What is a seed? Seeds are containers of new life. – Seeds are formed in the ovaries of flowers, which become fruit. – Seeds ensure continuing life as well as provide food and other products
Kinds of Seeds Monocot – Monocots are plants that have a seed with one seed leaf known as a cotyledon. The embryo in the seed will have one leaf. As the embryo grows, the leaves develop with parallel venation. – Corn, wheat, rice, all grasses Dicot – Dicots are plants that have a seed with two cotyledons. The embryo in the seed has two leaves. Leaves of a dicot have net venation. – Tomatoes, beans, petunias, trees
Parts of a seed - Dicot Outside – Seed coat – Hilum – Micropyle Inside – Cotyledons – Radicle – Hypocotyl – Epicotyl – Plumule
Parts of a seed - Monocot Outside – Seed coat – Seed scar – Silk scar Inside – Endosperm – Radicle – Hypocotyl – Epicotyl – Cotyledon – Plumule
Plant Reproduction How Seeds are Formed: Flowers AG-BAS-8-(c, d), SB2, SB2 (e)
What is a flower? A flower is the reproductive part of a flowering plant. They are modified leaves. – Some have attractive colors and fragrances – This is to attract pollinators
Types of Flowers Flowers are categorized in two ways – Complete or incomplete – Perfect or imperfect
Complete Flower Has all 4 parts: – Sepals – protects the developing bud – Petals – attracts pollinators – Stamens – male reproductive structure – Pistil – female reproductive structure
Incomplete Flowers They do not have all of the principle parts – Some flowers do not have a sepal and petals. For example: the flower in wheat and oats. – In some cases the female and male flower parts are separate on plants. – Both are needed to produce a seed
Perfect vs Imperfect Perfect flower: It has the stamen and the pistil in the same flower An imperfect flower has the male sex organs or the female sex organs, but not both on the same flower
Monoecious vs Dioecious Plants may have both male and female imperfect flowers on them. They are called monoecious plants – Corn is a monoecious plant. – Others include: Squash, melons and pumpkins Dioecious is when some plants have male flowers and others have female flowers. – Strawberries are dioecious – Also, gourds and bradford pears
Flower combos Flowers can be combinations of complete and incomplete and perfect and imperfect – Wheat- incomplete and perfect – Cotton- complete and perfect
Pollination The transfer of pollen from an anther to a stigma of a flower of the same species – Pollen may be moved by wind, insects, birds and other natural means. – Flowers may be cross-pollinated Involves two different plants. Pollen from anther in one plant is moved to the stigma on another plant. – or self-pollinated It involves flowers on the same plant. Pollen moved from one flower on one plant to another on the plant.
Fertilization It is the union of the pollen cell with the ovule (egg). Pollen grain develops two sperm. One of the sperm unites with the ovule in the ovary and forms an embryo. The other sperm forms tissue known as endosperm in the embryo.
Fertilization Initiates the growth of the fruit and seed A flower that is not fertilized will not produce seed. An ovary that has been fertilized forms fruit. In some cases, the ovary grows very large and has a seed inside. Some examples are watermelons, cucumbers, green peppers and tomatoes. The seeds that are formed are products of the parents.
Types of Fruits All fruit can be classified into two types. – Fleshy Those that have large fibrous structure surrounding the seed Apples, pears, blackberries, oranges, grapes – Dry Fruit that develops as a pod or in a hull Pods can usually be easily divided half. – Beans, peas, peanuts and cotton have pods Hull fruits do not have definite seams in the shell – Pecans, acorns, corn, oats, wheat, dandelions
Seed Scattering Some seeds have structures that help them float long distances in the air. Some attach to animal coats. Some are eaten and spread through defecation. Some are dropped/buried by animals. As plants are domesticated, humans develop systems of dispersing and planting seeds.