Physiological Functions of Acid and Neutral Invertases in Growth and Sugar Storage in Sugar Cane

The roles of acid invertases, pH optima about 5, and neutral invenase, pH optimum 7, have been examined during growth and maturation of stalks of sugar cane (Saccharum officinarum) and hybrid cultivars. Bound acid invertases are found in the outer space which includes the cell wall. A soluble acid invertase occurs in immature, elongating internodes, and is located both in the outer space and the vacuole of storage parenchyma cells. This enzyme disappears when internode growth ceases. The outer space component appears to be the major controller for dry matter input accompanying cell extension growth. The vacuolar component appears to be concerned with regulation of both turgor pressure and internal sugar pools. The neutral invertase increases during maturation. The level of enzyme activity correlates with the level of hexoses. This enzyme appears to be part of a system controlling sugar flux in mature storage tissue.