Photosynthetic evidence from Suaeda glauca explains why seedlings of this species from saline soils has higher biomass than that from non-saline soils

Suaeda glauca L. is leaf succulent halophyte. Its seed oil content is high and rich in unsaturated fatty acids with high edible and medicinal value. Shoot length and dry weight of S. glauca from saline soils (SS) are higher than that from non-saline soils (NSS). However, the mechanism has not been elucidated. In this work, high-throughput Illumina RNA-sequencing (RNA-seq) was used and photosynthetic traits were evaluated in the species from different habitats, one occurs in SS, and another has been cultivated in NSS for over two decades. There were 1824 DEGs between S. glauca from NSS and SS. Some DEGs were mapped to photosynthesis and photosynthesis-antenna proteins. Notably, genes associated with subunits of photosynthesis and light-capturing complexes (LHCs) showed higher expression levels in the species from SS compared to plants from NSS. This was accompanied by higher potential efficiency of PSII photochemistry (Fv/Fm), actual PSII efficiency (ΦPSII), electron transport rate (ETR), enzyme activity and gene expression of GAPDH and Rubisco in SS seedlings. This study provides evidence that seedlings of S. glauca from SS had higher photosynthetic efficiency compared with that from NSS, thus facilitating their photosynthate accumulation and growth in the SS population, i.e., this characteristic in SS population may be weakened when the species is cultivated in NSS for long time.