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Grows during the winter
The leaf´s growth occurs at the part of the leaf
that is attached to the stalk. As new leaf material grows, the older parts
are "pushed forward". The stalk and holdfast live for several years. Sugar
wrack can be up to 3,5 years old.
The sexless variety of sugar wrack is born during the
spring and has grown a few centimetres by the summer. During the following
year, it grows in length during the winter, in width during the spring
and increases in thickness during the summer. It reproduces and creates
many sexed plants during the autumn and winter, thereafter the leaf is
usually broken apart.
For an alga to grow it needs light to photosynthesise,
and nutritive
substances. An important nutritive component is nitrogen. Variations
in the supply of these substances are great. During the swedish winter months,
light is in shortage, but nitrogen is abundant and the opposite situation
exists during the summer months. This is a problem for Marine algae, as
the ideal situation would be that both components should be abundant at
the same time. The next page describes how kelp copes with these variations
and how it grows during the winter and summer.
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