Scabiosa caucasia Development (page 6)
Carpel growth and pollen attachment
After the anthers are shed the styles grow in length. The stigmas (end of the style) are indented in shape. After a brief delay, the stigmas change in shape and lose their indentations. They then support pollen adhesion. The pollen then begins to swell as a result of dehydration. This is part of the process of pollen activation. A tube will then grow down style the from the activated pollen to produce fertilisation in the ovary.
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Style elongation is occurring even in the central florets
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The characteristic pincushion flower morphology is now evident. A few of the stigmas toward the bottom of the images have become adhesive to the pollen.
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The rear of the large outer petals is supported by the green sepals.
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The stigmas are indented in shape at an early stage of style growth.
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Close up of and indented stigma with one pollen grain attached to it by a corner. Note that at this stage the pollen is still partially dehydrated.
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A high-resolution image shows that the epidermis of the style is covered with small polygonal epidermal cells. The style epidermis consists of much larger cells that are elongated along the plane of growth.
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When the stigmas become receptive to pollen they can be densely covered in pollen
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8 flattened triangular pollen grains are adherent to this style
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Pollen adheres to the epidermal cells and also sticks together.
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2 stigmas with swollen pollen. some are still unactivated.
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Two stigmas with attached pollen. The one on the left might also have a yellow pollen from another species attached to it.
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Pollen on the styles of five stigmas