STOLON

A stolon is a specialized type of horizontal above-ground shoot, a colonizing organ that arises from an axillary bud near the base of the plant. The stolon differs from the typical vegetative shoot of that same plant in having much longer and, typically, thinner internodes, and the horizontal stolon also has a strong tendency to form adventitious roots at the nodes.

A mother plant produces stolons often in several compass directions, permitting cloning, i.e., vegetative reproduction, by producing young ramets (plantlets) around the plant. The stolon connecting mother plant with each ramet initially provides the pathway for a flow of nutrients and water to the new plantlet, or even some nutrients from the plantlet back to the mother plant, but that physical connection is eventually severed or becomes dysfunctional as the plantlet develops its nutritional independence. After the stolons are severed, a mother plant is encircled by satellite plantlets, which soon grow larger, filling in any space between the plants. In this way, stoloniferous species usually colonize open ground by forming a continuous ground cover, and thereby can exclude other species by crowding them out. Understandably, therefore, many species that have been domesticated as turfgrasses and ground covers are stoloniferous, forming dense clonal monocultures.

The most common textbook example of a stolon is the strawberry (Fragaria), in which the mother plant forms plantlets on stolons during spring growth. In the case of strawberry, the stolon is often termed a runner. Some authors treat a runner as a specialized form of the stolon, in which the leaves on the stolon are reduced to very small or minute scales, in contrast to the stolon, on which some leaf blade can be observed, so that the stolon is actually a photosynthetic unit. By itself, a runner is not a self-sustaining structure, merely a connector between ramet and mother plant. In both cases, the leaves of the typical vegetative shoot are different from the stoloniferous shoots, i.e., the plant is heteroblastic.

Many plants that have above-ground stolons also form horizontal, below-ground rhizomes. Good examples of this can be found among grasses, such as bermudagrass (Cynodon dactylon).

Numerous plants grow by forming stems next to the substrate. If the plant is lying on the substrate but does not form adventitious roots, the growth habit is termed procumbent. If the plant is lying on the substrate and forms adventitious roots, the growth habit is termed either repent or stoloniferous. Using the term stoloniferous generally requires that the plant must have two different types of vegetative shoots, not only one type, the creeping shoot.

Examples of Stoloniferous Plants

Stoloniferous plants are generally found in habitats where water is abundant or soil is very wet during the season when stolons are formed. For example, one notable California wetland species that spreads via stolons is yerba mansa, Anemopsis californica (Family Saururaceae). Widespread stoloniferous herbs of wet habitats are the buttercup Ranunculus flammula (Family Ranunculaceae) and mudwort, Limosella subulata (Family Scrophulariaceae).

  1. Among aquatic plants are the highly successful floating aquatic water hyacinth, Eichhornia crassipes, in which thick, white stolons enable this species to clone at an alarming high rate. Other wideranging and highly competitive stoloniferous floating aquatics are water soldier (Stratiotes aloides, Family Hydrocharitaceae), water-lettuce (Pistia stratiotes, Family Araceae), Hydrocharis morsus-ranae (Family Hydrocharitaceae), and Potentilla palustris (Family Rosaceae). Wetlands also may include marsh claytonia (Claytonia palustris, Family Portulacaceae), tinker's penny (Hypericum anagalloides, Family Hypericaceae), and the fireweed Epilobium palustre (Family Onagraceae). Myosotis scorpioides is a stolon-like plant of shallow water. In tidal coastal salt marsh, the fleshy Jaumea carnosa and the saltgrass Distichlis spicata both may spread via stolons.
  2. In addition to species of strawberry (Fragaria), other stoloniferous herbs of the rose family (Rosaceae) can be found. Species that appear in the flora of California are Indian strawberry (Duchesnea indica) and Geum reptans. Rosaceous stoloniferous herbs are successful in a variety of habitats, including sand dunes and wet mountain meadows. Acaena can be a colonizer of open habitats via stolons.
  3. Woodland and high elevation habitats may have stoloniferous species of pussytoes, Antennaria (Family Asteraceae). In the southern Southern Hemisphere, e.g., in Patagonia, can be found the small-leaves species of Gunnera, e.g., G. magellanica (Family Haloragaceae), which colonize via stolons.
  4. Saxifraga stolonifera (Family Saxifragaceae) is an interesting shade-loving woodland perennial that forms thin red stolons during spring growth.
  5. The cultivated white or Irish potato (Solanum tuberosum, Family Solanaceae) forms its edible tuber at the tip of a stolon. The stolons grows from an axillary bud at the base of the shoot, and its tip, forming a tuber, becomes buried in the leaf litter and loose soil around the plant, where the tuber develops.
  6. Hens and chickens, Sempervivum (Family Crassulaceae), form dense mats of leaf succulent rosettes via stolons.
  7. Grass species commonly used as turfgrass are stoloniferous, and they also spread via aggressive creeping rhizomes.
  8. Lawns can be formed by the stolon-producing Dichondra, a dicotyledon. Several other dicotyledons herbs found in the lawns of North America spread via stolons, including a weedy sorrel, Oxalis corniculatus and the nitrogen-fixing white clover, Trifolium repens.
  9. Other stoloniferous species that you may encounter include clump-forming species of Episcia (Family Gesneriaceae) in tropical forests or Shortia (Family Diapensiaceae) in cool temperate areas.

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