A field study on the growth and development ofDumontia contorta |
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Authors: | R Pot B Klein H Rietema C van den Hoek |
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Institution: | (1) Advisory Group of Vegetation Management, Bornsesteeg 69, 6708 PD Wageningen, The Netherlands;(2) Present address: Department of Marine Biology, Biological Centre, University of Groningen, PO Box 14, NL-9750 AA Haren, The Netherlands |
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Abstract: | Young, crustose plants ofDumontia contorta grown in the laboratory from carpospores were transferred in September 1983 to their natural habitat in Lake Grevelingen
(SW Netherlands). The number of upright fronds per crust, length of upright fronds, and diameter of crusts were determined
monthly until October 1984 and the presence of tetrasporangia was noted. Although fronds were initiated from crusts throughout
the period of short daylengths (<13 h light per day, i.e. from September to March), the majority of the fronds was initiated
in October and November when short daylengths coincided with optimum temperatures for frond initiation (ca 10–20°C). By April,
i.e. within 5–6 months, these plants had reached maximum sizes and had become fertile; subsequently, the plants decayed. The
successively smaller numbers of fronds that were formed in December and January also reached maximum sizes after ca 5–6 months,
i.e. by May and June, but these fronds remained much smaller than the fronds initiated in October–November, possibly because
of lower temperatures and light levels at the start of their growth. It is suggested that the fronds have a fixed maturation
period (ca 5–6 months) irrespective of their size and the moment of their initiation. Crusts were shown to “oversummer” and
to produce new fronds at the onset of shortday conditions in September 1984.
Dedicated to Dr. Dr. h. c. Peter Kornmann on the occasion of his eightieth birthday. |
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