 %, adaxial epidermis and cuticle thickness 9 %, and abaxial epidermis and cuticle thickness 6 %. Variation in leaf size during leaf expansion might be attributed to a combination of cells density and length, and it is confirmed by the significant (p<0.001) correlations among these traits. Q. ilex leaves reached 90 % of their definitive structure before the most severe drought period (beginning of June - end of August). The high leaf mass area (LMA, 15.1±0.6 mg cm-2) at full leaf expansion was indicative of compact leaves (2028±100 cells mm-2). Air temperature increasing might shorten the favourable period for leaf expansion, thus changing the final amount of biomass per unit leaf area of Q. ilex. and L. Gratani, A. Bonito.
Global climate change may act as a potent agent of natural selection within species with Mediterranean mountain ecosystems being particularly vulnerable. The aim of this research was to analyze whether the phenotypic plasticity of Sesleria nitida Ten. could be indicative of its future adaptive capability to global warming. Morphological, anatomical, and physiological leaf traits of two populations of S. nitida growing at different altitudes on Mount Terminillo (Italy) were analyzed. The results showed that leaf mass per unit leaf area, leaf tissue density, and total leaf thickness were 19, 3, and 31% higher in leaves from the population growing at 1,895 m a.s.l. (B site) than in leaves from the population growing at 1,100 m a.s.l. (A site), respectively. Net photosynthetic rate (PN) and respiration rate (RD) peaked in June in both A and B leaves [9.4 +- 1.3 μmol(CO2) m-2 s-1 and 2.9 +- 0.9 μmol(CO2) m-2 s-1, respectively] when mean air temperature was 16 +- 2°C. R D/P N was higher in B than in A leaves (0.35 +- 0.07 and 0.21 +- 0.03, respectively, mean of the study period). The mean plasticity index (PI = 0.24, mean of morphological, anatomical, and physiological leaf traits) reflected S. nitida adaptability to the environmental stress conditions at different altitudes on Mount Terminillo. Moreover, the leaf key traits of the two populations can be used to monitor wild populations over a long term in response to global change., L. Gratani, M. F. Crescente, V. D’Amato, C. Ricotta, A. R. Frattaroli, G. Puglielli., and Obsahuje bibliografii
Morphological (dry mass, DM; surface area, LA; leaf mass per area, LMA), anatomical (leaf thickness, L), phenological (leaf life span, LL), and physiological (net photosynthetic rate, PN) leaf traits of the evergreen species co-occurring in the Mediterranean maquis developing at Castelporziano (Rome) were tested. The correlation analysis indicated that LMA variation was tightly associated with LL variations: Cistus incanus and Arbutus unedo had a short LL (4±1, summer leaves, and 11±1 months, respectively) and low LMA (153±19 g m-2) values, Quercus ilex, Phillyrea latifolia, and Pistacia lentiscus high LMA (204±7 g m-2) and long LL (22±3 months), Erica arborea, Erica multiflora, and Rosmarinus officinalis a short LL (9±2 months) and an either high (213±29 g m-2, R. officinalis and E. multiflora) or low (115±17 g m-2, E. arborea) LMA. LMA values were significantly (p≤0.05) correlated with PN (r≥0.68). In the tested species, LMA increased in response to the decrease of the total rainfall during the leaf expansion period. LMA variation was due to the unequal variation of DM and LA in the considered species. LMA is thus a good indicator of evergreen maquis species capability to respond to climate change, in particular to total rainfall decrease in the Mediterranean basin. and L. Gratani, L. Varone.
Differences in leaf traits among the dune species developing along the Latium coast were analysed. Cakile maritima Scop. subsp. maritima, Elymus farctus (Viv.) Runemark ex Melderis subsp. farctus, Ammophila arenaria (L.) Link subsp. australis (Mabille) Lainz, Ononis variegata L., Pancratium maritimum L., Eryngium maritimum L., and Anthemis maritima L. were considered. The considered species showed a similar net photosynthetic rate (PN) and chlorophyll content (Chl) during the year, with a peak from the end of April to the middle of May [13.0±3.6 μmol (CO2) m-2 s-1 and 0.63±0.21 mg g-1, respectively, mean values of the considered species], favoured by air temperature in the range 13.3-17.5°C, and 6% of soil water availability. In June-July, the increase of air temperature (Tmax = 28.4°C), associated with a lower water availability (42 mm, total rainfall of the period) and a 1% of soil water availability determined a significant decrease of P N (59%, mean of the considered species) and Chl (38%), and an increase of the carotenoid (Car)/Chl ratio (59%). The significant correlation between PN and stomatal conductance (gs) (p<0.05) explained 67% of P N variations. Moreover, the correlation between P N and leaf temperature (Tl) underlined that the favourable Tl enabling 90-100% of the highest PN for the considered species was within the range 23.4 to 26.6°C. P N decreased below half of its maximum value when Tl was over 35.8 and 37.4°C for E. farctus subsp. farctus and A. arenaria subsp. australis, respectively and over 32.2°C for the other considered species (mean value). Leaf mass area (LMA) varied from 6.8 ± 0.7 mg cm-2 (O. variegata) to 30.6 ± 1.6 mg cm-2 (A. arenaria). PCA (principal component analysis) carried out using the considered morphological and physiological leaf traits underlined that the co-occurring species were characterised by different adaptive strategies: E. farctus and A. arenaria photosynthesized for a long period also when air temperature was over 35.8 and 37.4°C, respectively, because of their lower transpiration rates [E, 1.4 ± 0.1 mmol (H2O) m-2 s-1], which seemed to be controlled by the highest LMA. On the contrary, A. maritima and C. maritima subsp. maritima had a higher PN (on an average 52% higher than the others) in the favourable period, allowed by the highest succulence index (SI, 85.7 ± 9 mg cm-2) and the lower LMA. The results allowed us to hypothesize that A. arenaria and E. farctus might be at a competitive advantage relative to the other considered species with respect to the increase of air temperature, by their ability to photosynthesize at sufficient rates also during summer. and L. Gratani, L. Varone, M. F. Crescente.
Plant traits of Malcolmia littorea growing at the Botanic Garden of Rome and transplanted from the wild population developing along the Latium coast (Italy) were analyzed. The highest photosynthetic rates [PN, 22.5 ± 0.5 μmol(CO2) m-2 s-1], associated to the highest chlorophyll content (Chl, 60 ± 5 SPAD units), and respiration rates [R, 11.1 ± 0.2 μmol(CO2) m-2 s-1] were reached in spring, when mean air temperature (Tm) was in the range 17°C to 23°C. PN, Chl, and R decreased by 86, 38, and 59% in summer when mean maximum air temperature (Tmax) was 30.3 ± 2.6°C. Leaf water potential decreased by 34% in summer compared to the spring value, and it was associated to a relative water content (RWC) of 74 ± 4%, and to a water-use efficiency (WUE) of 2.15 ± 0.81 μmol(CO2) mmol-1(H2O). Moreover, also low air temperatures determined a significant PN and R decreases (by 52 and 40% compared to the maximum, respectively). Responsiveness of gross photosynthetic rate (Pg) to R was higher than that to PN as underlined by the slope of the regression line between the two variables. The results underlined a low tolerance to both high- and low air temperatures of M. littorea. The selected key traits (R, WUE, Chl) by the discriminant analysis might be used to monitor the M. littorea wild population in the long time. The ex situ cultivated plants could be propagated and used to increase the individuals number of the wild population. and L. Gratani ... [et al.].
Morphological, anatomical and physiological frond traits of Cheilanthes persica (Bory) Mett. ex Kuhn were studied to analyze its adaptive strategy. Mean frond life span is about 340 d. Mature fronds are characterized by 91 g m-2 areal dry mass (ADM) and 217 g m-2 succulence. The reduction of frond water content in July (dehydration phase) caused a 51 % decrease in frond surface area (SA). Fronds were dry in August (desiccation phase); nevertheless, in September they showed an increased SA (rehydration phase). Chlorophyll (Chl) a/b ratio, above 3, and the well developed palisade parenchyma (two layers, total thickness of 103.9 µm) are typical for sun leaves. Chl and carotenoid contents and net photosynthetic rate (PN) increased during frond development until the highest values in April-May (maturity phase). When mean air temperature reached 31.3 °C, stomatal conductance (gs) decreased by 34 % and PN by 33 %. The high pigment contents can dissipate the excess of radiant energy, particularly under unfavourable conditions, when PN is low. Rather high PN was found during the rehydration stage. The pronounced decline of mesophyll activity during the declining phase was confirmed by the lowest PN. and L. Gratani, M. F. Crescente, G. Rossi.
Morphological and physiological traits of Crepis pygmaea L. subsp. pygmaea and Isatis apennina Ten. ex Grande growing at different altitudes in the Gran Sasso Massif (Abruzzo, Italy) were analyzed. The two populations of C. pygmaea and I. apennina growing at the highest altitude (Cp2 and Ip2 at 2,310 m a.s.l. and 2,350 m a.s.l., respectively) had a lower leaf mass area (LMA) than the two populations growing at the lowest altitude (Cp1 and Ip1 at 2,250 m a.s.l. and 2,310 m a.s.l., respectively). Leaf tissue density (LTD) had the same LMA trend, decreasing 23 and 10% in C. pygmaea and I. apennina, respectively, from the highest to the lowest altitude. C. pygmaea and I. apennina had the highest photosynthetic rates
(PN) in July decreasing on an average 17 and 30%, respectively, in August and 50 and 38%, respectively, in September. Leaf respiration (R) in Ip1 and Ip2 had the same trend as Cp1 and Cp2, showing the highest rates in September. Global warming could drive C. pygmaea and I. apennina toward higher altitudes in the Gran Sasso Massif. Nevertheless, C. pygmaea with the higher plasticity index (PI) both at physiological and at morphological levels (0.50 and 0.35, respectively) might have a competitive advantage over I. apennina over the long term., L. Gratani ... [et al.]., and Obsahuje bibliografii
We analyzed the physiological response of the Mediterranean evergreen species (Arbutus unedo L., Cistus incanus L., Erica arborea L., Erica multiflora L., Phillyrea latifolia L., Pistacia lentiscus L., Quercus ilex L., and Rosmarinus officinalis L.) to winter low air temperatures. In occasion of two cold events, in February 2005 (T min = 1.8 °C), and January 2006 (T min = 3.1 °C and minimum T air = -0.40 °C during the nights preceding the measurements), R. officinalis, C. incanus, and E. multiflora had the highest net photosynthetic rate (PN) decrease (73 %, mean value) with respect to the winter PN maximum, followed by A. unedo (62 %), P. latifolia and P. lentiscus (54 %, mean value), E. arborea (49 %), and Q. ilex (44 %). Among the considered species, Q. ilex was able to maintain PN near the maximum for 150 min during the day, A. unedo, P. lentiscus, E. arborea, P. latifolia, E. multiflora, and R. officinalis for 60 min, and C. incanus for 30 min. The calculated mean winter daily PN ranged from 7.9±0.6 (Q. ilex) to 2.8±0.5 (R. officinalis) µmol(CO2) m-2 s-1. During the study period, chlorophyll (Chl) content decreased by 36 % on an average in the two cold events, and the carotenoid (Car) to Chl ratio increased by 133 % in Q. ilex, having the highest value in January 2006. Principal component analysis underlined the highest cold resistance of Q. ilex by high
PN and high Car/Chl ratio. On the contrary, R. officinalis and C. incanus had the lowest cold resistance by the highest PN decrease and the lowest Car/Chl (C. incanus). Thus, winter stress could be an additional limitation to Mediterranean evergreen species production, and the capacity of the species to maintain PN near 90-100 % during winter is determinant for biomass accumulation. and L. Varone, L. Gratani.
Effects of Quercus ilex acorn size on seedling morphological and physiological traits were analysed. The study was carried out with five populations from different geographical areas and covering an aridity gradient. Seedling morphological traits (height and total leaf area) were analyzed during the first growing year. Physiological traits (net photosynthesis, stomatal conductance, leaf transpiration, and intrinsic water-use efficiency) were analysed at different air temperatures during spring, summer, and winter months, and in response to water stress. There were significant correlations among the considered acorn (volume, fresh mass) and seedling traits. Differences in growth and physiological traits among the considered populations were found. The larger differences in the growth parameters were observed during the first growing season, and they could be justified by the significant differences among acorn size. On the contrary, the physiological response to air temperature and aridity was more related to the geographical origin of the considered populations than to acorn size. Q. ilex acorn and seedling traits more tolerant to drought might have a high potential for vegetation recovery in afforestation projects and restoration programmes particularly under water-limited environments or in degraded areas. and A. Bonito ... [et al.].
The relationship between net photosynthetic (PN) and leaf respiration (R) rates of Quercus ilex, Phillyrea latifolia, Myrtus communis, Arbutus unedo, and Cistus incanus was monitored in the period February 2006 to February 2007. The species investigated had low R and PN during winter, increasing from March to May, when mean air temperature reached 19.2 °C. During the favourable period, C. incanus and A. unedo had a higher mean PN (16.4±2.4 µmol m-2 s-1) than P. latifolia, Q. ilex, and M. communis (10.0±1.3 µmol m-2 s-1). The highest R (1.89±0.30 µmol m-2 s-1, mean of the species), associated to a significant PN decrease (62 % of the maximum, mean value of the species), was measured in July (mean R/PN ratio 0.447±0.091). Q10, indicating the respiration sensitivity to short-term temperature increase, was in the range 1.49 to 2.21. Global change might modify R/PN determining differences in dry matter accumulation among the species, and Q. ilex and P. latifolia might be the most favoured species by their ability to maintain sufficiently higher PN and lower R during stress periods. and L. Gratani, L. Varone, R. Catoni.
The relationship between chlorophyll (Chl) content and net photosynthetic rate (PN) in an isolated Quercus ilex tree, growing inside Villa Pamphili Park in Rome, was explored. The highest PN was in March, May, and September (10.1 μmol m-2 s-1, maximum rate). PN decreased by 65 % (with respect to the yearly maximum) when leaf temperature reached 34 °C, and by 50 % when leaf temperature was 9 °C. The highest Chl contents were in April, October [1.47 g kg-1 (d.m.), maximum value], and December. The lowest Chl content was found in July (0.78 g kg-1). The decrease of PN in July was in close connection with the decrease of Chl content. On the contrary, the high Chl content during winter did not correspond with PN of this season. Discordances between Chl content and PN over the year influenced the regression analysis, which although positive did not show very high correlation coefficients (r = 0.7). The high Chl (a+b) content during most of the year indicated that the photosynthetic apparatus remained basically intact also during stress periods. and L. Gratani, P. Pesoli, M. F. Crescente.
Leaf adaptatíons of Quercus ilex L., Phillyrea latifolia L. and Pistacia lentiscus L. to various environmental conditions námely from the viewpoint of the differences of leaf area, dry mass, chlorophyll (Chl) content, sclerophylly index, succulence index and net photosynthetic rate are shown. Irradiance was the most important factor to miluence leaf temperature, stomatal conductance (g^) and transpiration rate (E). Under canopy layer low red-far red ratio reduced Pn- Shade leaves were enriched by Chl b. Chl content and sclerophylly index were good leaf characteristics to express adaptability of plants to microclimate.
Cistus salvifolius L. is the most widely spread Cistus species around the Mediterranean basin. It colonizes a wide range of habitats growing from sea level to 1,800 m a.s.l., on silicolous and calcicolous soils, in sun areas as well as in the understory of wooded areas. Nevertheless, this species has been mainly investigated in term of its responsiveness to drought. Our aim was to understand which leaf traits allow C. salvifolius to cope with low-light environments. We questioned if biochemical and physiological leaf trait variations in response to a reduced photosynthetic photon flux density were related to leaf morphological plasticity, expressed by variations of specific leaf area (SLA) and its anatomical components (leaf tissue density and thickness). C. salvifolius shrubs growing along the Latium coast (41°43'N,12°18'E, 14 m a.s.l., Italy) in the open and in the understory of a Pinus pinea forest, were selected and the relationships between anatomical, gas exchange, chlorophyll (Chl) fluorescence, and biochemical parameters with SLA and PPFD variations were tested. The obtained results suggested long-term acclimation of the selected shrubs to contrasting light environments. In high-light conditions, leaf nitrogen and Chl contents per leaf area unit, leaf thickness, and Chl a/b ratio increased, thus maximizing net photosynthesis, while in shade photosynthesis, it was downregulated by a significant reduction in the electron transport rate. Nevertheless, the increased pigment-protein complexes and the decreased Chl a/b in shade drove to an increased light-harvesting capacity (i.e. higher actual quantum efficiency of PSII). Moreover, the measured vitality index highlighted the photosynthetic acclimation of C. salvifolius to contrasting light environments. Overall, our results demonstrated the morphological, anatomical, and physiological acclimation of C. salvifolius to a reduced light environment., G. Puglielli, L. Varone, L. Gratani, R. Catoni., and Obsahuje bibliografii
The most representative evergreen shrub species growing in the low mediterranean maquis modified their leaf characteristics during the year, but the response to climate varied among the species. The reál sclerophyllous species, Quercus ilex L., Phillyrea latifolia and Pistacia lentiscus, showed a convergence in higher leaf thickness and lower net photosynthetic rate (P^) compared with Arhuíus unedo L. and Cistus incanus L. Under summer stress they maintained a substantial positive carbon balance. Pistacia was one of the most tolerant species to the drought, it maintained a substantial positive balance over a wide range in temperature. Arhutus and Cistus had relatively thin leaves with a higher succulence index and higher ihe more characteristic sclerophyllous species. The superiority of Cistus in carbon uptake over all the spacies was maintained throughout most of the year by its morphological leaf properties: low leaf thickness, high chlorophyll contents. Besides, Cistus shed most of its leaves before summer, thus reducing its evaporative surface.
Leaf respiration (R L) of evergreen species co-occurring in the Mediterranean maquis developing along the Latium coast was analyzed. The results on the whole showed that the considered evergreen species had the same R L trend during the year, with the lowest rates [0.83 ± 0.43 μmol(CO2) m-2 s-1, mean value of the considered species] in winter, in response to low air temperatures. Higher R L were reached in spring [2.44 ± 1.00 μmol(CO2) m-2 s-1, mean value] during the favorable period, and in summer [3.17 ± 0.89 μmol(CO2) m-2 s-1] during drought. The results of the regression analysis showed that 42% of R L variations depended on mean air temperature and 13% on total monthly rainfall. Among the considered species, C. incanus, was characterized by the highest R L in drought [4.93 ± 0.27 μmol(CO2) m-2 s-1], low leaf water potential at predawn (Ψpd = -1.08 ± 0.18 MPa) and midday (Ψmd = -2.75 ± 0.11 MPa) and low relative water content at predawn (RWCpd = 80.5 ± 3.4%) and midday (RWCmd = 67.1 ± 4.6%). Compared to C. incanus, the sclerophyllous species (Q. ilex, P. latifolia, P. lentiscus, A. unedo) and the liana (S. aspera), had lower R L [2.72 ± 0.66 μmol(CO2) m-2 s-1, mean value of the considered species], higher RWCpd (91.8 ± 1.8%), RWCmd (82.4 ± 3.2%), Ψpd (-0.65 ± 0.28 MPa) and Ψmd (-2.85 ± 1.20 MPa) in drought. The narrow-leaved species (E. multiflora, R. officinalis, and E. arborea) were in the middle. The coefficients, proportional to the respiration increase for each 10°C rise (Q10), ranging from 1.49 (E. arborea) to 1.98 (A. unedo) were indicative of the different sensitivities of the considered species to air temperature variation., R. Catoni, L. Varone, and L. Gratani., and Obsahuje bibliografii