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The C3–CAM (crassulacean acid metabolism) intermediate species Yucca gloriosa L. is invading coastal dunes in central Italy, causing a loss in biodiversity and habitat. In order to investigate its competitive success, a number of ecophysiological traits were analysed: CAM activity (through carbon isotope composition, δ13C, and cell acidification), photochemical efficiency of PSII (operating and maximum photosystem II quantum yield), stomatal conductance, relative water content, and succulence index (SI). Analyses were conducted over the course of one year, to assess yucca's response to seasons and the shoreline-inland ecological gradient. The species displayed high physiological plasticity, a factor that might prove decisive in enhancing carbon fixation and water-use efficiency across the seasons, and accordingly its level of invasiveness. Temperature seemed crucial in controlling photosynthetic metabolism, a fact borne out by seasonal changes seen in δ13C and SI. Some stress symptoms appeared in winter, including a slight reduction of photochemical performance, and the shoreline–inland ecological gradient did not have any significant effects. All the plants analysed were intermediate C3–CAM: given that yucca cannot reproduce sexually in Europe, the entire population of the area studied might conceivably share the same carbon fixation pathway. The results obtained may help afford a better understanding of the ecophysiological features of Y. gloriosa in a Mediterranean dunal ecosystem, along with the dynamics of the invasion process, allowing a more efficient approach to be adopted in programmes for managing this environment. [ABSTRACT FROM AUTHOR]

Tomato and pepper leaves were clipped with black leaf clips for dark adaptation under solar radiation in the late spring or early summer 2010 in southern Italy. The leaves showed highly variable maximum PSII quantum yield (F/F = 0.026−0.802) using a continuous-excitation fluorometer Pocket PEA. These results were confirmed using the modulated fluorometer FMS1 on tomato leaves in mid summer, with F/F as low as 0.222 ± 0.277 due to nearly equal minimum (F) and maximum (F) fluorescence emission. A significant clip effect on F/F occurred after only 12 (tomato) or 25 (pepper) min. Increasing the leaf temperature from 25 to 50°C reportedly induced an F increase and Fm decrease so that F/F approached zero. The hypothesis that black leaf clips overheated under intense solar irradiance was verified by shrouding the clipped leaves with aluminum foil. In clipped leaves of pepper, F/F with the black clip/Pocket-PEA was 0.769 ± 0.025 (shrouded) and as low as 0.271 ± 0.163 (nonshrouded), the latter showing a double F and 32% lower F. An 8% clip effect on F/F was observed with the white clip/ FMS1. To avoid the clip effect in high irradiance environments, F/F measurements with black clip/ Pocket PEA system required leaf dark adaptation with radiation-reflecting shrouds. It would be useful if manufacturing companies could develop better radiation-reflecting leaf clips for the Pocket PEA fluorometer. [ABSTRACT FROM AUTHOR]