BIO.12.B

Examples of asexual reproduction:

• Budding occurs when a complete offspring grows from the parent plant at a particular spot such as when multiple new potato plants grow from the eyes of a single potato.
• Fragmentation occurs when a new plant grows from a small portion of the parent that broke off and rooted in the ground. This occurs most often in mosses.
• Vegetative propagation occurs when new plants are generated from the vegetative components of the parent plant, such as runners, rhizomes, or tubers.
• Spore formation occurs in ferns. Ferns alternate generations between asexual haploid plants and sexual diploid plants.

Sexual reproduction in plants occurs through multiple different mechanisms, including flowering plants (angiosperms) and conifers (gymnosperms).
 

Tropisms are directional growth responses of plant organs to environmental stimuli. Positive tropisms occur when the plant grows toward the stimulus and negative tropisms cause a plant to grow away from the stimulus. Different parts of the plant may respond positively or negatively to the same stimulus. For example, stems are negatively gravitropic and roots are positively gravitropic. One hormone that has been shown to participate in gravitropism and phototropism is auxin. Auxin accumulates within parts of the plant and stimulates elongation. The signals responsible for hydrotropism and thigmotropism have yet to be determined.

Another way in which plants respond to the environment is dormancy. Some plants go dormant in the winter to survive cooler temperatures and drier weather.

Plants also respond to illness. If a plant becomes infected, it will often kill the cells surrounding the diseased tissue so the infection does not spread. A plant can also produce hormones or toxins like salicylic acid to fight pathogens.