phs-199904-0009 ArticleInAPeriodical 1999 Photosynthetica 36 4 https://ps.ueb.cas.cz/artkey/phs-199904-0009.php https://doi.org/10.1023/A:1007092004582 547-555 SobradoM.A. Leaf Photosynthesis of the Mangrove Avicennia Germinans as Affected by NaCl In leaves of the mangrove species Avicennia germinans (L.) L. grown in salinities from 0 to 40 ‰, fluorescence, gas exchange, and δ<sup>13</sup>C analyses were done. Predawn values of F<sub>v</sub>/F<sub>m</sub> were about 0.75 in all the treatments suggesting that leaves did not suffer chronic photoinhibition. Conversely, midday F<sub>v</sub>/F<sub>m</sub> values decreased to about 0.55-0.60 which indicated strong down-regulation of photosynthesis in all treatments. Maximum photosynthetic rate (P <sub>max</sub>) was 14.58 ± 0.22 µmol m<sup>-2</sup> s<sup>-1</sup> at 0 ‰ it decreased by 21 and 37 % in plants at salinities of 10 and 40 ‰, respectively. Stomatal conductance (g <sub>s</sub>) was profoundly responsive in comparison to P <sub>max</sub> which resulted in a high water use efficiency. This was further confirmed by δ<sup>13</sup>C values, which increased with salinity. From day 3, after salt was removed from the soil solution, P <sub>max</sub> and g <sub>s</sub> increased up to 13 and 30 %, respectively. However, the values were still considerably lower than those measured in plants grown without salt addition.