*2.2. E*ff*ect of Chilling Stress on Dry Weight, Protein, Chlorophyll, and Carotenoid Content*

The dry weight (DW) of shoots was increased by 1.8%, 17.3%, and 56.5%, respectively, at 28 ◦C after 0.5 h, 12 h, and 48 h of light exposure (Figure 2A). However, the accumulation of dry matter was significantly inhibited under chilling stress. Shoot DWs were 10.3% and 20.7% lower after 12 h and 48 h at 18 ◦C compared with those at 28 ◦C. More severely, DWs at 12 ◦C were 13.2% and 34.1% lower after 12 h and 48 h of light exposure compared with those at 28 ◦C, and showed no significant change compared with the seedlings before the light exposure.

At 28 ◦C, protein contents of seedlings rose to 16.38, 22.74, and 37.90 mg·g−<sup>1</sup> fresh weight (FW) after 0.5 h, 12 h, and 48 h of greening, respectively (Figure 2B). Low temperature reduced protein

accumulation of rice seedlings during the greening process. There were only 22.41 mg·g−<sup>1</sup> FW at 18 ◦<sup>C</sup> and 17.31 mg·g−<sup>1</sup> FW at 12 ◦C after 48 h of light exposure.

Chlorophyll during the greening process was significantly increased at 28 ◦C. However, chlorophyll levels were 77.1% lower at 18 ◦C and 97.5% lower at 12 ◦C than at 28 ◦C (Figure 2C). Carotenoids at <sup>28</sup> ◦C increased to 0.21 mg·g−<sup>1</sup> FW after 48 h of greening, while chill-stressed rice seedlings accumulated much lower levels of carotenoids (Figure 2D).

**Figure 2.** Dry weight (DW, **A**), soluble protein (**B**), chlorophyll (**C**), and carotenoids (**D**) of control (28 ◦C) and chill-stressed (18 ◦C and 12 ◦C) rice seedlings after 0 h, 0.5 h, 12 h, and 48 h greening. Six day old etiolated seedlings were treated with 18 ◦C or 12 ◦C cold stress. Seedlings were harvested at 0 h, 0.5 h, 12 h, and 48 h of greening and their DW, protein, chlorophyll, and carotenoid contents were measured. The error bars represent standard deviations of three independent biological replicates. Different letters indicate significantly different at *p* < 0.05 according to Duncan's multiple range tests.
