Fiber and seed type of hemp (Cannabis sativa L.) responded differently to salt-alkali stress in seedling growth and physiological indices

Abstract Hemp ( Cannabis sativa L.) cultivars Yunma 5 (YM5, fiber-type) and Bamahuoma (BM, seed-type) were seriously affected by salt-alkali stress during germination, while the knowledge about the salt tolerance during seedling stage is deficient. Here, responses of hemp ( Cannabis sativa L.) seedlings of the cultivars YM5 and BM to the stress of different concentrations of NaCl and Na 2 CO 3 were investigated to explore the salt tolerance of hemp. Results showed that the plant height, dry weight and root length of YM5 and BM seedlings gradually decreased as the concentration of NaCl or Na 2 CO 3 increased. Although physiological indices such as EC (Electrical conductivity), SOD (Superoxide dismutase) and Pro (Proline) increased as the salt concentration increased, the increase extent was significantly greater in YM5 than in BM. Under the conditions of 100 and 200 mM NaCl, BM had greater dry weight and root length, and lower Pro content than YM5. However, under the stress of 100 and 200 mM Na 2 CO 3, the opposite results were recorded, with the exception for lower chlorophyll content and higher SOD activity in BM than in YM5. These findings indicated that BM had a stronger NaCl tolerance than YM5. Moreover, morphological indices of the two cultivars under Na 2 CO 3 stress were stunted more than under NaCl stress, and the seedlings died when Na 2 CO 3 concentration increased up to 300 mM. Some up-regulation of salt-tolerant genes were observed in the two hemp cultivars, a higher expression under NaCl stress than under Na 2 CO 3 stress, and a higher expression in YM5 than in BM were recorded. Findings from the study indicated that hemp seedling is more sensitive to Na 2 CO 3 stress, and the tolerance of hemp to salt stress varies with salt type and salt concentration, although both cultivars can withstand moderate doses of NaCl and Na 2 CO 3 .