Land Plants – The Angiosperms

Characteristics of Angiosperms Are the most widespread land plants Comprised of 250,000 to 400,000 known species Are vascular plants with more specialized xylem and phloem Produce reproductive structures known as flowers Have a reduced male gametophyte (3 cells) and a reduced female gametophyte (7 cells) which decreases the time needed in which to reproduce

Flowers Reproductive organ of the angiosperm Designed to attract insects and other pollen bearing animals to aid in the best pollen transfer and dispersal Pistil

Stamen i. Composed of a filament and anther with two pollen sacs. ii. In pollen sacs, microspores become pollen grains. iii. Stamens usually grouped around pistil.

Pistil i. Usually in center of flower. ii. Stigma is enlarged sticky knob to collect pollen. iii. Style is slender stalk.

Flowers Ensure fertilization of the ovule and possible development of fruit containing seeds Arise most commonly from the shoot or the axil of a leaf Most flowers are hermaphroditic but often are structured in a way that prevents self fertilization Have sepals and petals - sepals are usually green and leaf-like and protect the bud of the flower as it grows - petals are often colored and delicate structures that attract pollinators by color, scent and nectar

An orchid….. Note: We usually use a lily to show the anatomy of a flower as it is a complete flower. In different flowers the structures will vary in their appearance or may not be visible at all.

An iris….. Try to label the parts of this iris on your own! Pistil = Carpel

Why Flower?. Unlike gymnosperms, flowers attract pollinators to carry pollen from flower to flower. c. Flowers and pollinator have co-evolved; for example: blue, yellow, and ultraviolet colors are within range of bee sight and pattern may lead bee to nectar at flower base. d. While bee collects nectar and pollen for food, pollen is also inadvertently carried to next flower.

Imperfect Flowers An imperfect flower is a flower that has only male parts or female parts. A perfect flower has both male and female parts on the flower.

Incomplete Flowers Incomplete flowers are missing one or more of the four main parts of a flower: sepals, petals, stamens or pistil

Reproductive structures of flowers MALE PARTS –Comprised of one or two whorls of stamens Stamen is the filament topped by an anther The structure of the stamen often allows for specialized pollination and prevents self fertilization Produce microspores in the stamens which undergo meiosis to produce pollen which covers the anthers FEMALE PARTS –Comprised of one or more pistils Pistil is made up of the stigma (sticky tip), style (stalk through which the pollen tube grows) and the ovary Produce megaspores in the ovule which undergo meiosis to produce the egg cell Lily pollen Microscopic anther with pollen grains Ovule

Flower parts Ovule inside a flower Stigma Pollen on antherStigma, Style, 6 stamens

Cactus flower pollen

Angiosperm Life Cycle : The Lily NOTES Double Fertilization occurs in angiosperms: each pollen grain contains two sperm. One sperm (N) fertilizes the egg (N) and goes on to form the zygote (2N). The other sperm fertilizes the 2 polar nuclei (2N) in the embryo sac and goes on to produce the endosperm (3N) Endosperm is the highly nutritive tissue that provides food for the embryo, cotyledons and young seeding *Remember that seeds often are enclosed by fruit in angiosperms

Double Fertilization Forming the endosperm (3N)

Seed Anatomy

Monocotyledons “Monocots” MONOCOT ExamplesGrasses, grains, lilies, daffodils, tulips Cotyledon #One, single Leaf veins areParallel Vascular tissue (xylem and phloem) arranged in Bundles Roots areFibrous (adventitious) Flower parts occur in Multiples of 3, (trimerous) Secondary growth? Rare Approximately 23% of all Angiosperms are Monocotyledons

Dicotyledons “Dicots” DICOT ExamplesMaple, Oak, Elm, Sunflowers, Roses Cotyledon #2, double Leaf veins areNetworked Vascular tissue (xylem and phloem) arranged in Rings (forms annual rings in stems viewed in cross section of a stem/trunk) Roots areTaproots Flower parts occur in Groups of 4 or 5 Secondary growth? Frequent Approximately 75% of all Angiosperms are Dicotyledons

Dicot Seedling

Fruit i. Include: milkweed pods, peas and beans, tomatoes, oranges, watermelon, etc. ii. Function to disperse seeds using wind, gravity, water, and animals to area suitable for germination.

Why are angiosperms more successful than gymnosperms in a land environment? Angiosperm seeds are better protected Herbaceous, soft tissues are able to survive 1 to a few years Angiosperms can go from seed to seed in less than one year as opposed to the years this may take in gymnosperms The xylem cells in angiosperms are more efficient than in gymnosperms Pollination is more successful as angiosperms are not simply reliant upon the wind. This increases the occurrence of cross fertilization which in turn increases genetic variety

Pollination Pollination is often achieved through the use of insects that are attracted to certain colors, structures or scents on the flower. The orchid below is called a Bee orchid and has evolved to actually look like a female bee. Obviously, it is pollinated specifically by bees.

Economical and Ecological Importance Economical Importance Imperative to the field of agriculture in the form of both product and feed for animals Human food source Wood, paper, fiber (cotton, flax, hemp) Used in the production of some medicines Decorative landscaping, florist industry Perfumes and beauty products Ecological Importance Food and habitat for wildlife Soil retention

Leaf Anatomy