Foreword
The colours of terrestrial plants are very familiar. The predominant green of photosynthetic tissues, especially leaves, is due to chlorophylls and masks the yellow
carotenoids that are also present, though these are revealed in autumn leaves, along
with red anthocyanins, as the green chlorophyll is degraded prior to leaf fall. The
bright colours of flowers and fruit provide striking contrast and attract insects and
other vectors for pollination and seed dispersal. In the oceans of the world, terrestrial plants are replaced by algae, which may be macroalgae (seaweeds) or
microalgae (phytoplankton). These do not have flowers or fruit, so major classes of
plant pigments—anthocyanins and other flavonoids, betalains and quinones—are
not produced in the aquatic environment. Algae, however, do use pigments for their
natural photosynthesis.
Photosynthesis in algae of all classes is similar in principle to that in land plants,
taking place in chloroplasts and requiring pigments to harvest and use the available
light energy. The intensity of the available light, however, decreases as water depth
increases, and not all wavelengths of light penetrate water, especially seawater, to
the same extent. Red light, which would be absorbed by chlorophylls, is mostly
absorbed in the first few metres of water depth, and it is largely blue and green light
that penetrates to greater depths. So the role of accessory light-harvesting pigments,
carotenoids and phycobiliproteins, is much more important, to make the most
efficient use of the available light for photosynthesis. Also, algae that may become
exposed to bright sunlight during part of the day must be able to withstand a high
level of light energy. Adaptation to low or high light intensity is, therefore, an
important feature of algal life patterns.
Algae, including microalgae, use three kinds of pigments in photosynthesis,
generally located in pigment–protein complexes. Chlorophyll is essential for photosynthesis. Chlorophyll a occurs universally in algae of all classes. Chlorophyll
b is largely or entirely restricted to green algae (Chlorophyta), whereas chlorophylls
c and d occur in many classes. Many green algae have carotenoid compositions
rather similar to those of green leaves, but other classes of algae contain many
different carotenoids. These have occupied the attention of carotenoid chemists for
many years, and carotenoid compositions have been used in chemosystematic
vii
The colours of terrestrial plants are very familiar. The predominant green of photosynthetic tissues, especially leaves, is due to chlorophylls and masks the yellow
carotenoids that are also present, though these are revealed in autumn leaves, along
with red anthocyanins, as the green chlorophyll is degraded prior to leaf fall. The
bright colours of flowers and fruit provide striking contrast and attract insects and
other vectors for pollination and seed dispersal. In the oceans of the world, terrestrial plants are replaced by algae, which may be macroalgae (seaweeds) or
microalgae (phytoplankton). These do not have flowers or fruit, so major classes of
plant pigments—anthocyanins and other flavonoids, betalains and quinones—are
not produced in the aquatic environment. Algae, however, do use pigments for their
natural photosynthesis.
Photosynthesis in algae of all classes is similar in principle to that in land plants,
taking place in chloroplasts and requiring pigments to harvest and use the available
light energy. The intensity of the available light, however, decreases as water depth
increases, and not all wavelengths of light penetrate water, especially seawater, to
the same extent. Red light, which would be absorbed by chlorophylls, is mostly
absorbed in the first few metres of water depth, and it is largely blue and green light
that penetrates to greater depths. So the role of accessory light-harvesting pigments,
carotenoids and phycobiliproteins, is much more important, to make the most
efficient use of the available light for photosynthesis. Also, algae that may become
exposed to bright sunlight during part of the day must be able to withstand a high
level of light energy. Adaptation to low or high light intensity is, therefore, an
important feature of algal life patterns.
Algae, including microalgae, use three kinds of pigments in photosynthesis,
generally located in pigment–protein complexes. Chlorophyll is essential for photosynthesis. Chlorophyll a occurs universally in algae of all classes. Chlorophyll
b is largely or entirely restricted to green algae (Chlorophyta), whereas chlorophylls
c and d occur in many classes. Many green algae have carotenoid compositions
rather similar to those of green leaves, but other classes of algae contain many
different carotenoids. These have occupied the attention of carotenoid chemists for
many years, and carotenoid compositions have been used in chemosystematic
vii