Chapter 24Reproduction of Seed Plants Sporophytes Gametophytes are the gametes (egg and sperm) Sporophytes are the plants Gametophytes
Life Cycle of Gymnosperms Turn to page 611, Figure 24-4 Cone scale Life cycle of gymnosperms takes place in cones which are produced by the mature sporophyte plant. Ovule Pollen cones – produce male gametophytes Seed cones – produce female gametophytes Ovules – found at the base of each scale, this is where the female gametophyte develops Ovules
Fertilization and Development Text page 611 Pollen tube – structure containing two haploid sperm nuclei Zygote – new diploid sporophyte plant Generally takes 2 years to complete Zygote grows into an embryo, and becomes encased in a what will soon become a seed. Pollen grain has 2 nuclei!
Structure of flowers Specialized leaves: NOT involved in reproduction... Sepals – outermost circle of floral parts; protects flower bud 2. Petals – found just inside the sepal; often brightly colored; attract insects Text page 612
Structure in Flowers:Reproduction • Specialized leaves: • ARE involved in reproduction... • 3. Stamen – contains the male parts of the flower • Anther – oval sac producing pollen grains • Filament – stalk that supports the anther
Structure in FlowersReproduction • Specialized leaves: • ARE involved in reproduction... • Carpel (Pistils) – makes up the female part of the flower; stigma, style, and ovary • Ovary – contains ovules where the female gametophyte are produced • Style – stalk leading to the ovary • Stigma – top of the style; sticky
Flower variety Flowers vary greatly in shape, color, and size.
Flower Variety The typical flower produces both male and female gametophytes. But, sometimes, male and female gametophytes are produced in separate flowers on the same plant... Like on corn! Tassel = flower that produces male gametophytes Silk = style of a flower that contains the female gametophyte
Composite Flowers Often called compound flowers A simple flower has one reproductive system... A compound flower is a whole colony of flowers with their own petals, and multiple reproductive systems. A sunflower is not a single flower, but a row of outer petals around many small flowers Incomplete flower = missing sepals Perfect flower = has both stamen and pistil Complete flower = has pistil, sepal and stamen Imperfect flower = staminate or pistillate..
Life Cycle of Angiosperms Reproduction takes place within the flower Seeds develop inside protective structures. 4 haploid cells are produced in the anther Each cell becomes a pollen grain In the ovary, 4 haploid cells form, but three disintegrate. Remaining cell divides into 8 nuclei within a membrane called a embryo sac. One of the 8 nuclei is the egg nucleus. This is the gametophyte of the flowering plant
Pollination Most angiosperms are pollinated by animals, not wind... Advantage? Animals carry pollen from one flower to another. What is the advantage to the animal?
Double Fertilization Text page 616 • A pollen grain lands on the stigma and begins to grow a pollen tube. • The pollen tube grows into the style, eventually reaching the ovary and entering the ovule. • Two distinct fertilizations take place: • sperm and egg nuclei fuse together new plant embryo • other nuclei form endosperm, a rich food supply for plant
24-2: Seed Development & Germination Development of the seed was a major factor in the success of plants on land A seed enclosed within a fruit offers something else... A better start to its new life!
Seed & Fruit Development Fruit – applies to any seed that is enclosed within its embryo walls Which of these foods are fruits? As Angiosperm seeds mature, the ovary walls thicken to form a fruit that encloses the developing seeds.
Plant Ovary (fruit) Lab Assignment: Bring in a plant ovary for our lab. You may choose any ovary, from the grocery store or out of your yard. We will dissect the plant ovaries... and possibly eat a few
Seed Dispersal Dispersal by Animals: Seeds are covered with a tough coating enabling them to pass through the digestive system unharmed Seeds dispersed by animals are typically contained in fleshy, nutritious fruits
Dispersal by Wind and Water Seeds dispersed by wind or water are typically lightweight, allowing them to be carried in the air or to float on the surface of the water
Seed Dormancy Dormancy – time in which an embryo is alive, but not growing Environmental factors such as temperature, and moisture can cause a seed to end dormancy and germinate
Seed Germination Germination – the early growth stage of the plant embryo Monocots Usually, the single cotyledon remains underground • Dicots (one of two ways) • cotyledons emerge above ground and • protect early leaves • cotyledons remain below the soil, • providing food for the growing seedling
24-3: Plant Propagation & Agriculture Seed plants are essential to human life The earliest humans gathered plants for food, shelter, and medicine
Vegetative Reproduction Vegetative reproduction - the production of new plants from horizontal stems, plantlets, or underground roots Occurs when plants are well adapted to an area Plantlets Stolen – long, trailing horizontal stems that produce roots Can reproduce very quickly!
Plant Propagation When a plant has a desired characteristic, we want copies. There are a variety of methods... Text p. 622 Cuttings – cut a length of stem that includes buds (meristematic tissue)
Plant Propagation Other methods... Text p. 623 To reproduce seedless or woody plants without strong root systems, we use grafting or budding. Grafts – stems are used Budding – buds are used Scion – the stem or bud of a plant Stock – root plant to which scion is attached
Agriculture Agriculture - the systematic cultivation of plants Worldwide Patterns of Agriculture North America has some of the richest, most productive cropland in the world. • Most of the people in the world depend on a few crop plants for the bulk of their food supply... • Wheat • Rice • Corn
Changes in Agriculture Increases in crop yields has lowered prices, and fed more people on less land. As our population on Earth increases, what else can we do?