What happens when a pollen grain lands on the stigma of a carpel How does an embryo form?

Fertilization Process

 � �

Within 2 to 3 minutes, the pollen left on stigma starts to germinate, to grow pollen tube toward the egg cell.
Pollen tubes are the pathways for sperm to reach the egg.

3. Penetration of PollenTube into the Ovule

The pollen tube reaches the ovule.
It happens within 15-60 minuts after the pollen tube starts growing.
�

�
�

4. Fertilization

The rice plant carries out double fertilization as many other higher plants do.

Step 1: Fertilization of the Egg
Step 2: Fertilization of the Polar Nuclei in the Embryo Sac

5. Division of the Fertilized Egg (Zygote)

Fertilization is completed.
In the following morning, the fertilized egg begins cell division to develop into an embryo.
An embryo is a baby of the plant, which is kept dormant in the seed until the right condition for germination comes.
� �
How does the seed, the grain, develop?  Go to the grain development page� next ! �
�

© 2012 by National Association of Biology Teachers. All rights reserved. Request permission to photocopy or reproduce article content at the University of California Press’s Rights and Permissions Web site at http://www.ucpressjournals.com/reprintinfo.asp.

2012

You do not currently have access to this content.

Parts of Flowers

Flowers are beautiful to us, but for the plant they serve a critical function. Flowers are how plants produce seeds to reproduce. In many cases, the flower contains male and female parts, roughly equivalent to the male and female sexes of animals. The male parts of the flower are called the stamens and are made up of the anther at the top and the stalk or filament that supports the anther. The female elements are collectively called the pistil. The top of the pistil is called the stigma, which is a sticky surface receptive to pollen. The bottom of the pistil contains the ovary and the narrowed region in between is called the style. The male contribution or pollen is produced in the anther, and seeds develop in the ovary. Many of the fruits we eat are the thickened ovary walls surrounding the seeds.

Not only does the flower contain the sexual parts necessary for reproduction, they are also like flashy roadside billboards advertising a rich supply of nectar and pollen ready and waiting for pollinating insects and other creatures.

That is the bargain offered. Flowers trade rewards (in the form of sugary nectar and pollen) in return for the service that insects and other pollinators perform. Pollination is simply the transfer of pollen grains from an anther to a stigma. Fertilization occurs much later when the pollen grains germinate on the stigma and send down a pollen tube which releases the sex cells to fertilize the ovules. After fertilization, the ovules become the seeds, and the ovary wall becomes the fruit.

The sexual nature of flowers and the role of the many forms, colors and scents in attracting pollinators was discovered in 1759 by Arthur Dobbs.

Angiosperms. Flowering plants that have a condensed shoot tip specialized for reproduction.

Anthers. The bright yellow sacs that produce and contain the pollen grains.

Composites. Flowers such as daisies, sunflowers and their relatives that are made up of lots of tiny flowers but look just like a single flower.

Filament. The thin stalk that supports the anther in the male portion of the flower.

Gametes. The sex cells of a flower, both male and female. The gametes are porduced within the anthers of the male part and the ovary of the female part of the flower.

Gymnosperms. Plants that produce seeds without flowers, such as conifers.

Nectar. A sugary liquid reward for pollinators that is produced by the nectaries.

Nectaries. The tissue at the base of a flower (or elsewhere) that secrete nectar. Some plants, such as cotton, have nectaries on the leaves or stems. These are called extrafloral nectaries, and may serve to attract beneficial insects. An example is the extrafloral nectaries of peonies (a flower) that attract ants that in turn protect the unopened flower buds from caterpillars.

Ovary. The base of the female portion of the flower containing the ovules which become seeds.

Perfect flower. Perfect flowers contain both the male parts and female parts within a single flower structure.

Petals. The colorful, thin structures that surround the sexual parts of the flower. Not only attract pollinators, but also protect the pistil and stamen. May also produce a scent.

Pollen grains. The powdery particles that contain the male sex cells (gametes). Also a nutritious, protein-rich food for bees.

Pollination. The act of transferring pollen from the anther to the stigma. The pollen may be carried by the wind or water, but is usually transported by a go-between insect, bird or bat.

Sepals. Commonly green, leaflike structures that protect the bud prior to opening.

Stamen. Male part of flower consisting of anther and filament.

Stigma. Sticky surface where the pollen lands and germinates.

Return to homepage

What happens when a pollen grain lands on the stigma of a carpel?

What happens to pollen grains when they reach the stigma?

What happens after pollen lands on the stigma of a flower?