Department of Agronomy, University of Georgia, 30602, Athens, GA, USA.
Photosynth Res. 1986 Jan;10(1-2):101-12. doi: 10.1007/BF00024189.
Species in the Laxa and Grandia groups of the genus Panicum are adapted to low, wet areas of tropical and subtropical America. Panicum milioides is a species with C3 photosynthesis and low apparent photorespiration and has been classified as a C3/C4 intermediate. Other species in the Laxa group are C3 with normal photorespiration. Panicum prionitis is a C4 species in the Grandia group. Since P. milioides has some leaf characteristics intermediate to C3 and C4 species, its photosynthetic response to irradiance and temperature was compared to the closely related C3 species, P. laxum and P. boliviense and to P. prionitis. The response of apparent photosynthesis to irradiance and temperature was similar to that of P. laxum and P. boliviense, with saturation at a photosynthetic photo flux density of about 1 mmol m(-2) s(-1) at 30°C and temperature optimum near 30°C. In contrast, P. prionitis showed no light saturation up to 2 mmol m(-2) s(-1) and an optimum temperature near 40°C. P. milioides exhibited low CO2 loss into CO2-free air in the light and this loss was nearly insensitive to temperature. Loss of CO2 in the light in the C3 species, P. laxum and P. boliviense, was several-fold higher than in P. milioides and increased 2- to 5-fold with increases in temperature from 10 to 40°C. The level of dark respiration and its response to temperature were similar in all four Panicum species examined. It is concluded that the low apparent photorespiration in P. milioides does not influence its response of apparent photosynthesis to irradiance and temperature in comparison to closely related C3 Panicum species.
黍属的 Laxa 和 Grandia 组中的物种适应于热带和亚热带美洲的低湿地带。米草 Panicum milioides 是一种具有 C3 光合作用和低表观光呼吸的物种，被归类为 C3/C4 中间型。Laxa 组中的其他物种是具有正常光呼吸的 C3 型。普列里姆 Panicum prionitis 是 Grandia 组中的 C4 物种。由于米草 Panicum milioides 具有一些介于 C3 和 C4 物种之间的叶片特征，因此将其对光照和温度的光合响应与密切相关的 C3 物种，如 laxum 和 boliviense，以及与 prionitis 进行了比较。表观光合作用对光照和温度的响应与 laxum 和 boliviense 相似，在 30°C 时，光合光通量密度约为 1 mmol m(-2) s(-1)时达到饱和，温度最适接近 30°C。相比之下，prionitis 表现出在 2 mmol m(-2) s(-1)以下没有光饱和，最适温度接近 40°C。米草 Panicum milioides 在光照下向 CO2 自由空气中的 CO2 损失较低，并且这种损失几乎不受温度的影响。在 laxum 和 boliviense 这两种 C3 物种中，光照下的 CO2 损失比米草 Panicum milioides 高几倍，并随着温度从 10°C 到 40°C 的升高而增加 2-5 倍。在所有四种被研究的 Panicum 物种中，暗呼吸的水平及其对温度的响应是相似的。因此，与密切相关的 C3 Panicum 物种相比，米草 Panicum milioides 中低的表观光呼吸不会影响其对光照和温度的表观光合作用响应。
