The Photosynthetic Characteristics in Chaling Common Wild Rice (Oryza rufipogon Griff.) under the Cold Stress
Chaling common wild rice (CWR, Oryza rufipogon Griff.), distributed in Chaling county, Hunan province, China, is one of the only two wild rice populations grown northernmost in the world. Although the cold tolerance of Chaling CWR is extremely strong, its photosynthetic characteristics under the cold stress remain unknown. In this study, we determined the net photosynthetic rate (Pn), total chlorophyll (Chl) and total carotenoid (Car) contents, maximum quantum yield of PSII (Fv/Fm), apparent quantum yield (AQY), and carboxylation efficiency (CE) of leaves from Chaling CWR at tiller stage under cold stress (15 ℃) and normal temperature condition (28 ℃). These photosynthetic parameters were compared with standard rice cultivars including typical indica Guangluai 4, indica Y liangyou 1 (a Chinese super high grain yield hybrid), and typical japonica Nipponbare under the same conditions. All photosynthetic parameters in Chaling CWR were significantly (P £ 0.05 or P £ 0.01) higher than those in standard rice cultivars under the cold stress. The ratios of these parameters from Chaling CWR under the cold stress to those under the normal temperature were 47.9% ~ 84.9%, much higher than those from standard rice cultivars, which were 3.1% ~ 73.8%. Taken together, these data show the photosynthetic characteristics of Chaling CWR under the cold stress are excellent. The finding would generate an enormous benefit if the trait of the cold stress tolerance of Chaling CWR is transferred to the cultivated rice via the breeding or other genetic approaches.
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