Download Aquatic Plants • To take in sufficient oxygen, many aquatic plants

Aquatic Plants
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To take in sufficient oxygen, many aquatic plants have tissues with large air-filled spaces
through which oxygen can diffuse.
The reproductive adaptations of aquatic plants include seeds that float in water and delay
germination for long periods.
Many aquatic plants grow quickly after germination, extending the growing shoot above
the water’s surface.
Salt-Tolerant Plants
When plant roots take in dissolved minerals, a difference in concentration of water molecules is
created between root cells and the surrounding soil. This concentration difference causes water
to enter the root cells by osmosis. For plants that grow in salt water, this means taking in much
more salt than the plant can use. The roots of salt-tolerant plants are adapted to salt
concentrations that would quickly destroy the root hairs on most plants. The leaves of these
plants have specialized cells that pump salt out of the plant tissues and onto the leaf surfaces,
where it is washed off by rain.
Desert Plants
Plants that live in the desert biome are called xerophytes. They must tolerate a variety of
extreme conditions, including strong winds, daytime heat, sandy soil, and infrequent rain. Plant
adaptations to a desert climate include extensive roots, reduced leaves, and thick stems that can
store water.
Cactuses have root systems that spread out for long distances just beneath the soil surface or
reach deep down into the soil. To reduce water loss due to transpiration, their leaves have been
reduced to thin, sharp spines. Cactuses have thick green stems that carry out photosynthesis and
are adapted to store water. Their stems swell during rainy periods and shrivel during dry spells,
when the plants are forced to use up their water reserves.
Seeds of many desert plants can remain dormant for years, germinating only when sufficient
moisture guarantees them a chance for survival. When rain does come, the plants mature,
flower, and seed in a matter of weeks or even days, before the water disappears.
Nutritional Specialists
Carnivorous Plants
Some plants that live in wet and acidic environments with little or no nitrogen present obtain
nutrients using specialized leaves that trap and digest insects. The leaf secretes enzymes that
digest the insect and release nitrogen for the plant to use. The best known of the carnivorous
plants is the Venus’ flytrap.
Parasites
Some plants extract water and nutrients directly from a host plant. Like all parasites, these plants
harm their host organisms and sometimes even pose a serious threat to other species.
Epiphytes
Epiphytes are plants that are not rooted in soil but instead grow directly on the bodies of other
plants. Most are found in the tropical rain forest biome, but they also grow in other moist
biomes. Epiphytes are not parasites. They gather their own moisture, generally from rainfall,
and produce their own food.
Chemical Defenses
Plants are an important source of food for insects. Many plants defend themselves against
insect attack by manufacturing compounds that have powerful effects on animals. Some of
these chemicals are poisons that can be lethal if eaten. Others act as insect hormones,
disrupting normal development and preventing insects from reproducing.