Plant growth conditions
Oryza sativa L. ‘Notohikari’ wild-type, Rubisco-sense and
antisense rice plants were used (Makino et al., 2000; Suzuki et al.,
2007). Seeds were imbibed at 30 °C for three days and were subsequently
grown on a plastic net floating on tap water for 3 weeks in an
environmentally controlled phytotron (NK system, Japan). Subsequently,
rice seedlings were grown in hydroponic culture (Makino et al., 1994).
Here, we used six different Pi application conditions by changing
NaH2PO4 concentration: 0.06 (low-Pi),
0.6 (control-Pi), 1.2,1.8, 2.4, and 3.0 mM. Na+concentration was normalized by applying NaCl. The pH of the hydroponic
culture was adjusted to 5.2 with 6 M HCl, and it was replenished twice
in a week. The chamber was maintained at 60 % relative humidity with a
14-h light (28 oC) and a 10-h dark (25oC) photoperiod. The light intensity was 500-600 µE
m−2 s−1. All physiological and
genetical analyses were performed for fully and newly expanded leaves
after 70 days of their germination.