Contractile roots

Contractile root [ Botany ]

Dictionary of botanic terminology - index of names

A contractile root is a thickened specialized root at the base of a corm, bulb, rosette or other organ which is designed to shrink vertically under conditions of seasonal drought that helps position this plant part at an appropriate level in the ground.

Contractile roots of Haworthia emelyae v. comptoniana pull the plant deeper into the soil to protect the plant from sun and heat during the dry season.

Contractile roots are found in many plants species mainly at the base of an underground organ (bulb, corm, succulent rosette, etc.)

The contractile roots continually pull the plants deeper into the ground as the stem elongates so the it remain subterranean or at an appropriate level in the ground.. Contractile roots are usually broad, fleshy, vertical, tapering, wrinkled looking and very distinct of the rather cylindrical fine absorbent roots and are capable of incredible effort.

In most cases, contractile roots not only produce a strong pulling force on but also push away the substratum and create a soil channel in which plant movement is made easier. For example in Haworthia the fleshy contractile roots swell with moisture in the wet season creating a space in the substrate then - after the full drying out of soil during the dry season - a considerable parts of this roots die off leaving empty spaces in the substratum that allow plant movement with minimum or no resistance, at the same time the other roots dehydrates and shrinks vertically, drawing the plant down into the ground. This is repeated early permitting the top of the plant to remain constantly at the soil level.

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Holdfast roots [ Botany ]
Dictionary of botanic terminology - index of names

Some species of climbing plants develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place.

Climbing plants, like the poison ivy (Toxicodendron radicans), Boston ivy (Parthenocissus tricuspidata), and trumpet creeper (Campsis radicans), develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place. Usually the Holdfast roots die at the end of the first season, but in some species they are perennial. In the tropics some of the large climbing plants have hold-fast roots by which they attach themselves, and long, cord-like roots that extend downward through the air and may lengthen and branch for several years until they strike the soil and become absorbent roots.

Major references and further lectures:
1) E. N. Transeau “General Botany” Discovery Publishing House, 1994