What do angiosperms produce

Some fruits are derived from separate ovaries in a single flower, such as the raspberry. Other fruits, such as the pineapple, form from clusters of flowers.

Additionally, some fruits, like watermelon and orange, have rinds. Regardless of how they are formed, fruits are an agent of seed dispersal. The variety of shapes and characteristics reflect the mode of dispersal. Wind carries the light dry fruit of trees and dandelions.

Water transports floating coconuts. Some fruits attract herbivores with color or perfume, or as food. Other fruits have burs and hooks to cling to fur and hitch rides on animals.

Like gymnosperms, angiosperms are heterosporous. Therefore, they generate microspores, which will generate pollen grains as the male gametophytes, and megaspores, which will form an ovule that contains female gametophytes. Each pollen grain contains two cells: one generative cell that will divide into two sperm and a second cell that will become the pollen tube cell.

Figure 3. The life cycle of an angiosperm is shown. Anthers and carpels are structures that shelter the actual gametophytes: the pollen grain and embryo sac. Double fertilization is a process unique to angiosperms. If a flower lacked a megasporangium, what type of gamete would not form?

If the flower lacked a microsporangium, what type of gamete would not form? Without a megasporangium, an egg would not form; without a microsporangium, pollen would not form. The ovule, sheltered within the ovary of the carpel, contains the megasporangium protected by two layers of integuments and the ovary wall.

Within each megasporangium, a megasporocyte undergoes meiosis, generating four megaspores—three small and one large. Only the large megaspore survives; it produces the female gametophyte, referred to as the embryo sac. The megaspore divides three times to form an eight-cell stage. Four of these cells migrate to each pole of the embryo sac; two come to the equator, and will eventually fuse to form a 2 n polar nucleus; the three cells away from the egg form antipodals, and the two cells closest to the egg become the synergids.

When a pollen grain reaches the stigma, a pollen tube extends from the grain, grows down the style, and enters through the micropyle: an opening in the integuments of the ovule. The two sperm cells are deposited in the embryo sac. A double fertilization event then occurs. One sperm and the egg combine, forming a diploid zygote—the future embryo. The other sperm fuses with the 2 n polar nuclei, forming a triploid cell that will develop into the endosperm, which is tissue that serves as a food reserve.

The zygote develops into an embryo with a radicle, or small root, and one monocot or two dicot leaf-like organs called cotyledons. This difference in the number of embryonic leaves is the basis for the two major groups of angiosperms: the monocots and the eudicots. Seed food reserves are stored outside the embryo, in the form of complex carbohydrates, lipids or proteins. The cotyledons serve as conduits to transmit the broken-down food reserves from their storage site inside the seed to the developing embryo.

The seed consists of a toughened layer of integuments forming the coat, the endosperm with food reserves, and at the center, the well-protected embryo. Most flowers are monoecious or bisexual, which means that they carry both stamens and carpels; only a few species self-pollinate.

Both anatomical and environmental barriers promote cross-pollination mediated by a physical agent wind or water , or an animal, such as an insect or bird. They are also an excellent shape for species like pines that rely on wind pollination why? Examine slides of the megaspore mother cell. Observe the structure of the strobilus female pine cone and note the megasporophylls and megasporangia.

You will need to look at several sporangia , and possibly more than one slide, to actually find the megaspore mother cell. Notice that the sporangia sitting on the sporophylls are directly exposed to the outside air. Gymnosperm means "naked seed". Examine slides of the male strobilus pine cone. Note the microsporangia and the microsporophylls. You can switch to high power and observe the pollen grains in the sporangia or switch to the pollen grain slide.

Notice the two large wings looks like Mickey Mouse. These wings were presumed to aid in wind pollination, but recent evidence suggests they help the pollen grain float up through the micropyle to the egg. Examine the pine cones on display. The smaller male cones are only on the tree for a short time.

Ephedra is the natural source of the drug ephedrin , which is used to treat hay fever, sinus headaches, and asthma eg. Zamia floridana is the only cycad native to the U. Ginkgos are used for bonsai, as a source of herbal medicine, and as popular urban shade trees because of their yellow autumn foliage and their resistance to air pollution. Conifer seeds are very complex structures, containing cells from three generations of the tree.

Can you figure out which tissues come from which generation of the conifer? Just as Gymnosperms forced non-seed plants into the ecological background, the evolution of Angiosperms, sometime during the Cretaceous, forced gymnosperms into restricted habitats.

Wherever the earth was cold or dry, gymnosperms could prevail. But in all other habitats, flowering plants rapidly became the dominant plant life. Flowering plants are able to survive in a greater variety of habitats than gymnosperms. Flowering plants mature more quickly than gymnosperms, and produce greater numbers of seeds.

The woody tissues of angiosperms are also more complex and specialized. Their seeds are enclosed in a fruit for easy dispersal by wind, water, or animals. The leaves of angiosperms are mostly thin, extended blades, with an amazing diversity of shapes, sizes, and types. The surface of the pollen grain has a complex three-dimensional structure.

This structure is unique for each species, like a floral thumbprint. It also means that pollen grains, which are abundant in the fossil record, allow us to reconstruct ancient plant communities, and these communities in turn tells us about ancient climates.

All angiosperms produce flowers , reproductive structures that are formed from four whorls of modified leaves. Most flowers have showy petals to attract pollinators, bribing insects and other animals with nectar, to get them to carry the male gametophyte through the air to another flower. Animal pollination is common in angiosperms, in contrast to the mostly wind-pollinated gymnosperms. The ovules in angiosperms are encased in an ovary, not exposed on the sporophylls of a strobilus, as they are in gymnosperms.

Angiosperm means "covered seed". The ovules develop into seeds , and the wall of the ovary forms a fruit to contain those seeds. Fruits attract animals to disperse the seeds. Flowers consist of four whorls of modified leaves on a shortened stem: sepals , petals , stamens an anther atop a slender filament , and one or more carpels.

Imagine a broad leaf with sporangia fastened along the edges of the leaf. Some ferns actually look like this. Now fold that leave over along the midrib, and you've enclosed the sporangia in a protected chamber. You've just made a carpel. The carpels are fused together to form a pistil , which consists of a stigma upper surface , a style long, slender neck , and an ovary round inner chamber at the bottom containing one or more ovules.

The flower is analogous to the strobilus of pines and more primitive plants, except that only the inner two whorls stamens and carpels actually bear sporangia. The base of the flower is called the receptacle , and the tiny stalk that holds it is the pedicel. The life cycle of flowering plants is described in more detail below. Microspores develop in microsporangia in the anthers , at the tip of the stamen.

Each anther has four microsporangia. Microspores develops by meiosis from the microspore mother cell. These microspores develop into pollen grains. Pollen grains are the male gametophytes in flowering plants.

Inside the pollen grain, the microspore divides to form two cells, a tube cell and a cell that will act as the sperm. Cross walls break down between each pair of microsporangia, forming two large pollen sacs.

These gradually dry out and split open to release the pollen. Meanwhile, inside the ovary, at the base of the carpel, the ovules, are developing, attached to the wall of the ovary by a short stalk. The megasporangia is covered by an integument , protective tissues that are actually part of the parent sporophyte. The megaspore mother cell divides by meiosis to produce four haploid megaspores.

Three of these megaspores degenerate, and the surviving fourth megaspore divides by mitosis. Each of the daughter nuclei divides again, making four nuclei, and these divide a third time, making a grand total of eight haploid nuclei. This large cell with eight nuclei is the embryo sac. This embryo sac is the female gametophyte in flowering plants.

One nucleus from each group of four migrates to the center. These are called the polar nuclei. The remaining three nuclei of each group migrates to opposite ends of the cell. Cell walls form around each group of three nuclei. The mature female gametophyte thus consists of only seven cells, three at the top, three at the bottom, and a large cell in the middle with two nuclei.

One cell of the bottom three cells will act as the egg. When the pollen grain reaches the stigma of the carpel, it germinates to form a pollen tube. This pollen tube will grow through the neck or style, all the way down to the bottom of the carpel, to a small opening called the micropyle. The male gametophyte has two cells. One is the tube cell, the other will act as a sperm. As the pollen tube grows closer to the embryo sac, the sperm nucleus divides in two, so the mature male gametophyte has three haploid nuclei.

While the pollen tube is entering the ovule, the two polar nuclei in the female gametophyte fuse together, making one diploid nucleus. Figure 18 This diagram shows egg development within the ovule within an enclosed carpel. What is left of the female gamete that gives rise to the egg is called an embryo sac. The embryo sac develops from one diploid cell megaspore mother cell.

Meiosis gives rise to four spores: three disintegrate and only one remains. This megaspore divides by mitosis to produce the embryo sac. The number of mitoses that occur vary by species, but the model used here is the lily in which three mitoses occur to form an embryo sac with 8 haploid nuclei. Angiosperms There are over , species of angiosperms. Angiosperms are flowering plants. They make up around 80 percent of all the living plant species on Earth.

Flower Power Angiosperms are vascular plants. They have stems, roots, and leaves. Unlike gymnosperms such as conifers and cycads, angiosperm's seeds are found in a flower. Angiosperm eggs are fertilized and develop into a seed in an ovary that is usually in a flower. The flowers of angiosperms have male or female reproductive organs.