Plant Growth and Reproduction                                                     Chapter 2, Lesson 7

Seeds A seed is an un-developed plant with stored food sealed in a protective covering known as a seed coat.

Germination The process of a seed sprouting into a new plant.

Germination These are different stages in the germination process.

Seedling A young plant that grows and develops from a seed. All seeds grow from a seed to a seedling to an adult plant.

Seedling Most seeds swell as they take in water. The seed coat splits open. A root grows out of the seed. Then a tiny stem appears.

Seedling One or two leaves grow from the stem, and the young seedling beings to grow. If the condition are just right, the seedling will mature into an adult plant. Then it will make seeds of its own.

Seedling In some plants the time from seed to adult takes only days. A bean plant matures in just a few months. A peach seed takes several years to become a tree.

Life Cycle of a Peach Tree

Parts of a Seed In order for a seed to germinate (the process of a seed sprouting into a new plant) it needs. A seed must move from the flower to a place where it can sprout. Most seeds need water and warm temperatures to germinate.

Parts of a Seed Once the seedling begins to grow, it needs the right amount of light. The leaves of the growing plant need light to make oxygen. A seedling also needs oxygen from the air and nutrients from the soil.

Pollen Male sex cells are found in the pollen. The pollen grains are like a soft powder.

Anther The pollen is produced by the anthers. Pollen Anther

The female sex cells (eggs) are found in the pistil.

Pollination The transfer of a pollen grain to the pistil. Plants rely on insects, birds, mammals, wind, or water to help with pollination.

This is a flower. The pistil is the tall green stalk. This illustration does not reflect the anthers.

A pollinator comes and deposits pollen which lands on the pistil. How does that help? A bee might go to one flower and get a little pollen on its back. If it goes to another flower of the same species, that pollen can land on the pistil.

Pollen grains (yellow) are located on the top of the pistil. The pollen then travels down the pollen tube (yellow) until it reaches the ovaries.

The ovary then fertilizes the egg. Fertilization is the joining of a female sex cell and a male sex cell into one cell.

Ovary The ovary is a structure containing egg cells. It is the ovary that grows to produce the protective fruit.

How Are Seeds Carried Away? Once a seed forms, it needs a place to grow. The best chance of survival is to be in its own space, away from the parent plant. Why? A parent plant may soak up water and nutrients the seedling needs from the soil.

How Are Seeds Carried Away? Therefore, a seeds best chance of survival is when it is carried away, or dispersed, from the parent. Seeds disperse in many different ways.

How Are Seeds Carried Away? Some plants scatter their own seeds. The protective, fleshy fruits explode to shoot their seeds away from the parent plant. Pea and bean plants keep their seeds in a pod. When the seeds are ripe and the pod has dried, the pod burst open and peas and beans are scattered.

How Are Seeds Carried Away? Many seeds are carried by animals. The fleshy fruit may attract animals that eat the seeds along with the fruit. The seeds may fall to the ground as the animals eat the fruit. If the seeds are eaten, the animals will pass them out in their droppings.

How Are Seeds Carried Away? Other seeds are carried by the wind or water. A dandelion seeds have a “parachute” of feathery hairs. They are light enough for the wind to carry them long distances.

How Are Seeds Carried Away? Seeds may also become attached to human’s clothing and shoes.

How Are Seeds Carried Away? Some seeds may also hitch a ride on an animal’s fur and fall off in some new place.

The Life Cycle of Flowering Plants

Ferns Ferns are green plants which can capture energy from the sun through photosynthesis. They do not have seeds, but instead simply use spores to reproduce.

Moss Plants Do not produce flowers. Do not produce seeds. They reproduce by creating spores.

Spores A spore is a cell in a seedless plant. Plants such as mosses and ferns use spores to reproduce. Spores do not have sex cells. Each spore is produced by the parent plant. The parent plant sheds the spores locally. The spore-generating organs are frequently located on the undersides of leaves.

Moss Spores The egg is fertilized. The fertilized egg grows into a thin stalk with a spore case on top. The spore case opens, the spores are released. Spores land on damp ground and may grow into new moss plants. The life cycle begins again.

Fern Spores On a fern, spores are found on the bottom side of the leaf. As the spore case matures and ripen, millions of spores are released and scattered into the air. When carried by wind currents, a small number of them fall on damp surfaces and soils. Here they form into a small, flat, kidney-shaped body.

Fern Spores This body gets its food by pushing roots into the soil. Eventually, this plant body grows male and female organs. Sperm from the male organ fertilizes an egg from the female organ. This produces a new plant. The new plant produces spores, and the process begins again.

Fern Spores The yellow spores are unopened. The brown spores are opened.

The End