Reproduction in the seagrass Zostera novazelandica on intertidal platforms in southern New Zealand |
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Authors: | D L Ramage D R Schiel |
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Institution: | (1) Marine Ecology Research Group, Zoology Department, University of Canterbury, Private Bag 4800, Christchurch 1, New Zealand, NZ |
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Abstract: | This study investigates the reproductive periodicity and reproductive output of the seagrass Zostera novazelandica on two intertidal reefs. Peak numbers of flowering shoots occurred during March (late summer) of two years at both sites
and no flowering shoots occurred during the winter months of July to September. There were greater numbers of flowering shoots
in seagrass patches in the low intertidal zone (up to an average of 55 per 0.1 m2) compared to the middle (up to 20 per 0.1 m2) and upper (up to 9 per 0.1 m2) zones, and about three times greater reproductive output in patches associated with tidepools compared to those not bordering
tidepools. The average number of inflorescences per shoot was 3.1 (±0.25) at one site vs 1.2 (±0.08) at the other, and showed
a progressive decrease from the lower shore to the upper shore. Patches associated with tidepools had twice the number of
inflorescences per shoot (2.8 ± 0.24) than patches not bordering tidepools (1.5 ± 0.16). The number of flowering shoots was
highly correlated with leaf width, leaf length, and ramet density, while the leaf-area index decreased from the lower shore
to the upper shore. The reproductive effort of plants, as measured by the percent biomass invested in flowering shoots during
peak reproduction, was significantly different between sites, tidepool associations, and shore level. For all the variables
measured, there was considerable spatial variation, with significant interaction terms between most factors investigated.
In laboratory experiments, more inflorescences were produced at light intensities of 30 and 300 μE m−2 s−1 than at 100 μE m−2 s−1. At a salinity of 17‰, 1.5 × the number of flowers was produced than at 33‰, while none was formed at 70‰. Plants cultured
at 5 °C had about three times the number of inflorescences than those at 15 °C, while none was formed at 25 °C.
Received: 25 June 1997 / Accepted: 24 September 1997 |
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