Biomass partitioning and photosynthesis in the quest for nitrogen- use efficiency for citrus tree species

Author(s)

Dovis, Veronica L. ^[1] ; Erismann, Norma M. ^[2] ; Machado, Eduardo C. ^[2] ; Quaggio, Jose A. ^[3] ; Boaretto, Rodrigo M. ^[1] ; Mattos Junior, Dirceu ^[1]

Affiliation

^[1] Inst Agron IAC, Ctr Citricultura Sylvio Moreira, Rod Anhanguera Km 158, BR-13490000 Cordeiropolis - Brazil

^[2] Inst Agron IAC, Ctr Pesquisa & Desenvolvimento Ecofisiol & Biofis, Lab Fisiol Vegetal Coaracy M Franco, Av Doutor Theodureto de Almeida Camargo 1500, BR-13075630 Campinas - Brazil

^[3] Inst Agron IAC, Ctr Solos & Recursos Ambientais, Av Barao de Itapura 1481, BR-13020902 Campinas - Brazil

• Document type: Journal article
• Source: TREE PHYSIOLOGY; v. 41, n. 2, p. 163-176, FEB 2021.
• Web of Science Citations: 0

Abstract

Optimizing the use of nitrogen (N) for food production is a major challenge in agricultural systems. The transformation of N into crop production results from intricate pathways, depending on plants, as well as the environment and fertilization regimes, which affect the N-use efficiency (NUE) of plants. In this context, lemon trees {[}Citrus limon (L.) Burm. f.] attain maximum harvest index at lower leaf N concentrations compared with sweet orange trees {[}Citrus sinensis (L.) Osbeck], and the processes governing these plant responses are not well known. The aim of this study was to understand how the higher NUE in lemons trees is constructed based on growth and biomass partitioning evaluation, as well as photochemical and biochemical characteristics of photosynthesis. To attain this goal, we evaluated growth, photosynthesis and biochemical characteristics in lemon and sweet orange trees under two different N levels over 14 months. We hypothesized that higher NUE in lemon trees is affected by plant capacity to grow with economy on nutrient resources. Furthermore, lemon trees could be more efficient in CO2 assimilation in non-limiting environmental conditions. We found that higher NUE in lemon trees was explained in part by the ability of trees to invest greater biomass in leaves instead of roots, even though this species exhibited lower relative recovery efficiency of N from the substrate than the sweet orange. We also found that lemon trees had a higher relative growth rate than sweet oranges, despite the fact that net CO2 assimilation and dark respiration were similar between the two species. As a consequence, we suggested that lemons could exhibit a lower biomass construction cost than oranges. Because lemon presented lower N concentration than sweet orange trees, the former exhibited better photosynthetic N-use efficiency (PNUE: 55-120 mmol CO2 g N-1 day(-1)) compared with the sweet orange (PNUE: 31-68 mmol CO2 g N-1 day(-1)). Lemon trees also exhibited a higher relative rate of electron transport per unit of chlorophyll (ETR/chlor: 350-850) compared with orange trees (ETR/chlor: 300-550) at both low and at high N supply. These characteristics were likely associated with transport facilitation of CO2 to the catalytic sites of plants. In fact, improved growth of lemon trees results from an array of events explained mostly by increase in leaf area and associated low construction cost despite N supply. (AU)

• FAPESP's process: 14/50880-0 - INCT 2014: comparative and functional genomics and citrus-assisted breeding
• Grantee: Marcos Antonio Machado
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 14/18151-8 - Photochemical and Biochemical Characterization of Photosynthetic System and Nitrogen Partitioning: a Nitrogen-Use-Efficiency relationship in Citrus
• Grantee: Veronica Lorena Dovis
• Support Opportunities: Scholarships in Brazil - Post-Doctoral