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|Title:||Photosynthesis and biomass accumulation in young sugarcane plants grown under increasing ammonium supply in nutrient solution|
|Author:||Pissolato, Maria D.|
Silveira, Neidiquele M.
Machado, Eduardo C.
Zambrosi, Fernando C. B.
Ribeiro, Rafael V.
|Abstract:||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 mu mol 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|
|Appears in Collections:||IB - Artigos e Outros Documentos|
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