Plant Reproduction Ch 7

Seed Plant Reproduction Seed plants are well adapted to the demands of life on land. The gametes of seed plants can achieve fertilization even without water. The gametes of seed plants are usually hidden deep within the tissues of the plant. In gymnosperms they are found in the cones In angiosperms they are found inside flowers

Gymnosperm reproduction In cone bearing plants there are male and female cones. The males release pollen grains which are carried by the wind. Some reach female cones and stick to the scales of their cones. Once fertilization occurs an embryo develops in a seed

Structure of Flowers Flowers are the reproductive organs that are composed of four components; sepals, petals, stamens and pistils Sepals: outermost flower parts that are usually green and look similar to leaves. They enclose the buds before they open and help protect the flower. Petals: usually brightly colored and found just inside the sepals. They attract insects and other pollinators to the flower. Stamens: composed of the anther and filament. The filament is a long thin stalk that supports an anther at the tip. The anther produces the pollen grains

Pistils: are the innermost floral parts also called carpels Pistils: are the innermost floral parts also called carpels. They produce the female gametes. Each pistil has a broad base forming an ovary. Each pistil narrows into a stalk called the style which has the stigma at the top where pollen can stick Typically flowers contain both male and female parts. But some produce separate flowers for the male and separate flowers for the female on the same plant though

Pistil

Angiosperms Reproduction Reproduction takes place in the flower and is called pollination. Pollination can be done by wind, insects, and animals. Pollen is carried from flower to flower Bright colors and nectar attract animals. Animal have adapted to help them find flowers and enable them to reach nectar deep within certain flowers. Pollination benefits both the plant and the pollinator Then seeds develop inside protective structures of the plant

Seed Development Once fertilization is complete the embryo starts to develop inside a seed. As angiosperm seeds mature the ovule thickens and forms a fruit that encloses the developing seeds A fruit is a ripened ovary that contains seeds. They include apples, grapes, peas, corn, beans, cucumbers, and tomatoes. Whether it tastes sweet or not, if it contains a seed it is a fruit Fruits may be fleshy (apples, grapes tomatoes) or tough (beans & corn)

Seed Dispersal The purpose of fruit is to entice animals to eat them and then they disperse the seeds usually without even noticing. The seeds are not harmed during digestion and later are eliminated from the animal. The fruit provides nutrition for the animal and also helps the plant disperse its seeds Many seeds are not enclosed in fruit but have adaptations for dispersal by wind and water. These seeds are usually lightweight allowing them to be carried by wind or water Tumble weeds are full of seeds that are dispersed by the wind. Coconuts float and their seeds can be carried by water.

Seed Dormancy Many seeds will not grow when they first mature. They enter a period of dormancy when the embryo is still alive but not growing. This length varies in different plants. Temps and moisture can cause a seed to end dormancy and germinate Seed dormancy allows for seeds to germinate under ideal growth conditions. Here mid-summer or mid-winter would not be a good time for a new plant to grow but spring conditions are ideal Seeds can stay dormant for days, weeks, or months

Seed Germination Seed germination is the early growth stage of the plant embryo. When seeds germinate they absorb water causing the seed coat to swell and crack open. The young root begins to grow first then leaves will appear

Plant Agriculture The earliest humans gathered plants for food, shelter, and medicine. Many plants can reproduce by vegetative reproduction which is where new tiny plants or plantlets are produced along their stems. These new plants can stay attached to the parent or if they fall to the ground they can take root Plants can also reproduce by growing horizontal stems like strawberry plants and bamboo

Plant Production To produce the best offspring botanist can use cuttings, grafting, or budding to make identical copies of a plant Cuttings: a grower cuts from the plant a length of stem that includes a number of buds. That stem is partially buried in soil. Grafting & Budding: usually works best when the plant is dormant to produce new plants. A piece of stem or bud is cut from the parent plant and attached to another plant. The cut piece is called the scion and the plant it is attached to is called the stock

Review Questions Where are the gametes of seed plants? In gymnosperms? In angiosperms? What is pollen? What is the embryo protected in? What are flowers? What are the sepals? What are the petals? What are the stamens? What is the filament? What is the anther?

What are the pistils? Where does reproduction take place? What does pollination? What attracts animals & insects to plants? Who benefits from pollination? Where do you find the seed? What is the fruit? What is its purpose? What are the THREE ways seeds are dispersed?

What is dormancy? How long does it last? What is germination? What does the seed grow first? What is vegetative reproduction? What plants are examples of this? What do you do in cutting? In grafting & budding?