Page 252 - (DK) Ocean - The Definitive Visual Guide

250 PLANT LIFE

Flowering Plants

PLANTS CONQUERED LAND, and
DOMAIN Eucarya Seawater Plants
then land-based flowering plants
KINGDOM Plantae Seagrasses are monocotyledons (the group of flowering plants with
grew to be among the most narrow, straplike leaves), but are not true grasses, and they do not share
DIVISION Trachaeophyta
abundant and diverse life-forms a single evolutionary origin. There are 59 species in 5 families, although
CLASS Angiospermae the Ruppiaceae, living mainly in brackish water, is not always accepted
on Earth. However, relatively
SPECIES 260,000 as a seagrass family. Salt-marsh plants are mainly small and herbaceous,
few have adapted to the poor with early colonizers including the salt-excreting cord grass and small
soil, salt spray, and drying wind of coastal dunes and succulents, such as common
cliffs. These few include some fascinating plants found glasswort. Further salt-tolerant
flowering plants grow farther up the
nowhere else. Few flowering plants have returned to shore in established salt marshes,
the sea: salt-marsh plants and mangroves get wet at high forming a dense, grassy turf. Salt
tide, but only the seagrasses live fully submerged. marshes (see p.124) form in cooler
climates, and are replaced in tropical
seas by mangroves—trees with
Anatomy characteristic aerial roots. There
Flowering plants, technically called angiosperms, uniquely possess fruit are 16 families and 54 species of
and flowers, unlike mosses, seaweeds, and other algae. They are adapted mangroves. Like seagrasses, they do
to life in air, absorbing fresh water through their roots. If they take salt not have a single
water into their vascular system, water from their own cell origin, so the
sap is attracted to the more concentrated salts and sucked mangrove habit
out by osmosis. This is fatal to cells, but mangroves cope evolved separately,
by excreting the salt, while succulents partition it within several times.
their cells. Seagrasses have fully adapted by matching
their cells’ salt concentration to that of seawater. Most EELGRASS
seagrasses have a similar form, with thin, grasslike blades Seagrasses, such as this
MANGROVES SUBMERGED eelgrass in a Scottish
that allow easy exchange of nutrients and gases. Mangroves
When the tide is in, mangroves sea loch, can be found
grow in mud that lacks oxygen by growing aerial roots to form a mini-jungle of arching from the cold waters of
waterproof assist gas exchange in their underground roots. Many roots where small fish hide. Alaska to tropical seas.
seed case
angiosperm seeds are killed by seawater, but those
of the coconut can stay viable at sea for long Coastal plants
periods inside a waterproof case. Seagrasses are
germinating
plant water-pollinated, and to A greater variety of flowering plants can grow above the high-water
GERMINATING SEED increase the chances of a mark. Salt-tolerant grasses are important constituents of the upper parts
This coconut is a fruit—a defining
characteristic of flowering plants. The pollen grain catching onto of salt marshes, and at the seaward edge of sand-dune systems, grasses are
coconut has the marine adaptations of a female stigma, pollen is often the first to stabilize the shifting sand. In sand and sheltered gravel
buoyancy and a waterproof case. released as a sticky string. at the top of the shore, a few deep-rooted plants grow. A much wider
variety of flowers and a few mosses colonize sand dunes and
slacks just inland from the coast. Here they are
subjected to salt spray but never inundated by
tides. Nitrogen fixers thrive in these poor,
sandy soils. In warmer climates, annuals
bloom like desert flowers after
seasonal rains. On cliff-tops, plants
may be fertilized by sea-bird guano,
stimulating lush growth.

OCEAN LIFE COASTAL FLOWERS DUNE-SLACK FLORA

Here, in dune slacks behind
The beautiful pink flower heads of sea
a beach in the Canary Islands,
pink transform rocky seashores and salt
annual plants bloom for a short
marshes in late spring. The sea pink’s
period after rain. They flower
compact cushions resist wind and cold.
and produce seeds quickly before
drying up in the summer sun.