Plant Adaptation Up Close

Exhibition Panels

Dodder
PARASITIC PLANTS are adapted to live off the hard work of other plants. Using specialized structures they invade the tissue of the host plant, extracting food, minerals, and water. While they injure their hosts, they rarely kill them. There are over 3000 parasitic plant species worldwide, most of which have a narrow range of host species.
The stem of dodder, Cuscuta species, slowly circles around searching for a nearby host. If it encounters a suitable one, it coils around the host and produces small appendages on its stem, which are modified roots called haustoria. The haustoria penetrate the host plant and extract food.. Mature dodder plants look like yellow-orange spaghetti, with little or no chlorophyll. They flower but remain leafless.
Electron photomicrograph, Polaroid type 55 film
Digitally colorized giclée print
© 2005 Joan Wiener
Dodder shoot working its way behind slender pink hairs of a coleus leaf
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Salvinia
FLOATING AQUATIC PLANTS have structural adaptations that prevent them from sinking. By staying afloat they are able to absorb maximum sunlight and can easily exchange gases with the atmosphere. In addition, floating plants may heavily shade the water below, reducing the number of submersed species that compete with them for nutrients.
Salvinia is a genus of free-floating water ferns. Their fronds (leaves) stay afloat because they have wettable hairs on the underside and water-resistant hairs on the top side. Salvinia minima is rootless-highly modified, submersed fronds look like and function as clumps of roots.
Electron photomicrograph, Polaroid type 55 film
Digitally colorized giclée print
© 2005 Joan Wiener
Hydrophobic hair on the top of a frond
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Boston Ivy
VINES are well adapted to compete with trees and shrubs for sunlight. Rather than having evolved to survive in a shaded understory, vines climb over other plants and objects to position themselves where they receive more sun. Several diverse climbing mechanisms have evolved.
Boston ivy, Parthenocissus tricuspidata, has a unique climbing adaptation. Its disk-tipped tendrils are actually modified leaves. The disks secrete an adhesive substance, allowing the plant to cling to sheer surfaces such as rock cliffs (or Ivy League buildings), an ecological niche not available to most vines.
Electron photomicrograph, Polaroid type 55 film
Digitally colorized giclée print
© 2005 Joan Wiener
A single suction cup facing down with its stalk rising up.
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Resurrection
DROUGHT-TOLERANT PLANTS have adaptations enabling them to live in dry environments. Such adaptations are essential since plants are composed mostly of water. One adaptation is to store water in enlarged organs. Another is to prevent water loss from the leaves or stems. Some plants cease growth or drop their leaves during dry periods.
Resurrection plant, Selaginella lepidophylla, evolved long before flowering plants. During drought it becomes dry, turns brown, and rolls inward to survive. It can remain dormant for decades, looking dead. After a rain, however, it absorbs water, restores chlorophyll to its leaves, and grows rapidly.
Electron photomicrograph, Polaroid type 55 film
Digitally colorized giclée print
© 2005 Joan Wiener
Overlapping leaves of a hydrated resurrection plant
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Tillandsia
EPIPHYTES are nonparasitic plants that have adapted to grow upon or attach to other living plants without ever having roots in the soil. Positioned in the trees and on cliffs, they escape predation from ground-dwelling animals and receive more light than plants on the forest floor.
Spanish moss, Tillandsia usneoides, is not a moss at all, but rather a relative of the pineapple plant. Epidermal leaf scales absorb water directly from the atmosphere, a necessary adaptation since Spanish moss is rootless. Nutrients are obtained from the mineral-rich water dripping onto it from the trees above.
Electron photomicrograph, Polaroid type 55 film
Digitally colorized giclée print
© 2005 Joan Wiener
Young leaves unfurling. Circular leaf scales developing a characteristiccheckerboard interior.

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Echeveria
DESERT PLANTS are adapted to living in intense heat and sun. While sunlight is needed for plants to make their own food (carbohydrate), the powerful sun can damage a plant’s chlorophyll or DNA. Many plants have adapted by deflecting or blocking sunlight, while a few orient their leaves away from direct sunlight.
In climates with intense sunlight, many species have adapted by developing dense leaf hairs that block out some light. This Mexican plush plant, Echeveria pulvinata, glimmers as countless epidermal hairs deflect light away from its leaf surface.
Electron photomicrograph, Polaroid type 55 film
Digitally colorized giclée print
© 2005 Joan Wiener
Leaf surface showing numerous multicellular hairs
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CARNIVOROUS PLANTS are adapted to soils that are low in nitrogen, an element that is critical for plants to synthesize protein. Their protein needs are met by consuming insects or in rare cases small animals. Various adaptations have evolved to lure, capture, and digest prey.
Venus Flytrap
Venus flytrap, Dionaea muscipula, lures insects into colorful, nectar-containing traps, which are remarkable modified leaves. The traps have three trigger hairs on each side, which when touched cause the trap to close suddenly. Interlocking teeth along the edge prevent escape, while digestive fluids break down all but the insect's exoskeleton. Flytraps are native to a very limited region within 100 miles of Wilmington, North Carolina.
Electron photomicrograph, Polaroid type 55 film
Digitally colorized giclée print
© 2005 Joan Wiener
Two views of the outer edge of a trap
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© 2005 Botanic Garden of Smith College

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