Jonathan A. Keogh

A method for inducing rapid germination in seed of Discaria toumatou Raoul

Abstract A reliable technique for achieving rapid seed germination in matagouri or wild Irishman (Discaria toumatou Raoul), an endemic woody shrub with seed which had previously proved difficult to germinate, is documented. Seed collected from the wild gave >80% germination within 14 days of commencing treatment when scarification, by immersion in 98% sulphuric acid for 24 minutes, was followed by imbibition with a solution of 1(H-4 M gibberellic acid. The provision of aeration at room temperature (20 ± 3°C), during imbibition with the gibberellic acid solution, resulted in increased germination percentages and rates.

Macrocystis pyrifera in New Zealand: testing two mathematical models for whole plant growth

A Leslie-Lewis matrix projection model and a Markov chain model for whole plant growth in the giant Kelp,Macrocystis pyrifera, are developed and compared. Parameters of the models are estimated from field data gathered from several plants in New Zealand over a four-month period. Interpretations of the results are discussed.

Sodium pentobarbitone-induced relaxation in the abalone Haliotis iris (Gastropoda): effects of animal size and exposure time

Abstract Different-sized Haliotis iris (20–160 mm shell length (SL)) were subjected to the anaesthetic sodium pentobarbitone and the time taken for animals to release from aquaria walls and recover from the anaesthetic recorded. In a second experiment, animals remained in the anaesthetic bath for 0, 30 or 60 min after release from aquaria walls and were then allowed to recover. In both experiments, heart rate was used as an indicator of animal health and measured using ultrasonography, a non-destructive method not previously reported for this purpose in abalone. Heart rate was measured before, at release, during recovery, and 8 days after relaxation in the first experiment and before, at release, and during recovery in the second experiment. No deaths attributable to sodium pentobarbitone were recorded in either experiment. Larger animals took longer on average to release from aquarium walls and longer to recover than did smaller animals. Heart rate of the small abalone ( 70 mm SL). Heart rate of medium to large abalone was depressed during relaxation to about half (13±5 beats per minute (bpm)) that recorded prior to relaxation (26±6 bpm). Some treated animals (17%) exhibited arrhythmia immediately after relaxation or during recovery in both experiments. Animals did not feed until 1–2 days after recovery. In the second experiment, longer immersion time resulted in further depression of heart rate and longer recovery time.

Mass distribution in the fronds of macrocystis pyrifera from New Zealand and California

The mass distribution along the fronds of Macrocystis is examined for plants collected from California and New Zealand. Analysis of fronds classified according to length and condition yields polynomial curves for cumulative mass as a function of distance above the holdfast. Models for this functional relationship are discussed. Similarities and differences between the deep-water California plant and the shallow-water New Zealand plant are highlighted.

Transoceanic dispersal in the amphiantarctic genus Discaria: An evaluation

Abstract The hypothesis that the presence of Discaria in New Zealand can be attributed to the dispersal of a sea-borne fruit of an ancestral species is examined. It was shown by experiment that all capsules sank after 42 days in seawater, that proportionately more of those that sank early in the experiment had two or more hard seeds, that the germination percentage of seeds that float is considerably less (33%) than those that sink (100%), and that seeds which imbibed full salinity seawater showed a 60% reduction in germinability compared with controls. The nature of the fruit, a dry dehiscent capsule, the existence of a foramen in the inner fruit wall, and the preponderance of two or fewer seeded fruits also mitigate against possible hydrochory of the fruit and the subsequent establishment of an obligately outcrossing ancestor.