Lesson 1 Understanding Sexual Reproduction in Plants

Next Generation Science/Common Core Standards Addressed! HS ‐ LS1 ‐ Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells. [Assessment Boundary: Assessment does not include identification of specific cell or tissue types, whole body systems, specific protein structures and functions, or the biochemistry of protein synthesis.] WHST.9 ‐ 12.7 Conduct short as well as more sustained research projects to answer a question (including a self generated question) or solve a problem; narrow or broaden the inquiry when appropriate; synthesize multiple sources on the subject, demonstrating understanding of the subject under investigation. (HS ‐ LS1 ‐ 3) HSSIC.A.1 Understand statistics as a process for making inferences about population parameters based on a random sample from that population. (HS ‐ LS2 ‐ 6)

Bell Work! 1. Discuss the importance of plant propagation 2. Explain the difference between sexual and asexual reproduction 3. Identify the major parts of a seed 4. List the function of each major part of a seed

Terms! Cotyledon Cross pollination Diploid Embryo Endosperm Epicotyl (plumule) Fertilization Gametes Genes Haploid Hybrids Hypocotyl Pollination Radicle Seed Seed coat Self pollination Sexual reproduction Zygote

Interest Approach Look at the sample of plants that I have brought in for you. What are the two categories of plants that are displayed? How important do you think flowers are to a plant? How are plants more successful at reproduction than animals?

What Would Happen if Plants Did Not Have the Ability to Reproduce? Plants are essential for life as we know it on earth They are the ecological producers of our planet They produce food and shelter for other organisms, produce oxygen to support animal respiration, and enrich our environment Throughout history people have relied on seeds and plant parts to grow new plants for food and fiber. Livestock production would be impossible without plants!

In more recent times, knowledge of plant reproduction has resulted in the development of plant hybrids that have enabled large scale agricultural production of food and fiber plants

How Is Sexual Reproduction Different From Asexual Reproduction? Sexual reproduction occurs when the male sperm carried in the pollen unites with the female egg within a flower Most plants reproduce their own kind in nature by seeds that are the result of sexual reproduction The male sex cell (sperm) and the female sex cell (egg) are known as gametes The union of gametes produces the seed that contains the embryo plant and stores food

Both the male sperm and the female egg contribute genetic information to the new embryo plant This results in new combinations of genes producing new traits that add vigor to the offspring The offspring resulting from this new combination of genes is known as a hybrid People have greatly improved agricultural crops through hundreds of years of hybridization

The genes, made from DNA, are located in chromosomes Normal cells contain a pair of chromosomes and are said to be diploid Reproductive cells, the egg and sperm, contain a single chromosome and are said to be haploid

Fertilization unites the single chromosome in the sperm nucleus with the single chromosome in the egg nucleus This enables the fertilized egg or zygote to have a complete pair of chromosomes (diploid) Plant fertilization is unique because the sperm contains two nuclei Causes the plant to become double fertilized One sperm nucleus unites with the egg nuclei to produce a zygote The second sperm nucleus unites with the nuclei of the embryo sac that develops into the endosperm

Fertilization Process Pollen Stigma Ovary Egg Two sperm nuclei Pollen tube Second nucleus Egg nucleus One sperm fertilizes egg One sperm fertilizes second nucleus to form endosperm

Pollination is the transfer of the male sperm carried in the pollen to the female part of the flower, the stigma Plants rely on insects, wind and water to transfer the pollen to the stigma In addition, plants depend on animals to help with this process Birds, insects, bats and other animals are attracted to brightly colored, scented flowers These animals transfer pollen from the anthers of the flowers they visit to the stigmas of other flowers

Pollination Pollen grains (contain sperm) Stigma Ovule Ovary Egg cellA bat is covered with pollen from this flower. It will transfer this pollen to another flower when it searches for more nectar.

Pollination

Types of Pollination A. When the pollen of a plant pollinates a flower on the same plant, it is called self-pollination Many plants have this ability, others do not B. When the pollen of a plant pollinates the flower on another plant of the same species, it is said to be cross- pollination

What Are the Major Parts of a Seed & Where Are They Located? A seed is a living entity that serves as a bridge between generations of a plant It is formed in the pistil of the flower and develops from the ovule following fertilization As the fertilized egg (zygote) grows and develops, it becomes the embryo of the seed

Parts of the Embryo The embryo contains the root, stem and leaf of a complete plant In addition to this, it also contains stored food to support development and growth of the embryo The seeds of dicot plants have food stored cotyledons. In monocot seeds, most food is found in the endosperm The embryo’s root is called the radicle, the stem the hypocotyl and the leaf the epicotyl Surrounding the embryo & endosperm is a protective seed coat

Embryo Parts Seed coat Epicotyl Cotyledons Hypocotyl Seed coatEndosperm Epicotyl Hypocotyl Radicle Cotyledon

What Is the Function of Each Major Part of a Seed? Each part of the seed has a specific function to help ensure that a healthy new plant will emerge from the seed The seed is a living entity which contains the embryo plant & everything necessary for its growth & development Dicot plants (soybean, pea, oak) have two cotyledons while monocots (corn, coconut, lilies) have only one cotyledon in its seed

Seed Parts & Functions RadicleLower part of the hypocotyl; forms the first root; first to emerge from the seed HypocotylDevelops into the true stem EpicotylAbove the hypocotyl; develops into a pair of small leaves Tip is sometimes called the plumule – it is the terminal bud of the first shoot to emerge form the seed

EndospermFound in monocots in an area of high concentration of food; food source for the embryo CotyledonStores food absorbed from the endosperm when the seed is formed; provides energy until the plant produces its own food Seed coatSurrounds the seed and protects it from injury and dehydration

Summary Why are plants essential on earth? How is sexual reproduction different from asexual reproduction? What is another name for the sex cells of a plant? How is a haploid gene different from a diploid gene? Explain the process of pollination. What are the two types?

Summary Continued How does fertilization in a plant occur? What part of the seed is the primary root? What is the function of a cotyledon? What part of the plant develops into the true stem? How is a monocot different from a dicot? What protects the seed before it germinates?

The End!