The following types of leaves were compared: (i) leaves with a
red visual appearance (2nd to 5th leaf from the top of the stem),
and (ii) leaves with a green visual appearance (5th to 8th leaf from
the top of the stem). All leaves measured were tri- or penta-foliate
and fully expanded, from stems with 13 to 16 leaves, when flower
bud was not yet or barely visible.
Rockwool slabs of the plant samples were cut to make the plants
transportable and plants were pruned in order to remove the bent
shoots and reduce the upright shoots to 4 per plant.
Photosynthesis measurements were carried out on the top
leaflet, with a LICOR 7000 CO2/H2O Gas analyzer (LI-COR, Lincoln,
NE, USA) connected to a custom made leaf chamber (area:
4.52cm2). The conditions inside the leaf chamber were kept
constant (temperature 26 ◦C, CO2 concentration 380 ppm, O2 concentration
2%, RH 72%, air flow rate 204mol s−1).