Rice plants were sampled after completing SPAD reading. The whole plant weight was recorded for fresh weight, and then separated into leaves, stems and roots. The first and third fully expanded leaves were chosen for the analysis of chlorophyll a (Chl a), chlorophyll b (Chl b), sum of chlorophyll a and chlorophyll b (TChl), ratio of chlorophyll a and chlorophyll b (Chl a/Chl b), and total carotenoid (Car) contents according to Li et al. (2000). The leaf samples were extracted in 95% ethanol and an UV-2550 UV–vis spectrometer (SHIMADZU Co., Ltd.) was used to determine absorbance at 665, 649 and 470 nm. Leaves and stems were put into oven-dried at 105 ◦C for half an hour to rapidly stop metabolism and then at 70 ◦C until constant dry weight. The dried leaves were ground and analyzed for Leaf N concentration by Kjeldahl after acid digest. Leaf N concentration (LNC) was expressed in %.