Title: Sink strength affects assimilate distribution and photosynthesis in sugarcane.
Abstract: It has been suggested that sucrose accumulation by sugarcane is regulated at the level of the sink, and strong evidence exists that sink tissues exert an influence on the net photosynthetic rates and carbon status of source organs. A role of sugar molecules as effectors of this relationship has also been established. The existence of a robust sugar-dependent relationship between source and sink tissues in sugarcane could represent a potentially fundamental limiting factor for sucrose accumulation in the stalk and consequently play a major role in overall sucrose crop yield. In this study, the relationship in sugarcane between photosynthetic source tissue and sink material was examined through manipulation of sink strength of field grown Saccharum spp. hybrid cv. N19 (N19). To enhance sink strength, all leaves, except for the third fully-expanded leaf, were enclosed in 90% shading cloth for varying time periods. In this way, leaves that served as source were converted to sink, producing an overall increase in plant sink strength. Variations in sucrose, glucose and fructose levels were then measured and the effects on gas exchange characteristics and leaf fluorescence recorded. Following a decline in sucrose concentrations in young internodal tissue and shaded leaves, significant increases in the light saturated photosynthetic rate (Jmax), carboxylation efficiency (Vrubisco) and electron transport rate were observed in non-shaded leaves after 6-8 days of shading treatment. Changes in carbon partitioning due to shading were further examined based on the uptake of a CO2 label. It was concluded that increased sink strength is correlated with a decrease in overall source assimilate availability which in turn may act to up-regulate source leaf photosynthetic capacity. This relationship will be investigated further by identifying putative regulatory occurrences using genomic, proteomic and metabolomic strategies.
Publication Year: 2005
Publication Date: 2005-01-01
Language: en
Type: article
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Cited By Count: 3
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