Rosangela Catoni

The amount of pectin in the cell wall is considered a critical element regulating cell wall porosity. Thus, it is likely to influence the diffusional processes particularly that from the substomatal cavities to the carboxylation sites in the chloroplast stroma (i.e. mesophyll conductance, g_m). We analyzed in four deciduous species (Acer campestre, Crateaugus monogyna, Corylus avellana, Quercus robur) the correlation between pectin and g_m in two phase of leaves development (i.e. mature green leaves and senescent leaves). Results showed that in A. campestre, C. monogyna and Q. robur to higher value of pectin in mature green leaves corresponded the higher g_m value. Taking into account this result, we can assume that a higher amount of pectins is associated to an increased cell wall hydrophilicity and elasticity, thus increasing g_m because CO₂ molecules cross the wall dissolved in water. An opposite behavior was observed in C. avellana. Graphical Abstract

As a part of a larger study concerning the carbon sequestration capability by hazelnut orchards in Italy, we analyzed the total amount of carbon dioxide (CO₂) removed over the year from the atmosphere through the net assimilation rates in two hazelnut orchards in Piedmont (i.e., the second region in Italy for surface and production). In particular, considering the key role played by the structural traits in affecting carbon sequestration potential, we assessed the impact of two different training systems widely diffused in the region: single trunk in orchard_A and bush-like in orchard_B. The results showed that plants in orchard_A and orchard_B sequestered 10.6 ± 1.8 and 25.7 ± 4.2 kg (CO₂) plant⁻¹ month⁻¹, respectively. Higher CO₂ sequestration in the plants in orchard_B was due to their higher leaf area index relative to plants in orchard_A. The mean CO₂ sequestration from orchard_A and orchard_B per area was 4.25 ± 1.72 and 8.57 ± 3.41 Mg (CO₂) ha⁻¹ month⁻¹, respectively. We also estimated the total amount of CO₂ emission by the management over the entire production season in 157.335 kg CO_2eq ha⁻¹ by summing the contribution of diesel fuel, machinery and fertilization practices and considering that the total amount of CO₂ sequestered by the two hazelnut orchards over the entire study period was estimated in 26 Mg (CO₂) ha⁻¹ in orchard_A, and in 51 Mg (CO₂) ha⁻¹ in orchard_B, they had an effective positive role as carbon sink at this local level.

Mesophyll conductance (g_m) has received over time much less attention than stomatal conductance (g_s), although it affects leaf photosynthesis to about the same extent as stomatal conductance does. The objective of this study was to analyze the g_m trend in five understory herbaceous species growing in a close-canopy forest in the north-west of Italy. In particular, three of analyzed species were monocots: Carex brizoides Lam., Carex pilosa Scop., and Oplismenus undulatifolius P. Beauv and the others dicots species: Circaea lutetiana L., and Pulmonaria officinalis Ced. The results showed, on one hand, the absence of correlation between g_m and the considered environmental variables in the forest understory (i.e. air temperature, photosynthetic photon flux density and carbon dioxide concentration). Moreover, we carried out a principal component analysis considering all the analyzed morphological and physiological variables for the five species. The following correlation between the first component, related to the leaf mass per unit of leaf area and the leaf tissue density, and g_m seem to suggest a key role of the leaf structural features in determining g_m variations across the five species.

Invasive alien plant species (IAPs) represent one of the main biological threats to biodiversity worldwide. Information about their phenotypic plasticity are needed to increase awareness about their future invasive potential. A study about phenotypic plasticity in response to contrasting light regimes and its quantification by a plasticity index (PI) of two IAPs (Ailanthus altissima and Robinia pseudoacacia) inside a Strict Nature Reserve was conducted. R. pseudoacacia showed a 70% higher PI, with a strongly greater value at morphological leaf level, associated with a greater ability to survive and grow in forest understory, explaining its greater widespread. Otherwise, A. altissima showed its highest PI at physiological level, which was associated with the ability to colonize and grow in environments with high-light regimes. Based on these results, the conservative management has limited the presence of A. altissima by its lower ability to grow in forest understory. In fact, the small-scale gaps in the forest infrastructure, that could allow its recruitment, are originated only from the death of a single tree or small group of trees. Regarding R. pseudoacacia, it is critical to maintain this type of management because any disturbances resulting in large openings could further promote its presence inside the Reserve.

The study analyzed the variations of physiological, morphological and anatomical leaf traits during its development in Corylus avellana L. saplings. Three different phases were identify during leaf development: the first phase (hereafter IP) considered in the developing leaves, the second phase (IIP) in the mature green leaves and the third phase (IIIP) in the senescent leaves. In particular, variations in parameters estimated from the photosynthetic light response curves, in chlorophyll fluorescence variables and in morphological leaf traits were analyzed during the three phases. The principal component analysis (PCA) carried out using all the considered morphological characters (leaf mass per area - LMA, and leaf tissue density - LTD) and physiological traits (the maximum net photosynthetic rates - A_Nmax, dark respiration rates - R_D, light compensation point - LCP, light saturation point – LSP, maximum quantum yield - ɸ_max, fluorescence-based maximum quantum yield of PSII photochemistry - F_v/F_M and effective quantum yield of PSII photochemistry - ɸ_PSII) showed a complete separation among the considered phases. The results showed that the major differences occur between the phases IP and IIP. In particular, a greater variation was found for LMA, A_Nmax, R_D. On the contrary a lower variation was observed for ɸ_max which remain quite constant from IP to IIP indicating that chloroplasts present in juvenile leaves are fully functional.

The seasonal trend of plant carbon dioxide (CO₂) sequestration is related to the photosynthetic activity, which in turn changes in response to environmental conditions. Great interest has turned to the CO₂ sequestration (CS) potential of temperate forests which play an important role in global carbon (C) cycle contributing to the lowering of atmospheric CO₂ concentration. In such context, the CS of an unmanaged old broad-leaf deciduous forest developing inside a Strict Nature Reserve, and its variations during the year were analyzed considering the monthly variations of leaf area index (LAI) and net photosynthetic rates (N_P). Overall, the total yearly CS of the forest was 141 Mg CO₂ ha⁻¹ year⁻¹ with the highest CS value monitored in June (405 Mg CO₂ month⁻¹) due to the highest LAI (5.0 ± 0.8 m² m⁻²) and a high N_P in all the broadleaf species. The first CS decline was observed in August due to the more stressful climatic conditions that constrained N_P rates. Overall, the total CS of the forest reflects the good ecological health of the ecosystem due to its conservative management.

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 ...

Variations in physiology and metabolic products of Cistus creticus subsp. eriocephalus along an altitudinal gradient (350–750 m.a.s.l.) within the Monti Lucretili Regional Natural Park (central Italy) were studied. The results showed that the phenol production was in relationship with the net photosynthetic rates and the chlorophyll content. In particular, the increasing caffeic acid (CA) content with altitude suggested its role in providing an additional photo-protection mechanism, by its ability to consume photochemical reducing power and acting as an alternative C-atom sink under high light conditions. The metabolic production was tested by high performance thin layer chromatography (HPTLC) fingerprint analysis, highlighting the potential of this technique in biologic studies.