PRODUCTION AND COMPOSITION OF EXTRAFLORAL NECTARS OF 2 LIANAS FROM FRENCH-GUIANA, STIGMAPHYLLON-CONVOLVULIFOLIUM AND PASSIFLORA-GLANDULOSA - COMPARISON WITH THE PRIMARY METABOLITES FROM PHLOEM SAP - 1ST RESULTS

The extrafloral nectaries secretion of two species of liana from Frenc h Guiana (Stigmaphyllon convolvulifolium, Passiflora glandulosa) is co llected each two hours during the secretory period. Some qualitative a nd quantitative tests are realised on nectar during two season dry (oc tober-november) and wet (april-may). The secretion observed is differe nt for the two species in dry season. Some differences are observed in the primary metabolites composition between the two nectars. Sugars a re the most important metabolites of the nectar and they are more conc entrated than in phloem sap. P. glandulosa contains more sucrose than S. convolvulifolium. Perharps, it is due to the action of the enzyme i nvertase contained in the nectar of S. convolvulifolium which hydrolys es the sucrose. The other primary metabolites are found in nectar in s mall quantity and in the same concentration than in phloem sap. The im portant quantity of carbohydrates in extrafloral nectar suggests an ac tive transport of these compounds during the secretion. Many oxalate o f calcium crystals are observed in the parenchyme cells of nectaris. T he chelation of the ion Ca2+ which inhibits the ATPase can be a possib le role for the crystals. These action can facilite the active transpo rt of sugars during the secretion stage. The first function of the sec retion seems to be the exsudation of sugars. The secretory phenomene a ppears to be dependant of the transport and the accumulation of the ca rbohydrates in the leaf carrier of nectaries. Otherwise, production of nectar is completly different during the two seasons (dry and wet) fo r S. Convolvulifolium and suggests that secretion is modulated by the water flux into plants. The nectariferous secretion seems to be depend ant of an equilibrium between water supply and photosynthetic activity of the plant.