Presentation on theme: "Leaves have many functions 1. Leaves are the photosynthetic organ of a plant; usually they are composed of 2 parts: the blade and petiole. 2. Leaves are."— Presentation transcript:
Leaves have many functions 1. Leaves are the photosynthetic organ of a plant; usually they are composed of 2 parts: the blade and petiole. 2. Leaves are the main site of evaporation of water from the plant. 3. Gas exchange carbon dioxide for photosynthesis and oxygen from photosynthesis and for respiration are usually exchanged through the leaves.
Function of Leaf Tissues Cuticle – waxy covering prevents water loss Upper and Lower Epidermis - Protection Palisade Mesophyll Cells – main photosynthetic tissue Bundle Sheath Cells - give some rigidity and protection to the enclosed vascular tissue. Xylem – transports water Phloem – transports sugars Spongy Mesophyll Cells – create spaces for gas exchange Guard Cells – regulate the flow of water Stomata – openings in the leaf, exchange of gases Vein (Vascular bundle)– transportation Sclerenchyma – strength and support
Most of the photosynthesis takes place in the palisade cells… in the chloroplasts.
Stomata - are the "pores" in leaves (and stems) through which CO 2 is taken in and O 2 is released during photosynthesis. Plants control when stomata are open or closed and the width of the opening (formed by two guard cells that expand and contract to open and close the space between them).
Flowers are the reproductive structures of the plant. - Attract pollinators, and protects the reproductive structures - Protects young flower base of the flower - Site where the eggs are produced -
The Male Reproductive Structures are called the Stamens. They consist of two parts: The anther -- a small case in which the pollen grains form The filament -- a slender stem that supports the anther
The Female Reproductive Structure is called the Pistil. It consists of three parts: The stigma -- the pollen grains stick to this small sticky pad The style -- the pollen grains grow down through this stem-like cylinder The ovary -- this is where the young seeds (eggs) wait for the chromosomes in the pollen (sperm), and where they grow into mature seeds…. Which contain the embryos. also called a Carpel
Pollination is the transfer of pollen from the male part of the plant to the female part of the plant.
Insect Pollination The pollen is transferred to the stigma by an insect.
Water Pollination orchids are usually water-pollinated plants. The pollen is transferred (washed) to the stigma by water (rain).
Wind Pollination conifers are usually wind-pollinated plants. The pollen is transferred (blown) to the stigma by wind.
Self-Pollination Pollen from plant A pollinates plant A… the offspring now is composed of the DNA from only one parent. Self-pollination ensures genetic continuity….. every generation is genetically identical.
Cross-Pollination Pollen from plant B is transferred to plant A… the offspring now is composed of the DNA of both parents. Cross- pollination creates diversity.
Germination a plant starts to grow…. Germination is triggered by Cytokinin.
Gymnosperms (cone-bearing plants) Gymnosperms reproduce using cones The Female cone is called the “Seed” cone… it contains the eggs (which become seeds after fertilization) The Male cone is called the “Pollen” cone… the pollen contains the sperm cells.
Double Fertilization each pollen grain contains two sperm cells….. One sperm cell fertilizes the egg (2n - which becomes the embryo), the other fertilizes the polar nuclei. (3n – which eventually becomes the endosperm)
Seeds - Store and digest foods - Attachment point to Ovule - Opening for sperm tube - Protection Embryonic root - Embryonic leaves - Epicotyl Hypocotyl - Embryonic Stem
Monocot and Dicot Seeds Monocots have one cotyledon (seed leaf), Dicots have two cotyledons (seed leaves)
Fruit a mature plant ovary that encloses a seed, or seeds, and provides nourishment and protection Pericarp Floral Tube Mesocarp Seed Exocarp Endocarp
Fruit a mature plant ovary that encloses a seed, or seeds, and provides nourishment and protection