Sugar Partitioning Between Growth and Storage in Sugarcane Internodes.

Sugarcane (Saccharum spp. hybrids) stores large amounts of sugar in internodes of the stalk, while wild species (e.g. S. spontaneum) store more insoluble cell wall material (fiber) and little sugar. The reason for this difference is not clear. To test the hypothesis that the activity of soluble acid invertase (SAI) in elongating internodes influences the deposition of sugar in fully-elongated internodes, growth, sugar content, and SAI activity were measured in ‘HoCP 00-950’ (HoCP), a high-sucrose commercial hybrid, and 7 F₁ hybrids of HoCP 00-950 x ‘MPTH 97-216’, a S. spontaneum from originally from Thailand. Internodes of HoCP were shorter after elongation and had a lower fresh weight than internodes of the hybrids. However, HoCP internodes had the same dry weight as the hybrid internodes until the last sampling date, when the dry weight of HoCP internodes was greater than that of the hybrids. Water content decreased more slowly in internodes of HoCP than the hybrids. More total sugar accumulated in internodes of HoCP than in the hybrids, and more of that sugar was sucrose. On a protein basis, activities in elongating internodes of the hybrids were on average higher than in HoCP. This supports the hypothesis that SAI activity of elongating internodes influences the deposition of sugar in sugarcane internodes.