The pH was
brought to 6.0±0.1 by the addition of Ca(OH)2 and the solution
was aerated. Except where indicated, the density of plants was set
in four plants per pot. According to the increase in plant size, solutions
were renewed either daily or every 2 days, which helped to
minimize nutrient depletion in the pots. Temperature in the growth
chamber was 22 ◦C (day/night) and the relative humidity 85%. The
photon flux density of photosynthetically active radiation at the
plant level was 180molm−2 s−1. To attenuate the potential effect
of the differences in plant height on light interception, the pots
containing dwarf plants were placed 4 cm higher on day 12 after
sowing. On that day, half of the pots were randomly selected and
received a solution of the same composition as that above described
except that KCl was not included, while the other half received the
complete solution detailed above. On day 28 after sowing, plants
were harvested 3 h after the beginning of the day period. Shoot
and root fresh weights were recorded for each individual plant.
Individual leaf blades of the third and fourth leaves were used to
determine chlorophylls a and b, while protein carbonylation, lipid
peroxidation, and superoxide dismutase (SOD) and ascorbate peroxidase
(APX) activities were determined for the blade of the fifth
lea