Sucrose Mobilisation in Sugarcane Stalk Induced by Heterotrophic Axillary Bud Growth

摘要

A theoretical high-yield sugarcane biofactory can be idealised as containing culm tissue that functions as a secondary source tissue rather than a sink. To investigate this potential process, heterotrophic axillary bud outgrowth from sugarcane (Saccharum spp. hybrids) setts was used as a model system to demonstrate that sucrose is a mobilisable carbon source. The outgrowth and subsequent biomass accumulation of axillary buds from two-eye setts of mature sugarcane stalks grown in the dark was used tomeasure carbon mobilisation from sett internode pith tissue. After 42 days growth 99.0±0.72% of sett internode pith sucrose was depleted and 2.66±0.16 g of new tissue accumulated. Comparison with a control treatment in which axillary buds were excisedat day zero demonstrated that carbon mobilisation was driven by the accumulation of new biomass. Profiling of soluble carbohydrates (viz. sucrose, glucose and fructose), starch, total soluble protein, total amino nitrogen, free amino acids and total insoluble material showed that the sucrose stored in the sett internode pith was the only available carbon source of sufficient size at day zero for the observed biomass accumulation. Other metabolites mobilised were glucose, fructose and some amino acids, notably isoleucine and leucine that were depleted in shoot treatment setts at day 42.