R. Catoni

Relationship between net photosynthesis and leaf respiration in Mediterranean evergreen species

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.

Corylus avellana responsiveness to light variations: morphological, anatomical, and physiological leaf trait plasticity

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.

Morphological, anatomical and physiological leaf traits of Q. ilex, P. latifolia, P. lentiscus, and M. communis and their response to Mediterranean climate stress factors

BackgroundLimitations to plant growth imposed by the Mediterranean climate are mainly due to carbon balance in response to stress factors. In particular, water stress associated to high air temperature and irradiance in summer causes a marked decrease in CO2 assimilation. Air temperature sensitivity of photosynthesis (PN) differs from that of leaf respiration (RD). PN often decreases sharply at temperature above its optimum while RD increases exponentially over short term rises in temperature. Nevertheless, the impact of water deficit on RD is still far from clear with reports in literature including decreases, maintenance or increases in its rates. The ratio RD/PN can be considered a simple approach to leaf carbon balance because it indicates the percentage of photosynthates that is respired.ResultsThe results underline different morphological, anatomical and physiological traits of the evergreen species co-occurring in the Mediterranean maquis which are indicative of their adaptive capability to Mediterranean stress factors. The ratio RD/PN varies from 0.15 ± 0.04 in autumn, 0.24 ± 0.05 in spring through 0.29 ± 0.15 in winter to 0.46 ± 0.11 in summer. The lower RD/PN in autumn and spring underlines the highest PN rates during the favorable periods when resources are not limited and leaves take in roughly three to five times more CO2 than they lose by respiration. On the contrary, the highest RD/PN ratio in summer underlines the lowest sensitivity of respiration to drought. Among the considered species, Quercus ilex and Pistacia lentiscus have the largest tolerance to low winter temperatures while Phillyrea latifolia and Myrtus communis to drought, and Phillyrea latifolia the highest recovery capability after the first rainfall following drought.ConclusionsThe Mediterranean evergreen specie shows a different tolerance to Mediterranean climate stress factors. The predicted global warming might differently affect carbon balance of the considered species, with a possible change in Mediterranean shrublands composition in the long-term. Understanding the carbon balance of plants in water limited environments is crucial in order to make informed land management decisions. Moreover, our results underline the importance of including seasonal variations of photosynthesis and respiration in carbon balance models.

Physiological and morphological leaf trait variations in two Apennine plant species in response to different altitudes

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.

Photosynthetic and leaf respiration activity of Malcolmia littorea (L.) R. Br. in response to air temperature

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.

Physiological differences of five Holm oak (Quercus ilex L.) ecotypes growing under common growth conditions were related to native local climate

An increase in the frequency and intensity of extreme climatic conditions is expected for the Mediterranean area as a response to climate change. As a consequence, the ability of Mediterranean plant species to adapt to complex and stressful environmental conditions plays an important role in driving their future distribution. The adaption of plant species may be expressed by ecotypes already adapted to local climate. Our goal was to analyse the seasonal physiological behaviour of five Quercus ilex ecotypes coming from different Italian geographical areas (from the north to the south) in order to test if ecotypes maintained their physiological traits when grown in the same environmental conditions. Measurements of gas exchange, biochemistry and chlorophyll fluorescence carried out during winter, spring and summer underlined that the response of the considered ecotypes reflected the climate of the original provenances, particularly under suboptimal conditions. The ecotypes from the northernmost and the southernmost limits were the most sensitive to high and low temperatures, respectively. Our results can be used to advance hypotheses about the respone of Q. ilex to climate change.

Variations in leaf respiration across different seasons for Mediterranean evergreen species

Leaf respiration (RL) 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 RL 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 RL 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 RL variations depended on mean air temperature and 13% on total monthly rainfall. Among the considered species, C. incanus, was characterized by the highest RL 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 RL [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.

Carbon gain optimization in five broadleaf deciduous trees in response to light variation within the crown: Correlations among morphological, anatomical and physiological leaf traits

Abstract Leaf trait variations in five deciduous species (Quercus robur, Corylus avellana, Populus alba, Acer campestre, Robinia pseudoacacia) growing in an old broadleaf deciduous forest in response to light variation within the tree crown was analyzed. Net photosynthetic rate (PN), leaf respiration rate (R) and the photosynthetic nitrogen use efficiency were, on average, more than 100% higher in sun than in shade leaves. A. campestre and C. avellana sun leaves had the highest specific leaf area (SLA, 156.0 ± 17.9 cm2 g-1) and the lowest total leaf thickness (L, 101.9 ± 8.8 μm) underlining their shade-tolerance. Among the shade-intolerant species (Q. robur, P. alba and R. pseudoacacia), Q. robur had the lowest SLA and the highest L in sun leaves (130.6 ± 10.0 cm2 g-1 and 160.8 ± 9.6 μm, respectively) since shade-intolerant species typically have thicker leaves. The higher PN decrease in respect to R decrease from sun to shade leaves attested the higher sensitivity of PN than R to light variations within the crown. This determined a 69% lower R/PN in sun than in shade leaves. This result is further attested by the significant correlation between PN and the relative photosynthetic photon flux density. The shade-tolerant species have a 76% higher R/PN ratio than the shade-intolerant ones. The measured leaf phenotypic plasticity (PI = 0.35) was in the range of broadleaf deciduous species. Plasticity is a key trait useful to quantify plant response to environmental stimuli. It is defined as the ability of a genotype to produce different phenotypes depending on the environment. Among the considered species, Q. robur showed the highest PI (0.39) and P. alba the lowest (0.29). Knowledge on phenotypic plasticity is important in making hypotheses about the dynamics of the studied forest in consideration of environmental stress factors, including invasive species competition and global climate change.

Fatty acid content profile and main constituents of Corylus avellana kernel in wild type and cultivars growing in Italy

Abstract The kernel composition (moisture, ash, protein, carbohydrate, calories, fat, monounsaturated and polyunsaturated fatty acids) of two hazelnut (Corylus avellana L.) cultivars (‘Tonda Gentile Trilobata’ and ‘Tonda Gentile Romana’) and of two wild types growing in different climatic conditions (north-west and central Italy) was evaluated. The main kernel component was fatty acid (65.9 ± 1.8%, mean value), and the most abundant fatty acid in hazelnut was oleic acid (C18:1) (83.5 ± 1.0%, mean value). The saturated fatty acids are the minor compounds in kernel hazelnut, resulting in a unsatured fatty acid to saturated (U/S) fatty acid ratio of 9.0 ± 1.6. Compared to other tree nuts and vegetable oils, hazelnut oil is among the ones with the highest contents of monounsaturated and the lowest content of saturated fatty acid. Thus, hazelnut may be beneficial for the human diet preventing cholesterol-based atherosclerosis and ischemic cardiovascular diseases.

Carbon Stock Estimation in an Unmanaged Old-Growth Forest: A Case Study from a Broad-Leaf Deciduous Forest in the Northwest of Italy

SUMMARY The aim of the study was to evaluate the carbon storage capability of an unmanaged old-growth deciduous forest developing inside a Natural Reserve. Our research aims to emphasize how the conservative management, by determining the actual structure and species composition, resulted in a high carbon storage capability. The results highlight that the forest stores a large carbon amount (CTot = 418 Mg C ha-1) with the greater pool in the aboveground biomass and in the soil (42%). In particular, among the most abundant species, Populus spp. and Quercus robur are the major carbon sink of the forest, accounting for 31% and 63% of the forest aboveground biomass. In addition, the total economic benefits from carbon storage of the forest of 11 209