Ecophysiological attributes could be causes for rarity in plants. We tested the hypothesis that a species’ ability to regulate photosynthesis and growth in response to environmental factors is indicative of its environmental resilience and that this is linked to its conservation status. In this study, the ecophysiology of Graptophyllum reticulatum, an Australian endangered endemic species, was compared with that of its three closely related and more common congeners G. ilicifolium, G. excelsum and G. spinigerum. Ecophysiological attributes were measured on the four species in their natural habitats and under artificially imposed environmental stresses, including changed soil conditions, excess light and low water availability, in a glasshouse experiment. Photosynthesis was determined at the photosystem II and leaf level using chlorophyll a fluorescence and gas exchange techniques. Applied to the chlorophyll fluorescence transient of leaves, the JIP test provides a Performance Index which quantifies the main steps in PSII photochemistry including light energy absorption, excitation energy trapping, and conversion of excitation energy into electron flow. At the leaf level, gas exchange measurements allow determination of maximum CO2 assimilation rates, intercellular CO2 concentrations, stomatal conductance for water vapour and instantaneous water use efficiency. Growth analysis was performed to assess relative growth rates and physiological and morphological responses. Analysis of physiological differences and responses indicated that, compared to its more common relatives, the endangered G. reticulatum was an intrinsically slow growing species, exhibited the lowest fitness when growing in favorable environments and was most sensitive to excess light stress. Photoinhibition is therefore likely to restrict the endangered species to shade habitats. Compared with the endangered G. reticulatum, the vulnerable G. ilicifolium and common G. spinigerum species were better adapted to high light and changed nutrient levels, but were more susceptible to water stress. The rare G. excelsum had the fastest growth rate and the highest fitness in favorable environments. Based on the ecophysiological attributes examined here, it is proposed that excess light is likely to be the most critical abiotic factor restricting distribution of the endangered species in a fragmented landscape. The survival of the species may be most dependent on the intactness of the habitat over-storey. In contrast, the vulnerable G. ilicifolium showed strong susceptibility to water limitation, and survival might be threatened if climate change alters habitat water relations to cause, for example, more pronounced dry periods. The rare G. excelsum which had highest carbon gain and growth in the experiments carried out in this study, may become the most successful adaptation out of the rainforest environment due to its tolerance to higher light and limited water availability. To examine the generality of the link between rarity and ecophysiology with Graptophyllum species, two dipterocarp species, narrowly endemic Dipterocarpus condorensis and local common Shorea roxburghii that are actually co-located in South-eastern Vietnam were studied. Findings in this case study confirmed the usefulness of the comparative approach based on physiological measurements, either in situ or ex situ, to explain plant rarity. The results of this study indicate ecophysiological research is a tool for examining causes of rarity and possible abiotic threats. The information gained allows assessment of environmental resilience of species and contributes essential knowledge for management and conservation of threatened plants. Such knowledge is also useful for ex situ conservation including propagation, translocation and re-introduction in restoration programs.

Many commercial crops of Cucurbita maxima and C. pepo are grown from Fl hybrid seed in New Zealand. Conventional methods of Fl seed production are labour intensive and expensive. Applying Ethrel sprays at 300ppm at the two and four leaf stage to the seed bearing parent delayed male flowering for sufficient time to allow insect pollination and eliminate 90% of the labour previously needed. After field trials the technique was used on a commercial scale. A satisfactory yield of pure Fl seed with a high germination percentage was produced. The variation between cultivars in response to Ethrel means that each one must be tested. It is shown that the degree and type of epinasty of pot plants sprayed with Ethrel can be used to determine the appropriate concentrations for field trials of C. pepo. The increase in female flower numbers, the shift in position of these flowers on the mainstem and the suppression of male flower numbers is brought about by two mechanisms. Ethrel sprays caused male flower bud abortion and an increase in the number of female flowers developing. More than one flower bud is borne in each leaf axil and if male, the bud aborts and can be replaced by a subsidiary undifferentiated bud which develops as a female. At the two to four leaf stage of plant development and shortly afterwards a large number of flower buds are developing to the stage of sexual differentiation. Spraying with Ethrel at these time is very effective in influencing sex expression. The release of ethylene by Ethrel breakdown continues for several days and the continuous exposure to ethylene is another reason for Ethrel’s effectiveness. The time course of ethylene release from aqueous Ethrel solutions was determined in some physical systems as well as from cotyledon and leaf surface contact. Some ethylene was released when Ethrel was applied to soil. When Ethrel was dried on surfaces or in soil its breakdown was much reduced, but on rewetting proceeded again. Spraying only one leaf with Ethrel still caused responses from other parts of the plant indicating transmission of a stimulus. This was not caused by aerial diffusion from the sprayed leaf. Although several effects of ethylene were studied major emphasis was placed on epinasty, stimulation of endogenous ethylene and its distribution between plant parts, the abortion of male flowers and the induction of female flowers. When aminoethoxyvinylglycine (AVG) was applied with Ethrel, the plants show epinastic responses and male flower abortion but not female flower induction, endogenous ethylene production or transfer of stimuli of Ethrel effects within the plant. Ethylene gas was similarly ineffective on plants treated with AVG. Ethylenebiodynthesis is blocked at the stage producing aminocyclopropane-1-carboxylic acid (ACC) the immediate precursor of ethylene. Assays showed ACC to be below detectable levels in AVG treated plants. Ethrel alone caused high levels of ACC and ACC was found in high levels in plant apices if leaf one was sprayed with Ethrel. ACC is mobile in plants and a firm correlation is shown between female flower bud production and the presence of ACC. It was concluded the ethylene released from Ethrel sprays caused epinasty and male flower bud abortion as well as promoting endogenous ethylene production via ACC. Ethrel sprays release ethylene in sufficient quantity for long enough for very high levels of ACC to be produced and ACC is transported throughout the plant, but preferentially to metabolic sinks, e.g. the plant apices, where embryonic buds respond by developing as female flower buds. Increased ethylene levels were also recorded at these sites. Because ACC has been shown to cause a plant response formerly attributed to ethylene it is now essential to investigate the whole spectrum of ‘ethylene’ effects in plants.

Auckland, the largest city in New Zealand, with a population of approx. 700,000, is notorius for its high incidence of respiratory allergies, particularly asthma. At a conservative estimate, one in every ten persons in the region suffers from allergic asthma and/or rhinitis (hay fever). In the Auckland Hospital Board area alone, there were 58 deaths from asthma in 1979 and 57 in 1980 (an average of 5 per month). Asthma and rhinitis affect people of all ages. To investigate the reason for the high incidence of these respiratory allergies, an aerobiological study of the qualitative and quantitative composition of the air spora was thus undertaken. To include a reasonably representative cross section of the region for air sampling three localities from near the centre of the city to the western suburban fringe were chosen along a 20km axis encompassing commercial, residential, agricultural, horticultural and forested environments. A Burkard 7-day recording volumetric spore trap was operated continuously at each locality, from 1 September 1979 to 31 August 1980. Counting and identification of spores and pollen grains were undertaken within 5 random microscope fields along each of 12 traverses across the spore trap tapes representing alternate hours of the day on Mondays and Tuesdays. Data were converted to concentrations (numbers m-3 of air). Of a total of 38 spore or pollen categories recorded, 24 displayed seasonal and circadian periodicities. The survey revealed that there was considerable contamination of the atmosphere by spores of various fungi, particularly in summer and autumn with peaks at all sites in autumn. It is of interest that the admission rate of patients with "status asthmaticus" in the two year period January 1979 – December 1980, was also high in summer and autumn with peaks in both years in April (autumn). Fungal spores >3μm constituted c. 99% of the Auckland air spora in all seasons, even spring, the chief pollen season. Basidiospores were the most abundant type of the region. Amongst indentified basidiospores, Ganoderma and Coprinus predominated. Basidiospores ascribable to Hypholoma, "Calvatia-Bovista" Tilletiopsis, Entoloma and Thelephora were also recorded. Ascospores of various genera were also abundant at all sites. Among them, those ascribable to the genus Leptosphaeria were most common, followed by "Hypoxylon-Xylaria", Pleospora and Venturia. Conidia of Cladosporium were one of the principal components. Other conidia recorded, although in small numbers, belonged to the genera Polythrincium (trifolii), Epicoccum, Pithomyces (chartarum), Stemphylium, Alternaria, Periconia, Torula, Helicomyces, Helminthosporium (Drechslera), Pestalotia, Cryptostroma, Tetraploa, Arthrinium and Monilia. Conidia of "Aspergillus-Penicillium" type were the most prevalent at the city site. A comparison of the air spora at the three localities revealed major quantitative but not qualitative differences. The suburban locality emerged with higher spore concentrations than the urban and forested sites. The relationships between some meteorological factors and the 14 most prevalent categories of the air spora were analysed. Cladosporium and Polythrincium showed a significant correlation with temperature; unidentifiable ascospores were correlated with midnight temperature, humidity and, strongly, with rainfall; Leptosphaeria correlated with rainfall and midnight temperature. Unidentifiable coloured and hyaline basidiospores as well as Ganoderma and Coprinus were positively correlated with temperature. Coloured basidiospores and Ganoderma also showed a significant "negative" correlation with wind speed. On the basis of the aerobiological findings and a potential link with asthma admissions to hospital a total of 67 aqueous and lyophilized extracts from basidiomycetous fungi collected in the Auckland region were prepared in buffered saline, with W/V standardized concentration, for immunological studies. 'Total protein' content of the extracts were estimated. A total of 129 allergic patients both "heterogeneous group" and diagnosed, attending hospital allergy clinic, were tested by the skin prick method. Over 10% of the patients reacted positively to the crude extracts of the following fungi: Ganoderma mastoporum*, Ganoderma applanatum**, Scleroderma albidum*, Coprinus micaceus*, Lycoperdon compactum*, Hydnum crocidens var. badius**, Xeromphalina podocarpi***, Auricularia polytricha***, Agaricus bisporus*,Bovista brunnea*, Panaeolina foenisecii**, Hypholoma acutum**, Calvatia* sp. Pseudohydnum gelatinosum***, Trametes versicolor***, Favolaschia calocera***, Cortinarius*, Tyromyces*** sp. and Hydnum crocidens**. Allergenicity to many of these genera has rarely been investigated or reported. The findings of the investigation suggest that fungal spores in general, and basidiospores in particular, may play an important role in the high incidence of allergic asthma and rhinitis in the Auckland region. * spores alone extracted ** hymenial tissue extracted *** whole sporophores extracted / Whole document restricted, but available by request, use the feedback form to request access.

The flowering plant family Alseuosmiaceae comprises three genera of shrubs: Alseuosmia A. Cunn. from New Zealand; Memecylanthus Gilg and Schltr. and Periomphale Baill. (=Pachydiscus Gilg and Schltr.) from New Caledonia. These genera are readily excluded from their traditional position in the Caprifoliaceae by virtue of their alternate leaves, valvate corolla lobes and their southern hemisphere distribution. Four species of Alseuosmia, including one hitherto undescribed species, are accepted here. The New Caledonian genera are poorly represented in herbaria; they may each be monotypic. Condensed tannin (leucocyanidin) and ellagitannin are abundant in all Alseuosmia tissues. Other simple phenolic compounds here (as detected in acid hydrolysates) include quercetin, kaempferol, caffeic acid and p-coumaric acid. Triterpenoid saponins are abundant in leaf tissue; alkaloids and probably iridoid compounds too, are absent. Tannin is found throughout the ovary tissue of Alseuosmia and in the inner and outer epidermises of the ovular integument. The floral vascular anatomy is detailed for the Alseuosmiaceae and reviewed for eight allied families. No features of the vascular system imply particular affinity of the Alseuosmiaceae with any of these allies. Within this family the association of different morphological and anatomical floral features supports the contention that primitive characters tend to be associated with one another in their distribution throughout the members of a taxon. The primary vascular pattern in the stem of Alseuosmia is of an open (sympodial) nature. The mature nodal anatomy is 3-trace trilacunar. All genera have a stem endodermis with prominent Casparian banding, and in Alseuosmia at least this endodermis passes through the secondary and quaternary stages (lignification-suberisation of walls; accumulation of phenolic compounds) as found in a typical root endodermis. All species of Alseuosmia lack rays in the secondary wood, whereas memecylanthus and Periomphale have extremely tall (indefinitely-prolonged?) rays. The vessels of these genera are relatively primitive (end-plate angle c.10-19°, no bars per scalariform plate c.16-37), and thus are comparable to vessels of the Escalloniaceae and Caprifoliaceae. The root periderm has a cortical origin in Alseuosmia and the root pith is persistent. Multicellular uniseriate hairs are found in the leaf axils in all Alseuosmiaceae. Hairs with similar structure and development are found in some genera of Pittosporaceae but not, so far as is known, in other related groups. Within Pittosporum, these uniseriate hairs appear to be homologous with the T-hairs many species have. The chromosome number of 2n=18 probably characterises all the species of Alseuosmia. A. macrophylla A. Cunn. is an obligate outbreeder with an incompatibility mechanism operating at the stylar level, while A. pusilla is self-compatible. Pollinating agents for the species are unknown. No internal barriers to hybridism exist between A. macrophylla and A. banksii A. Cunn. and the hybrid swarm between these species is recognised here as A. X quercifolia A. Cunn. Neither do internal barriers exist between A. macrophylla and A. pusilla, but differences in flowering time and mode of breeding help to keep these species separate in the field. Mature pollen of Alseuosmia is trinucleate: the ovule is uni-tegmic-tenuinucellate. The distinctness of the Alseuosmiaceae is upheld and its affinities are suggested to be with the Escalloniaceae, and to a lesser extent, with the Pittosporaceae.

This thesis demonstrates some of the potential of Phyllocladus trichomanoides D. Don (tanekaha) for dendrochronological research, especially dendroclimatology. The type of vegetation associated with sites producing a chronology showed no obvious pattern. The resulting non-specific range of suitable sites for dendrochronological sampling was thought to be a favorable species characteristic. Standardization of tree-ring series using a 50-year Gaussian filter resulted in 28% improvement of retained common variance above that obtained from using conventional polynomial filters. The problem of autocorrelation was investigated. Tanekaha had a consistent autocorrelation pattern through both space (i.e. latitudinal and altitudinal ranges) and time (preserved forest and contemporary stands). P. glaucus (toatoa) also showed a spatially consistent yet distinctive pattern. These different diagnostic patterns implied a non-climatic cause (i.e. physiological), illustrating the need to ensure their removal before species chronologies are compared or used for climate modelling. Low order autoregressive models (ARMA(p,0)) were used to filter out the significant levels of autocorrelation. Subsequent comparison of the chronologies showed a consistent and highly significantly correlated pattern between both sites and species. The paucity of information about the physiology of Phyllocladus spp. led to the testing of several climatic variables in response function analyses. The "best" variables (based on only statistical evidence) were minimum monthly temperature, monthly total raindays and an optimal 12 month span of August (t) to July (t+1). Preliminary attempts with response functions using different combinations of predictor (climate variables) and predictand (chronologies) data sets generally failed to verify. Neither the extent of time from which the response functions were based (no analogue situation) nor a supposed "physiological shock" period (poor growth period) were the causes for non-verification. Further investigation showed that, for both the individual and combined chronologies, the temperature response was similar but rainfall varied. The instability through time of the rainfall response was particularly disconcerting since it broke one of the fundamental assumptions used in dendroclimatology. It was therefore concluded that climatic reconstruction could be attempted only on the temperature data. The temperature data of three seasons (spring, summer and autumn) were tried with transfer function models. Of these the summer season explained the most variance and had the highest reduction of error(RE) values. The selected model used the period 1918 to 1982 for calibration and 1853 to 1917 for verification. Summer temperatures from 1982 to 1750 were reconstructed. The reconstruction modeled only c.30% of the variance but was highly correlated to the summer temperature series developed by Norton (1983). This was interpreted as further independent verification of the reconstructed series. The summer temperatures reconstructed from 1982 to 1750 were concluded to have been similar to the recorded pattern from 1853. The same regressors were applied to the buried forest chronology and the summer temperatures reconstructed from 105 BC to AD 175. Because of the non-continuous tree-ring record no comment can be made of actual ambient conditions in comparison to those of today. However, the reconstructed pre-Taupo summer series did show increased variation towards the time of the eruption and more pronounced cool summers than hot ones. Another applied use of a tanekaha chronology was demonstrated with 14C dating. A statistically significant fit of 14C ages was obtained between twelve contiguous decades from the buried forest tanekaha chronology with that from a Northern hemisphere decadal calibration curve based on Sequioadendron giganteum(Stuiver & Becker 1986). This "wiggle-matching" to the calibration curve places the year of the Taupo eruption as AD 177±18 10. An Independent check of the "new" date was conducted using the most reliable data of Healy et al. (1964) with the same calibration series as described above. A date of AD177±4 44 was obtained which supports the wiggle-matched date. The confidence interval of the wiggle-matched date also coincides with the date proposed by Wilson et al. (1980) of AD186 (based purely on ancient written records).

A total of six hundred and sixteen fungal and two hundred and thirty two bacterial isolates were obtained either from the sapwood of Pinus radiata or from other sources, including UV mutagenesis. All isolates were screened on Pinus radiata wood chips for their survival and colonisation attributes. Of these isolates, two hundred and eighty two failed to grow or caused permanent deep seated discolourations or decay and were eliminated from the study. The remaining five hundred and sixty six isolates were assessed for their antagonistic ability against sapstain. In a dual screen on Pinus radiata wood chips, one hundred and twelve fungal and four bacterial isolates inhibited the growth of the known sapstain fungus, Ophiostoma piceae. In a second biological control screen, on Pinus radiata wood blocks, isolates of Gliocladium viride, Gliocladium roseum, Trichoderma hamatum, Trichoderma harzianum, Trichoderma sp., Trichothecium roseum and an isolate of the Thelephoraceae proved inhibitory to the sapstain isolates Ophiostoma piceae and Sphaeropsis sapinea providing between 94 and 100% control. These isolates were considered for further examination in the field. The remaining isolates provided poor or inconsistent inhibition or were mould fungi and, therefore, not suitable for direct application. All fungal and bacterial isolates that had shown inhibitory ability in the initial biological control screen and the remaining non-staining bacteria were examined for their ability to produce non-volatile metabolites that were inhibitory to sapstain. The bacterial isolates were examined in a preliminary dual plate screen in which 91 isolates were identified as producing inhibitory compounds. The best of these bacterial isolates were screened, with the fungal isolates, in a non-volatile metabolite trial utilising filter sterilised culture filtrates. Isolates of Bacillus sp., Fusarium solani, Gliocladium roseum, Gliocladium virens, Trichoderma harzianum, Trichoderma sp., Trichoderma viride and Trichothecium roseum were found to be significantly inhibitory to the growth of Ophiostoma piceae at concentrations of 50% or less. However, the filtrates did not provide adequate sapstain control, when tested on Pinus radiata wood block, to prompt consideration for further examination in the field. Studies are currently examining several of these isolates for the production of biologically active compounds. The six most promising isolates, from the wood chip and wood block trials, were tested in the field for their ability to control sapstain on unseasoned Pinus radiata sapwood and/or peeled logs. These were Gliocladium viride (FK75), Trichoderma hamantum (FK561), Trichoderma harzianum (FK228), Trichoderma sp. (FK247), Trichothecium roseum (FK238) and an isolate of the Thelephoraceae (FK33). The fungi were prepared as mycelial/spore homogenates. For application to the timber, the homogenates were mixed with 0.2% Alcosorb gel, producing 108 cfu/ml suspensions, these suspensions were applied by dipping. Diluted homogenates, 108 cfu/ml, were applied as spray treatments to the logs. All of the biological control agent treatments reduced the level of sapstain on either the logs or timber with Trichoderma harzianum (FK228), Trichoderma sp. (FK247) and Trichothecium roseum (FK238) providing control equivalent to that of the fungicides NP-1 and Diffusol for portions of the trial. Trichoderma sp. (FK247) and Trichothecium roseum (FK238) gave sapstain control in excess of 90% for the first 30 days of the timber trial equalling the control provided by NP-1 and Diffusol. In another trial, Trichoderma harzianum (FK228) was more effective than NP-1, providing 60% sapstain control, after six months, on the internal tissue of Pinus radiata logs. The six isolates selected for the field trials were examined in additional studies. In a dual inoculation study, Trichoderma sp. (FK247) exhibited localised antibiotic ability causing the lysis of mycelium of sapstain fungi. There was no evidence of mycoparasitic action by any of the six isolates. Trichoderma harzianum (FK228), Trichoderma sp. (FK247) and Trichothecium roseum (FK238) were observed to degrade cellulose. However, neither these nor the other isolates caused a significant change in the mechanical properties of Pinus radiata timber when compared to untreated controls. Decreasing pH or the addition of nitrate were identified as having potential for the promotion of biological control agent growth. The potential of mixed biological control agent inoculations was also examined. While these results are preliminary, they are extremely encouraging and provide a basis from which future studies can develop.

Aquatic macrophytes possess an internal lacunar system of proliferated intercellular airspaces. Lacunar gas exchange processes were investigated in Egeria densa Planch., a submerged freshwater angiosperm. Investigations of oxygen exchange between Egeria shoot segments and the water revealed that up to 17% of the photosynthetically-produced oxygen is retained within the lacunae. A consequence of this partitioning, which results from the relatively low solubility of oxygen in water, is the development of internal lacunar pressures up to 20 kPa above atmospheric pressure. This storage of oxygen in Egeria casts doubts on oxygen-based measurements of productivity in aquatic macrophytes, unless both internal and external sinks are monitored. Pressurisation also revealed that storage is greater in static water than in flowing water, suggesting that boundary layer limitations to oxygen transfer can also affect partitioning. Pressures fall to sub-atmospheric values in the dark, due to respiratory consumption of the internal oxygen. The Egeria respiratory gas exchanges in the dark demonstrated a steady concentration gradient between plant and water within an hour of darkening. However, the material steadily consumes approximately 30% of its respired oxygen from the lacunae, rather than the water. This oxygen supply is again due to the low oxygen solubility. The lacunae also assist the radial oxygen supply into the respiring tissue; it was found that the Michaelis-Menten constant for the respiratory response to oxygen tension in Egeria was some two to three times greater in material with infiltrated lacunae than in uninfiltrated material. Oxygen storage in the stem lacunae resulted in a longitudinal (shoot to root) movement of this gas, which was monitored using a bicompartment apparatus. The root oxygen release rate varied with light intensity and water flow rate in a similar manner to the internal pressure changes. Further experiments, involving measurements of the oxygen flux rates in the Egeria rhizosphere, demonstrated that this root oxygen loss is capable of effecting substantial diurnal oxygen fluctuations in the surrounding sediment. These processes may be interrupted by natural infiltration of the airspaces, but the factors involved here remain uncertain. The mean internal oxygen transport rate in Egeria (6.28 μ102 h-1) was consistent with estimates of lacunar oxygen concentration gradients calculated from Fick's Law, suggesting that diffusion is the oxygen transport mechanism in Egeria. However, by connecting shoots into manometers, internal pressure gradients of some 0.9 kPa m-1 were detected. These gradients were 103 -fold greater than the pressure gradient required to account for oxygen transport in Egeria, but were transient features, as the pressure equilibrated throughout the lacunar system 20 - 30 minutes after a dark/light change. Mass flow was therefore proposed as a transitory, but potentially significant, contribution to oxygen transport. Root to shoot carbon dioxide transport was measured using 14CO2 tracing. The CO2 uptake (mean internal transport = 4.96 μ1CO2 h-1) represented <10% of the total carbon fixed; the concentration of root-derived carbon in shoot tissue declined rapidly from the root insertion point. These results are compared with those of previous studies, and the significance of the Egeria lacunar system assessed.

Two Coelomycete genera, Ascochytula Died. and Ascochytella Tassi, were studied in order to determine their generic affinities, especially with Ascochyta. Ascochytula obiones (Jaap) Died., the type species of Ascochytula, is considered to be congeneric with Ascochyta pisi Lib., the type species of the earlier genus, Ascochyta Lib. Ascochytula is thus reduced to synonymy with Ascochyta. Of the thirty-six species and two varieties named in, or directly associated with, Ascochytula, twenty are herein described as species of Ascochyta and four are excluded from Ascochyta. The remaining species were either not examined, or are nomina dubia. The following names are proposed: Ascochyta asparagina (Petrak) comb. nov., A. deformis (P. Karsten) comb. nov., A. dorycnii (Petrak) comb. nov., A. ludwigiana (Petrak) comb. nov., A. moravica (Petrak) comb. nov., A. obiones (Jaap) comb. nov., A. phlomidicola nom. nov., and A. ulicis (Grove) comb. nov. Ascochytella Tassi, which has often been confused with Ascochytula, is also synonymised with Ascochyta. The original thirteen species in Ascochytella were examined, and A. vicina (Sacc.) Tassi chosen as the lecto-type species. Most of the thirteen species are regarded as being either misplaced in Ascochytella, or nomina dubia, and only four, including the lectotype, are accepted as species of Ascochyta. The name, Placodiplodia canthiifolia (Cooke & Massee) comb. nov. is proposed. The type species of Ascochyta, and of six related genera, Ascochytulina Petrak, Coniothyrium Corda. Diplodina Westend., Pseudodiplodia (P. Karsten) Sacc., Scolecosporiella Petrak, and Stagonospora (Sacc.) Sacc. were studied to determine the distinctions between these six genera and Ascochyta. Microdiplodia Allescher and Diplodia Fr. are also discussed, in relationt to Ascochyta. Ascochyta paspali (H. Sydow) Punith. (≡ Ascochytula paspali H. Sydow), which causes a leaf stripe disease of Paspalum dilatatum Poir., an important perennial grass of northern North Island pastures, was examined in detail. At some temperatures, under controlled climate conditions, the fungus significantly reduced the yield of P. dilatatum. A. paspali was found to grow systemically, as mycelium within the xylem vessels, and was able to infect all parts of the plant, including the roots and seeds. Green leaves sometimes became infected systemically without production of visual symptoms. Infected seed is suggested as a means for disease spread. No teleomorph for A. paspali was found, and the fungus is thought to over-winter in the dormant grass. The seasonal fluctuation in levels of P. dilatatum and of the disease was studied in two Northland pastures with paspalum as a component. One pasture was studied for fourteen months, and the other for four months. Disease levels, and paspalum levels, were determined by point quadrat analysis and by sorting of randomly cut samples. Levels of both the host and of the disease peaked in summer, while both were at low levels, or apparently absent, over the winter months.

Several ecological aspects of the Manukau Harbour related to its benthic flora end fauna, water chemistry, sedimentology, and bacteriology were investigated. Vertical colour aerophotographs were taken of all vegetated tidelands within the Harbour and six vegetation types were indentified, mapped, and discussed in terms of their ecological significance. Meadows of the intertidal seaweed Gracilaria secundata var. pseudoflagellifera near the Manukau Sewage Oxidation Ponds were found to have increased virtually logarithmically in extent since the commencement of operations of the Manukau Purification Works. The possible relation of this increase to contributions of mutrients and fine sediments from the Ponds is considered. The effects of stress, sediment type, and the presence of macrovegetation on benthic faunal community structure are studied. The majority of the findings are somewhat inconclusive; however it is found that mangrove swamps and eelgrass flats clearly appear to increase faunal species diversity. Water and sediment nutrients were examined and found to be at high levels in the north-east region of the Harbour. It is concluded that sediments probably undergo less temporal variation in nutrient levels than do overlying waters and might therefore provide a more cost-effective method of studying cultural eutrophication in the Manukau and similar harbours. Sediment particle size distribution was looked at and it was determined that sediments are extremely fine near the Manukau Sewage Oxidation Ponds, coarser but still muddy in most of the inlets of the Harbour, and sandy in most of the open Harbour intertidal flats remote from pollution sources. Counts of coliform bacteria were made and levels in intertidal sediments were found to be generally higher than in overlying waters but not less temporally variable. It was also determined that waters and sediments of the north-east region of the Harbour are of poor sanitary quality. Several management considerations are discussed in relation to the results of the study. Further research needs are outlined terms of 22 research projects addressed to waste water management, land erosion control, and tidelands managements.

Liverworts were the first plants to successfully make the transition from water to land and thus had to develop morphological and physiological features to overcome novel environmental constraints. The relative simple structure of liverworts in comparison to vascular plants implies that they have to combat environmental stress at a cellular level. Liverworts are an important part of the New Zealand flora. Leafy liverworts such as Jamesoniella colorata, Isotachis lyallii and Lepidolaena taylorii display a spectacular range in colouration within a single population. The leaves can vary from pale green in shaded habitats to bright red in more exposed places. A thalloid species, Monoclea forsteri, lacks such pigmentation but it might possess some unique cellular features to deal with stressful conditions. This thesis aims to study the cellular characteristics that allow liverworts to cope with extreme environmental conditions, with emphasis on (red) auxiliary pigments. Genetic analysis of liverwort populations revealed a highly clonal structure, which suggests that red colouration of liverwort leaves is a phenotypic response, and not a result of genotypic differences. Indeed, the red pigment could be induced in I. lyallii at relatively modest irradiance levels. The red leaves absorbed about 10% more photosynthetically active radiation than green leaves from the same species. Although the chemical characteristics of the red pigment remained elusive, it has light attenuation characteristics similar to anthocyanins in vascular plants. Its cellular location inside the cell wall is ideal for intercepting potentially damaging light quanta and can thereby protect the underlying chloroplasts from high light fluxes. The light energy that is absorbed by the red pigment did not translate into an enhanced protection from chilling-stress through leaf warming. The photosynthetic apparatus of liverworts has acclimated to the environmental conditions that these plants are most likely to experience in their habitat. Gametophytes from shady environments had lower chlorophyll a to b ratios than gametophytes found in sunnier places. This illustrates the need for a more efficient light-harvesting system in the former to collect all of the available light. In addition, plants from sunny environments had lower chlorophyll to carotenoid ratios than plants found in shady environments, which suggests that the photoprotective properties of carotenoids are better developed in the former. This was confirmed by measurements of chlorophyll a fluorescence which clearly showed a greater potential for nonphotochemical quenching in gametophytes from exposed habitats than gametophytes found in sheltered places, both during high light treatment and desiccation. A better developed photo-protective system (i.e. non-photochemical processes and lightscreening pigments) allowed the red-leaved gametophytes to better deal with high light stress as well as desiccation than their green-leaved counterparts. Measurements of photosynthetic responses revealed that red gametophytes were photoinhibited less and their recovery was more complete from a high light treatment of 1800 μmol/m2/s than the greens. Similarly, measurements of photosynthetic responses and oxidative damage indicated that the red morph was better protected from high light fluxes that occur during drought-stress than the green morph. Determination of cell water relations showed that the red pigment in J. colorata did not influence the water balance during drought. In conclusion, this study has presented evidence that liverworts from exposed habitats are better equipped to deal with abiotic stressors such as high light and dehydration than liverworts from more sheltered environments. Changes in pigment composition, concentration and location are likely to play an important role in liverwort protection from environmental stress – most noticeably a red pigment with photo-protective attributes.