Sobrado M.A. author text journal article 1999 In leaves of the mangrove species Avicennia germinans (L.) L. grown in salinities from 0 to 40 ‰, fluorescence, gas exchange, and δ¹³C analyses were done. Predawn values of F_v/F_m were about 0.75 in all the treatments suggesting that leaves did not suffer chronic photoinhibition. Conversely, midday F_v/F_m values decreased to about 0.55-0.60 which indicated strong down-regulation of photosynthesis in all treatments. Maximum photosynthetic rate (P _max) was 14.58 ± 0.22 µmol m^-2 s^-1 at 0 ‰ it decreased by 21 and 37 % in plants at salinities of 10 and 40 ‰, respectively. Stomatal conductance (g _s) was profoundly responsive in comparison to P _max which resulted in a high water use efficiency. This was further confirmed by δ¹³C values, which increased with salinity. From day 3, after salt was removed from the soil solution, P _max and g _s increased up to 13 and 30 %, respectively. However, the values were still considerably lower than those measured in plants grown without salt addition. δ13C; carbon discrimination; down-regulation; fluorescence; intercellular CO2 concentration; photoinhibition; salinity; stomatal conductance; succulence; water use efficiency 10.1023/A:1007092004582 https://ps.ueb.cas.cz/artkey/phs-199904-0009.php https://ps.ueb.cas.cz/artkey/phs-199904-0009.php continuing 36 4 547 555 1999 03003604 periodical academic journal