phs-200802-0007 ArticleInAPeriodical 2008 Photosynthetica 46 2 https://ps.ueb.cas.cz/artkey/phs-200802-0007.php https://doi.org/10.1007/s11099-008-0033-9 202 SobradoM. A. Leaf characteristics and diurnal variation of chlorophyll fluorescence in leaves of the 'bana' vegetation of the amazon region In six dominant species of the Amazonian 'Bana' vegetation, leaf blade characteristics, pigment composition, and chlorophyll (Chl) fluorescence parameters were measured in young and mature leaves under field conditions. Leaf δ<sup>13</sup>C was comparable in the six species, which suggested that both expanding and expanded leaves contained organic matter fixed under similar intercellular and ambient CO<sub>2</sub> concentration (C <sub>i</sub>/C <sub>a</sub>). High leaf C/N and negative δ<sup>15</sup>N values found in this habitat were consistent with the extreme soil N-deficiency. Analysis of Chl and carotenoids showed that expanding leaves had an incomplete development of photosynthetic antenna when compared to adult leaves. Dynamic inactivation of photosystem 2 (PS2) at midday was observed at both leaf ages as F<sub>v</sub>/F<sub>m</sub> decreased compared to predawn values. Adult leaves reached overnight F<sub>v</sub>/F<sub>m</sub> ratios typical of healthy leaves. Overnight recovery of F<sub>v</sub>/F<sub>m</sub> in expanding leaves was incomplete. F<sub>0</sub> remained unchanged from midday to predawn and F<sub>v</sub> tended to increase from midday to predawn. The recovery from midday depression observed in adult leaves suggested an acclimatory down-regulation associated with photo-protection and non-damage of PS2.