title: Increased sink strength offsets the inhibitory effect of sucrose on sugarcane photosynthesis.
abstract: Spraying sucrose inhibits photosynthesis by impairing Rubisco activity and stomatal conductance (gs), whereas increasing sink demand by partially darkening the plant stimulates sugarcane photosynthesis. We hypothesized that the stimulatory effect of darkness can offset the inhibitory effect of exogenous sucrose on photosynthesis. Source-sink relationship was perturbed in two sugarcane cultivars by imposing partial darkness, spraying a sucrose solution (50mM) and their combination. Five days after the onset of the treatments, the maximum Rubisco carboxylation rate (Vcmax) and the initial slope of A-Cicurve (k) were estimated by measuring leaf gas exchange and chlorophyll fluorescence. Photosynthesis was inhibited by sucrose spraying in both genotypes, through decreases in Vcmax, k, gsand ATP production driven by electron transport (Jatp). Photosynthesis of plants subjected to the combination of partial darkness and sucrose spraying was similar to photosynthesis of reference plants for both genotypes. Significant increases in Vcmax, gsand Jatpand marginal increases in k were noticed when combining partial darkness and sucrose spraying compared with sucrose spraying alone. Our data also revealed that increases in sink strength due to partial darkness offset the inhibition of sugarcane photosynthesis caused by sucrose spraying, enhancing the knowledge on endogenous regulation of sugarcane photosynthesis through the source-sink relationship.
authors.affiliation: Department of Plant Biology, Institute of Biology, University of Campinas, Campinas, SP, Brazil. Electronic address: rvr@unicamp.br.
authors.forename: Rafael V
authors.initials: RV
authors.lastname: Ribeiro
authors.affiliation: Laboratory of Plant Physiology "Coaracy M. Franco", Centre for Research and Development in Ecophysiology and Biophysics, Agronomic Institute, Campinas, SP, Brazil. Electronic address: caruso@iac.sp.gov.br.
authors.forename: Eduardo C
authors.initials: EC
authors.lastname: Machado
authors.affiliation: Laboratory of Plant Physiology "Coaracy M. Franco", Centre for Research and Development in Ecophysiology and Biophysics, Agronomic Institute, Campinas, SP, Brazil. Electronic address: zeroagro@yahoo.com.br.
authors.forename: José R
authors.initials: JR
authors.lastname: Magalhães Filho
authors.affiliation: Department of Biochemistry and Molecular Biology, Federal University of Ceará, Fortaleza, CE, Brazil. Electronic address: karlamlobo@gmail.com.
authors.forename: Ana Karla M
authors.initials: AK
authors.lastname: Lobo
authors.affiliation: Department of Biochemistry and Molecular Biology, Federal University of Ceará, Fortaleza, CE, Brazil. Electronic address: momartins@yahoo.com.br.
authors.forename: Márcio O
authors.initials: MO
authors.lastname: Martins
authors.affiliation: Department of Biochemistry and Molecular Biology, Federal University of Ceará, Fortaleza, CE, Brazil. Electronic address: silveira@ufc.br.
authors.forename: Joaquim A G
authors.initials: JA
authors.lastname: Silveira
authors.affiliation: Centre for Crop Systems Analysis, Department of Plant Sciences, Wageningen University & Research, Wageningen, The Netherlands. Electronic address: xinyou.yin@wur.nl.
authors.forename: Xinyou
authors.initials: X
authors.lastname: Yin
authors.affiliation: Centre for Crop Systems Analysis, Department of Plant Sciences, Wageningen University & Research, Wageningen, The Netherlands. Electronic address: paul.struik@wur.nl.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Struik
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D003624:Darkness; D004579:Electron Transport; D005453:Fluorescence; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism*; D010788:Photosynthesis / Q000187:drug effects*; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D054046:Plant Stomata / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D018526:Plant Transpiration / Q000187:drug effects; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism*; D031786:Saccharum / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology; D013395:Sucrose / Q000494:pharmacology*
chemical_list: D002734:Chlorophyll; D013395:Sucrose; D010730:Phosphoenolpyruvate Carboxylase; D012273:Ribulose-Bisphosphate Carboxylase
keywords: Photosynthesis; Saccharum; Source-sink; Sucrose; Sugarcane