| The mesophyll conductance (gm) and leaf hydraulic conductance (Kleaf) are two important physiological processes that influence photosynthesis, because they have a directly impact on chloroplast carbon dioxide concentration and water supply, respectively. However, few studies have been carried out to explore the coordination between them. Although previous studies have investigated the correlations between leaf structural features(palisde thickness; ratio of palisade to sponge mesophyll thickness) as well as foliage vein structural traits(major vein density; minor vein density; inter-veinminor distance; total vein density)and leaf hydraulic conductance, and relationships between leaf morphological characteristic(leaf dry mass per area)and mesophyll conductance, there are still a lot of debates. In the present study, we select a total of nine dominant plants from a mangrove forest in Hainan Island:Lumnitzera racemosa, Sonneratia alba, Sonneratia caseolaris, Hibicus tilisaceus, Aegiceras corniculatum, Xylocarpus granatum, Heritiera littoralis and Acrostichum aureum. The objectives of this study were to analysis the relationships among leaf anatomical traits, mesophyll conductance and leaf hydraulic conductance in these species from a stressful environment. Our results indicated that the leaves of these species possess either dense spongy tissue or abundant hypodermis. There was a significant relationship between total vein density and stomatal density, indicating a structural coordination between water supply and transpiration in mangrove plants. We found a large variations in Kleaf(0.78～5.50mmol·m-2·s-1·MPa-1), gm (0.06-0.36mol·m-2·s-1), Amax (7.23～23.T1μmol·m-2·s-1), LMA (56.03～159.6g·m-2), palisade thickness (51.92-197.47μm), spongy thickness (77.34-492.66μm) across the nine species and variations in VLAmajor (0.7～7.85mm·mm-2), VLAminor (1.07～27.7 mm·mm-2), VLA (1.76～35.55 mm·mm-2), IVD (32.91～407.33μm) across the eight species (Acrostichum aureum werenot included). Mesophyll conductance was significantly correlated with Amax. However mesophyll conductance is not significantly correlatedwith leaf dry mass per area, and the reason is that there is no relationship between leaf dry mass per area and leaf thickness as well as leaf density. There was no significant relationship between Kleaf and vein density and Amax. Decoupled leaf economic and hydraulic traits for plants growing in mangrove forests indicates more possible leaf traits combinations, thus diverse plant adaptation strategies enabling them to co-occur in the stressed habitat. |
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