39 research outputs found
Floral Longevity and Nectar Secretion of Platanthera chlorantha (Custer) Rchb. (Orchidaceae)
Comparative Account of Nectary Structure in Hexisea imbricata (Lindl.) Rchb.f. (Orchidaceae)
Budowa nektarnika ostrogowego u Dendrobium finisterrae Schltr. (Dendrobiinae, Orchidaceae)
To date, the structure of the nectary spur of Dendrobium finisterrae has not been studied in detail, and the present paper compares the structural organization of the floral nectary in this species with the spurs of other taxa. The nectary spur of D. finisterrae was examined by means of light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It is composed of a single layer of secretory epidermis and several layers of small and compactly arranged subepidermal secretory cells. The secretory cells have thick cellulosic cell walls with primary pits. The secretory tissue is supplied by vascular bundles that run beneath in ground parenchyma and are additionally surrounded by strands of sclerenchymatous fibers. The flowers of the investigated species displayed morphological features characteristic of bee-pollinated taxa, as they are zygomorphic, creamy-green coloured with evident nectar guides. They also emit a weak but nice scent. However, they possess some characters attributed to bird-pollinated flowers such as a short, massive nectary spur and collenchymatous secretory tissue that closely resembles the one found in the nectaries of certain species that are thought to be bird-pollinated. This similarity in anatomical organization of the nectary, regardless of geographical distribution and phylogeny, strongly indicates convergence and appears to be related to pollinator-driven selection
Nectary Structure and Nectar Secretion in Maxillaria coccinea (Jacq.) L.O. Williams ex Hodge (Orchidaceae)
Nectar resorption and translocation in Cucurbita pepo L. and Platanthera chlorantha Custer (Rchb.)
Nectar resorption and sugar translocation were studied in Cucurbita pepo (Cucurbitaceae) and Platanthera chlorantha
(Orchidaceae) by micro-autoradiography. In both species, nectar
was resorbed in pollinated and unpollinated flowers and ovules developing into seeds were found to be the main sugar sink. In C. pepo, the mobility of resorbed sugars in pollinated female flowers was higher than in unpollinated ones; male flowers showed lower mobility of resorbed sugar. In P. chlorantha, radioactivity was detected in pollinated flowers below and above labelled unpollinated ones: the nearer the flower, the stronger the
accumulation of label in developing fruits
Nectary structure in Symphyglossum sanguineum [Rchb.f.] Schltr. [Orchidaceae]
Ornithophily occurs in a great number of orchid species but despite this, researchers have largely neglected to investigate their nectaries. The aim of this study is to describe the nectary structure of Symphyglossum sanguineum, a species presumed to be pollinated by hummingbirds. The nectary is located at the free margins of auricles, which form a channel for the passage of nectar. The nectary, which consists of a single-layered epidermis and 2-3 layers of subepidermal cells, is supplied by collateral, vascular bundles. The nectary cells of S. sanguineum, like those of other ornithophilous orchids, have thick cellulose cell walls. A remarkable feature of these nectary cells is the dissolution of the middle lamella and the subsequent separation of epidermal cells. It is possible that this latter process facilitates the flow of the nectar to the nectary surface. The cuticle covering the nectary epidermis has micro-channels, but unlike the other species of ornithophilous orchids studied to date, it neither becomes disrupted nor detached from the epidermal cells. Abundant mitochondria, lipid droplets and smooth endoplasmic reticulum (SER) with an osmiophilic material are present in the cytoplasm of nectary cells. Some plastids with few lamellae contain numerous vesicles and osmiophillic globules whereas others accumulate starch. SER lamellae are often closely associated with plastids and the contents of the former organelles closely resemble osmiophillic globules. Secretory vesicles are common, especially near the outer, tangential wall indicating that granulocrine secretion possibly occurs in S. sanguineum.Ornitofilia wyst臋puje u wielu Orchidaceae, lecz nektarniki storczyk贸w zapylanych przez ptaki rzadko s膮 przedmiotem bada艅. Celem niniejszej pracy by艂o zbadanie struktury nektarnik贸w Symphyglossum sanguineum, gatunku przypuszczalnie zapylanego przez kolibry. Nektarnik w kwiatach S. sanguineum znajduje si臋 na wolnych kraw臋dziach auriculi, kt贸re s膮 wytworem war偶ki. Auricule tworz膮 kanal, przez kt贸ry przes膮cza si臋 nektar na powierzchni臋 labellum. Nektarnik zbudowany jest z jednowarstwowej epidermy i 2-3 warstw kom贸rek subepidermalnych. Jest on zaopatrywany przez kolateralne wi膮zki przewodz膮ce. Kom贸rki nektarnika S. sanguineum maj膮 grube celulozowe 艣ciany kom贸rkowe. Charakterystyczn膮 cech膮 nektarnika jest rozpuszczenie blaszek 艣rodkowych w 艣cianach niekt贸rych kom贸rek epidermy wydzielniczej, co powoduje ich rozsuni臋cie. Przypuszczalnie proces ten u艂atwia przes膮czanie si臋 nektaru na powierzchni臋 nektarnika. Kutykula pokrywaj膮ca kom贸rki epidermy wydzielniczej ma mikrokanaliki, lecz w przeciwie艅stwie do kom贸rek nektarnik贸w innych dot膮d badanych ornitofilnych storczyk贸w, nie p臋ka ani te偶 nie tworzy uwypukle艅 pod wp艂ywem wydzielanego nektaru. Cytoplazma kom贸rek wydzielniczych zawiera liczne mitochondria, krople lipidowe i g艂adkie retikulum endoplazmatyczne (SER) wype艂nione osmofilnym materia艂em. Niekt贸re plastydy w kom贸rkach nektarnika maj膮 nieliczne tylakoidy i p臋cherzyki oraz osmofilne globule, podczas gdy w innych plastydach znajduj膮 si臋 ziarna skrobi. B艂ony SER s膮 w kontakcie z plastydami, a osmofilny materia艂 zawarty w SER przypomina ciemno wybarwione globule w plastydach. Liczne p臋cherzyki wydzielnicze w s膮siedztwie 艣ciany kom贸rkowej wskazuj膮 na mo偶liwo艣膰 sekrecji p臋cherzykowej
Evidence for the dual role of floral secretory cells in Bulbophyllum
Floral epidermal cells of most species of Bulbophyllum Thouars studied to date produce both lipid-rich foodrewards
and fragrance. Since fragrances largely consist of terpenoids and have an affinity for lipophilic stains, the
simultaneous presence of lipid-rich food-rewards frustrates identification of fragrance-secreting cells by conventional
histochemistry. Furthermore, since both lipid-rich food-rewards and fragrances are probably synthesized
by a similar complement of organelles, interpretation of TEM images can prove difficult. All members of section
Racemosae Benth. & Hook. f. investigated to date, however, are unusual in their secretion of a predominantly
proteinaceous food-reward, and lipids are seemingly absent. This might enable their use as models for the identification
and characterization of fragrance-secreting tissues and organelles.
Three members of sect. Racemosae were chosen, namely Bulbophyllum dissitiflorum Seidenf., B. lilacinum Ridl.
and B. tricorne Seidenf. & Smitinand. All produced food-rewards. Of these, one (B. dissitiflorum) lacked fragrance
and was used as a control, whereas the remaining two species produced fragrance. Having established that the
food-reward was mainly proteinaceous in each case, and did not test positively for lipid, we undertook further
histochemical investigations, as well as light microscopy, SEM and TEM. Specialized palisade-like epidermal
cells of all species contained protein bodies and rough endoplasmic reticulum consistent with the production
and secretion of a protein-rich food-reward. Cuticular pores were also present. In fragrant species, these cells
also contained abundant smooth endoplasmic reticulum, oil droplets and many, well-developed, spherical plastids
with numerous plastoglobuli, similar to those found in the osmophores (fragrance-producing structures) of
other orchids. Indeterminate, osmiophilic cytoplasmic inclusions were also present. By contrast, the non-fragrant
species lacked oil droplets and other osmiophilic inclusions and the plastids were scant, poorly developed, often
elongate or irregular in shape and contained few plastoglobuli. Smooth endoplasmic reticulum was also less frequent.
Since food-rewards tested negatively for lipid, it is probable that any oil droplets present were involved in
fragrance production, especially since they were absent from the non-fragrant species. Thus, the unusual absence
of lipids from the food-rewards of sect. Racemosae provided a rare opportunity, permitting, for the first time, the
unraveling of these two secretory processes (food-reward and fragrance) in Bulbophyllum and clearly demonstrating
the plasticity of these cells and their dual role in secretion
Ekofizjologiczne aspekty reabsorpcji nektaru
A number of approaches, both direct and indirect, have shown that nectar is reabsorbed by numerous plant species, irrespective of the age or sex of the flower. Furthermore, reabsorption occurs regardless of whether or not the flower has been pollinated. Reabsorption helps to maintain concentration of nectar and their viscosity and thereby encourages continued visits by pollinators. Conversely, the capacity to vary concentration of nectar sugars may confer evolutionary advantage by encouraging visits by more than one kind of pollinator and this is particularly important in regions where there is a paucity of pollinators. A further important role of nectar reabsorption is the maintenance of the energy equilibrium of the plant. A number of studies have shown that nectar production involves considerable energy expenditure requiring as much as 37% of the plant's daily production of energy by photosynthesis. The increased metabolic costs incurred by the plant during nectar production and secretion can reduce its growth and reproduction during the following season. Reabsorption of nectar that has not been collected by pollinators enables the plant to conserve at least some of the energy reserved for the secretion of nectar. Sugars reabsorbed from nectar can be re-used for the development of fruit and ovules - processes which demand large quantities of sugar. Despite convincing evidence for the reabsorption of nectar, few detailed studies have addressed the transport and incorporation of reabsorbed sugars. One of the questions that remain to be answered is 'What is the cellular basis for nectar reabsorption by the nectary?'.Nektar jest resorbowany w kwiatach ro艣lin z r贸偶nych rodzin botanicznych, mi臋dzy innymi Apiaceae, Brassicaceae, Cucurbitaceae, Combretaceae czy Orchida- ceae. Reabsorbcja nektaru spe艂nia kilka niezwykle wa偶nych funkcji i wyst臋puje niezale偶nie od stadium kwitnienia, p艂ci kwiatu czy zapylenia. W kwiatach typu otwartego, reabsorpcja cukr贸w umo偶liwia regulacj臋 koncentracji, kt贸ra wzrasta na skutek parowania wody z nektaru. Z kolei w kwiatach innych ro艣lin mo偶liwo艣膰 zmiany koncentracji nektaru stanowi pewn膮 adaptacj臋 do zapylania przez szersze spektrum gatunk贸w, co jest niezwykle wa偶ne w sytuacjach deficytu zapylaczy w 艣rodowisku. Inne funkcje resorpcji nektaru dotycz膮 energetycznego bilansu ro艣lin. Wyniki niekt贸rych bada艅 wykazuj膮, 偶e produkcja nektaru wymaga du偶ego nak艂adu energii metabolicznej i mo偶e poch艂ania膰 dziennie do 37% energii uzyskanej z fotosyntezy. Dlatego te偶 niekt贸re ro艣liny odzyskuj膮 przynajmniej cz臋艣膰 energii wydatkowanej na produkcj臋 i sekrecj臋 nektaru poprzez reabsorpcj臋 cukr贸w, je艣li nektar nie jest pobrany podczas zapylenia. Cukry te ro艣liny wykorzystuj膮 g艂贸wnie jako materia艂y zapasowe w rozwijaj膮cych si臋 owocach i nasionach, kt贸re s膮 silnymi akceptorami asymilat贸w. Mechanizm reabsorpcji nektaru na poziomie kom贸rkowym wymaga dalszych szczeg贸艂owych bada艅
Por贸wnanie budowy osmofor贸w w kwiatach Stanhopea graveolens Lindley i Cycnoches chlorochilon Klotzsch (Orchidaceae)
The structure of the osmophores in Stanhopea graveolens
and Cycnoches chlorochilon was studied by means of
light microscopy (LM), scanning electron microscopy (SEM)
and transmission electron microscopy (TEM). The scent glands
are located in the basal part of the labellum. The surface of the
osmophores is wrinkled or rugose, which increases the area of
fragrance emission. On the surface of the epidermis, remnants of
secretion are noticeable in S. graveolens, but these are absent in
C. chlorochilon. The osmophore tissue is composed of secretory
epidermal cells and several layers of subepidermal parenchyma,
and it is supplied by vascular bundles that run in ground parenchyma.
The secretory cells have large nuclei, a dense cytoplasm
with numerous ER profiles, lipid droplets, and plastids with a
substantial amount of starch, which are probably involved in the
synthesis of volatile substances. In the cell walls of the osmophore
cells, numerous pits with plasmodesmata occur that are likely
to take part in symplastic transport of the scent compounds.
The structure of the osmophores is similar in both investigated
species. Both S. graveolens and C. chlorochilon are pollinated
by euglossine bees, and such similarity results from adaptation
to effective scent emission and attraction of pollinators.W niniejszej pracy badano struktur臋 osmofor贸w
w kwiatach Stanhopea graveolens Lindley oraz Cycnoches
chlorochilon Klotzsch wykorzystuj膮c mikroskopi臋
艣wietln膮 (LM), skaningow膮 elektronow膮 (SEM)
oraz transmisyjn膮 elektronow膮 (TEM). Gruczo艂y wydzielaj膮ce
zapach zlokalizowane s膮 u podstawy war偶ki.
Powierzchnia osmofor贸w jest pomarszczona lub
brodawkowata, co u艂atwia emisj臋 substancji zapachowych.
W SEM na powierzchni epidermy u S. graveolens
widoczne s膮 pozosta艂o艣ci wydzieliny, natomiast
u C. chlorochilon pomimo tego, 偶e wydzielina pokrywa
war偶k臋 艣wie偶ych kwiat贸w, to w SEM nie jest widoczna.
Tkanka osmoforowa jest utworzona z kom贸rek
wydzielniczych epidermy oraz kilku warstw subepidermalnych
kom贸rek mi臋kiszowych i jest zaopatrywana
przez wi膮zki przewodz膮ce zlokalizowane w mi臋kiszu
zasadniczym. Kom贸rki wydzielnicze maj膮 du偶e j膮dro,
g臋st膮 cytoplazm臋, ER, krople lipidowe oraz plastydy
z ziarnami skrobi. W 艣cianach kom贸rek osmofor贸w
znajduj膮 si臋 liczne jamki z plazmodesmami, kt贸re
przypuszczalnie bior膮 udzia艂 w symplastycznym transporcie
zwi膮zk贸w zapachowych. Osmofory badanych
gatunk贸w maj膮 bardzo podobn膮 budow臋 anatomiczn膮.
Zar贸wno S. graveolens jak i C. chlorochilon s膮 zapylane
przez pszczo艂y Euglossine, natomiast podobie艅stwa
w strukturze ich osmofor贸w wynikaj膮 z przystosowania
do efektywnego wydzielania zapachu, a tym samym
skutecznego zwabiania zapylaczy