Structure and Pollination in Azalea Blossoms

Azalea shrubs are of the genus Rhododendron, and are a common backyard plant found throughout the northern hemisphere and in Australia as a non-native, usually cultivated species. Typically Azaleas bloom from winter to spring.

Pollination and Fertilisation:

For Azalea flowers to develop into mature seeds, fertilisation must occur between the gametes of two plants, via pollenation carried out by smaller insect pollinators. The gap between the stamen and the style has a mean distance of 10mm. This has an effect on the species suitable to act as pollinators because of size (the diameter is ~50mm), and wieght limitations- flexible stems mean that birds are unable to land on the flowers, however butterflies, bees, beetles are able to move between the blossoms. Pollen (male gametes) from the stamens brush off onto the insect visitors, and is carried to another flower and caught on the stigma. Once pollination has occured, the male gamete travels down the style from the stigma to the ovary where fertilisation occurs. In the following days, the petals drop off and the seeds begin to mature within a fruit.

Flower Morphology:

Azalea flowers are characterised by their bright, vivid pigmentation which aids in the attracting of visitors. Flowers have five petals, with a mean size ranging from 30-60mm. Eight stamen (~25mm) and one style (~40mm) are situated from the floral axis, and depending on tugidity, orientation and age of the flower, are usually within 20mm of each other at the tips.
Ovary showing female gamteophytes.

Pollen Morphology:

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The pollen in Azalea flowers is produced in the microsporangia of the stamen, and has a tetaporate structure. The microgametophytes travel in clusters, carried by wind or insect pollinators, and each had a diameter of ~670um.

Nectar Characterisation:

The typical volume of netcar and sugar content per flower is fairly low and in clipped blossoms has a tendancy to dry out, as such we were not able to observe or measure nectar within the flower.