11.3: Root Systems

Taproots

Figure \(\PageIndex{1}\): The carrot vegetable we eat is the taproot of a carrot plant. The large, central root (what we call a carrot) is a taproot and has many much smaller lateral roots that emerge from the sides. These are not root hairs, which would appear more like a microscopic fuzz at the ends of these lateral roots. Photos by Maria Morrow, CC-BY 4.0.

Figure \(\PageIndex{2}\): Some plants invest far more in their below ground tissues than their above ground ones. In this image, an enormous taproot of the small, prostrate plant Abronia latifolia (the yellow sand verbena) has been explosed as the dune sand has blown away from this area over time. How does investment in this taproot structure benefit this plant, considering the shifting, sandy environment? Photo by Maria Morrow, CC-BY 4.0.

Netted Roots

Figure \(\PageIndex{3}\): The netted root system of Zea mays. There are many roots of approximately the same diameter that then branch off into smaller roots. There is, distinctly, no one larger root. This is a netted root system. Photo by Maria Morrow, CC-BY 4.0.

Contractile Roots

Figure \(\PageIndex{4}\): The base of a dandelion rosette, showing a contractile root. The central root shown, where the leaves of the rosette meet at the base, looks like a compressed slinky. This is a contractile root, which can respond to seasonal changes in water availability to keep the dandelion plant at ground level. As water swells the soil, it can rise up. In response, this contractile root can swell with water, extending and allowing the plant to stay at the surface. In the case of a drought, the root can contract as the soil level drops. Photo by Melissa Ha, CC-BY 4.0.

Adventitious Roots

Figure \(\PageIndex{5}\): Adventitious roots of a kalanchoe plant. Many house plants reproduce themselves easily, lending to their cultivation and sale. The kalanchoe is extending a branch outward and producing new roots from its stem tissue. Notice the seven projections traveling down from the branch. These are adventitious roots, because they are produced by the stem. If this branch were cut off, it could be established as a new plant, due to the presence of these roots. Photo by Melissa Ha, CC-BY 4.0.

Figure \(\PageIndex{6}\): Vining plants frequently produce adventitious roots. This image shows two English ivy stems, a younger one on the top and a much older one on the bottom. The young stem has small clusters of adventitious roots emerging from the stem at nodes opposite to the leaves. Two of these are indicated by black arrows. On the older stem, adventitious roots emerge along the entire length, making it look hairy. There are a few particularly dense clusters, indicated by arrows. Photo by Maria Morrow, CC-BY 4.0.

Prop Roots.

Figure \(\PageIndex{7}\): Zea mays also has prop roots that emerge from the stem. Above the netted root system, there is a short collar, then sheathing leaves emerge, indicating the transition to shoot tissue. At the base of these leaves, several prop roots are emerging. These prop roots, whose function is to give the plant extra stability from above ground, are also adventitious roots. Photo by Maria Morrow, CC-BY 4.0.

Pneumatophores

Figure \(\PageIndex{8}\): Mangroves grow in the intertidal zone where they spend much of the day inundated by water. Roots need to take in oxygen for cellular respiration. On strategy to gain access to oxygen is the development of aerial roots called pneumatophores (lung-bearers). The many pointed structures emerging from the soil under these Avicennia trees in Mumbai are pneumatophores. Photo by Dr. Raju Kasambe, CC BY-SA 4.0, via Wikimedia Commons.