Plant cultivation and salt treatments
Seeds of S. alterniflora were sampled and the fully developed
seeds were picked out and vernalized at 4 oC for at
least 4 weeks. After vernalization, every five seedlings with same size
were planted in a pot (14 cm height, 12 cm diameter) with clean sands.
The young seedlings were irrigated with 1/2 strength Hoagland solution
and grown in greenhouse for 2 weeks. The environmental condition in
greenhouse was set as followed: 50-70% relative humidity, 25-28oC daily temperature, 12/12 h day/night photoperiod
and 700-1000 μmol m-2 s-1 light
intensity.
After 2 weeks, the seedlings with same size were divided into three
groups. Seedlings in group 1 were irrigated with full-strength Hoagland
solution without sea salt (0‰ salinity); seedlings in group 2 were
irrigated with full-strength Hoagland solution with 15‰ sea salt (15‰
salinity); seedlings in group 3 were irrigated with full-strength
Hoagland solution with 30‰ sea salt (30‰ salinity). At the beginning of
salt treatment, the salinity in group 2 and group 3 were gradually
increased by 5‰ every days until reached the preset salinity condition.
The Hoagland solution with or without salt addition were replaced every
3 days to maintain the preset salinity. Each salinity treatments had at
least 150 seedlings. The seedlings subjected to different salinity
treatments were grown in greenhouse for 150 days. Each treatment had 3
replicates.