Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/1998
Publication Date: N/A
Interpretive Summary: Selection of sugarcane varieties with higher sucrose concentrations is desirable. Three enzymes that break down sucrose (acid invertase, neutral invertase and sucrose synthase) or make sucrose (sucrose-phosphate synthase) may determine the rate at which sugar is accumulated by sugarcane, and how much sugar the stem can hold. Stem sections of seven commercial varieties were sampled at intervals from July until December during two growing seasons. Growth of each section took about 25 days, but section sugar content increased for about 57 days. Two enzymes, soluble acid invertase and sucrose synthase, had peaks of activity during growth, while two enzymes, neutral invertase and sucrose-phosphate synthase, increased during development. Sugar accumulation rate was not correlated with activity of any enzyme assayed. Sucrose content during development was correlated with sucrose-phosphate synthase and the difference between sucrose-phosphate synthase and acid invertase. However, differences in final sucrose content between varieties could not be explained by differences in any enzyme. This research will benefit other sugarcane scientists.
Technical Abstract: Identification of sugarcane (Saccharum spp. hybrids) genotypes with higher sucrose concentrations is desirable. Activities of sucrose- metabolizing enzymes during development of internodal storage tissue may determine the rate of total sugar accumulation and final sucrose concentration. Internodes of seven commercial cultivars were tagged prior to elongation and sampled at intervals from July until December during two growing seasons. Internode elongation was completed by about 380 C d (base temperature 18 C). Dry matter accumulated until about 800 C d. Sucrose cleavage enzymes, soluble acid invertase and sucrose synthase, had peaks of activity during elongation, then declined to lower levels. Neutral invertase and sucrose-phosphate synthase activities increased during development. Sugar accumulated, and the sucrose to total sugar ratio approached 1.0, although the combined sucrose cleavage activity of the invertases and sucrose synthase in most internodes was greater than the synthetic activity of sucrose-phosphate synthase. Sugar accumulation rate was not correlated with activity of any enzyme assayed. Sucrose content during internode development was correlated with sucrose- phosphate synthase activity and the difference between sucrose-phosphate synthase and acid invertase activities. Sucrose content of mature internodes was not correlated with any enzyme activity. The data do not support the hypothesis that sucrose synthase activity is related to the rate of sugar accumulation, but do support the hypothesis that sucrose- phosphate synthase and acid invertase play key roles in determining sucrose concentration during maturation in sugarcane internodes.