Apoplasmic barrier in the extrafloral nectary of Citharexylum myrianthum (Verbenaceae)

Nectar Secretion, Morphology, Anatomy and Ultrastructure of Floral Nectary in Selected Rubus idaeus L. Varieties

“…This well-developed intercellular contact maintaining the continuity of the protoplasts has also been described in the ultrastructure of nectaries in other species [66,68,85,115]. Plasmodesmata with an enlarged cavity at the midline of the wall participate in the active symplastic transport of nectar metabolites derived from phloem sap [87,93,103,106,110,116]. ER membranes present in plasmodesmata are routes of diffusion of lipid signaling molecules between cells from the innermost to outermost nectary layer [106].…”

“…This study and literature data reported the presence of Golgi apparatus, mitochondria, ER profiles, and dictyosome vesicles in the vicinity of the plasmalemma. Filled vesicles were fused with the membrane, transferring the transported material into the periplasmic space, which was formed by the folds of the protein-lipid membrane and increased during anthesis [68,93,103,106]. As reported by Kram et al [113], most of the metabolites of starch hydrolysis are packed into the endoplasmic reticulum (ER) or dictyosome vesicles and secreted through the fusion with the plasma membrane (granulocrine secretion).…”

“…Horner et al [101] and García et al [102] reported the presence of smooth and rough endoplasmic reticulum in nectary epidermis and parenchyma cells in Glycine max and Passiflora spp. In turn, rough endoplasmic reticulum was found in nectary cells in Citharexylum myrianthum, Erythrina speciosa, Prunus laurocerasus, Prunus persica, and Robinia viscosa [72,76,[103][104][105][106], whereas a smooth endoplasmic reticulum was observed in Geranium macrorrhizum and G. phaeum and several species from the families Anacardiaceae and Orchidaceae [82,96,106,107]. Different types of endoplasmic reticulum membranes in nectary cell protoplasts have been described.…”

“…Plasmodesmata with an enlarged cavity at the midline of the wall participate in the active symplastic transport of nectar metabolites derived from phloem sap [87,93,103,106,110,116]. ER membranes present in plasmodesmata are routes of diffusion of lipid signaling molecules between cells from the innermost to outermost nectary layer [106]. In turn, the plasmalemma adheres to the anticlinal walls and creates a junction inhibiting lateral diffusion and preventing the movement of substances through the apoplast [106,117].…”

“…ER membranes present in plasmodesmata are routes of diffusion of lipid signaling molecules between cells from the innermost to outermost nectary layer [106]. In turn, the plasmalemma adheres to the anticlinal walls and creates a junction inhibiting lateral diffusion and preventing the movement of substances through the apoplast [106,117]. Wist and Davis [66] described a symplastic route between phloem elements with companion cells and nectary parenchyma and epidermis cells, which is dependent on intercellular plasmodesma junctions.…”