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File: pollen Modified from E. Moctezuma & others for BSCI 442 (Sze)
Objectives:
Get familiar with the parts of flowers: male and female organs
Observe pollen germination and tube growth in real time.
Test the conditions that stimulate pollen germination and tube growth.
Observe cytoplasmic streaming (due to vesicle traffic).
Introduction
Flowering plants, or angiosperms, are the largest and most successful plant group in the world. From giant eucalyptus trees to minuscule duckweeds, from desert cacti to water lilies, these familiar plants dominate the world. They play a significant role in providing food and shelter for animals and other organisms. There are over 250,000 species of flowering plants and they are all vascular seed plants that have flowers and fruits. Angiosperms derive their name from the Greek words angion (vessel) and sperma (seed). The flower contains the vessel that houses the seed. It is also the organ for sexual reproduction.
A typical flower is composed of modified leaves arranged in four whorls (circles) on the end of an enlarged portion of the stem called the receptacle. The calyx is the outer (and lowest) whorl of floral parts and often functions to enclose and protect the flower bud before it opens. Individual members of the calyx, usually green, are called sepals. Moving inward, the second whorl of floral parts is the corolla. Individual members of the corolla are called petals, which are often conspicuously colored to attract insects or birds that serve as pollinators. Plants that are wind-pollinated or that self-pollinated do not have colorful petals, such as the model plant Arabidopsis.
Fig. 1. Arabidopsis plant and flower (Taiz Fig 16.1)
Sepals and petals are considered the sterile parts of a flower because they