References:
 

Plants and People, pages 72-83.

On Food and Cooking, page 146.
 

What are the parts of a flower?

What is a sepal?
what is a petal?
what is a stamen?

What is an anther?

What is a carpel?

What is a style?
What is a stigma?
What is an ovary?

What is an ovule?

What is an integument?
What is a micropyle?

How are ovules fertilized?

What is a seed?
 

The perianth consists of modified trophophylls. These modified leaves are used to attract animals to the flower. The next two sets of modified leaves are modified sporophylls. Plants, like humans, produce two types of gametes, male gametes called sperms and female gametes called eggs. Within flowers, spores are produced, germinate and develop into gametophytes. The third set of modified leaves in flowers are modified sporophylls called STAMENS are sporophylls that enclose sporangia that produce the male gametophytes, which develop from tiny spore called MICROSPORES. The parts of a stamen that contain the sporangia are called ANTHERS. Meiosis occurs in anthers to produce microspores, and microspores germinate to produce microgametophytes called POLLEN. Sperm are produced in pollen when they are mature.

The fourth and final set of modified leaves in flowers are called CARPELS.  A carpel is a leaf that has folded around ovules that are on it's surface, forming an inner chamber called an OVARY. Carpels are very highly modified to receive pollen. Pollen lands on a sticky, hairy top part called the STIGMA. Pollen germinate on the stigma and a pollen tube grows down through a long STYLE, under the ovary and into the ovules, where the pollen then deposit 2 non flagellated sperm cells.

Ovules consist of a sporangium called a megasporangium, surrounded by tissue called an INTEGUMENT. Flowering plant ovules have 2 integuments. At the top of the integument is a hole called a MICROPYLE, where pollen and pollen tubes can enter the ovule.

Inside the megasporangium, megaspores are produced. Megaspores germinate to produce megagametophytes. In flowering plants, mature megagametophytes are tiny, and ideally consist of 8 nuclei, one of which is the EGG NUCLEUS. Mature megagametophyes of flowering plants are called EMBRYO SACS.

When sperms enter the embryo sac, on fuses with the egg nucleus to produce a zygote, and one sperm fuses with two nuclei called POLAR NUCLEI to form endosperm. Once this DOUBLE FERTILIZATION has taken place, the ovule becomes a SEED. As the seed grows, the endosperm may develop into nutritive tissue (the main part of a corn seed is endosperm) and the zygote develops into a small plant consisting of an embryonic root called a RADICLE and an embryonic shoot called a PLUMULE.

The integument, the walls of the ovary and/or the pedicel can develop into thick fleshy or hard tissues that form the bulk of FRUITS, that we will look at during our next lecture. Fruits function as food sources for the seed or as food sources that attract animals who eat the fruits, and travel as they digest the fruit; the seeds pass through the digestive system of the animal and are deposited elsewhere. Such animal mediated seed dispersal is critical to many plants, as it gets their offspring away from the crowded conditions where the parents grew. Birds in particular are very good seed dispersers. Since the seeds are excreted along with other animal excrement, the seed is provided with a natural fertilizer by the animal, which more than compensates for the loss of the tissue that was digested by the animal.

Flowers are adaptations to animal POLLINATION, the transfer of the pollen from one plant to the carpel (the stigma) of another plants. Plants may produce aromatic compounds called ESSENTIAL OILS to attract POLLINATORS (animals that transfer pollen) to aid the showy floral display of the petals and sepals. Flowers may also produce NECTAR, a sugar solution, as a reward for animals that visit plants.

Some flowering plants are no animal pollinated, and pollen is transferred from one plant to another by wind. Such wind pollinated plants do not produce showy petals and sepals, and often contain only stamens and carpels.

There is a great deal of variation in flowers. Some, like wind pollinated plants, have only stamens and carpels. A flower lacking any of the 4 basic parts (sepals, petals, stamens or carpels) is considered to be INCOMPLETE. Flowers having all 4 basic parts are COMPLETE. Since they have both sexes represented in a flowers, such flowers are considered PERFECT. Flowers with only one sex are considered IMPERFECT. A male flower is STAMINATE and a female flower is PISTILLATE.

Plants that have flowers with only one sex are DIOECIOUS (2 kinds of plants, males and females) and plants that have flowers of both sexes, either in the same flower or in different flowers, as long as they are on the same plant, are MONOECIOUS.

As suggested by the term pistillate, the female part of a flower is called a PISTIL. A pistil may contain one  (a simple pistil) or several carpels (a compound pistil).

Most flowers are parts of elaborate branching systems called INFLORESCENCES. The part of broccoli that we eat is an inflorescence, foe example. There are a number of different kinds of inflorescences, defined by how the flowers are arranged on the main stem of the inflorescence. We have reviewed enough terms for one lecture today, but I will ask that you know one kind of inflorescence, the UMBEL, that is the inflorescence of the carrot family of plants. An umbel is an inflorescence where the pedicels of the flower all originate at one point, and radiate out to form a flat surface of flowers.