Transcript FLOWERS
FLOWERS The sexual reproductive structures of angiosperms What is a flower? • A flower is a highly modified shoot bearing specialized appendages (modified leaves). • Angiosperms are considered the flowering plants. • Both monocots (ie grasses) and dicots (ie petunias) flower. Pedicel • The floral stalk is referred to as the pedicel. Receptacle • The modified shoot (or floral axis) is called the receptacle. Perianth • The perianth consists of the outer protective and/or colorful structures. The perianth includes the sepals and petals, collectively known as the calyx (sepals) and corolla (petals). Perianth Parts • If the sepals and petals are distinctively different in appearance, they continue to be known as sepals and petals. • If sepals and petals are undifferentiated in appearance (ie many cactus flowers), they are collectively described as tepals. Androecium • The androecium comprises all the stamens of the flower. Stamens are usually differentiated into an anther and a filament. Each anther usually contains four pollen sacs. Pollen Sacs • Each anther usually contains four pollen sacs, or microsporangia, which are often confluent (joined) in two pairs. • The pollen sacs are joined to each other and to the filament by a connective. • Pollen grains (microgametophytes) are produced in the pollen sacs. Gynoecium • The gynoecium comprises all the carpels of the flower. Carpels are typically composed of a stigma, a style, and an ovary (unique to angiosperms). Locule and ovule • The compartment, cavity, or chamber within an ovary or anther is called a locule. • Ovule is the structure in seed plants comprised of the female gametophyte. After fertilization, it develops into the seed. Nectary • A nectary is a nectar-producing gland, often forming projections, lobes, or disklike structures. Nectaries are often produced near the base of the androecium and gynoecium. These are for the production of nectar or other pollinator attractants, such as oils or fragrances. Three major parts of flowers (PAG) • Perianth (outer protective and/or colorful structures). • Androecium (pl. androecia) – pollen producing structures. • Gynoecium (pl. gynoecia) – ovule producing structures. Complete Flower • Has all three major parts (PAG) • Perianth • Androecium • Gynoecium Incomplete Flower • If one or more of the three major floral parts (PAG) is missing, the flower is considered to be incomplete. Bisexual or perfect flower • If at least the androecium and gynoecium are present, the flower is termed bisexual or perfect. Unisexual or imperfect flower • If either the androecium or gynoecium is lacking, the flower is unisexual or imperfect. • If only the androecium is present, the flower is considered staminate. • If only the gynoecium is present, the flower is considered carpellate. Monoecious Species • In a monoecious plant species, both staminate and carpellate flowers are borne on a single plant (ie pumpkins) Dioecious species • In a dioecious plant species, the staminate and carpellate flowers are borne on separate individual plants (ie green ash) Polygamous species • In a polygamous plant species, there are both bisexual (perfect) and unisexual (imperfect) flowers on the same plant. • Perfect flowers have both androecium and gynoecium present. • Imperfect flowers are either staminate or carpellate. Corona • Some flowers have an extra series of floral parts, often showy, called coronas. These may be outgrowths of the perianth parts, stamens, or receptacles, and they are extremely diverse in form and function. Floral Symmetry • Radial Symmetry Two or more planes bisecting the flower through the center will produce symmetrical halves. These flowers are called regular. Floral Symmetry • Bilateral symmetry • Arranged so they can be divided in symmetrical halves on only one plane. These flowers are called irregular. Floral Symmetry • Asymmetrical – • Flowers that have no plane of symmetry. Fusion of floral parts • Connate – petals united to petals • Distinct – petals distinct from each other • Adnate – fusion of unlike parts like stamens united to petals. • Free – unlike parts are not fused. Superior and inferior ovaries • Flowers in which the perianth and androecium are below the gynoecium are called hypogynous. The ovary of such flowers is said to be superior. • Flowers in which the perianth and stamens appear to be attached to the upper part of the ovary are called epigynous. The ovary of such flowers is said to be inferior. Hypogynous and epigynous flowers