Sink strength regulates photosynthesis in sugarcane

Authors

  • A. J. McCormick,

    1. South African Sugarcane Research Institute (SASRI), Crop Biology Resource Centre, Private Bag X02, Mt Edgecombe, 4300, South Africa;
    2. University of KwaZulu-Natal, School of Biological and Conservation Sciences, Howard College Campus, Durban, 4041, South Africa;
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  • M. D. Cramer,

    1. University of Cape Town, Botany Department, Private Bag XI, Rondebosch, 7701, South Africa;
    2. School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, 35 Stirling Highway, WA 6009, Australia
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  • D. A. Watt

    1. South African Sugarcane Research Institute (SASRI), Crop Biology Resource Centre, Private Bag X02, Mt Edgecombe, 4300, South Africa;
    2. University of KwaZulu-Natal, School of Biological and Conservation Sciences, Howard College Campus, Durban, 4041, South Africa;
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Author for correspondence: A. J. McCormick Tel: +27 21 5087462 Fax: +27 21 5087597 Email: Alistair.mccormick@sugar.org.za

Summary

  • • The relationship in sugarcane (Saccharum spp.) between photosynthetic source tissue and sink material was examined through manipulation of the sink:source ratio 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% shade cloth for varying periods of time. Variations in sucrose, glucose and fructose concentrations were measured and the effects of shading on the leaf gas exchange and fluorescence characteristics recorded. Changes in carbon partitioning caused by shading were examined based on the uptake and translocation of fixed 14CO2.
  • • Following a decline in sucrose concentrations in young internodal tissue and shaded leaves, significant increases in the CO2-saturated photosynthetic rate (Jmax), carboxylation efficiency (CE) and electron transport rate were observed in unshaded leaves after 8 d of shading treatment.
  • • It was concluded that up-regulation of source-leaf photosynthetic capacity is correlated with a decrease in assimilate availability to acropetal culm sink tissue. Furthermore, a significant relationship was revealed between source hexose concentration and photosynthetic activity.

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