Sugar accumulation in growing subhooks of etiolated Pisum sativum seedlings - Stimulation of sugar exudation and invertase activity in epicotyls by gibberellic acid

Abstract

S. 1992. Sugar accumulation in growing subhooks o£ etiolated Pisum sativum seedlings -Stimulation of sugar exudation and invertase activity in epicotyls by gibberellic acid. -Pbysiol. Plant. 84: 106-112.The epicotyl of 5-day-old derooted cuttings of pea (Pisum sativum L. cv. Alaska) with and without cotyledons exuded sucrose and glucose in the presence of EDTA. The amount of sugars exuded was greatly affected by the position at which the epicotyl was cut. The largest amount of sugars was exuded when the epicotyl was cut 2 mm below the hook, leaving the growing subhook. Gibberellic acid (GA) substantially increased the amount of sugars exuded from the epicotyl in the presence of cotyledons but only slightly in their absence. GA stimulated sugar exudation from the cotyledonary node as well as from the epicotyl. In cuttings with cotyledons. GA enhanced invertase activity in the apoptast, and in the intracellular soluble and bound fractions in the growing subhook. In decotylized cuttings, GA enhanced only soluble invertase activity. GA did not affect invertase activity in the epicotyl below the subhook. These results suggest that GA stimulates sugar accumulation in the growing subhook by stimulating not only phloem loading of sucrose in the cotyledons but also unloading in the subhook.

Suppression of sugar accumulation in coleoptile and mesocotyl cells by light irradiation to etiolated maize seedlings

“…Gibberellins increase the amount of osmotic solutes, such as sugars in shoots of various plants, when they stimulate the elongation growth of shoots (Miyamoto et al, 1993). Gibberellins increased the amounts of sucrose exuded from the cotyledons (Miyamoto et al, 1992). In addition, the SPS and INCW activities were enhanced by gibberellins (Cheikh et al, 1992;Wu et al, 1993).…”

Plant growth processes in Arabidopsis under microgravity conditions simulated by a clinostat.

“…the final length of stems. Gibberellin has been reported to enhance stem elongation through its action on increasing the osmotic pressure (Miyamoto et al 1992). From this point, there is a possibility that disturbance in gibberellin action enhancing the final height of plants is involved in inhibition of inflorescence elongation on a clinostat.…”