Diurnal Behavior of Sugarcane Acid Invertase in Early-Juvenile and Early-Adult Plants Treated with Polaris

Abstract

The diurnal behavior of sugarcane acid invertase was examined in 5- and 14-week old plants treated with Polaris (N,N-bis [phosphonomethyl] glycine). A commercial plant growth regulator and in vivo inhibitor of cane invertase, Polaris was administered as an aqueous foliar spray at 0645 h. Immature stem samples were harvested at 2-h intervals from 0630 to 1830 h on day of treatment and throughout the following two days. In plantlets, Polaris produced a major shift in the time of maximum invertase action with in 2 h after application and without inhibiting the enzyme. Polaris persistently inhibited invertase during the third day without distorting the time or magnitude of enzyme fluctuation. Similar effects were produced in young-adult plants having greatly lengthened and elaborated transport pathways. Neither the natural fluctuations nor chemical-induced changes were accompanied by changes in tissue sucrose, reducing sugars, or soluble protein. Results are discussed in the context of two control systems for acid invertase: one governing its synthesis in immature stem tissue and inhibited by Polaris, the other governing its diurnal behavior, possibly located in leaf tissues, and only temporarily distorted by Polaris.