Coastal wetlands and low-lying coastal grasslands are increasingly susceptible to salt water intrusion (SWI) influenced by storm surge and sea-level rise. Our aim was to understand physiological and growth responses of dominant coastal grassland species, Spartina patens (Ait.) Muhl. (Poaceae) and Fimbristylis castanea (Michx.) Vahl. (Cyperaceae), to increased saline flooding as expected with sea-level rise or saltwater intrusion. We hypothesized that S. patens would exhibit greater resistance to salt stress due to wider distribution. Both species were subjected to saltwater flooding at 0, 5, 10, and 20 ppt (parts per thousand) for 16 weeks. Physiological, morphological, and biochemical responses were measured at the end of the experiment. Biomass and tissue chlorides were quantified above- and belowground. Physiology was minimally affected by increased saltwater. Relative growth rate and aboveground biomass were reduced in both species at 20 ppt. Both species maintained belowground biomass, with increased root and leaf tissue chlorides as salinity increased. The results did not support our hypothesis and found that both species are impacted by saltwater flooding, but S. patens exhibited more signs of stress at 20 ppt. However, both species exhibited tolerance to long-term salt stress through different mechanisms. Spartina patens excretes salts and allocates resources belowground, whereas F. castanea maintains root:shoot and exhibits higher relative water content. Maintaining or allocating biomass belowground with increasing salinity may be important in future sea-level rise and saltwater intrusion scenarios as low-lying coastal systems are at higher risk of erosion. Reduction in plant size (aboveground biomass) may impact function of coastal grasslands.

在风暴潮和海平面上升的影响下，沿海湿地和低洼的沿海草原越来越容易受到盐水入侵（SWI）的影响。我们的目的是了解主要沿海草地物种Spartina patens（Ait。）Muhl的生理和生长响应。（禾本科）和Fimbristylis castanea（密歇根州）。（莎草科），因为海平面上升或盐水入侵，盐渍泛滥的情况有所增加。我们假设S. patens由于分布较广，因此对盐胁迫具有更大的抵抗力。两种物种分别在0、5、10和20 ppt（千分之一）下进行了16周的盐水淹没。在实验结束时测量生理，形态和生化反应。定量定量地上和地下的生物量和组织氯化物。盐水增加对生理的影响很小。两种物种的相对生长速率和地上生物量均在20 ppt时降低。两种物种都保持地下生物量，随着盐分增加，根和叶组织氯化物增加。结果不支持我们的假设，并且发现两种物种都受到咸水淹没的影响，但是S. patens在20 ppt时显示出更多的压力迹象。但是，这两种物种都通过不同的机制表现出对长期盐胁迫的耐受性。Spartina patens排泄盐分并在地下分配资源，而F. castanea则保持根：芽并显示出较高的相对含水量。随着未来海平面上升和咸水入侵的情况，维持或分配盐分增加的地下生物质可能很重要，因为低洼的沿海系统极易遭受侵蚀。减少植物大小（地上生物量）可能会影响沿海草原的功能。