Trade-off between leaf chlorophyll and betacyanins in Suaeda salsa in the Liaohe estuary wetland in northeast China

Aims Pigment composition is an important functional trait that can be affected by environmental factors. The objective of this study was to investigate the effect of soil salinity on pigment composition in Suaeda salsa by comparing chlorophyll and betacyanin content in the Liaohe estuary wetland, a typical coastal wetland in northeast China. Methods We investigated the plant biomass, percentage of red leaves and pigment content (chlorophyll a, chlorophyll b and betacyanins) in S. salsa in intertidal and supratidal zones of the upper, middle and lower reaches of the Liaohe estuary wetlands. The Na+ content of both the soil and plant was also measured. Full analysis of variance and multivariate analysis were used to compare differences in pigment content and Na+ content between the supratidal and intertidal zones. Important Findings Pigment composition was significantly affected by soil salinity. With increasing soil salinity, the percentage of red leaves was higher in the intertidal zone than in the supratidal zone. In all three reaches, plants had lower chlorophyll a content and higher betacyanin content in the intertidal zone than in the supratidal zone. Compared to chlorophyll a, chlorophyll b was less sensitive to soil salinity. There were no differences in chlorophyll b content between the intertidal and supratidal zones in the upper and lower reaches. Furthermore, pigment composition was associated with both the plant tissue and soil Na+ content. Compared to the supratidal zone, the intertidal zone had a higher Na+ content in plants. There was a negative relationship between plant chlorophyll content and soil Na+ content, but a positive relationship between betacyanin content and soil Na+ content. Overall, the results indicated that there might be a trade-off between leaf chlorophyll and betacyanin content in S. salsa to maintain its growth and survival in high salinity environments.