In brief, the seedlings were transferred into a deoxygenated box filled with high purity N2.
The root of each seedling was immersed in a beaker with 150 ml 0.2-strength Hoagland’s solution
(deoxygenated), and covered with layer of paraffin oil about 2 cm thick in order to prevent reaeration. The stems of the seedlings were covered with plastic parafilm to protect them form the oil. 30 ml of titanium(III) citrate stock buffer (the buffer was a mixture of 600 ml 0.2 M sodium citrate, 60 ml 1.16 M TiCl3 and 70 ml saturated sodium carbonate, pH ¼ 5.6) was then injected into deoxygenated 0.2-strength Hoagland solution with a syringe. Controls (6 blank beakers without plants but with the same set-up as the planted beakers) were also prepared simultaneously.
Then all beakers with and without plants were transferred to a climate chamber
with an average irradiance of 300 mmol m2 s1
, temperature of 30 C and relative
humidity of 60%. After incubation for 24 h, any colour change in the buffer was determined at 527 nm.