Growth patterns in some indo-west-pacific seagrasses |
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Affiliation: | 1. Marine Benthic Ecology and Evolution, Centre for Ecological and Evolutionary Studies, University of Groningen, P.O. Box 11103, 9700 CC Groningen, The Netherlands;2. Community and Conservation Ecology, Centre for Ecological and Evolutionary Studies (CEES), University of Groningen, P.O. Box 11103, 9700 CC Groningen, The Netherlands;3. Department of Aquatic Ecology & Environmental Biology, Nijmegen University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands;4. Animal Ecology Group, Centre for Ecological and Evolutionary Studies (CEES), University of Groningen, P.O. Box 11103, 9700 CC Groningen, The Netherlands;5. Department of Marine Ecology, NIOZ Royal Netherlands Institute for Sea Research, NL-1790 AB Den Burg, Texel, The Netherlands;1. Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Droevendaalsesteeg 10, 6708 PB Wageningen, The Netherlands;2. Institute of Ecology and Biodiversity, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands;3. Waternet, Post Box 8169, 1005 AD Amsterdam, The Netherlands;4. B-Ware Research Centre, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands |
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Abstract: | The plastochrone interval of the rhizomes (PIR) was determined in the monopodially branching seagrasses Cymodocea rotundata Ehrenb. et Hempr. ex Aschers. (1981), Cymodocea serrulata (R.Br.) Aschers. et Magnus (1981), Syringodium isoetifolium (Aschers.) Dandy (1982), Halodule uninervis (Forssk.) Aschers. (1982) and Halophila ovalis (R.Br.) Hook.f. (1982). The growth rate during 1981 was in all species, including Thalassia hemprichii (Ehrenb.) Aschers., constant during the year and the PIR amounted to 6.7 days (Cymodocea serrulata) and 3.9 days (Cymodocea rotundata). However, the PIR observed in 1982 showed in all species a unimodal pattern and a decrease during June, July and August. The PIR was 6.3 days in Halodule uninervis while an interval of 5.2 days was calculated in Syringodium isoetifolium.The growth rates of the horizontal and vertical axes (rhizomes and shoots) were correlated. A regression between the number of leaves on the shoot and the number of nodes on the rhizome resulted for most species in a linear correlation. The slopes of the calculated correlation were rather similar in the tree species with a comparable morphology: 0.44 in Cymodocea serrulata, 0.43 in Cymodocea rotundata and 0.49 in Halodule uninervis. In Syringodium isoetifolium, the longevity of the leaves increased during ageing of the shoot.The proliferation ratio (the ratio shoots/rhizome apices) was measured in all species. A maximum of 0.41 was observed in Thalassia hemprichii. This species and Cymodocea rotundata showed a unimodal pattern. In the last species, the ratio ranged from 0.03 to 0.13. The ratio was constant during the year in Cymodocea serrulata and Syringodium isoetifolium. Proliferation by means of monopodially branching of the rhizome was of little importance in Halodule uninervis. The pattern of proliferative and reiterative branching in the Cymodoceoideae is illustrated by an image of 123 days of growth in the fastest growing specimen.Most species showed growth in fronts. The expansion of monospecific seagrass fringes was monitored by repetitive mapping. The pattern of succession in subtidal meadows was determined. |
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