When an insect collects nectar from a flower, some pollen from the stamens sticks to its body. When the insect flies to another flower, some pollen may rub off onto the pistil of another flower. Plants would not be able to produce seeds and make new plants if it weren't for insect helpers. Flower - Where the seed develops. Flowers have bright colors or a special scent to attract insects. Sepals - The outer green parts of the base of the flower that look like leaves.
They protect the flower bud before it opens. Inside the sepals are colored petals. The stamen is made up of two parts: the anther and filament. The anther produces pollen male reproductive cells. The filament holds the anther up. During the process of fertilization , pollen lands on the stigma, a tube grows down the style and enters the ovary. Pineapples and figs are examples. A seed contains all of the genetic information needed to develop into an entire plant.
It is made up of three parts Figure 22 :. Germination is when a seed embryo goes from a dormant state to an active, growing state Figure Before any visual signs of germination appear, the seed must absorb water through its seed coat. It also must have enough oxygen and a favorable temperature.
Some species, such as celery, also require light. Others require darkness. If these requirements are met, the radicle is the first part of the seedling to emerge from the seed. It develops into the primary root and grows downward in response to gravity. From this primary root, root hairs and lateral roots develop. Between the radicle and the first leaflike structure is the hypocotyl , which grows upward in response to light. Because seeds are reproductive structures and thus important to a species' survival, plants have evolved many mechanisms to ensure their survival.
The seed leaves, or cotyledons , encase the embryo. They usually are shaped differently than the leaves the mature plant will produce. Monocots produce one cotyledon, while dicots produce two. One such mechanism is seed dormancy. Dormancy comes in two forms: seed coat dormancy and embryo dormancy.
In seed coat dormancy , a hard seed coat does not allow water to penetrate. Redbud, locust and many other ornamental trees and shrubs exhibit this type of dormancy. A process called scarification is used to break or soften the seed coat. In nature, scarification is accomplished by means such as the heat of a forest fire, digestion of the seed by a bird or mammal, or partial breakdown of the seed coat by fungi or insects.
It can be done mechanically by nicking the seed coat with a file, or chemically by softening the seed coat with sulfuric acid. In either instance, it is important to not damage the embryo.
Embryo dormancy is common in ornamental plants, including elm and witch hazel. These seeds must go through a chilling period before germinating. To break this type of dormancy, stratification is used. The length of time required varies by species. Even when environmental requirements for seed germination are met and dormancy is broken, other factors also affect germination:.
Many weed seeds are able to germinate quickly and under less than optimal conditions. The anther rests on top of the filament and contains the pollen. The anther is usually yellow. Flowers generally have the same number of stamens as petals.
The female part of a flower, called the pistil, consists of three parts: the stigma, the style and the ovary, according to Illinois Extension. The stigma is the sticky portion of the pistil that collects pollen from visiting bees and butterflies. The style connects the stigma to the ovary. The ovary holds the ovules that grow into seeds when pollen is collected and transported to the ovary.
These flowers do not need another flower to pollinate the plant.
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