Nectar can be gathered under the cuticle and released by the cuticle rupture under the growing pressure to the exterior Durkee ; Curry et al.
During the floral lifespan, the residues of the secreted material were higher on the hypochile cells. The heterogeneous nature of the secreted material lipoid-carbohydrate and lipid globules in the cell walls, as well as in the cytoplasm, were also localised in both studied Epipactis species. The number of lipid bodies was diminished during anthesis not visible in the 5th day in Sudan III, only visible in TEM , which suggest their utilisation. In the orchid secretory cells, lipid bodies are present in the plastid neighbourhood, which suggest their participation in the production of exuded substances and their transport by ER profiles Davies et al.
Apart from sugars glucose, fructose, sucrose , the nectar could contain lipids, amino or organic acids, enzymes, antioxidants, vitamins, mineral ions and secondary metabolites Baker and Baker ; Galetto et al. In nectaries of about The presence of collateral vascular bundles defines the transport through apoplast. The nectar constituents, sugar and water, are transported via sieve tubes to nectariferous cells, noted in E. The presence of starch grains is a common feature of nectaries and osmophores Stern et al.
Starch is utilised as a source of energy for production of nectar and scent Vogel ; Pacini and Nepi ; Nepi The abundant starch grains were gradually reduced from bud stage. In sectional profile, the plastids had one starch grain in the nectary cells at the beginning of anthesis, alike in H.
Some plastids had polymorphic shapes, as in H. During the anthesis, the number of plastoglobuli within the plastids increased, as in E. The lipoid—carbohydrate—phenolic materials have been demonstrated in the end of anthesis.
The phenolic material was the same as in plastoglobuli in the fifth day of anthesis; however, such little amount was difficult to prove by histochemical test on dihydroxyphenols. Fragrance constituents are possibly produced in plastoglobuli, and then transported to the intraplastidal membranes, crossing the plastid envelope to the profiles of ER or migrating independently and finally reaching the plasmalemma and to the cell exterior.
Fahn proposed a model of nectar secretion, when the pre-nectar is transported through the symplast of the secretory parenchyma, then it is loaded to ER or dictyosomes.
The vesicles originated from ER or dictyosomes are fused with irregular plasmalemma, and the nectar is released to the exterior. The features such as irregular plasmalemma, the secretory vesicles that fuse with it, fully developed dictyosomes, numerous profiles of ER indicate vesicle-mediated process of secretion, which were frequently reported in orchid secretory cells i. Kowalkowska et al. The remarkable feature was the presence of periplasmic space in the third day of anthesis, which was not reported previously in E.
In orchid flowers, it has been described in Bulbophyllum levanae and B. The occurrence of periplasmic spaces is possibly associated with merocrine secretion, when after the transport of exudation outside the cell, the cell continues its secretory activity. The substances could be transported by vesicles to the periplasmic space via granulocrine secretion and then to the external surface Fahn ; Pacini and Nepi ; Paiva Cuticular canals micro-channels were reported in hypochile and knob cells.
Such co-existence was distinctly shown in B. However, in many nectaries, the way of pre-nectar transport could be simultaneous: both apoplastic and symplastic pathways Davis et al.
The plasmodesmata in anticlinal walls were also visible in epidermis of E. On the other hand, the apoplastic route is continued as a continuum of cell walls. The carbohydrates transported to the nectary phloem may simultaneously be transferred to the nectary surface by a combination of these routes. Mitochondria were abundant macroorganelle in floral nectaries in E. Their number suggests the eccrine secretion, where the produced energy is used in active transport of pre-nectar carbohydrates to cross the plasmalemma Eriksson ; Davis et al.
The large amount of nectar secreted during anthesis, high temperatures during summer and alcohol present in scent profile could also suggest the occurrence of nectar fermentation. The alcoholic fermentation changes the sugar profile of nectar by reducing the total concentration of sugar and decreasing the amount of sucrose Herrera et al. As the nectar composition is precisely related to pollinator preferences Baker and Baker ; Raguso , this change may influence the plant—pollinator relationship.
In all tepals, numerous idioblasts with raphides of calcium oxalate were visible, which possibly help to prevent herbivory Prychid and Rudall We believe that the meticulous knowledge of floral architecture and production of attractants for pollinators will give more data that will be useful for future projects of plant conservation planning. Skip to main content Skip to sections. Advertisement Hide.
Download PDF. Floral nectary and osmophore of Epipactis helleborine L. Crantz Orchidaceae. Open Access. First Online: 09 June Keywords Epipactis helleborine ssp. Introduction The plant nectaries diverse greatly in topography, anatomy, ultrastructure and secretion processes.
The pollinated and unpollinated flowers were collected from Epipactis helleborine ssp. The flowers were shaded by pink, with large and distinct knobs of the epichile and the concave hypochile at the base. Table 1 The collected flowers of Epipactis helleborine. The non-hinged lip was consisted from two parts Fig. A callus was placed at the base of epichile and composed of two lateral knobs and the third smaller central longitudinal knob. Open image in new window. The utilisation of starch grains started in bud stage from the epidermis as they were decreased comparing to the parenchyma Fig.
The ABB test revealed some proteins only on the epidermal cells of hypochile Fig. The cuticle surface of hypochile cells was covered by secreted material, which had diffused through cuticle forming micro-channels Fig. The tissue of knobs was built by a single layer of epidermis, 2—3 layers of subepidermis and parenchyma with intercellular spaces Fig.
However, the raphides were present in the all parts of flower. In this stage, the secretory material was found on the knobs in small amount Fig.
During the floral lifespan, the utilisation of starch was clearly visible—large number in parenchyma, but not found in the epidermis in the first day Fig. In the Auramine O test, the cuticle separation was also noticed Fig. The vascular bundles in lip tissue were collateral Fig. The idioblasts with raphides were localised in the whole floral parts, however in greater number in the knobs Fig. TEM research showed the residues of secretory materials on hypochile cells Fig. The plastids with internal membranes, mitochondria, dictyosomes, profiles of RER occurred in dense cytoplasm Fig.
fp39mohd.dev3.develag.com/nissan-x-estela-2007-manual-de-dueos.php In the 16th day of anthesis 2nd locality , the proteins were detected on the cuticle of hypochile cells Fig. The secretory materials were also present under the cuticle and on the surface of hypochile and knobs, with phenolic content Fig. Similarly, but in the fifth day the last day of floral lifespan on the first locality , the lipoid-carbohydrate bulges in subcuticular space and phenolic material on the cuticle surface on knobs appeared Fig.
The vesicles were fused with plasmalemma Fig. Few micro-channels were noticed in cuticle Fig. After the pollination, the flowers were quickly withered. The starch grains were utilised during the anthesis.
The test for presence of dihydroxyphenols revealed very slight reaction of plastids probably plastoglobuli and thin layer on cuticle Fig. The epidermal cells of hypochile the first day of anthesis, first locality revealed strongly distended cuticle on the outer tangential walls with residues of secreted substances upon the cuticle Fig. The cell walls outer tangential, inner tangential, anticlinal of epidermis contained numerous globules, probably lipid bodies Fig. In the flowers of the more shaded second locality, a few amount of secreted material was located on the cuticle surface, crossing the cuticle and as micro-channels Fig.
Moreover, the irregular plasmalemma and periplasmic space were visible Fig.