12.4: Modified Shoots

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Horizontal Stems

A diagram of a horizontal stem that looks like a root — Figure \(\PageIndex{1}\): Rhizome of *Polygonatum multiflorum*. a=Bud of next year’s aerial shoot; b=Scar of this year’s, and c, d, e=scars of three preceding years’ aerial shoots; w=adventitious roots. Diagram by AnonymousUnknown author, Public domain, via Wikimedia Commons.

Another view of the rhizome, showing adventitious roots emerging. — Figure \(\PageIndex{2}\): Rhizome of *Alpinia purpurea.* Adventitious roots emerge from stem tissue that travels horizontally underground. Rhizomes can be distinguished from roots by the presence of nodes. Note the layers created by the sheathing, papery leaves of the rhizome. Below the stem, root like structures sprout out horizontally, but there are distinct sections or nodes to these structures (roots). Photos by Filo gèn', CC BY-SA 4.0, via Wikimedia Commons.

The base of an Iris showing many morphological structures emerging from around the same area. — Figure \(\PageIndex{3}\): There is a lot going where these *Iris* shoots meet the roots. The shoots are emerging upward in the left hand corner, showing a pinkish hue from anthocyanin pigments. True roots emerge from the base of these shoots, pointing in the opposite direction and pigment-free. A large rhizome travels horizontally from the cluster of shoots and three nodes are indicated. A stolon (a horizontal above ground stem) emerges above the rhizome. Image by JonRichfield, CC BY-SA 4.0, via Wikimedia Commons.

Ginger shoots arise from the ginger rhizome, which is thick, has short internodes, and papery leaves. — Figure \(\PageIndex{4}\): Examples of horizontal stems. Ginger rhizomes are thick and belowground (top), and stolons of this spider plant are aboveground with long internodes (bottom). Top image by Sengai Podhuvan (CC-BY-SA), and bottom image by Eptalon (CC-BY-SA).

Several long, white stolons emerge from a spider plant — Figure \(\PageIndex{4}\): Examples of horizontal stems. Ginger rhizomes are thick and belowground (top), and stolons of this spider plant are aboveground with long internodes (bottom). Top image by Sengai Podhuvan (CC-BY-SA), and bottom image by Eptalon (CC-BY-SA).

Three distinct plants are connected by horizontal stems (stolons) — Figure \(\PageIndex{5}\): A stolon is an above ground horizontal stem. Some plants, such as strawberries (right) or the spider plant in Figure \(\PageIndex{4}\), use stolons to asexually reproduce clonal plants. Drawing on left by Pearson Scott Foresman, Public domain, via Wikimedia Commons. Photo on right by Amy Change, CC-BY-SA.

Strawberry plants connected by crisscrossing, above ground stems — Figure \(\PageIndex{5}\): A stolon is an above ground horizontal stem. Some plants, such as strawberries (right) or the spider plant in Figure \(\PageIndex{4}\), use stolons to asexually reproduce clonal plants. Drawing on left by Pearson Scott Foresman, Public domain, via Wikimedia Commons. Photo on right by Amy Change, CC-BY-SA.

Storage Stems

Potato tubers in the soil. They are oval, expanded structures. — Figure \(\PageIndex{6}\): Potato tubers are expanded, belowground stems modified for starch storage. Each "eye" on a potato is a node where a new shoot could emerge. First image by pxhere (public domain). Second image by Robin Corps and uploaded to flickr.com on January 23, 2006, licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license.

A potato tuber with a shoot growing out of one of the nodes — Figure \(\PageIndex{6}\): Potato tubers are expanded, belowground stems modified for starch storage. Each "eye" on a potato is a node where a new shoot could emerge. First image by pxhere (public domain). Second image by Robin Corps and uploaded to flickr.com on January 23, 2006, licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license.

A corm cut longitudinally reveals a thick, white stem — Figure \(\PageIndex{7}\): Both corms (left) and bulbs (right) are similar looking modifications for storage. The *Crocosmia* corm has a thick, expanded stem stores starch, and the leaves that surround it are non-photosynthetic and papery. The onion bulb has a relatively small stem surrounded by thick, fleshy leaves. Corm image by JonRichfield (CC-BY-SA), and onion image by Amada44 (CC-BY-SA).

An onion bulb cut longitudinally has a small stem and layers of thick, fleshy leaves. — Figure \(\PageIndex{7}\): Both corms (left) and bulbs (right) are similar looking modifications for storage. The *Crocosmia* corm has a thick, expanded stem stores starch, and the leaves that surround it are non-photosynthetic and papery. The onion bulb has a relatively small stem surrounded by thick, fleshy leaves. Corm image by JonRichfield (CC-BY-SA), and onion image by Amada44 (CC-BY-SA).

Sharp Armaments

A hawthorn stem with sharp, brown thorns arising from the axils above each leaf. — Figure \(\PageIndex{8}\): Thorns (first) and prickles (second). The thorns of the hawthorn are derived from the whole stem. They arise from axillary buds in the axils just above the leaves. The sharp projections on the rose stem are technically classified as prickles because they are derived from only the surface tissues of the stem. First image by Rasbak (CC-BY-SA), and second image by Ingrid Taylar (CC-BY).

Close-up of a rose stem with red, triangular prickles — Figure \(\PageIndex{8}\): Thorns (first) and prickles (second). The thorns of the hawthorn are derived from the whole stem. They arise from axillary buds in the axils just above the leaves. The sharp projections on the rose stem are technically classified as prickles because they are derived from only the surface tissues of the stem. First image by Rasbak (CC-BY-SA), and second image by Ingrid Taylar (CC-BY).

Several spines from a cactus. — Figure \(\PageIndex{9}\): Cactus spines are not stems, but modified leaves. These spines have a thick cuticle and stomata can be seen as darker green areas within the pale white cuticle. Photo by André Karwath aka Aka, CC BY-SA 2.5, via Wikimedia Commons.

Climbing

A wild cucumber, with small, oval, spiky fruits and scattered tendrils. The thin, pale tendrils coil around surrounding structures. — Figure \(\PageIndex{10}\): The tendrils of the wild cucumber plant arise from stems. Other plants, such as *Lathyrus*, make tendrils from leaf tissue. Image by erwin66as (public domain)

Photosynthesis

A young asparagus plant has not yet formed cladophylls. The actual leaves are reddish, triangular scales along the stem. — Figure \(\PageIndex{11}\): Cladophylls in *Asparagus* (left) and actual leaves of young asparagus marked by black arrows (right). Left image by DenesFeri (CC-BY-SA), and right image by Sam Saunders (CC-BY-SA).

Cladophylls of butchers broom are flattened like leaves. They are rounded and come to a point at the end. — Figure \(\PageIndex{12}\): Cladophylls in butchers broom (*Ruscus*) are flattened like leaves. A flower arises from a node within the cladophyll. Image by Rosser1954 (CC-BY-SA).

Cladophylls of Christmas cactus are flattened stem segments. — Figure \(\PageIndex{13}\): Phylloclades in Christmas cactus. Image by Mokkie (CC-BY-SA).