Transcript FLOWERS
Flowers HortBotany Lesson Plan #9 Flowers: A Marvelous Innovation Flowering plants first appeared around 140 million years ago (Upper Jurassic). Oldest flower fossil is 125 million years old. The dominant forms of plant life were gymnosperms, cycads, and ferns. Today Flowering plants (Angiosperms) are now the dominant form of plant life over most of the earth’s land surface. Ferns are rarely dominant and gymnosperms are dominant only in cold, or seasonally cold locations. Cycads are hanging on by a thread. Why have flowering plants been so successful? Angiosperm Flowers • Ovaries protect ovules and developing seeds; mature into fruits that promote seed dispersal • Floral structure encourages pollinator fidelity; nectar and pollen to reward pollinators • Fast reproductive cycle compared to gymnosperms Structure of flowers Flowers are composed of four whorls. From the outside in, they are: • Calyx (sepals) • Corolla (petals) • Androecium (stamens) • Gynoecium (pistils) Calyx • Outermost whorl • Usually green • Protects developing flower • Made up of SEPALS • Sepals free or not Sepals • Usually green; leaflike structures that protect the flower, as it forms and emerges. • Sometimes sepals are colorful Calyx • The group of sepals on a flower Corolla • Is usually colorful and showy • Attracts pollinators • Guides pollinators • Is composed of petals • Petals may be united or separate Petals • Located just inside the sepals • Leaf-like and often very colorful Corolla • The collection of petals on a flower Perianth • The sepals and the petals of a flower. (Not the reproductive parts.) Tepals • When there is no clear distinction between the sepals and the petals...they are called “tepals”. HIPPEASTRUM 'MARMADUKE’ Androecium • Is composed of stamens • Stamens have filaments and anthers • Pollen is produced in anthers • Stamens can be free or united Stamens • Male reproductive parts of a flower • Arranged around the female parts Anther • Part of the stamen • Produces and holds pollen Filament • Stalk that holds up the anther Gynoecium • Is composed of pistils • A pistil is composed of an ovary, style, and stigma. Pistil = 1 or more carpels • Each theoretical leaf unit is termed a carpel • A pea pod is a mature pistil made up of 1 carpel • Pistils with 2 style branches and/or chambers in the ovary are said to have 2 carpels • Pistils with 3 style branches and/or chambers are said to have 3 carpels etc. Stigma • Found at the end of the pistil • Has a sticky surface to catch pollen Style • The neck of the pistil Ovary • Part of the pistil that contains the ovules Ovule • The part of the flower in which the eggs are produced and seeds develop Ovary Position • I. Above the calyx and corolla (ovary superior) • II. Ovary partially inferior • III. Below the calyx and corolla (ovary inferior) Ovary position: I superior II partially-inferior III inferior. a androecium g gynoecium p petals s sepals r receptacle. Hypanthium If the corolla and calyx are attached to a cup or tube that is then attached to the receptacle, the cup or tube is called a hypanthium. Receptacle • The top floral whorls are attached to the receptacle – the tissue where the stalk to the flower changes to being part of the flower Pedicels • Flowers are borne on pedicels • Think of a pedicel as the stalk to a flower Attracting Pollinators • To survive, species must reproduce • Pollination is the first major step in the reproduction of seed plants like gymnosperms and angiosperms • Flowers persuade animals to serve as pollinators, preferably faithful pollinators • To get the right pollen, flowers need to be memorable so … Start thinking like a pollinator • Is there a reward? • How can I find another like this one? – Symmetry – Color pattern – Odor • Will it be safe for me? – Corolla – united or separate petals – Corolla more important than calyx – why? • Can I reach the reward and is it adequate? – nectaries and androecium insect pollination hummingbird pollination bat pollination wind pollination; eastern cottonwood catkins Complete vs. Incomplete Flowers Complete flowers • Have all 4 basic parts: • Sepals, petals, stamens and pistil Incomplete Flowers • Flowers that are missing one of the four basic parts Perfect vs. Imperfect Flowers Perfect Flowers • Flowers that have both male and female parts Imperfect flowers • Flowers that lack one of the sex structures Monoecious vs. Dioecious Monoecious = 1 House • refers to a species • separate male and female flowers on the same plant Black Alder male catkins and female strobili Dioecious = 2 Houses • refers to a species • separate male and female flowers on different plants Common Winterberry male flowers Common Winterberry female flowers Common Winterberry fruit What about corn? Monoecious or dioecious? Corn is monoecious The End