Optimal plant growth in many species is achieved when the two major forms of N are supplied at a particular ratio. In this pot experiment, the effects of five different ammonium: nitrate ratios (ANRs) (0: 100, 12.5: 87.5, 25: 75, 37.5: 62.5, and 50: 50) on photosynthesis efficiency in chilli pepper (Capsicum annuum L.) plants were evaluated. The results showed that an ANR of 25: 75 increased the contents of chl a, leaf area and dry matter, whereas chl b content was not affected by the ANRs. Regarding chlorophyll fluorescence, an ANR of 25: 75 also enhanced the actual photochemical efficiency, photochemical quenching and maximum photosynthetic rate. However, the 0: 100 and 50: 50 ANRs resulted in higher values for nonphotochemical quenching. An inhibition of maximal photochemical efficiency was found when 50% NH4+ was supplied at the later stage of plant growth. The addition of 25% or 37.5% NH4+ was beneficial for gas exchange parameters and the 25% NH4+ optimised the thylakoid of chloroplasts. Compared with nitrate alone, 12.5-50% NH4+ upregulated glutamate dehydrogenase (GDH), the large subunit and the small subunit of Rubisco. It can be concluded that the 25: 75 ANR accelerated N assimilation through active GDH, which provides a material basis for chloroplast and Rubisco formation, resulting in the increased photosynthetic rate and enhanced growth in chilli pepper.
Bibliographical noteFunding Information:
This research was financially supported by the National Key Research and Development Program of China (2016YFD0201005).
- chlorophyll fluorescence
- gas exchange parameter
- glutamate dehydrogenase
- photosynthetic pigment
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't