Biology of Flowering Plants

Flower Morphology and Sexual Reproduction

• Flowers and fruits are the least affected by environmental changes, making them important for angiosperm classification.
• The essential steps of sexual reproduction in flowers include: meiosis, pollination, fertilization, fruit and seed development, seed and fruit dissemination, and seed germination.

Flower Structure

• A typical flower consists of four whorls of modified leaves: sepals, petals, stamens, and carpels, all attached to the receptacle.
• Sepals enclose the other flower parts in the bud and are generally green.
• Petals are the conspicuous, colored, attractive flower parts, collectively known as the corolla.
• Stamens form a whorl, lying inside the corolla, and consist of a slender stalk (filament) and an anther.
• The whorl or grouping of stamens is called the androecium.
• Carpels comprise the central whorl of modified floral leaves, known as the gynoecium.

Pistil and Receptacle

• A pistil may be composed of a single carpel or several united carpels in the center of the flower.
• A pistil consists of three distinct parts: the ovary, style, and stigma.
• The ovary contains ovules, the style supports the stigma, and pollen is deposited on the stigma.
• The receptacle is the enlarged end of the flower stem or stalk to which the sepals, petals, stamens, and pistils are attached.

Additional Terms

• The term perianth refers to the calyx and corolla collectively.
• A tepal refers to an individual part of the perianth, often used to describe flowers with morphologically indistinguishable calyx and corolla.
• An involucre is a collection of bracts that subtend flowers or compact clusters of flowers.