Increased sink strength offsets the inhibitory effect of sucrose on sugarcane photosynthesis

• Published in: Journal of plant physiology Vol. 208; pp. 61 - 69
• Main Authors: Ribeiro, Rafael V., Machado, Eduardo C., Magalhães Filho, José R., Lobo, Ana Karla M., Martins, Márcio O., Silveira, Joaquim A.G., Yin, Xinyou, Struik, Paul C.
• Format: Journal Article
• Language: English
• Published: Germany Elsevier GmbH 01.01.2017; Elsevier Science Ltd
• Subjects: adenosine triphosphate; Carboxylation; Chlorophyll; Chlorophyll - metabolism; Conductance; Cultivars; Darkening; Darkness; electron transfer; Electron Transport; Fluorescence; Gas exchange; genotype; Genotype & phenotype; Genotypes; leaves; Offsets; Phosphoenolpyruvate Carboxylase - metabolism; Photosynthesis; Photosynthesis - drug effects; Plant Leaves - drug effects; Plant Leaves - enzymology; Plant Leaves - physiology; Plant Stomata - drug effects; Plant Stomata - enzymology; Plant Stomata - physiology; Plant Transpiration - drug effects; Resistance; Ribulose-bisphosphate carboxylase; Ribulose-Bisphosphate Carboxylase - metabolism; Saccharum; Saccharum - drug effects; Saccharum - enzymology; Saccharum - physiology; Source-sink; Source-sink relationships; Spraying; Stomata; Stomatal conductance; Sucrose; Sucrose - pharmacology; Sugar; Sugarcane; A; Saccharum; Sucrose; Rubisco; D+S; PEPC; Rd; A380; SPS; SL; Vcmax; ϕPSII; Sugarcane; Suc; NSL; k; gs; SuSy; Jatp; Ref; s; Dark; Source-sink; SAI; NI; Photosynthesis
• ISSN: 0176-1617; 1618-1328; 1618-1328
• DOI: 10.1016/j.jplph.2016.11.005

•Source-sink relationship was perturbed in two sugarcane cultivars.•Exogenous sucrose reduces photosynthesis through biochemical and stomatal limitations.•Both Rubisco and PEPC activities were down-regulated by sucrose spraying.•Increased sink demand nulled the inhibitory effect of sucrose on sugarcane photosynthesis. 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-Ci curve (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, gs and 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, gs and Jatp and 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.