TITLE:
CO2 Demand-Supply Coordination in Photosynthesis Reflecting the Plant-Environment Interaction: Extension and Parameterization of Demand Function and Supply Function
AUTHORS:
Lei Wang, Qing-Lai Dang
KEYWORDS:
Photosynthesis, Gas Exchange Measurement, Demand Function, Supply Function, Laisk Method, Light Response Curve
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.14 No.2,
February
28,
2023
ABSTRACT: Photosynthesis consists of a
biochemical process named demand and a CO2 diffusion process named
supply function. The intersection (Ci, An)
at equal to the demand function and the
supply function reflects a steady state of the plant subjected to the
environment. The intersections of these demand-supply functions under
different photosynthetically active radiation (PAR) can be fitted to a
regression line (names DSF) in which slope (ΔAn/ΔCi) can be defined as dsf.
We found that DSF information was embedded in both Laisk method (CO2 response curve (A/Ci) measured at three sub-saturated
PARs, and their intersections were used to estimate daytime respiration (Rd),
and CO2 compensation point (Ci*) and light
response curve measurements, which could be used to estimate dsf values. This study investigated the relationship between dsf and
the parameters related to the biochemical process and the CO2 diffusion process of photosynthesis. The results showed that dsf was
negatively correlated with gs, apparent carboxylation efficiency,
and apparent quantum yield. This suggests that DSF may coordinate the influence
of environmental conditions (light, CO2 and water) on photosynthesis
in the biochemical and CO2 diffusion process. Moreover, dsf was independent of gas exchange measurement conditions and showed species
specificity. In conclusion, we speculated that dsf seems to be a comprehensive parameter that might be related to the intrinsic
adaptation mechanism of plants to environmental conditions. We proposed an
auxiliary line perpendicular to the DSF and used it to improve the stability of Ci* and Rd estimated from the Laisk dataset.