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Plant function and evolutionary biology
RESEARCH ARTICLE

Promoting pepper (Capsicum annuum) photosynthesis via chloroplast ultrastructure and enzyme activities by optimising the ammonium to nitrate ratio

Jing Zhang A , Jianming Xie https://orcid.org/0000-0002-7493-2164 A G , Yantai Gan B , Jeffrey A. Coulter C , Mohammed Mujitaba Dawuda A D , Jihua Yu A , Jian Lv A , Jing Li A , Xiaodang Zhang A , Chaonan Tang A , Cheng Wang A , Tianhang Niu A and Alejandro Calderón-Urrea E F
+ Author Affiliations
- Author Affiliations

A College of Horticulture, Gansu Agricultural University, Yingmen Village, Anning District, Lanzhou, 730070, P.R. China.

B Agriculture and Agri-Food Canada, Swift Current Research and Development Centre, Swift Current, SK, S9H 3X2, Canada.

C Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN 55108, USA.

D Department of Horticulture, Faculty of Agriculture, University for Development Studies, Post Office Box TL 1882, Tamale, Ghana.

E College of Plant Protection, Gansu Agricultural University, Lanzhou 730070, P.R. China.

F Department of Biology, College of Science and Mathematics, California State University, Fresno, Fresno, CA, USA.

G Corresponding Author. Email: xiejianming@gsau.edu.cn

Functional Plant Biology 47(4) 303-317 https://doi.org/10.1071/FP19149
Submitted: 29 May 2019  Accepted: 16 November 2019   Published: 3 March 2020

Abstract

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.

Additional keywords: chlorophyll fluorescence, gas exchange parameter, glutamate dehydrogenase, photosynthetic pigment, Rubisco.


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