Faculty of Forestry, Department of Forest Engineering, Division of Plant Physiology, Kahramanmaraş Sütçü İmam Üniversitesi, Kahramanmaraş, 46100, Turkey; Department of Bioengineering and Sciences, Kahramanmaraş Sütçü İmam Üniversitesi, Kahramanmaraş, 46100, Turkey.
Physiol Plant. 2015 Mar;153(3):454-66. doi: 10.1111/ppl.12240. Epub 2014 Jul 29.
In plants, most water is absorbed by roots and transported through vascular conduits of xylem which evaporate from leaves during photosynthesis. As photosynthesis and transport processes are interconnected, it was hypothesized that any variation in water transport demand influencing water use efficiency (WUE), such as the evolution of C4 photosynthesis, should affect xylem structure and function. Several studies have provided evidence for this hypothesis, but none has comprehensively compared photosynthetic, hydraulic and biomass allocation properties between C3 and C4 species. In this study, photosynthetic, hydraulic and biomass properties in a closely related C3 Tarenaya hassleriana and a C4 Cleome gynandra are compared. Light response curves, measured at 30°C, showed that the C4 C. gynandra had almost twice greater net assimilation rates than the C3 T. hassleriana under each increasing irradiation level. On the contrary, transpiration rates and stomatal conductance were around twice as high in the C3 , leading to approximately 3.5 times higher WUE in the C4 compared with the C3 species. The C3 showed about 3.3 times higher hydraulic conductivity, 4.3 times greater specific conductivity and 2.6 times higher leaf-specific conductivity than the C4 species. The C3 produced more vessels per xylem area and larger vessels. All of these differences resulted in different biomass properties, where the C4 produced more biomass in general and had less root to shoot ratio than the C3 species. These results are in support of our previous findings that WUE, and any changes that affect WUE, contribute to xylem evolution in plants.
在植物中，大部分水分被根部吸收，并通过木质部的维管束运输，在光合作用过程中从叶片蒸发。由于光合作用和运输过程是相互关联的，因此有人假设，任何影响水分利用效率（WUE）的水分运输需求变化，如 C4 光合作用的进化，都会影响木质部的结构和功能。有几项研究为这一假设提供了证据，但没有一项研究综合比较过 C3 和 C4 物种之间的光合作用、水力和生物量分配特性。在这项研究中，对密切相关的 C3 植物 Tarenaya hassleriana 和 C4 植物 Cleome gynandra 进行了光合作用、水力和生物量特性的比较。在 30°C 下测量的光响应曲线表明，在每个增加的辐照度水平下，C4 植物 C. gynandra 的净同化率几乎是 C3 植物 T. hassleriana 的两倍。相反，C3 的蒸腾速率和气孔导度约为 C3 的两倍，导致 C4 的水分利用效率比 C3 高约 3.5 倍。C3 的水力传导率比 C4 高约 3.3 倍，比导度高约 4.3 倍，比叶导度高约 2.6 倍。C3 每木质部面积产生的导管数量更多，导管也更大。所有这些差异导致了不同的生物量特性，其中 C4 产生的生物量总体上更多，根与茎的比例也比 C3 小。这些结果支持了我们之前的发现，即 WUE，以及任何影响 WUE 的变化，都有助于植物木质部的进化。
