Chapter 38-Angiosperm Reproduction and Biotechnology

List four floral parts in order from outside to inside a flower.

1) Sepal 2) Petal 3) Stamen 4) Carpel

Explain how a monocot and a dicot seed differ.

Dicots retain their food supply in the endosperm and transfer them to the rest of the embryo where the seed germinates. Monocot has a single cotyledon called scutellum which has a large surface area and is pressed against the endosperm, from which is absorbs nutrients during germination.

Describe the fate of the ovule and ovary after double fertilization. Note where major nutrients are stored as the embryo develops.

• Each ovule develops into a seed and the ovary develops into a fruit, enclosing the seed. As the embryo develops from the zygote, the seed stockpiles proteins, oils, and starch to varying degrees depending on the species. This is why seeds are such a major nutrient drain. Initially, carbohydrates and other nutrients are stored in the seed's endosperm but later, depending on the species, the swelling cotyledons of the embryo may take over this function

Describe the development and function of the endosperm.

•After double fertilization, the triploid nucleus of the ovule's central cell divides, forming a multinucleate "super cell" that has a milky consistency. This liquid mass, the endosperm, becomes multicellular when cytokinesis partitions the cytoplasm by forming membranes between the nuclei. Eventually, these "naked" cells produce cell walls and the endosperm becomes solid.

Distinguish between: o Bisexual and unisexual flowers

•Bisexual flowers: have BOTH stamens and carpels •Unisexual flowers: lack either stamens or carpels

Distinguish between: o Complete and Incomplete flowers

•Complete flowers: have all four of the basic floral organs •Incomplete flowers: lacking the sepals, petals, stamens, or carpels

Explain various methods that horticulturalists use to propagate plants from cuttings.

•Cuttings- Pieces removed, suitably treated, can give an entire plant -Example(s): potato eyes, African violet leaves, vine sections -Many cultivars are sterile, anyway •Grafting- -Piece of one stem inserted into another -Nearly all citrus (scion) are grafted onto lemon roots (stock) •Plant tissue culture- Excised cells grown in sterile conditions

Distinguish between monoecious and dioecious plant species.

•Dioecious: Plants that have flowers of one sex or the other. •Monoecious: Plants with flowers of both sexes.

Distinguish between pollination and fertilization.

•Fertalization is the union of egg and sperm where pollination is the transfer of pollen from an anther to stigma.

Explain by which generation, structure, and process gametes are produced.

•Gametes are produced in the Gametophyte generation(haploid) formed in the archegonia and antheridia

Describe the process of germination in a garden bean and corn plant.

•Germination depends on imbibition, which is the uptake of water due to the low water potential of the dry seed. Imbibing water causes the seed to expand and rupture its coat and also triggers metabolic changes in the embryo that enable it to resume growth. Following hydration, enzymes begin digesting the storage materials of the endosperm or cotyledons, and the nutrients are transferred to the growing regions of the embryo. The first organ to emerge from the germinating seed is the radical, which is the embryonic root.

In general terms, explain how the basic plant life cycle with alternation of generations is modified in angiosperms.

•In angiosperms, the sporophyte is the dominant generation: it is larger, more conspicuous, and longer lived than the gametophyte. Angiosperm gametophytes are the most reduced of all plants, consisting of only a few cells. The key derived traits of the angiosperm life cycle can be remembered as the three f's: flowers, double fertilization, and fruits.

Describe the development of the embryo sac and explain the fate of each of its cells.

•One cell in the megasporangium enlarges and undergoes meiosis producing 4 haploid megaspores. Only one megaspore survives which continues to grow and nuckleus divides by mitosis three times without cytokinesis resulting in one large cell with eight haploid nuclei. membranes then partition this mass into a multicellular female gametophyte called the embryo sac.

Name the structures that represent the male and female gametophytes of flowering plants.

•Pollen grain represents the male gametophytes and embro sac are the female gametophytes

Describe the natural mechanisms of vegetative reproduction in plants, including fragmentation and apomixes.

•Regions of undifferentiated, dividing cells sustain or renew plant growth. In addition, parenchyma cells throughout the plant can divide and differentiate into more specialized types of cells, enabling plants to regenerate lost parts. Detached vegetative fragments of some plants can develop into whole offspring. Such fragmentation, the separation of a parent plant into parts that develop into whole plants, is one of the most common modes of asexual reproduction. Apomixis is the production of seeds without pollination or fertilization. There is no joining or production of sperm and egg, instead a diploid cell in the ovule gives rise to the embryo, and the ovules mature into seeds.

From a diagram of an idealized flower, correctly label the following structures and describe the function of each: o Sepals o Petals o Stamen (filament and anther) o Carpel (style, ovary, ovule, and stigma)

•Sepals: Enclose and protect unopened floral buds •Petals: Attract pollinators •Stamen (filament and anther): Includes the anther and filament, they are the male reproductive organs that produce pollen •Carpel (style, ovary, ovule, and stigma): Includes the stigma, style, and ovary. They are responsible for the female gametophyte. They house the egg

Distinguish among simple, aggregate, and multiple fruit. Give an example of each type of fruit.

•Simple fruit: Fruits that are derived from a single carpel or several fused carpels. Example(s): Pea pod, nut, nectarine. •Aggregate fruit: Results from a single flower that has more than one separate carpel, each forming a small fruit. These fruitlets are clustered together on a single receptacle. Example(s): Raspberry. •Multiple fruit: Develops from an inflorescence, which is a group of flowers tightly clustered together. When the walls of the many ovaries start to thicken, they fuse together and become incorporated into one fruit. Example(s): Pineapple.

Explain by which generation, structure, and process spores are produced.

•Spores are produced in the sporophyte generation(diploid) inside the sporangium through meiosis.

Describe the development of a plant embryo from the first mitotic division to the embryonic plant with rudimentary organs.

•The first mitotic division of the zygote splits the fertilized egg into a basal cell and terminal cell. Terminal cell eventually gives rise to most of the embryo. The basal cell continues to divide, producing a thread of cells called the suspensor, which anchors that embryo to the parent plant. The terminal cell divides several times and forms a spherical pro-embryo attached to the suspensor. The cotyledon begin to form as bumps on the pro-embryo. The embryo elongates at the end of the embryo's axis where the suspensor attaches and embryonic root apex forms. After the seed germinates, the apical mersistems at the apices of shoots and roots sustain primary roots

Describe the mechanisms that prevent self-pollination.

•The most common anti-selfing mechanism in flowering plants is self-incompatibility, which is the ability of a plant to eject its own pollen and sometimes the pollen of closely related individuals. If a pollen grain lands on a stigma of a flower of the same plant, a biochemical block prevents the pollen from completing its development and fertilizing an egg. Recognition of "self" pollen is based on genes for self-incompatibility called S-genes. If a pollen grain has an allele that matches an allele of the stigma on which it lands, the pollen tube fails to grow. Depending on the species, self recognition blocks pollen tube growth by one of two molecular mechanisms: gametophytic self-incompatibility or sporophyte self-incompatibility.

Explain how fruit forms.

•The ovaries of a flower are what develop into the fruit. This occurs when the ovary wall becomes the pericarp, which is the thickened wall of the fruit.

Outline the process of double fertilization.

•The pollen grain lands on the stigma. If a pollen grain germinates, a pollen tube grows down the style toward the ovary. The pollen tube discharges two sperm into the female gametophyte within an ovule. One sperm fertilizes the egg, forming the zygote. The other sperm combines with the two polar nuclei of the embryo sacs large central cell, forming a triploid cell that develops into the nutritive tissue called endosperm. or.... -After landing on a receptive stigma (receptive tip of carpel), the pollen grain produces a tube that extends through the style to the ovary. Here, it discharges two sperm into the embryo sac. One sperm fertilizes the egg, the other gives rise to the nutritive material (endosperm!) on which the embryo will feed.