Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
UWA School of Agriculture and Environment, Faculty of Science, The University of Western Australia, Crawley, WA, Australia.
Ann Bot. 2018 Sep 24;122(4):605-615. doi: 10.1093/aob/mcy095.
Leaf tissue CO2 partial pressure (pCO2) shows contrasting dynamics over a diurnal cycle in C3 and Crassulacean Acid Metabolism (CAM) plants. However, simultaneous and continuous monitoring of pCO2 and pO2 in C3 and CAM plants under the same conditions was lacking. Our aim was to use a new CO2 microsensor and an existing O2 microsensor for non-destructive measurements of leaf pCO2 and pO2 dynamics to compare a C3 and a CAM plant in an aquatic environment.
A new amperometric CO2 microsensor and an O2 microsensor elucidated with high temporal resolution the dynamics in leaf pCO2 and pO2 during light-dark cycles for C3Lobelia dortmanna and CAM Littorella uniflora aquatic plants. Underwater photosynthesis, dark respiration, tissue malate concentrations and sediment CO2 and O2 were also measured.
During the dark period, for the C3 plant, pCO2 increased to approx. 3.5 kPa, whereas for the CAM plant CO2 was mostly below 0.05 kPa owing to CO2 sequestration into malate. Upon darkness, the CAM plant had an initial peak in pCO2 (approx. 0.16 kPa) which then declined to a quasi-steady state for several hours and then pCO2 increased towards the end of the dark period. The C3 plant became severely hypoxic late in the dark period, whereas the CAM plant with greater cuticle permeability did not. Upon illumination, leaf pCO2 declined and pO2 increased, although aspects of these dynamics also differed between the two plants.
The continuous measurements of pCO2 and pO2 highlighted the contrasting tissue gas compositions in submerged C3 and CAM plants. The CAM leaf pCO2 dynamics indicate an initial lag in CO2 sequestration to malate, which after several hours of malate synthesis then slows. Like the use of O2 microsensors to resolve questions related to plant aeration, deployment of the new CO2 microsensor will benefit plant ecophysiology research.
在 C3 和景天酸代谢（CAM）植物中，叶片组织 CO2 分压（pCO2）在昼夜周期中表现出相反的动态。然而，在相同条件下，同时和连续监测 C3 和 CAM 植物的 pCO2 和 pO2 缺乏。我们的目的是使用新的 CO2 微传感器和现有的 O2 微传感器，对水生环境中的 C3 植物和 CAM 植物进行非破坏性测量，以比较叶片 pCO2 和 pO2 动态。
一种新的电流 CO2 微传感器和一种 O2 微传感器，以高时间分辨率阐明了 C3 植物 Lobelia dortmanna 和 CAM 植物 Littorella uniflora 水生植物在光暗周期中叶片 pCO2 和 pO2 的动态。还测量了水下光合作用、暗呼吸、组织苹果酸浓度以及沉积物 CO2 和 O2。
在暗期，对于 C3 植物，pCO2 增加到约 3.5 kPa，而对于 CAM 植物，由于 CO2 被隔离到苹果酸中，CO2 主要低于 0.05 kPa。在黑暗中，CAM 植物的 pCO2 最初有一个峰值（约 0.16 kPa），然后下降到几个小时的准稳态，然后在暗期结束时 pCO2 增加。在暗期后期，C3 植物严重缺氧，而角质层渗透率较高的 CAM 植物则没有。在光照下，叶片 pCO2 下降，pO2 增加，尽管这两种植物的这些动态也有所不同。
pCO2 和 pO2 的连续测量突出了淹没的 C3 和 CAM 植物中组织气体组成的对比。CAM 叶片 pCO2 动态表明，最初在将 CO2 隔离到苹果酸中存在滞后，数小时后苹果酸合成减缓。与使用 O2 微传感器来解决与植物通气有关的问题一样，部署新的 CO2 微传感器将使植物生理生态学研究受益。
