TWO SAINFOIN (ONOBRYCHIS VICIIFOLIA SCOP.) CULTIVARS DIFFER IN THEIR RESPONSES TO NEUTRAL AND SALINE-ALKALI STRESS DURING SEED GERMINATION AND EARLY SEEDLING GROWTH

Salinity is one of the major environmental factors limiting plant growth and development. Two cultivars (the native Gansu, GS; and the imported Italian, IT) of sainfoin ( Onobrychis viciifolia Scop.) were exposed to two neutral salts (NaCl and Na2SO4) and two alkaline salts (Na2CO3 and NaHCO3) at concentrations ranging from 0-300 mM. After seven days seed germination rates and radicle and hypocotyl lengths were compared. Exposure only to 50 mM neutral salts did not affect significantly relative germination rates compared to control (0 mM). In contrast, higher concentrations of neutral salts and alkaline salts significantly inhibited germination rates and reduced radicle and hypocotyl lengths. Although the two cultivars were visually similar in appearance and had similar patterns in response to saline and alkaline stresses, GS had relatively higher threshold germination concentration compared to IT, and the radicles and hypocotyls of seedlings grown under NaCl and Na2SO4 were longer than for IT, indicating that GS is more salt-tolerant. Under neutral salt stress, the recovery germination percentage increased with higher salt concentration. However, under alkaline salt stress, the recovery germination percentage sharply decreased with increasing salt concentration. These results suggest that the damage caused by alkaline salts is more severe than those caused by neutral salts. The present study provides novel insights into the responses of seed germination to different types of salinity in an important forage species.

Automated summary

Salinity is a major environmental factor limiting plant growth. Both neutral salts and alkaline salts significantly inhibited seed germination rates and reduced radicle and hypocotyl lengths in two cultivars of sainfoin. The native cultivar exhibited higher salt tolerance compared to the imported one, with different responses to neutral salts and alkaline salts.