Organismic determinants and their effect on growth and regeneration in Gracilaria gracilis |
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Authors: | Albertus J Smit John J Bolton |
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Institution: | (1) Botany Department, University of Cape Town, PO Box Rondebosch, 7700 Cape Town, South Africa |
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Abstract: | The growth of Gracilaria gracilis (Stackhouse) Steentoft, Irvine et Farnham was examined by studying the effect of organismic
determinants such as thallus length, position along the thallus and branching. Knowledge of these factors is essential in
order to increase production from suspended seaweed rafts seeded with vegetative G. gracilis fragments. Seeding netlons with
seaweed material freshly collected from subtidal populations provided up to 30% higher relative growth rates than seaweed
maintained on the netlons for successive months. Initial seedstock length greatly affected growth rates and yields such that
30-cm thalli fragments resulted in growth rates 14% higher than for 10-cm fragments. This difference is suggested to be due
to the higher contribution to overall biomass by growth of lateral branches. Comparisons of the growth of apical and basal
fragments suggest that growth takes place over the entire length of the thallus, but that the apex contributes more to overall
elongation than does the proximal part. The removal of apical meristems resulted in an enhanced branching frequency with production
of four times as many branches as intact fragments. Evidence is also provided for extensive morphological differentiation
following long periods of rapid growth. These thalli have very high frequency of branching, are hollow due to the disintegration
of medullary cells and are considered to be completely senescent. These factors have implications for the successful cultivation
of G. gracilis on commercial mariculture systems.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | organismic determinants Gracilaria gracilis Rhodophyta regeneration growth mariculture |
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