Photosynthetic activity and water use efficiency of dune species: the influence of air temperature on functioning

摘要: Differences in leaf traits among the dune species developing along Latium coast were analysed. Cakile maritima Scop. subsp. maritima, Elymus farctus (Viv.) Runemark ex Melderis farctus, Ammophila arenaria (L.) Link australis (Mabille) Lainz, Ononis variegata L., Pancratium maritimum Eryngium and Anthemis L. considered. The considered showed a similar net photosynthetic rate (P N) chlorophyll content (Chl) during year, with peak from end of April to middle May [13.0±3.6 μmol (CO2) m−2 s−1 0.63±0.21 mg g−1, respectively, mean values species], favoured by air temperature range 13.3–17.5°C, 6% soil water availability. In June–July, increase (Tmax = 28.4°C), associated lower availability (42 mm, total rainfall period) 1% determined significant decrease P N (59%, species) Chl (38%), an carotenoid (Car)/Chl ratio (59%). correlation between stomatal conductance (g s) (p<0.05) explained 67% variations. Moreover, (T l) underlined that favourable T l enabling 90–100% highest for was within 23.4 26.6°C. decreased below half its maximum value when over 35.8 37.4°C E. A. australis, respectively 32.2°C other (mean value). Leaf mass area (LMA) varied 6.8 ± 0.7 cm−2 (O. variegata) 30.6 1.6 (A. arenaria). PCA (principal component analysis) carried out using morphological physiological co-occurring characterised different adaptive strategies: photosynthesized long period also 37.4°C, because their transpiration rates [E, 1.4 0.1 mmol (H2O) s−1], which seemed be controlled LMA. On contrary, C. had higher (on average 52% than others) period, allowed succulence index (SI, 85.7 9 cm−2) results us hypothesize might at competitive advantage relative respect temperature, ability photosynthesize sufficient summer.