Seed germination traits of Ailanthus altissima,Phytolacca americana and Robinia pseudoacacia in response to different thermal and light requirements

Invasion of alien plant species (IAS) represents a serious environmental problem, particularly in Europe, where it mainly pertains to urban areas. Seed germination traits contribute to clarification of invasion dynamics. The objective of this research was to analyze how different light conditions (i.e., 12-hr light/12-hr darkness and continuous darkness) and temperature regimes (i.e., 15/6°C, 20/10°C and 30/20°C) trigger seed germination of Ailanthus altissima (AA), Phytolacca americana (PA) and Robinia pseudoacacia (RP). The relationship between seed germination and seed morphometric traits was also analyzed. Our findings highlight that temperature rather than light was the main environmental factor affecting germination. RP germinated at all tested temperatures, whereas at 15/6°C seeds of AA and PA showed physiological dormancy. RP had a higher germination capacity at a lower temperature, unlike AA and PA, which performed better at the highest temperatures. Light had a minor role in seed germination of the three species. Light promoted germination only for seeds of PA, and final germination percentage was 1.5-fold higher in light than in continuous darkness. Seed morphometric traits (thickness [T], area [A] and volume [V]) had a significant role in explaining germination trait variations. The results highlight the importance of increasing our knowledge on seed germination requirements to predict future invasiveness trends. The increase in global temperature could further advantage AA and PA in terms of germinated seeds, as well as RP by enhancing the germination velocity, therefore compensating for a lower germination percentage of this species at the highest temperatures.     

Short‐term physiological plasticity: Trade‐off between drought and recovery responses in three Mediterranean Cistus species

Short‐term physiological plasticity allows plants to thrive in highly variable environments such as the Mediterranean ecosystems. In such context, plants that maximize physiological performance under favorable conditions, such as Cistus spp., are generally reported to have a great cost in terms of plasticity (i.e., a high short‐term physiological plasticity) due to the severe reduction of physiological performance when stress factors occur. However, Cistus spp. also show a noticeable resilience ability in response to stress factors. We hypothesized that in Cistus species the short‐term physiological response to stress and that to subsequent recovery can show a positive trade‐off to offset the costs of the photosynthetic decline under drought. Gas exchange, chlorophyll fluorescence, and water relations were measured in C. salvifolius, C. monspeliensis, and C. creticus subsp. eriocephalus during an imposed experimental drought and subsequent recovery. Plants were grown outdoor in common garden conditions from seeds of different provenances. The short‐term physiological response to stress and that to recovery were quantified via phenotypic plasticity index (PI_stress and PI_recovery, respectively). A linear regression analysis was used to identify the hypothesized trade‐off PI_stress–PI_recovery. Accordingly, we found a positive trade‐off between PI_stress and PI_recovery, which was consistent across species and provenances. This result contributes in explaining the profit, more than the cost, of a higher physiological plasticity in response to short‐term stress imposition for Cistus spp because the costs of a higher PI_stress are payed back by an as much higher PI_recovery. The absence of leaf shedding during short‐term drought supports this view. The trade‐off well described the relative variations of gas exchange and water relation parameters. Moreover, the results were in accordance with the ecology of this species and provide the first evidence of a consistent trade‐off between the short‐term physiological responses to drought and recovery phases in Mediterranean species.     

Vinyl ester-based cyclic peptide proteasome inhibitors

The 20S proteasome is a multicatalytic protease complex responsible for the degradation of many proteins in mammalian cells. Specific inhibition of proteasome enzymatic subunits represents a topic of great interest for the development of new drug therapies. Following our previous development of a new class of peptide-based inhibitors bearing a C-terminal vinyl ester residue as a pharmacophoric unit that are able to interact with the catalytic threonine, we report here the synthesis and biological properties of a new series of vinyl ester cyclopeptide analogues. Some of these derivatives were shown to inhibit the chymotrypsin-like activity of the proteasome at nanomolar concentration and their potency was found to depend on the size of the tetrapeptidic cyclic portion.     

Prediction of <Emphasis Type="Italic">Alternaria</Emphasis> and <Emphasis Type="Italic">Pleospora</Emphasis> concentrations from the meteorological forecast and artificial neural network in L’Aquila,Abruzzo (Central Italy)

In a previous work a 1-year time series of fungal spore concentrations was used to calibrate an artificial neural network for the estimation of Alternaria and Pleospora concentrations associated with observed meteorological variables in the atmosphere of L’Aquila, Italy. In this article the possibility to use the neural model calibrated with observed meteorological variables to predict the future fungal spore concentration from meteorological forecast is investigated. The results show that the proposed technique appears to be a suitable device to operationally predict the Alternaria and Pleospora concentrations a few days in advance. Emphasis is given to the actual use of these predictions for establishing a preventive strategy for allergy sufferers and for an appropriate use of fungicide treatments in agricultural activities, avoiding unsafe and useless pollution of the atmosphere, crops and fields.     

Leaf expansion in Rhamnus alaternus L. by leaf morphological, anatomical and physiological analysis

Morphological, anatomical and physiological traits of Rhamnus alaternus during leaf expansion were analysed. Bud break occurred when mean air temperature was 14.1 ± 1.2°C, and it was immediately followed by the increase of leaf area and leaf dry mass. The highest leaf expansion rates happened during the first 22 days of the process. Leaf area and leaf dry mass reached the steady-state value 46 and 62 days after bud break, respectively. Net photosynthesis increased from bud break to full leaf expansion, and total chlorophyll content had the same trend, confirmed by the correlation between the two variables. Leaf dark respiration peaked during the first 11 days of leaf expansion, then decreased and reached a steady-state value 34 days after bud break. R. alaternus completed cell division and cell enlargement of the epidermal tissue 28 days after bud break, and the ones of the mesophyll tissue at full leaf expansion. The results underline that morphological, anatomical and physiological leaf traits in R. alaternus are indicative of a less sclerophyllous species (i.e. higher specific leaf area) compared with other Mediterranean evergreen species. Moreover, the higher fraction of mesophyll volume occupied by the intercellular air spaces, and the ability to end the leaf expansion process before air temperature might be a limiting factor, makes R. alaternus closer to the mesophyte species.