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Notes on the self-pollination in Dendrobium biflorum (Orchidales, Dendrobiinae)

100%

Kowalkowska A. K., Margonska H. B.

Acta Societatis Botanicorum Poloniae

2012

tom 81

nr 3

The conditions favouring self-pollination are determined for a species of Dendrobium Sw. A survey of gynostemium micromorphology in collected flowers of Dendrobium biflorum revealed two stages of a unique form of autogamy: on germination of pollen tetrads, pollen tubes reached the stigmatic region without the pollen being displaced from the anther locules. This is the first time for this type of autogamy to be reported in Dendrobium biflorum. Pollen grains germinated directly from the locules, bypassing the stigma or falling or sliding down onto the stigmatic surface. The pollen tubes were long and reached the stylar canal. On The Society Islands, differences in exposure of the habitats to weather conditions and altitude gradients influence both composition and form of the vegetation, as well as the occurrence of pollinators. The form of autogamy described here may be the usual method of pollination found on The Society Islands (and even the whole of French Polynesia), where suitable pollinators are absent and/or growth conditions stressful.

The structure of the spur nectary in Dendrobium finisterrae Schltr. (Dendrobiinae, Orchidaceae)

100%

Kaminska M., Stpiczynska M.

Acta Agrobotanica

2011

tom 64

nr 1

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.

Ograniczanie wyników

1 Acta Agrobotanica

1 Acta Societatis Botanicorum Poloniae

1 Kaminska M.

1 Kowalkowska A. K.

1 Margonska H. B.

1 Stpiczynska M.

1 2012

1 2011

Wyniki wyszukiwania

Notes on the self-pollination in Dendrobium biflorum (Orchidales, Dendrobiinae)

The structure of the spur nectary in Dendrobium finisterrae Schltr. (Dendrobiinae, Orchidaceae)