Low salinity promotes the growth of broccoli sprouts by regulating hormonal homeostasis and photosynthesis

Broccoli sprouts produce several bioactive compounds and are recognized as a health-promoting vegetable. In this study, the effect of salinity (NaCl) on the growth of broccoli sprouts was investigated. Broccoli seeds were germinated for 4 and 8 d with spraying 0–120 mM NaCl and then harvested to evaluate changes in endogenous hormones, photosynthetic indices, chlorophyll fluorescence parameters and chloroplast ultrastructure. The growth of sprouts was significantly promoted by low salinity (40 and 80 mM NaCl) and inhibited by high salinity treatment (120, 160 and 200 mM NaCl). In 8-day-old sprouts treated with 80 mM NaCl, levels of abscisic acid, cytokinin, brassinolide, indole-3-acetic acid and gibberellic acid were significantly enhanced, while net photosynthetic rate increased in low salinity conditions was due to the elevated chlorophyll content and increased photosystem II activity. Furthermore, low salinity increased the leaf area maximally in both 4- and 8-day-old sprouts. Enlarged chloroplast and an increased number of grana also contributed to improved photosynthesis. Low salinity conditions induced endogenous growth hormone synthesis and improved photosynthesis, thereby promoting the growth of broccoli sprouts. This study provides a theoretical basis for the improved production of broccoli sprouts in low salinity conditions.