Dynamic light caused less photosynthetic suppression, rather than more, under nitrogen deficit conditions than under sufficient nitrogen supply conditions in soybean

Abstract

Background: Plants are always exposed to dynamic light. The photosynthetic light use efficiency of leaves is lower in dynamic light than in uniform irradiance. Research on the influence of environmental factors on dynamic photosynthesis is very limited. Nitrogen is critical for plants, especially for photosynthesis. Low nitrogen (LN) decreases ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and thus limits photosynthesis. The decrease in Rubisco also delays photosynthetic induction in LN leaves; therefore, we hypothesized that the difference of photosynthetic CO 2 fixation between uniform and dynamic light will be greater in LN leaves compared to leaves with sufficient nitrogen supply. Results: To test this hypothesis, soybean plants were grown under low or high nitrogen (HN), and the photosynthetic gas exchange, enzyme activity and protein amount in leaves were measured under uniform and dynamic light. Unexpectedly, dynamic light caused less photosynthetic suppression, rather than more, in LN leaves than in HN leaves. The underlying mechanism was also clarified. Short low-light (LL) intervals did not affect Rubisco activity but clearly deactivated fructose-1,6-bisphosphatase (FBPase) and sedoheptulose-1,7-bisphosphatase (SBPase), indicating that photosynthetic induction after a LL interval depends on the reactivation of FBPase and SBPase rather than Rubisco. In LN leaves, the amount of Rubisco decreased more than FBPase and SBPase, so FBPase and SBPase were present in relative excess. A lower fraction of FBPase and SBPase needs to be activated in LN leaves for photosynthesis recovery during the highlight phase of dynamic light. Therefore, photosynthetic recovery is faster in LN leaves than in HN leaves, which relieves the photosynthetic suppression caused by dynamic light in LN leaves.

Photosynthetic induction upon transfer from low to high light is affected by leaf nitrogen content in tomato

“…This finding is similar to the photosynthetic induction of dark-adapted leaves among canola genotypes (Brassica napus L.) (Liu, Zhang, Estavillo, Luo & Hu 2021), but was inconsistent with the phenomenon in soybean (Li et al 2020). In soybean, the induction rate of A N under high light after shading for 5 min was very fast (Pearcy, Krall & Sassenrath-Cole 1996;Li et al 2020). Furthermore, this fast photosynthetic induction in soybean was not affected by leaf N content (Li et al 2020).…”

“…Therefore, leaf N content significantly affect the photosynthetic induction after transition from low to high light in tomato. This finding is similar to the photosynthetic induction of dark-adapted leaves among canola genotypes (Brassica napus L.) (Liu, Zhang, Estavillo, Luo & Hu 2021), but was inconsistent with the phenomenon in soybean (Li et al 2020). In soybean, the induction rate of A N under high light after shading for 5 min was very fast (Pearcy, Krall & Sassenrath-Cole 1996;Li et al 2020).…”

“…In soybean, the induction rate of A N under high light after shading for 5 min was very fast (Pearcy, Krall & Sassenrath-Cole 1996;Li et al 2020). Furthermore, this fast photosynthetic induction in soybean was not affected by leaf N content (Li et al 2020). Therefore, the effect of leaf N content on fast photosynthetic (which was not certified by peer review) is the author/funder.…”

“…Furthermore, the stomatal opening during photosynthetic induction can be affected by environment conditions such as target light intensity, magnitude of change, g s at low light, the time of day and vapor pressure deficit (Kaiser et al 2020;Sakoda et al 2020;Eyland, van Wesemael, Lawson & Carpentier 2021). However, there have been few studies that examined the effect of leaf N content on the induction response of g s after transition from low to high light (Li et al 2020).…”

“…Plants grown under high nitrogen (N) concentration usually have higher biomass than plants grown under low N concertation (Makino 2011). An important explanation for this is that leaf photosynthetic capacity is related to the leaf N content in many higher plants (Yamori, Nagai & Makino 2011;Li et al 2020), since stromal enzymes and thylakoid proteins account for the majority of leaf N (Makino & Osmond 1991;Sudo, Makino & Mae 2003;Takashima, Hikosaka & Hirose 2004). Furthermore, stomatal conductance (g s ) and mesophyll conductance (g m ) under constant high light are also increased in plants grown under high N concentration, which speeds up CO 2 diffusion from atmosphere to chloroplast carboxylation sites and thus favors the operation of A N under constant high light (Yamori et al 2011).…”