Abstract:

Chaling wild rice, one of groups of common wild rice (Oryza rufipogon Griff), was found in Chaling county, Hunan province, and has not been studied on its photosynthesis at home and abroad. The objective of this study was to measure the photosynthetic parameters of flag leaves at flowering stage using Chaling wild rice with several super-high yielding or high-yielding rice cultivars (Liangyoupeijiu, Shanyou 63, V46, and 93-11) as controls. The net photosynthetic rate (P_n) of rice flag leaves was measured with the LI-6400 Portable Photosynthesis System from 9:00 to 17:00 at sunny day under natural condition. The response of Pn to light intensity was measured from 9:00 knowledge of photosynthesis of wild rice to 11:00 at sunny day under different light intensities of red-blue light provided by the LI-6400 machine. The responses of Pn to CO₂ concentration and temperature were measured from 9:00 to 11:00 at sunny day under different CO2 concentrations and different temperatures respectively, as well as 1 500 µmol photons m^-2 s^-1 of stable red-blue light provided by the LI-6400 machine. Photosynthetic pigment contents were measured by 7230G spectrophotometer. The results showed that the Pn of Chaling wild rice was much significently higher than that of cultivars in the afternoon and under high temperature (40℃ and 45℃). The light saturation point (LSP) of Chaling wild rice was 1 810 µmol photons·m^-2·s^-1, which was much significantly higher than that of cultivars (1 530–1 628 µmol photons m^-2 s^-1) except 93-11, and the light compensation point (LCP) of Chaling wild rice was 22.3 µmol photons m^-2 s^-1, without significant difference with that of cultivars (20.1–23.7 µmol photons m^-2 s^-1). There was no significant difference of AQY between Chaling wild rice and cultivars. The carboxylation efficiency (CE) and CO₂ saturation point of Chaling wild rice were 0.1511 mol m^-2 s^-1 and 644.5 μmol mol-1 respectively, significantly higher than those of cultivars (0.1277–0.1384 mol m^-2 s^-1 and 521.1–581.3 μmol mol^-1 respectively), and its CO₂ compensation point (52.7 μmol mol^-1) was a little higher than that of cultivars (42.7–50.1 μmol mol^-1). The chlorophyll content of Chaling wild rice was much significantly higher than that of cultivars. Based on the above results we think that the photosynthetic capacity of Chaling wild rice is stronger than that of super-high yielding or high yielding cultivar controls , especially under high temperature.

Key words: Chaling wild rice, Net photosynthesis rate, Gas exchange parameters of photosynthesis, Photosynthetic pigments