Page 280 - Algae Anatomy, Biochemistry, and Biotechnology

Algae and Men 263

FIGURE 7.7 Frond of Undaria pinnatifida.

Undaria is an annual plant with a life cycle similar to Laminaria. It has an alternation of gen-
erations with the large macroalga as the sporophyte and a microscopic gametophyte as the alternate
generation.
The ropes are immersed in seawater tanks containing fertile sporophytes in April–May, when
the water temperature is 17–208C, and let stand until about 100 spores per centimetre of twine have
become attached. The ropes are then lashed to frames submerged in seawater tanks until
September–November. When the young plants are 1–2 cm long, and the temperature falls
below 158C, the ropes are removed from the frames and wound around a rope that is suspended
by floats and anchored to the bottom at each end. However, a variation from the Laminaria culti-
vation is that the rope long-lines are suspended 2–3 m below the surface. In sheltered bays, the
ropes are placed 10 m apart; in open waters, where there is more movement, the single ropes are
assembled into a grid pattern using connecting ropes to hold the long-lines about 2 m apart.
Harvesting is in two stages. First the plants are thinned out by cutting them off at a point close
to the rope. This is done by pulling the rope over the edge of a boat, cutting and dragging the
plant into the boat. The remaining plants on the rope have plenty of space and continue to grow.
Harvesting finishes in April.
In Japan, the seeded strings are often cut into small lengths and inserted in the twist of a rope
that is then hung vertically from a floating rope, much the same as is done with Laminaria. Harvest-
ing in southern Japan is from March to May, but around Hokkaido it is from May to July.
After its accidental introduction, cultivation of Undaria has been undertaken also in France.
Here the above methods were found to be inappropriate because the high nutrient concentrations
in the water allowed a large variety of other plant and animal life (epiphytes) to grow on the
frames holding the strings. In the seeding method adopted by the French, the gametophytes are
formed and maintained in a sterile laboratory medium. One month before out-planting the game-
tophytes are brought to maturation. After fertilized eggs (zygotes) are formed, the solution with
the suspended zygotes is sprayed onto a nylon line that is wound around a frame. The zygotes