Department of Biology, University of New Mexico, Albuquerque, NM, 87131, USA.
New Phytol. 2019 Aug;223(3):1241-1252. doi: 10.1111/nph.15908. Epub 2019 Jun 20.
High concentrations of dissolved inorganic carbon in stems of herbaceous and woody C plants exit leaves in the dark. In the light, C species use a small portion of xylem-transported CO for leaf photosynthesis. However, it is not known if xylem-transported CO will exit leaves in the dark or be used for photosynthesis in the light in Kranz-type C plants. Cut leaves of Amaranthus hypochondriacus were placed in one of three solutions of [NaH CO ] dissolved in KCl water to measure the efflux of xylem-transported CO exiting the leaf in the dark or rates of assimilation of xylem-transported CO * in the light, in real-time, using a tunable diode laser absorption spectroscope. In the dark, the efflux of xylem-transported CO increased with increasing rates of transpiration and [ CO *]; however, rates of C in A. hypochondriacus were lower compared to C species. In the light, A. hypochondriacus fixed nearly 75% of the xylem-transported CO supplied to the leaf. Kranz anatomy and biochemistry likely influence the efflux of xylem-transported CO out of cut leaves of A. hypochondriacus in the dark, as well as the use of xylem-transported CO * for photosynthesis in the light. Thus increasing the carbon use efficiency of Kranz-type C species over C species.
高浓度的溶解无机碳在草本和木本 C 植物的茎中存在于离开叶子的黑暗中。在光下，C 种植物使用一小部分木质部运输的 CO 进行叶片光合作用。然而，目前尚不清楚木质部运输的 CO 是否会在黑暗中离开叶子，或者是否会在光下用于 Kranz 型 C 植物的光合作用。将苋菜的离体叶片置于三种[NaHCO3]溶解在 KCl 水中的溶液之一中，以使用可调谐二极管激光吸收光谱仪实时测量木质部运输的 CO 在黑暗中离开叶片的外排率或在光下木质部运输的 CO同化率。在黑暗中，木质部运输的 CO 外排率随着蒸腾和[CO]速率的增加而增加；然而，与 C 种植物相比，A. hypochondriacus 的 C 同化率较低。在光下，A. hypochondriacus 固定了供给叶片的木质部运输的 CO 的近 75%。Kranz 解剖结构和生物化学可能会影响苋菜离体叶片中木质部运输的 CO 在黑暗中的外排，以及木质部运输的 CO*在光下用于光合作用。因此，与 C 种植物相比，Kranz 型 C 种植物的碳利用效率更高。
