Plant Propagation

Chapter 16 - Propagation by Specialized Stems and Roots (Chapter 15 in the 7th and 8th editions of the textbook)

Plants that have evolved to survive a wide range of seasonally inhospitable environmental conditions such as bitter cold, severe heat/drought, intense wildfires, dense seasonal shading, etc., as resting (quiescent) or truly dormant fleshy underground structures are referred to as "geophytes" or "geophytic" plants. Familiar ornamental and edible geophytic plants includes amaryllis, daffodils, tulips, crocus, onion, garlic, ginger, sweetpotatoes, iris, asparagus, bananna and sympodial orchids among many, many others.

The fleshy underground structures include bulbs, corms, tubers, fleshy tuberous roots, tuberous stems, rhizomes and pseudobulbs.

What is particularly fascinating about many of these structures is that they are technically modified (oftentimes densely compressed) underground stems complete with nodes and internodes. Many of the strategies for propagating geophytes arising from modified stems, therefore, rely on the release of preformed axillary buds from the influence of apical meristem derived auxin (IAA). This is typically accomplished by removing the primary apical meristem through division of the dense, compressed stem, destruction of the apical meristem, or complete removal of subtending modified leaves (also known as "scales") for use as individual propagules that are in many ways similar to traditional leaf cuttings.

Propagation of geophytic plants that persist by means of resting or dormant true roots, meanwhile, often require treatments that trigger the formation of adventitious shoots. These shoots are then harvested as leafy, softwood stem cuttings that are then rooted. These rooted stem cuttings eventually grow into mature plants featuring their own fleshy roots that will survive the next cycle of inhospitable conditions below the soil surface.

(Reminder - because of the shifting of chapters in the new, 9th edition of the text book, the introduction screens for each of the videos below will reference "Chapter 15" - not Chapter 16.)