Life cycle and growth ofPotamogeton crispus L. in a shallow pond,ojaga-ike |
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Authors: | Hidenobu Kunii |
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Institution: | (1) Department of Biology, Faculty of Science, Tokyo Metropolitan University, Setagaya-ku, 158 Tokyo |
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Abstract: | The life cycle and growth ofPotamogeton crispus L. were studied in a shallow pond, Ojaga-ike. With respect to the shoot elongation and seed and turion formations, the life
cycle of this plant in the pond could be divided into following five stages: germination, inactive growth, active growth,
reproductive and dormant stages. It was suggested that the plant showed these successive stages depending mainly upon water
temperature. The turions germinated on the bottom in autumn when the water temperature fell below ca. 20 C. The plant showed
hardly any growth during winter (December—early March) when the temperature was below 10 C. In the spring when the bottom
water temperature rose to above 10 C (mid-March), the plant started to grow again and the shoot elongated rapidly at the rate
of 4.2 cm day−1 until the shoot apex reached the pond surface in late April. Both the increment of node number and the internodal elongation
were associated with this rapid shoot growth. On 10 May (last sampling date), the mean values of shoot length, internodal
length and the number of nodes estimated for 10 predominant plants were 238.2±5.6 cm, 7.1±0.8 cm and 34.9±4.0 cm, respectively.
The turion formation and flowering occurred during the period from mid-April to mid-May when the surface water temperature
ranged 19 and 22 C. The dry weight of a plant reached the maximum mean value of 1180 mg on 10 May. At its peak biomass, an
individual plant produced 1–10 turions (5.5 on average) of which the mean individual turion dry weight was 53.2 mg. The turion
dry weight accounted for ca. 42% of the total plant biomass m−2 at that time. |
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Keywords: | Aquatic plant Biomass Growth Life cycle Potamogeton crispus Turion |
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