2.1 Rice material and culture
conditions
The experiment was conducted in two growth chambers (CMP6050, Conviron,
Winnipeg, Manitoba, Canada) at the Yangzhou University in Yangzhou,
Jiangsu Province, China. Japanese rice variety Nipponbare (Oryza
sativa , ssp. japonica ) was used in the experiments. Nipponbare
is widely used in rice production, breeding, and molecular genetics
studies. It is the first rice variety being deeply genome sequenced as a
monocots model plant (Sasaki et al, 2005; Matsumoto et al, 2016).
Rice seeds were acquired from Yangzhou Agricultural Research Center, and
surface sterilized with disinfectant prochloraz (Jinbao, Yangzhou Suling
Agricultural Chemicals, Jiangdu, China) following the supplier
recommendation. Seeds were immersed in tap water for 48 hrs before
subjected to germination promotion at 32°C with a humidity of 85% in an
incubator for 15 hrs, and at 28°C till shoot and root appearance to
0.5~1 cm. The germinated seeds were screened for
uniformity and planted to soil in plastic trays at a spacing of 3.5 cm x
3.2 cm, with each tray containing 96 plants. The plastic tray contained
premixed soil, 12 cm in depth (Zhang et al, 2019), prepared in a similar
way as in field nursery for seedling.
During the growth period, soil was checked three times a day to keep its
moisture at saturated point but without persistent water layer. The
temperature of the growth chamber was preset to 30/22°C (actual records
at ± 0.67°C range) in the 12/12hrs day/night regime, respectively. The
illumination was programmed to 800 μmol photons m−2s−1 (actual records at ± 58 μmol photons
m−2 s−1) during the day and 0 at
night. The relative humidity was set at 70% (actual records range
65-80%).