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Floral nectary anatomy and ultrastructure in mycoheterotrophic plant, Epipogium aphyllum Sw. (Orchidaceae).

Święczkowska E, Kowalkowska AK - ScientificWorldJournal (2015)

Bottom Line: The floral analysis provides strong evidence to conclude that nectar is secreted on the upper surface of pink-coloured papillate ridges and epidermal (adaxial) cells at different place in spur, especially at the apex.The nectar secretion is not dependent on the colour form of E. aphyllum blooming shoots.The floral biology and ultrastructure differ from mycoheterotrophic plants known up to date.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Taxonomy and Nature Conservation, University of Gdansk, Wita Stwosza 59, 80-308 Gdańsk, Poland.

ABSTRACT
Epipogium aphyllum is a European-Asian obligatory mycoheterotrophic orchid containing no chlorophyll. Flowers are not resupinate with a sack-shape spur and cordate lip, which is divided into two parts: the basal (hypochile) and distal one (epichile). The floral analysis provides strong evidence to conclude that nectar is secreted on the upper surface of pink-coloured papillate ridges and epidermal (adaxial) cells at different place in spur, especially at the apex. The exudation on papillae has been observed through the entire anthesis and it has been stained on polysaccharides, proteins, and lipids. The dense cytoplasm of papillae contains profuse endoplasmic reticulum, plentiful vesicles (bigger ones with tannin-like materials), numerous mitochondria, sometimes dictyosomes, starch grains, and plastids with tubular structures. The large electron-dense bodies in cell walls are structurally the same as tannin-like materials from vesicles that are in contact with plasmalemma. The rupture of thin layer of swelled cuticle is caused by pressure of gathered substances exuded due to granulocrine secretion. The idioblasts with raphides occur mainly in tepals tissue. The dynamic changes of the nectar exudation, released through endocrine secretion, have been noticeable during the anthesis: both on the lip and inside the spur. The nectar secretion is not dependent on the colour form of E. aphyllum blooming shoots. The floral biology and ultrastructure differ from mycoheterotrophic plants known up to date.

No MeSH data available.


Related in: MedlinePlus

SEM studies of lip on the 8th day of anthesis. (a) Cordate epichile with papillate ridges. (b) Rounded (often sunken) cells from the furrow. (c) Rounded cells close to margin without secretions. (d) Papillate ridges with multicellular outgrowths. (e) Papillae with the cuticle swellings (arrows) at their backsides and secretion at their apices. (f) Secretion at the apex of papilla.
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fig2: SEM studies of lip on the 8th day of anthesis. (a) Cordate epichile with papillate ridges. (b) Rounded (often sunken) cells from the furrow. (c) Rounded cells close to margin without secretions. (d) Papillate ridges with multicellular outgrowths. (e) Papillae with the cuticle swellings (arrows) at their backsides and secretion at their apices. (f) Secretion at the apex of papilla.

Mentions: On the normal type of blooming shoots (Figure 1(c)), the lip consisted of two parts: basal hypochile and apical epichile (Figure 1(i)). The hypochile formed by the two short lateral lobes (Figure 1(i)) was prolonged into a sack-shape spur (Figure 1(c)) and relative to the epichile was set at right angle. The epichile was cordate, acute with irregular margins (Figures 1(i) and 2(a)). In contrast to other orchid species, Epipogium aphyllum possessed central furrow with pink smudge in epichile (Figure 1(i)), not in hypochile. On both sides, the furrow was surrounded by two pink papillate ridges leading to the upwardly located spur (Figures 1(c) and 1(i)). The papillate ridges (Figures 1(i) and 2(a)) were multicellular outgrowths with groups of rounded papillae at their apices (Figures 1(j) and 2(d)). The exudation was only present on the upper surface of papillae (Figures 2(d), 1(e), and 1(f)) through the whole flowering period. The nectar secretion was not recorded in the furrow of epichile (Figure 2(b)) or on other lip cells (Figure 2(c)). The most abundant secretion was observed on the 8th day of anthesis (Figures 2(e) and 2(f)). In some papillae, at their backsides, the cuticle swellings were observed (Figure 2(e)). Nevertheless, the flowers were collected on the 2nd, 3rd, 4th, 5th, 6th, and 8th days of anthesis, and the amounts of nectar presented on papillae were various. Comparing the results from collected flowers, we could draw a conclusion that the quantity of secretion from labellar papillae and spur showed some increasing tendency beginning from the 2nd day up to the 4th day of anthesis. There was decrease in the amount of nectar on the 5th day. Then, on the 6th day, the secreted nectar was increased up to the end of anthesis (the 8th day), where the highest quantity of secretory substances was observed in both the lip and the spur. The most intensive secretion was recorded at average daily temperatures from 17.1°C to 19.9°C. Above this temperature, only a small amount of secretion on the upper surface of papillae was noted.


Floral nectary anatomy and ultrastructure in mycoheterotrophic plant, Epipogium aphyllum Sw. (Orchidaceae).

Święczkowska E, Kowalkowska AK - ScientificWorldJournal (2015)

SEM studies of lip on the 8th day of anthesis. (a) Cordate epichile with papillate ridges. (b) Rounded (often sunken) cells from the furrow. (c) Rounded cells close to margin without secretions. (d) Papillate ridges with multicellular outgrowths. (e) Papillae with the cuticle swellings (arrows) at their backsides and secretion at their apices. (f) Secretion at the apex of papilla.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4390210&req=5

fig2: SEM studies of lip on the 8th day of anthesis. (a) Cordate epichile with papillate ridges. (b) Rounded (often sunken) cells from the furrow. (c) Rounded cells close to margin without secretions. (d) Papillate ridges with multicellular outgrowths. (e) Papillae with the cuticle swellings (arrows) at their backsides and secretion at their apices. (f) Secretion at the apex of papilla.
Mentions: On the normal type of blooming shoots (Figure 1(c)), the lip consisted of two parts: basal hypochile and apical epichile (Figure 1(i)). The hypochile formed by the two short lateral lobes (Figure 1(i)) was prolonged into a sack-shape spur (Figure 1(c)) and relative to the epichile was set at right angle. The epichile was cordate, acute with irregular margins (Figures 1(i) and 2(a)). In contrast to other orchid species, Epipogium aphyllum possessed central furrow with pink smudge in epichile (Figure 1(i)), not in hypochile. On both sides, the furrow was surrounded by two pink papillate ridges leading to the upwardly located spur (Figures 1(c) and 1(i)). The papillate ridges (Figures 1(i) and 2(a)) were multicellular outgrowths with groups of rounded papillae at their apices (Figures 1(j) and 2(d)). The exudation was only present on the upper surface of papillae (Figures 2(d), 1(e), and 1(f)) through the whole flowering period. The nectar secretion was not recorded in the furrow of epichile (Figure 2(b)) or on other lip cells (Figure 2(c)). The most abundant secretion was observed on the 8th day of anthesis (Figures 2(e) and 2(f)). In some papillae, at their backsides, the cuticle swellings were observed (Figure 2(e)). Nevertheless, the flowers were collected on the 2nd, 3rd, 4th, 5th, 6th, and 8th days of anthesis, and the amounts of nectar presented on papillae were various. Comparing the results from collected flowers, we could draw a conclusion that the quantity of secretion from labellar papillae and spur showed some increasing tendency beginning from the 2nd day up to the 4th day of anthesis. There was decrease in the amount of nectar on the 5th day. Then, on the 6th day, the secreted nectar was increased up to the end of anthesis (the 8th day), where the highest quantity of secretory substances was observed in both the lip and the spur. The most intensive secretion was recorded at average daily temperatures from 17.1°C to 19.9°C. Above this temperature, only a small amount of secretion on the upper surface of papillae was noted.

Bottom Line: The floral analysis provides strong evidence to conclude that nectar is secreted on the upper surface of pink-coloured papillate ridges and epidermal (adaxial) cells at different place in spur, especially at the apex.The nectar secretion is not dependent on the colour form of E. aphyllum blooming shoots.The floral biology and ultrastructure differ from mycoheterotrophic plants known up to date.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Taxonomy and Nature Conservation, University of Gdansk, Wita Stwosza 59, 80-308 Gdańsk, Poland.

ABSTRACT
Epipogium aphyllum is a European-Asian obligatory mycoheterotrophic orchid containing no chlorophyll. Flowers are not resupinate with a sack-shape spur and cordate lip, which is divided into two parts: the basal (hypochile) and distal one (epichile). The floral analysis provides strong evidence to conclude that nectar is secreted on the upper surface of pink-coloured papillate ridges and epidermal (adaxial) cells at different place in spur, especially at the apex. The exudation on papillae has been observed through the entire anthesis and it has been stained on polysaccharides, proteins, and lipids. The dense cytoplasm of papillae contains profuse endoplasmic reticulum, plentiful vesicles (bigger ones with tannin-like materials), numerous mitochondria, sometimes dictyosomes, starch grains, and plastids with tubular structures. The large electron-dense bodies in cell walls are structurally the same as tannin-like materials from vesicles that are in contact with plasmalemma. The rupture of thin layer of swelled cuticle is caused by pressure of gathered substances exuded due to granulocrine secretion. The idioblasts with raphides occur mainly in tepals tissue. The dynamic changes of the nectar exudation, released through endocrine secretion, have been noticeable during the anthesis: both on the lip and inside the spur. The nectar secretion is not dependent on the colour form of E. aphyllum blooming shoots. The floral biology and ultrastructure differ from mycoheterotrophic plants known up to date.

No MeSH data available.


Related in: MedlinePlus