Mandi+and+Co+(Azalea)

Group: Mandi, Emily, Bianca, Ashwin and Bella
 * __ Mandi and Co (Azalea) __**


 * Common name:** Azalea
 * Specific name:** //Rhododendron japonicum//

//**Pollination and Fertilisation**//
- Azaleas have heterozygous flowers, ie both the stamen (male reproductive organs) and carpel (female reproductive organs) are present in a single flower. In order for an azalea to produce a mature seed, fertilisation must occur. This involves the movement of a pollen grain from the anther to the stigma on the carpel. This process of pollination requires vectors to move the pollen, ideally from one shrub to another (cross pollination as opposed to self pollination, on the same bush). While abiotic vectors such as wind and water exist, the nature of the flower suggests that biotic vectors are used (see "Floral Morphology and Visitations").  - Fertilisation requires the pollen grain to send out a pollen tube down the style of the carpel to the ovary, where the ova reside. We were unable to determine if Azaleas have self incompatibility measures.

**//Floral Morphology and Visitations //**
- Azaleas rely on abiotic vectors for pollination. This is evident due to the morphology of the flower: it is not particularly large, and has the anthers clustered closely around the stigma, ensuring that any animals visiting would contact both male and female structures, allowing for collection of pollen, and also pollination of the stigmas, if the animal was already carrying pollen. The pollen was also irregularly shaped (see "Pollen Morphology") suggesting that wind is not the preferred vector for the pollen. - The major vector, we concluded, would be insects, particularly bees. This was due to the size of the flower, and the stems on which the flowers grew. With a small size (for precise sizes, see "Variability of Floral Morphology"), the flower would be very difficult for a bird to fit its beak or head into. Furthermore, each stem was very thin. This would make it very difficult for a bird to be able to stand stably on the stem while feeding. Similarly, each stem ended in three flowers in a cluster. With each flower having petals that spread more widely than the flower was deep, and far more widely than the anther and stigma reached, it would make it difficult for a bird to visit, and gain access to the flower. - On the other hand, bees would be well suited to visiting the flowers. The flowers are oriented to face upwards, meaning that any insect could land easily within the petal spread, and move towards the centre of the flower, where the anthers and carpel are located. The style and filaments were all approximately the same length, suggesting that an insect moving over the flower would collect and deposit pollen simultaneously. - Flowers were also oriented on stems of different length, to increase the number of flowers visible from a single point, thus maximising the shrub's exposure to a biotic pollinator's view.



//**Variability of Floral Morphology**//
 - The following structures on the Azalea were measured/counted:
 * Numbers of flowers per stem
 * Number of petals, stamen, and carpels per flower
 * Distance between carpel(s) and stamens
 * The width of the flowers, measured using calipers
 * The depth of the flowers, measured using calipers
 * Orientation of flowers

 - We found there were always three flowers on the ends of stems. The only exceptions  were in cases where there were two flowers. However, careful examination of the sepals found that one flower had been broken off or had fallen off.  - There were always 10 petals on each flower. Five of these made an inner ring, and five sat outside them. This is apparently a feature that Azaleas have been bred to produce, for human aesthetic appeal. Wild Azaleas only have one ring of five petals.  - There was always one carpel per flower, located in the centre of the flower.  - There were 5-6 stamens per flower. <span style="font-family: Arial,Helvetica,sans-serif;"> - Below measurements made from 18 flowers. carpel and stamen || 6.2 || 1.14 || <span style="font-family: Arial,Helvetica,sans-serif;"> - This suggests that the stamens and carpel are quite closely packed, which provides evidence for an animal vector which would come into contact with both male and female reproductive organs upon visiting the flower. <span style="font-family: Arial,Helvetica,sans-serif;"> - Carpels and stamens were relatively the same size in width and length, with mature flowers displaying taller stigmas that were bent further away. <span style="font-family: Arial,Helvetica,sans-serif;"> - The general orientation of individual flowers on their stems was horizontal to vertical. Flowers that open facing downwards are more difficult for insects to visit, so this observations further suggests an insect pollinator. <span style="font-family: Arial,Helvetica,sans-serif;">
 * **Structure** || **Average (mm)** || **SD** ||
 * Flower width || 37.5 || 3.50 ||
 * Flower depth || 29.6 || 2.83 ||
 * Distance between

**//<span style="font-family: Arial,Helvetica,sans-serif;">Pollen Morphology //**
<span style="font-family: Arial,Helvetica,sans-serif;"> - Pollen grains were obtained by rubbing a small (2x2x2mm) cube of fuchsin gel over an anther. This gel was then placed on a microscope slide, and melted using a hotplate. The pollen could then be easily observed using a light microscope. <span style="font-family: Arial,Helvetica,sans-serif;"> - The pollen was found to be irregularly shaped, described as tetraporate. This, it was inferred, was to allow the pollen to more easily attach itself to the fine hairs of a bee's abdomen or legs, allowing for transport from one flower to another. In addition to this, it was found that the stigmas of the Azalea had a sticky substance on them, no doubt to increase ease of adhesion of the pollen grains. <span style="font-family: Arial,Helvetica,sans-serif;"> - The number of pollen grains was calculated very approximately by dividing the slide up into 16ths, and counting the pollen grains under 40x magnification in four of the divisions, and extrapolating. It was found that around 1000 pollen grains were on the slide. This, however, was only a small percent of the pollen grains originally found on the single anther (of which there were 5-6 per flower). It is evident then that a single flower could produce many many thousands of pollen grains. And with potentially hundreds of flowers on a single shrub, Azaleas have evolved to produce pollen in massive quantities to increase the chance of pollination and fertilisation.

**//<span style="font-family: Arial,Helvetica,sans-serif;">Nectar Characterisation //**
<span style="font-family: Arial,Helvetica,sans-serif;"> - After sampling seven mature Azalea flowers, none of them were found to have nectar. - A possible explanation is that <span style="font-family: Arial,Helvetica,sans-serif;">self-pollination was the dominant method of fertilization, and therefore nectar provisions would not be needed to motivate possible pollinators <span style="font-family: Arial,Helvetica,sans-serif;"> - Another possible explanation (and probably the most likely) is that the nutrition in pollen (a good source of protein) is reward enough for pollinators, and the plant does not need to expend resources producing nectar. <span style="font-family: Arial,Helvetica,sans-serif;"> - A further explanation lies in the selective breeding by humans. It is possible that nectar production has been bred out of the flower. The plant no longer requires a nectar reward system, for the predominant pollinators, insects, have essentially been replaced with humans. Instead of a food reward, the reward for the human pollinator has been the aesthetic appeal in gardens!