This may seem like a silly question but it is not without answer. Of course in this case we are referring to the plant Capsella bursa-pastoris, commonly referred to as the shepherd's purse. This dicot earned its name because of the odd, slightly purse shaped, fruits that it produces. These fruits contain two chambers and are sometimes referred to as siliques. Each fruit contains several seeds which have to ability to remain dormant for long periods of time but have a short germination time. So to answer the initial question, Shepherd's need a purse to carry their seeds. Figure 1. Capsella bursa-pastoris with visible flowers and fruits. Image courtesy of blog.emergencyoutdoors.com. The flowers of this plant are small and white (See Fig. 1) and contain four petals and six stamens. This plant is gathered from the wild or cultivated to make food, medicine, and cosmetics. As mentioned previously, each fruit contains several seeds. Within each of these seeds is an embryo that is the source of life for future generations of the plant. Coincidentally the as the young embryo forms if reaches a stage when it resembles the heart shaped fruit that contains it. Figure 2. A diagram of the seed cross section as it develops. Diagram illustrated by Melissa Owens In the second image in the diagram the heart shaped embryo can be seen. The lobes of this heart shape with eventually develop into the cotyledons of the future plant. Another plant with a unique fruit structures Lilium sp. Many people are familiar with lilies as they are a beautiful and fragrant flower often grown indoors or added to bouquets. The lily contains a superior ovary that is located above the point at which the anthers attach. Unlike the shepherd's purse seeds are not the only form of reproduction for lilies. They also form a large bulb underground that is used as an overwintering structure. Some also from rhizomes that can produces more plants. A diagram of the lily ovary can be seen in Figure 3. Figure 3. Diagram of Lilium sp. ovary cross section. Diagram illustrated by Melissa Owens.The diagram illustrates the orientation of the ovule and the structures it contains. Here the placenta can been seen in the center. This is the source of nutrients for the developing seed. Each ovule is attached to the ovary by the funiculus. This connection will eventually be severed once the seed reaches maturity. Figure 4 (below) shows a more detailed image of the lily fruit cross section. Figure 4. Lilium sp. fruit cross section. Prepared and photographed by Melissa Owens at with TBO stain at 40X. It is amazing how every plant forms a different type of fruit to house it's seeds. Even though they may appear completely different, each contains the same fundamental structures that will form into a new plant after the seed has germinated.
Post by: Melissa Owens
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AuthorContent is created by students participating in the Plant Structure course at Oregon State University for Winter 2017. Archives
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