2.2. Growth conditions and planting
Seeds of Fraxinus angustifolia were germinated in trays in a
mixture of sand and potting soil in a growth chamber at 25 ◦C
and 60% of relative humidity. When seedlings had 2 leaves, about
100 seedlings of a similar size were selected. A subsample of 15
seedlings was harvested to obtain the following: fresh and dry
biomass of leaves, stems and roots. Dry weight was obtained after
at least 2 days in an oven at 70 ◦C. Each seedling selected for the
experiment was freshly weighed and then planted in one pot.
The experiment was conducted in a greenhouse at the University
of Córdoba (Spain) between July and November 2008. Due
to the natural conditions under which ash seedlings grow (under
an adults’ canopy in wet habitats where plant cover is high and
light availability is low), the experiment was conducted under a
shadow cloth (transmission of 10% of the total radiation available).
Thus, the photosynthetically active radiation (PAR) was
84
±
13 mol photon m−2 s−1 (mean
±
standard deviation) measured
with a canopy transmission meter (EMS-7, PP-system, UK) on
a clear day and the total daily mean radiation during the experiment was 2.4 mol m−2 day−1. The average temperature of the growth
period inside the greenhouse was 17
±
7 ◦C and the time of growth
was 124 days. The irrigation system was by dripping with a plastic
bottle of 0.5 L (model 011, S. A. R. L. IRISO, France). Altogether
6.5 L of water was added to each pot during the first 86 days, after
which watering was suppressed forcing the plants to use soil water
reserves.