High Nitrate or Ammonium Applications Alleviated Photosynthetic Decline of Phoebe bournei Seedlings under Elevated Carbon Dioxide

Abstract

Phoebe bournei is a precioustimber species and is listed as a national secondary protection plant in China. However, seedlings show obvious photosynthetic declinewhen grown long-term under an elevated CO2 concentration (eCO2). The global CO2 concentration is predicted to reach 700 μmol·mol−1 by the end of this century; however, little is known about what causes the photosynthetic decline of P. bournei seedlings under eCO2 or whether this photosynthetic decline could be controlled by fertilization measures. To explore this problem, one-year-old P. bournei seedlings were grown in an open-top air chamber under either an ambient CO2 (aCO2) concentration (350 ± 70 μmol·mol−1) or an eCO2 concentration (700 ± 10 μmol·mol−1) from June 12th to September 8th and cultivated in soil treated with either moderate (0.8 g per seedling) or high applications (1.2 g per seedling) of nitrate or ammonium. Under eCO2, the net photosynthetic rate (Pn) of P. bournei seedlings treated with a moderate nitrate application was 27.0% lower than that of seedlings grown under an aCO2 concentration (p < 0.05), and photosynthetic declineappeared to be accompanied by a reduction of the electron transport rate (ETR), actual photochemical efficiency, chlorophyll content, ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco), rubisco activase (RCA) content, leaf thickness, and stomatal density. The Pn of seedlings treated with a high application of nitrate under eCO2 was 5.0% lower than that of seedlings grown under aCO2 (p > 0.05), and photosynthetic declineoccurred more slowly, accompanied by a significant increase in rubisco content, RCA content, and stomatal density. The Pn of P. bournei seedlings treated with either a moderate or a high application of ammonium and grown under eCO2 was not significantly differentto that of seedlings grown under aCO2—there was no photosynthetic decline—and the ETR, chlorophyll content, rubisco content, RCA content, and leaf thickness values were all increased. Increasing the application of nitrate or the supply of ammonium could slow down or prevent the photosynthetic declineof P. bournei seedlings under eCO2 by changing the leaf structure and photosynthetic physiological characteristics.

Transcriptome and proteome analyses reveal high nitrate or ammonium applications alleviate photosynthetic decline of Phoebe bournei seedlings under elevated carbon dioxide by regulating glnA and rbcS

“…Plants receiving ammonium respond more positively to eCO 2 than those receiving nitrate because eCO 2 inhibited the assimilation of nitrate in shoots of C 3 plants [13]. These ndings are consistent with ours; however, the mechanisms underlying photosynthetic decline, especially the regulation of nitrogen remain poorly understood [10]. In this study, our aim was to further elucidate the mechanism involved in the alleviation of the photosynthetic decline of P. bournei seedlings under eCO 2 when applied with high nitrate or ammonium applications.With the development of molecular biology technology, transcriptomics and proteomics technologies are providing new ways of identifying target genes and proteins for research studies [14].…”

“…P. bournei seedlings show obvious photosynthetic decline when grown long-term under eCO 2 [8,9]. In our previous study [10], we showed that this decline could be alleviated by applying a high level of nitrate or ammonium and that the content of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and Rubisco activase (RCA) changed under different CO 2 concentrations and nitrogen supplies. We hypothesize that the application of high nitrate or ammonium regulates photosynthetic e ciency by affecting the content of Rubisco and RCA, while the change in the Rubisco and RCA content may re ect a difference in the nitrogen metabolism in P. bournei seedlings [11].…”

Elevated CO₂ mitigates the effects of cadmium stress on vegetable growth and antioxidant systems

“…Elevated CO 2 concentration can regulate photosynthesis by affecting the content and activity of Rubisco and RCA (Rubisco activase), key enzymes of photosynthesis, as well as gene expression, and affect the photosynthetic rate (Wang et al 2020). The growth and biomass of different types of vegetables in different soils were promoted under eCO 2 , and that CO 2 concentration had a significant effect on the biomass of the four vegetables used in the study.…”

Impacts of Climate Change on Tree Physiology and Responses of Forest Ecosystems

“…They identified differentially expressed genes and alterations in chlorophylls, starch, and soluble sugars in response to increasing CO 2 . The impact of elevated CO 2 was also assessed by Wang et al [2], who reported photosynthetic declines in Phoebe bournei Hemsl., an endemic tree threatened by habitat loss in China. However, they concluded that this negative impact of increased CO 2 may be alleviated by the application of ammonium or nitrate fertilization.…”