BIO 172, CH. 30 Reproduction and Demestication of Flowering Plants

Flase. The endosperm in a seed is not the embryo, but the food supply for the embryo.

True or false? The endosperm in a seed develops into the embryo.

The alternation of generations refers to the alternation between the diploid sporophyte and the haploid gametophytes in plants. In angiosperms, meiosis occurs in floral structures of the larger, diploid sporophyte, producing haploid microspores in the anthers and haploid megaspores in the ovaries. These microspores and megaspores divide by mitosis and form the haploid male and female gametophytes, respectively. Pollination occurs when the male gametophyte, contained in a pollen grain, is transferred to the stigma of a flower. Sperm travels to the female gametophyte, where fertilization (fusion of sperm and egg) forms a diploid zygote. The zygote develops into an embryo and eventually an adult sporophyte. The cycle repeats, each time allowing for the production and development of new individuals.

Alternation of generations in angiosperms

Flowers attract animal pollinators carrying pollen from other plants of the same species Fruits aid in the dispersal of seeds by wind or by animals that carry or eat the fruits. In many angiosperms, the male gametophyte contained in a pollen grain can be transported many miles away by wind or animal pollinators. Floral parts of the sporophyte protect the reduced female gametophyte from drying out and from UV radiation. Seeds protect and nourish plant embryos, and fruits protect the seeds. Seeds enable plant embryos to be dispersed long distances from the parent plant via wind or animals

As plants evolved and populated terrestrial environments, one challenge that had to be dealt with was the absence of water. Angiosperms have met this challenge, in part, with adaptations that enable them to reproduce without water. The following table lists some differences between nonvascular plants, such as mosses, and angiosperms. Note how the angiosperm adaptations enable them to reproduce in dry terrestrial environments.

During pollination, a pollen grain is transferred from an anther to a stigma. Once the pollen grain lands on a suitable stigma, it germinates and forms a pollen tube, a structure that grows down through the style to the ovary. Once in the pollen tube, the generative cell from the pollen grain divides by mitosis, forming two sperm. The sperm travel down the pollen tube and are discharged into the female gametophyte. In a process called double fertilization, one sperm fertilizes the egg, forming the zygote; the other sperm fuses with two polar nuclei in the female gametophyte, forming a triploid (3n) nucleus. The zygote develops into the plant embryo, and the triploid nucleus divides and gives rise to the endosperm. Double fertilization prevents the waste of the plant's resources by ensuring that the nutrient-rich endosperm only develops if the egg is fertilized. After double fertilization, the ovule starts to develop into a seed containing the plant embryo. As the embryo develops, the three tissue systems are established, and the cotyledons (seed leaves) form. The seeds of many species dry out as they mature. These dry seeds lie dormant until suitable germination conditions occur.

Fertilization and seed development

One sperm nucleus fuses with the egg to form a diploid zygote, whereas the other sperm nucleus fuses with two polar nuclei to form a cell that develops into endosperm. Angiosperms are unusual in that one sperm nucleus fuses with the egg and one sperm nucleus fuses with two polar nuclei to form a triploid cell that develops into a nutrient-rich tissue that nourishes the growing embryo.

How is fertilization in flowering plants different from fertilization in other plant groups?

enhanced survival of genetically favorable offspring In constant environments, asexually produced offspring have higher survival rates.

Which of the following is an advantage of asexual reproduction in plants?

The CO2 produced by biofuels will be absorbed by the crops used to produce them, creating a carbon-neutral cycle. Unlike taking deeply buried carbon sources such as oil and coal and releasing all of that carbon into the atmosphere, biofuels do not add to the carbon load already in the biosphere.

Which of the following is one possible advantage of biofuels versus oil?

The swellings that develop into cotyledons are located at the end of the embryo on top of the row of single cells.

Which of the following statements about seed formation in a flowering plant is true?

Petals

Which part of a plant attracts pollinators?

Pollination

Which process involves the transfer of pollen grains from an anther to a stigma?

Pollen tube The pollen tube is formed after a pollen grain is transferred to a receptive stigma and germinates, forming a tube that grows down through the style to the ovary of a flowering plant.

Which structure formed by the male gametophyte allows sperm to reach the ovary of a flowering plant?

Pollen grains are the male gametophytes of flowering plants; they contain a generative cell that develops into sperm.

Which term describes the male gametophytes of flowering plants?