2.1.1. Experiment 1 and 2: soil salinity and drought stress on
Arbutus unedo L. (Strawberry tree)
Fifteen plants of A. unedo, two years old, grown in the nursery of
the Castelporziano Estate (RM), were transplanted in 15 l pots filled
with a mixture of garden soil (60% of volume), sand (20%) and turf
(20%). The plants were placed inside a closed “walk-in” chamber
facility (2.5 m _ 3.9 m _ 3.0 m h) at the Department of Environmental
Biology, Sapienza University of Rome (Italy). Air temperature
was maintained at 24.2 ± 1.4 _C, and 20.7 ± 1.5 _C during the
day and night, respectively. Relative humidity was constantly
maintained at 62 ± 4%, and PAR of 500 mEm_2 s_1 was provided for
12 h per day by means of six metal halide lamps (1000 W, Philips
HPI-T). After 20 days of acclimation, 5 plants were kept as controls
and regularly irrigated with tap water, 5 plants were salt treated,
and for the other 5 plants the irrigation was suspended.
2.1.1.1. Experiment 1: soil salinity. Plants were irrigated twice a
week with 150mMNaCl for 30 days (8 salt doses). In order to avoid
salt shock, the first dose of 150 mM was supplied in three different
steps of 50 mM NaCl each. Measurements were made after the 8th
salt dose, on 2e3 fully developed, current year leaves (N ผ 10 and
11 for treated and control plants, respectively, Table 1).
2.1.1.2. Experiment 2: drought stress. The irrigation was suspended
for 30 days, whereafter measurements were made on 2e3 fully
developed, current year leaves per plant (N ผ 11 and 11 for treated
and control plants, respectively, Table 1). Leaf relative water content
(RWC) at the day of measurements was 97 ± 5.2% and
59 ± 12.4% for control and drought stressed plants, respectively.