Seeds of cotton (Gossypium hirsutum L. var. No.
200), canola (B. napus L. var. Haiola) and wheat (Triticum
aestivum L. var. No. 80) were sterilized with a
3% (v/v) sodium hypochlorite solution for 15 min and
washed with distilled water. They were incubated in
a moistened paper towel and germinated in the dark
at 25 ± 5
◦C for 10 d. Healthy seedlings with equal
sizes were transplanted into 7-L black plastic containers
filled with Hoagland nutrient solution. The nutrient
solution was adjusted daily to pH 6.5 ± 0.2 using
0.01 mol L−1 NaOH or HCl and was renewed weekly