2.3. Long-term experiment (30 days of salt stress)
Fifteen days after grafting, the plants were transplanted into
plastic containers of polyethylene containing 8 L of substrate (1 mm
to 5 mm in diameter, peat: vermiculite: perlite = 1:1:1, v/v/v), and
each container contained one seedling. The plants were arranged
at a density of approximately six plants/m2. The plants were irrigated
with normal nutrient solutions for the first five days after
transplant (Hoagland and Arnon, 1950) and then treated with
91 mM NaCl. The twelve treatments were replicated three times
and arranged in a randomized complete block design. Thirty six
plots were used, and each plot consisted of six plants. The amount
of irrigation solution applied for each plant was 0.2–1 L daily,
depending on plant growth stage and environmental conditions.
During the greenhouse culture, the plants were grown at day PPFD
1084 mol m−2 s−1 (average PPFD 275 mol m−2 s−1), day temperature
between 14 ◦C and 36 ◦C (average temperature 24 ◦C),
night temperature not lower than 13 ◦C, and day relative humidity
between 30% and 90% (average relative humidity 70%). After
30 days of NaCl treatment, the xylem sap was collected. The shoot
growth and Na+ concentrations were then measured.