Photosynthesis and biomass accumulation in young sugarcane plants grown under increasing ammonium supply in nutrient solution
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The aim of this study was to evaluate the sugarcane responses to varying ammonium:nitrate (NH4+:NO3−) ratio and to reveal how much NH4+ plants can tolerate before showing impairment of photosynthesis and growth. Sugarcane plants were grown in nutrient solution with the following NH4+:NO3− ratios (%): 20:80; 30:70; 40:60; 60:40; 70:30; and 80:20. The lowest photosynthetic rates, stomatal conductance, instantaneous carboxylation efficiency and leaf chlorophyll a content were found in plants supplied with higher than 60% NH4+. The leaf content of chlorophyll b proved to be more sensitive than chlorophyll a and decreases were found from 40% NH4+. We did not observe significant differences in leaf NO3− concentration under varying NH4+:NO3− ratio. However, plants that received 80% NH4+ showed the highest leaf NH4+ concentration and lowest leaf [NO3−]:[NH4+] ratio. The estimated leaf nitrogen content was higher in plants supplied with 20% and 30% NH4+. Taken together, our data revealed that sugarcane plants are sensitive to NH4+, with photosynthesis and plant growth being impaired when NH4+ supply was higher than 30% in nutrient solution. Root biomass was significantly reduced under high NH4+ supply, which explains decreases in stomatal conductance. Besides stomatal limitation, photosynthesis was also limited by low carboxylation efficiency under high NH4+ supply. Apparently, leaf NH4+ concentrations higher than 1.0 µmol g−1 were enough to impair photosynthesis. The balance between [NO3−] and [NH4+] in leaves was more correlated to photosynthesis than either [NO3−] or [NH4+] alone.
KeywordsNitrogen Root growth Saccharum spp. Nitrate
MDP acknowledges the scholarship provided by the São Paulo Research Foundation (FAPESP, Brazil; Grant No. 2017/11279-7). NMS acknowledges the fellowship granted by the National Program of Post-Doctorate (PNPD), Coordination for the Improvement of Higher Education Personnel (Capes, Brazil). ECM, LS and RVR acknowledge the fellowships granted by the National Council for Scientific and Technological Development (CNPq, Brazil).
- Boschiero BN (2017). Adubação nitrogenada em soqueiras de cana-de-açúcar: influência do uso em longo prazo de fontes e/ou doses de nitrogênio. PhD thesis, University of São Paulo, College of Agriculture Luiz de Queiroz. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-23012017-103942/pt-br.php. Accessed 17 April 2019
- Meinzer FC, Zhu J (1998) Nitrogen stress reduces the efficiency of the C4 CO2 concentrating system, and therefore quantum yield, in Saccharum (sugarcane) species. J Exp Bot 49:1227–1234Google Scholar
- Robinson N, Brackin R, Vinall K, Soper F, Holst J, Gamage H, Paungfoo-Lonhienne C, Rennenberg H, Lakshmanan P, Schmidt S (2011) Nitrate paradigm does not hold up for sugarcane. PLoS ONE 6:1–9Google Scholar
- Silveira NM, Marcos FC, Frungillo L, Moura BB, Seabra AB, Salgado I, Ribeiro RV (2017a) S-nitrosoglutathione spraying improves stomatal conductance, Rubisco activity and antioxidant defense in both leaves and roots of sugarcane plants under water deficit. Physiol Plant 160:383–395CrossRefGoogle Scholar
- Skopelitis DS, Paranychianakis NV, Paschalidis KA, Pliakonis ED, Delis ID, Yakoumakis DI, Kouvarakis A, Papadakis AK, Stephanou EG, Roubelakis-Angelakis KA (2006) Abiotic stress generates ROS that signal expression of anionic glutamate dehydrogenases to form glutamate for proline synthesis in tobacco and grapevine. Plant Cell 18:2767–2781CrossRefGoogle Scholar
- Su D, Fang Z, Li YL, Zhao B (2012) Effect of different NH4 +–N:NO3 −–N ratios on the growth of lilium. North Hortic 2:67–69Google Scholar