Introduction to Plant Reproduction 23.1 Reproduction Sexual reproduction –Joining of an egg and sperm Asexual reproduction –A single organism replicating its genetic material to split into two identical organisms. Vegitative Reproduction A form of asexual reproduction where a new plant grows from parts of an existing plant. Fast reproduction Examples: – Strawberry runners – Moss fragmentation – Potato eyes and buds Alteration of Generations Alteration of Generations Of Nonseed Nonvascular Plants Alteration of Generations Of Nonseed Vascular Plants Alteration of Generations Of Naked Seed Vascular Plants Alteration of Generations Of Flowering Seed Vascular Plants Alteration of Generations Fertilization: Nonvascular plants- Need a film of water for the sperm to reach the egg. Vascular plants- Do not need water for the sperm to reach the egg. Alteration of Generations As plants evolved, the sporophyte generation became larger: Nonvascular plants- Sporophyte depends on the gametophyte for support and nutrition. Vascular plants- Sporophyte lives independent of the gametophyte. Moss reproductive cycle Gametophyte dominant – Male= Antheridium – Female= Archegonium Antheridium Archegonium Moss reproductive cycle Antheridium- Male produces flagellated sperm that need water to get to the archegonium. Chemotaxis- Female archegonium produces chemicals that attract/direct the sperm. Moss reproductive cycle Moss reproductive cycle Sporophyte- Depends on the gametophyte for support and nutrition. Protonema- Spores that land in a favorable spot develop into a protonema (gametophyte generation). Fern reproductive cycle Sporophyte dominant Frond- feathery stems of a fern Sorus- underneath the frond –Produces spores Fern reproductive cycle Prothallus – The fern spore grows into a prothallus when it lands on damp, rich soil. – Heart shaped – Contains Antheridia & Archegonium Conifer reproductive cycle Sporophyte dominant Heterosporous- Produces two kinds of spores that develop into male and female cones. – Female cones –Made of many scales –2 ovules at the base of each scale –Each ovule produces a Megaspore which develops into the female archegonia. Conifer reproductive cycle – Male cones –Made of small scales that form microspores –4 microspores develop into a single pollen grain –Pollen grains are the male gametophyte that are transported on air currents Chapter 23.2 Flowers The Parts of a Flower • Most flowers have four parts: • sepals, • petals, • stamens, • Carpels (pistils) The parts of a flower • Sepals protect the bud until it opens. • Petals attract insects. • Stamens make pollen. • Pistils (carpel) grow into fruits which contain the seeds. Stamen (male) • Anther: pollen grains grow in the anther. • When the grains are fully grown, the anther splits open. • Filament: holds the anther Pistil (female) • Stigma • Style • Ovary Stigma – sticky place for pollen to attach Style – where pollen nuclei travels to reach the egg Ovary – where egg is located Modifications in Flowers Complete flowers – have all four organs (sepals, petals, stamens, and pistils) – M orning glory and tiger lily Incomplete flowers – lacks one or more of the four organs – Squash and corn Tiger Lily – a complete flower Incomplete Flowers Female Squash Flower Male Squash Flower Modifications in Flowers P erfect flowers- Have both stamens and pistils (E x: Lily) Imperfect flowers- E ither have a functioning stamen or pistil, but not both E x : Cucumber, Squash Pollination Mechanisms Animal pollination – hummingbirds & bees transfer pollen from plant to plant – Flowers are brightly colored or highly scented Wind pollination – lightweight and are carried by wind – Small flowers with little color or scent Self pollination – Able to pollinate flowers on same plant – Have both pistel and stamen Pollinators PHOTOPERIODICITY Plants flower based on the number of hours of darkness they are exposed to Short-day plants flower when days are short (fall, winter, spring) Ex: Pansy, Poinsettias PHOTOPERIODICITY Long-day plants flower when days are long (summer) Examples: – Potatoes – Clover – Spinach PHOTOPERIODICITY Intermediate-day plants- Grow when darkness is about equal to daylight. E x : Sugar Cane PHOTOPERIODICITY Day-neutral plantsHours of darkness does not effect flowering, as long as there is enough daylight to perform photosynthesis. E x: Corn, tomatoes, cotton, roses Chapter 23.3 Flowering P lants Flowering Plant reproductive cycle Sporophyte dominant Ovary- produces 4 megaspores, but 3 disintegrate and only one remains. Double fertilization – requires 2 sperm to fertilize the egg and make a seed. Seed – embryo (cotyledons), endosperm (food for embryo), seed coat (protect seed) Flowering Plant Reproduction 4 kinds of fruit 1. Simple Fleshy fruits- contain one or more seeds. Ex: Apples, Peach, grape, tomato, pumpkin 4 Kinds of fruit 2. Aggregate fruitMost berries. Many female parts fuse to form one fruit. Ex: Blackberries, strawberries, raspberries 4 Kinds of fruit 3. Multiple fruitFlowers fuse to form one fruit. Ex: Pineapples, figs 4 Kinds of fruit 4.. Dry fruit- Fruits that are dry. Ex: Nuts, grains, seed pods Seed Dispersal Water – Coconuts Wind – Dandelions Animals – Fruits attract animals that will eat the seeds so that the seeds can be carried far away where it won’t have to compete with its parent. Seed Germination Requires: – Water (swells and breaks seed coat) – Oxygen (cell respiration as seed grows) – Optimal Temperature (each plant requires a certain temperature to begin growth) Seeds will lie dormant in their hard seed coats waiting for optimal conditions.
