Pinus radiata is the dominant species of the plantations forests in New Zealand. The forest industry in New Zealand is heavily dependant on it. However, Pinus radiata can develop wood quality flaw called 'intra-ring checking'. The checks or splits appear in wood during kiln drying and usually affect the earlywood region of the wood. It lowers value of appearance grade timber leading to huge economic loses for the forest industry. This thesis presents a study that was undertaken as a part of ongoing collaborative work that is being carried out to understand wood quality issues in Pinus radiata, with a vision of improving its wood quality. This study was a part of that effort and was conducted with an aim to gain an insight into intra-ring checking, and the process of xylogenesis in Pinus radiata. The investigations for this study were carried out in two steps. The first step was to understand intra-ring checking. The location of intra-ring checking was determined by observing the checks using various microscopy techniques. Scanning electron microscopy confirmed that checking was as an intercell failure that usually occurs at the cm1/S1 boundary. A comparative study was also conducted to see if the checked wood had some inherent properties that made it more susceptible to checking. It was found that checking could be influenced by tracheid geometry and cell wall thickness. If the wood had large tracheids with thin walls, it was more likely to develop checks during drying. Lignin distribution in the cell wall layers was also seen to play an important role in checking. Lower lignin levels and disruption in the pattern of lignification of the cell wall layers increased the tendency of the wood to develop checks. Similarly, it the tracheids have larger pits then their tendency to check increases. Structural features that disrupt the uniformity of the interlocking pattern of the tracheid such as rays and resin canals could also play a role in checking. Checked wood tends to have more surface area occupied by ray tissue. However, resin canals do not seem to be directly involved in checking, though their arrangement could indicate disturbances during xylogenesis. The second step was to understand the process of xylogenesis in Pinus radiata especially with respect to the influence of auxin and boron on it. Nutrient and organ culture methods were manipulated and successfully used to study xylogenesis. An exhaustive comparative study was carried out to observe and measure selected wood properties. Microscopy and image analysis revealed that auxin and boron changes in the medium led to the alterations in the cell division, expansion and lignification. However, the analysis of the measurements and the observations displayed complex 'between-tree' and 'within-culture variations'. Clear trends did not emerge from the analysis hence, a confident conclusion on the association between auxin, boron and lignification could not be drawn from this organ culture study. The study has added to the knowledge about checking and wood properties associated with it. A new tool of organ culture had been established that can hlep future research on the process of xylogenesis in Pinus radiata.

Os inseticidas neonicotinóides são atualmente o principal grupo químico utilizado para o controle de insetos sugadores, constituindo-se uma boa opção para o controle de Diaphorina citri Kuwayama. Outra opção de controle do psilídeo tem sido a exploração do parasitóide Tamarixia radiata (Waterson). A compatibilidade dessas duas estratégias de controle poderia auxiliar na implementação de programas de manejo integrado de pragas na cultura do citros. No entanto, faltam estudos sobre a caracterização da suscetibilidade de D. citri para os inseticidas neonicotinóides e o impacto desses inseticidas sobre T. radiata. Sendo assim, os objetivos do trabalho foram o de caracterizar a suscetibilidade de D. citri a inseticidas neonicotinóides, realizar o monitoramento da suscetibilidade a esses inseticidas em populações de D. citri coletadas em pomares de diferentes regiões do Estado de São Paulo e avaliar os efeitos letais e subletais desses inseticidas sobre o parasitóide T. radiata. Os inseticidas avaliados foram: thiamethoxam, thiacloprid e imidacloprid. O método de bioensaio adotado foi o de contato residual para a caracterização da suscetibilidade de D.citri a esses inseticidas. O monitoramento da suscetibilidade a esses inseticidas em diferentes populações de D. citri foi realizado com concentrações diagnósticas baseadas na concentração letal 95 (CL95) de cada inseticida. Para avaliar os efeitos letais e subletais desses inseticidas sobre T. radiata foram realizados bioensaios de contato direto em adultos e pupas, toxicidade residual em adultos, e persistência da atividade biológica desses inseticidas sobre a superfície de folhas de citros. Entre os neonicotinóides testados, a maior toxicidade a D. citri foi observado com thiametoxam, seguidos por imidacloprid e thiaclopid. Os resultados do monitoramento apresentaram diferenças significativas na suscetibilidade das populações de D. citri aos inseticidas neonicotinóides. Para thiamethoxam, a sobrevivência estimada para as populações de D. citri testadas na concentração diagnóstica variou entre 5,5 e 16%, para thiacloprid variou entre 4,5 e 22,5 % e para imidacloprid entre 4 e 14%. Uma alta toxicidade desses inseticidas foi observada para adultos e pupas de T. radiata. No entanto, os efeitos subletais desses inseticidas a 10% da concentração recomendada sobre o estágio de pupa causou redução significativa no parasitismo somente com thiamethoxam. A emergência, longevidade e razão sexual de T. radiata não foram afetadas pelos inseticidas avaliados. A toxicidade residual de thiametoxam, thiacloprid e imidaclopid em folhas de mudas de citros foi relativamente elevada para adultos de T. radiata e com persistência de pelo menos 14 dias. / The neonicotinoids insecticides are currently the main chemical group used for controlling sucking pests and represent a good option for the control of Diaphorina citri Kuwayama. Another control alternative of this pest is the exploitation of parasitoid Tamarixia radiata (Waterson). The compatibility of these control strategies could be very helpful for the implementation of integrated pest management program in citrus. However, there are few studies on the characterization of the susceptibility of D. citri to neonicotinoid insecticides and the evaluation of the impact of these insecticides on T. radiata. Therefore, the objectives of this research were to evaluate the susceptibility of D. citri to neonicotinoid insecticides, to monitor the susceptibility to these insecticides in D. citri populations collected from different citrus groves in the State of São Paulo, and to evaluate the lethal and sublethal effects of these insecticides on T. radiata. The insecticides evaluated in this study were: thiamethoxam, thiacloprid e imidacloprid. A residual contact bioassay was used to characterize the susceptibility of D. citri to these insecticides. A diagnostic concentration bioassays based on lethal concentration 95 (LC95) of each insecticide were used for monitoring the susceptibility of D. citri populations. The lethal and sublethal effects of these insecticides on T. radiata were conducted by using direct contact bioassays on adult and pupal stages of T. radiata, residual contact bioassays and persistence of biological activity of these insecticides on citrus leaf surface. Among the neonicotinoid insecticides tested, the highest toxicity was observed with thiametoxam, followed by imidacloprid and thiaclopid. A significant difference in the susceptitibity to neonicotinoid insecticides was detected in D. citri populations. For thiamethoxam, the survivorship at diagnostic concentration varied from 5.5 to 16%, for thiacloprid varied from 4.5 to 22.5 %, and for imidacloprid from 4 to 14%. The toxicity of these insecticides was high to adult and pupal stages of T. radiata. However, the sublethal effects of these insecticides at 10% of the recommended rate on pupae stage caused the reduction of the parasitism capacity only with thiamethoxam. The emergence, longevity and sexual ratio of T. radiata were not affected by any insecticide tested. The residual toxicity of thiametoxam, thiacloprid and imidaclopid sprayed on citrus seedling leaves was relatively high to D. citri adults and lasted at least 14 days.

Needle-to-stem unit rate (NESTUR) is a stem growth index of conifer seedling trees that measures the efficiency of stemwood production per unit of needle growth. Five experiments were carried out in this thesis using progenies of two unrelated full-sib radiata pine crosses. The initial experiment (experiment 1) applied the bulked segregant analysis technique to determine whether RAPD analysis could be successfully extended to the development of molecular markers for NESTUR in radiata pine. The NESTUR values of 174 progenies of the full-sib family 12038 x 10946 were determined. Based on the genotypic analysis of the individuals, two quantitative trait loci (QTL) controlling NESTUR were identified at ANOVA P-levels of 0.01-0.001. An absence of RAPD fragment markers generated by primers OPE-06 and OPA-10 was associated with low NESTUR values, while primer UBC-333 generated a 550 bp band that was associated with high NESTUR values. Linkage to components of NESTUR (increments in stem diameter and stem volume) was demonstrated for one of the QTL, while the other was unique to NESTUR, and not shared with the components. There was a significant interaction between the two QTLs. Presence of OPA-101200 locus appeared to inhibit expression of the QTL linked to UBC-333 [subscript 550]. ¶ To further analyse the quantitative trait loci (QTLs) controlling NESTUR, a linkage map was constructed from RAPD markers segregating in 93 haploid progeny of another full sib cross (30040 x 80121) (experiment 2). Two hundred and sixty-two (262) markers were mapped to 14 linkage groups of at least 7 markers, ranging in size from 39 to 183 cM. The 14 linkage groups covered approximately 1511 cM of genetic map distance. ¶ In experiment 3, the linkage map was used to map QTLs controlling NESTUR, as well as increments in seedling stem diameter, volume, and height and needle volume. Altogether, five putative QTLs were detected for NESTUR, with explained variation ranging from 9 to 22%. Of the five QTLs detected, 3 were coincidental with those for stem growth in height, diameter and volume. The two QTL positions that were unique to NESTUR were flanked by QTLs for the component traits. Together, effects of the five QTLs explained 48% of the total phenotypic variation for NESTUR. ¶ Ability of identified markers to predict the phenotype and seedlings with growth potential was assessed in the cross 30040 x 80121, using six RAPD markers associated with NESTUR at ANOVA P-levels of 0.01-0.001 (experiment 4). The correlation between observed NESTUR and predicted values was 0.70. Differences in observed vs. predicted values were not large and did not indicate serious misclassifications, such as classification of an upper ranking individual into the lower group, or vice versa. ¶ Over a two-year growth period, the ability of NESTUR to predict stem growth was strongly affected by seedling age. In contrast, markers linked to NESTUR showed a consistent ability to predict stem growth, irrespective of seedling age. Compared with the top 1% of the original population, seedlings selected for their genotypic values showed a higher stem volume growth of 103% in the first year, and 76% in the second year. ¶ The expression of QTLs for stem volume, stem diameter, height, number of branches, number of whorls, and branches/whorl were compared at 5, 12, and 24 months of age. Two QTLs detected for height showed contrasting expression over two years, one was gradually reduced from LOD of 2.70 to 0.43 and the other increased from 1.12 to 2.45. Compared with the pattern observed for height, LOD scan profiles for diameter and volume showed less temporal change of peaks, suggesting that the genetic control for height growth is probably more unstable than that of diameter. QTLs controlling the phenotype at the time of measurement (ie the final phenotype) showed similar magnitude of effects on that trait's respective increments (or growth rate).

GnRH is a decapeptide hormone, which plays a major role in the process of mammalian reproduction. It is synthesized by the hypothalamus and binds to its cognate receptor on the pituitary, to bring about the release of gonadotropins LH and FSH. The gonadotropin releasing hormone receptor belongs to the family of G-protein coupled receptors that are characterized by the presence of seven putative transmembrane regions linked by extracellular and intracellular loops. It is a glycoprotein made up of 327 amino acids. During the last several years cloning of this receptor from a number of species has provided considerable insight into the molecular basis of interaction between GnRH and its receptor. The GnRH receptor has been cloned and sequenced from a large number of mammalian species such as human, sheep, cow, rat, mouse, etc. GnRH receptor is known to be unique among the G protein coupled receptors by virtue of the fact that it lacks a C terminal tail which has been implicated in coupling to G-proteins in several seven transmembrane domain receptors. Other members of this G-protein coupled receptor family such as the Luetinising hormone receptor, Follicle stimulating hormone receptor contain the characteristic cytoplasmic tail of about 68-72 amino acids, which is believed to possess a plasma membrane targeting signal sequence. Mutation studies carried out revealed that this C terminal sequence may be important in membrane trafficking in other G protein coupled receptors, since mutant forms of the receptor were not expressed on the plasma membrane. In many G-protein coupled receptors, part of the cytoplasmic tail is important for desensitization and internalization. However, the GnRH receptor is an exception in that its G protein coupling and desensitization functions are dependent on regions of the GnRH receptor other than the carboxy terminal cytoplasmic domain. It has been well established that binding of GnRH to its cognate receptor induces conformational change and it is suggested that the entire extracellular loop and transmembrane region are involved in binding and signal transduction. It is pertinent to note in this connection, that the use of both polyclonal and monoclonal antibodies has contributed significantly to the understanding of the interactions between ligands and their cognate receptors. Recent studies have established that there are several extrahypothalamic sites of production of GnRH, which include testes, lymphocytes, human placenta, mammary gland etc. Of these the production of GnRH in the human placenta has attracted attention in view of the demonstration that the placental chorionic gonadotropin production (CG) is regulated by placental GnRH. Our laboratory has been investigating the role of GnRH in regulation of Chorionic Gonadotropin (CG) using both in vitro human placental villi system and pregnant bonnet monkey as models. One important and interesting observation that has been made in our studies as well as by several others is that the affinity of the placental GnRH receptor to its ligand is quite low compared to the pituitary receptor. Available evidence indicates that the hypothalamic and the placental GnRH are similar in structure and consequently the difference in the affinity could be attributed to the differences between the pituitary and the placental GnRH receptor. Considering this, it will be ideal and of interest to compare the GnRH receptor from the pituitary and placenta of a species in which both in vitro and in vivo studies can be carried out. For obvious ethical reasons, in vivo studies cannot be carried out with humans. Since very little information is available on the GnRH receptor in non-human primates, as a first step we undertook the task of characterizing the GnRH receptor from the bonnet monkey pituitary and production of antibodies to it, since all the studies carried out so far with antibodies to GnRH receptor have employed antibodies generated to a small stretch of peptide in the extracellular region. Thus the objective of the present study is to clone and express the GnRH receptor from the pituitary of the bonnet monkey {Macaco radiata), raise antibodies and to characterize them functionally. Chapter 1 provides a general review of information currently available regarding structure of GnRH and its receptor as well as the results of studies using antibodies directed to the GnRH receptor fragments. Chapter 2 deals with the partial cloning of the GnRH receptor from the pituitary of the bonnet monkeys by the technique of RT-PCR. We were able to amplify a PCR fragment of 959bp corresponding to the almost full-length GnRH receptor sequence. Southern blot analysis using the full length human pituitary GnRH receptor cDNA as the probe revealed that the 959 bp product was able to hybridize to the probe, confirming the authenticity of the PCR product. Restriction mapping with three different restriction enzymes also gave the expected pattern. Additional evidence was obtained by cloning of this PCR product into expression vector pGEX 5X-2 and sequencing a number of clones. The sequences obtained were then subjected to homology search with other known GnRH receptor sequences available in the Genebank. The sequence was found to be 97% homologous to the human pituitary GnRH receptor sequence and also showed a high degree of homology with the GnRH receptor from other species. Although antibodies have been raised to the GnRH receptor by immunizing rabbits with synthetic peptides corresponding to extracellular regions of the receptor, most of the antibodies have a very low affinity towards the native receptor. Also results of studies using these antibodies indicated that the peptide antibodies failed to recognize the native receptor. Initially we made efforts to express the full-length receptor in E.coli BL21 cells. However, since we were not successful in our attempts to express the full length, we resorted to express a smaller fragment which corresponded to amino acids 164-266, that encompassed one extracellular, two transmembrane and one intracellular domain. Before we proceeded ahead to express this fragment, the authenticity of this fragment was established by southern hybridization, restriction mapping as well as sequencing. This monkey pituitary GnRH receptor fragment corresponding to 315 bp was cloned in the expression vector pGEX 5X-2 and the protein corresponding to this region was overexpressed as a recombinant fusion protein in E.coli. BL21 plys S strain. Overexpression of the protein was induced using IPTG and the lysate was subjected to electrophoresis on a SDS-PAGE gel A signal corresponding to 37Kda, which is in agreement with the expected size (GST portion of the fusion protein plus the peptide) was observed following induction with IPTG. The overexpressed protein was found to be localized to the inclusion bodies, and this was purified from inclusion bodies by cutting out the band corresponding to the overexpressed protein from the preparative SDS-PAGE gels and the protein was eluted out by electroelution. Sera from the rabbits, which were immunized with the overexpressed protein, were checked for the presence of antibodies by ELISA, using the purified protein as the antigen. After ascertaining the presence of high titre antibodies in the sera of immunized animals, the serum was used to detect the presence of GnRH receptor in the membrane preparations from rat pituitary, monkey pituitary and human placenta using the technique of western blotting. A signal corresponding to 68Kda was found in all the cases and the specificity of this signal was established by preabsorption of the antisemrn with pituitary and placental membrane preparations, which resulted in decrease in the intensity of the signal. . The antiserum was also used to localize the GnRH receptor in different tissues such as first trimester and term human placenta, sheep pituitary, monkey placenta, human pituitary and rat prostate by the technique of immunotlourescence using the confocal microscope. The results of the above studies are presented in Chapter 3. Chapter 4 deals with the functional studies carried out using the antiserum to GnRH receptor in an in vivo system using male and female rats. As discussed earlier, all the reported studies on use of antibodies to GnRH receptor have employed a small region of the extracellular portion of the receptor for the production of antibodies. However, the antibodies in the present study have been directed towards a larger fragment, and considering this, it was of interest to evaluate the effect of these antibodies in in vivo as well as in vitro systems. Two approaches were used to evaluate the effect of antibodies, namely passive and active immunization i.e. administration of antiserum to GnRH receptor fragment raised in rabbits and also immunization with the overexpressed recombinant GnRH receptor protein. This study was carried out in both immature as well as adult male rats and also in the cycling female rats. Several parameters were monitored, which included various androgen dependent parameters in the male reproductive tissue i.e. body weight, testes weight as well as the weight of accessory sex organ-the prostate and also the fertility status. In the female rats the changes in the weight of the ovary, uterus, serum E2 and P4 were monitored. No effect on the body weight, testis weight or prostate weight was noticed in the treated animals compared to the controls. Furthermore, an indication that the hypothalamo-pituitary-gonadal axis was not compromised in the passively immunized animals was obtained from the observation that there was no decrease in the serum and testicular testosterone levels. In fact, there was a significant increase in the serum and testicular testosterone levels. This suggested the possibility that the antibodies are exerting a ßßstimulatory effect. To ascertain this possibility, two androgen dependent parameters namely the levels of mRNA for TGF ß, which is androgen repressed gene and Prostatein Cl, which is an androgen induced gene were monitored. It was observed that there was a significant increase in the steady state mRNA level of Prostatein Cl in GnRH antiserum treated animals and a corresponding decrease in TGFß mRNA levels. Active immunization study with injection of the recombinant protein was also carried out in adult male rats. All immunized animals responded to the immunization by producing high titre antibodies, the presence of which was detected by ELISA using the recombinant protein as the antigen. The results of the study revealed that there was no change in the body weight, testis weight or prostate weight. However, there was a significant increase in the serum and testicular testosterone levels compared to the control animals. Fertility studies indicated that all the animals were fertile. However, as in the case of passive immunization studies, an increase in the mRNA levels of Prostatein Cl was noted although the level of TGFß, which is an androgen repressed gene could not be monitored in this case due to the very high levels of endogenous androgens present in these animals. Thus it appears that the antibodies produced both in rabbits as well as in rats were stimulatory in nature probably indicating some specific characteristic of the region of the receptor to which the antibody has been raised. The results obtained in the present study are of significance considering the fact that studies using the antibodies to LH receptor and TSH receptor, both of which belong to the G-protein coupled family also report production of stimulatory antibodies. Active immunization studies using the GnRH receptor protein in the female rats also revealed that the antibodies were not compromising the hypothalamo-pituitary-gonadal axis. Accordingly, there was no decrease in the serum or ovarian levels of estradiol 17ß and progesterone and there was no difference in the ovarian weight. However, a significant decrease in the uterine weight and difference in the histology of the uterus of the immunized animals was observed. This is of significance, considering the fact that the presence of the GnRH receptor has been reported in the uterus also. In an attempt to develop an in vitro system to monitor the effect of GnRH receptor antibody, an in vitro incubation system with the human placental villi, which is known to produce both GnRH and hCG was standardized. Sensitive ELISA and RIA were developed for GnRH and hCG, respectively to monitor their levels.The results of the studies on the effect of addition of GnRH receptor antibody to the immunoreactive hCG levels in the placental incubation medium are presented in Chapter 5. In addition, advantage was taken of the report of the presence of the specific receptors for GnRH in the Leydig cells of the rats, to evaluate the effect of the GnRH receptor antibodies on the function of leydig cells. Results of studies in which the effect of addition of GnRH receptor antibodies on the testosterone production by purified rat Leydig cells were monitored revealed that there was no inhibitory effect. Finally in the Chapter 6, a general discussion and critical evaluation of the results obtained in the study, in light of similar studies reported in literature are presented.

This thesis studied the influence of moisture content on the dynamic estimation of stiffness in wood of Pinus radiata D. Don. This is an important non-destructive measure for estimation of stiffness in standing trees, logs and lumber. Moisture content affects both acoustic velocity and density in the fundamental equation of dynamic MOE (DMOE = V²ρ, where V = acoustic velocity and ρ = density). Investigation included measurements with boards in the laboratory considering moisture contents below and above FSP as well as temperatures below and above 0°C. This also included field measurements of trees in contrasting climate sites and over different seasons including a long drought. Methods for measuring green density and moisture content and the patterns of variation of these parameters were also investigated. A secondary component of this thesis explored the wood quality and some mechanisms of tree response to water stress in two contrasting sites in terms or rainfall and water deficits in a region of Australia. The large increases in DMOE for frozen wood above the FSP (4.5 to 6 GPa) will limit the use of DMOE for grading logs in regions with freezing winters. Results from the experiment remeasuring young trees and the upper range of moisture content and temperatures above 0°C from the experiment with boards showed small to moderate variation in DMOE (0.1 to 1 GPa) which calls for further investigation on analytical procedures for adjustment of DMOE. Such procedures should consider that variations in acoustic velocity and density with changes in moisture content are not proportional and that there are counteracting effects between the two parameters. It remains to be investigated whether the typical variation (under normal climate conditions) in sapwood green density observed in our experiments has some implications for the use of DMOE. On the other hand, it is anticipated that the large differences along the stem and among stands in whole-section green density may bias DMOE measurements in logs for resource assessment. This also needs to be investigated. A comparison between acoustic velocity alone and DMOE for resource assessment under different scenarios is recommended. The study in two contrasting climate sites (high-altitude vs. warm-dry) in the Hume region of Forests NSW, Australia, including young (10-11 years) and mature trees (34 36 years) of radiata pine showed distinctive short and long-term responses of trees to cope with the water-limiting environment. In response to long-term water deficits the warm-dry site developed heartwood and thus reduced sapwood earlier and at faster rates than the high-altitude site. The onset of heartwood formation seemed to be triggered by some site threshold for water use as broadly indicated by the sapwood area/ha. The latter was consistently lower for the warm-dry site across the different stands. The warm-dry site also showed increased short-term responses to water stress and these were interpreted as seasonal mechanisms of the trees to cope with the limiting environment. The trees compensated for the lower available moisture and higher transpiration rates by lowering their saturation and disrupting water conduction at some points (cavitation). The inverse trends of cavitation spots and cavitation bands with height in the stem suggested the trees have different strategies to sacrifice conducting xylem depending on the position on the stem. Finally, it is suggested that saturation tended to fall to critical 'safe' levels as a result of water stress and this varied depending on age, site, and position in the stem. Significant decreases in DMOE and basic density were observed for the warm-dry site and were attributed to lower proportions of latewood due to lower rainfall for that site during the period of latewood formation. These showed no obvious association with any of the long-term water-stress traits (sapwood percentage and number of heartwood rings).

The introduction and establishment of a new and markedly different environment within a long established natural system provides an excellent opportunity to study the principles of adaptation and colonisation by native species. In Australia, an example is furnished by the conversion of large areas of native eucalypt forests to mono-cultured plantations of Monterey Pine (Pinus radiata). The principal aim of this study was to assess which species of native mammals, birds and higher plants are able to utilise or occupy such plantations. Successional aspects of community structure, and colonisation in pine forest systems, were investigated by considering stands of different ages. A variety of adjacent native eucalypt forests provided controls and indicated the range of potential colonisers. Various habitats in both forest types were studied with regard to potential nest sites and availability of food, in order to determine those habitats most favourable for mammals and birds. The effect, on wildlife, of clearing eucalypt forests, but leaving forest remnants along gullies, was also assessed.

Pinus radiata is the dominant species of the plantations forests in New Zealand. The forest industry in New Zealand is heavily dependant on it. However, Pinus radiata can develop wood quality flaw called 'intra-ring checking'. The checks or splits appear in wood during kiln drying and usually affect the earlywood region of the wood. It lowers value of appearance grade timber leading to huge economic loses for the forest industry. This thesis presents a study that was undertaken as a part of ongoing collaborative work that is being carried out to understand wood quality issues in Pinus radiata, with a vision of improving its wood quality. This study was a part of that effort and was conducted with an aim to gain an insight into intra-ring checking, and the process of xylogenesis in Pinus radiata. The investigations for this study were carried out in two steps. The first step was to understand intra-ring checking. The location of intra-ring checking was determined by observing the checks using various microscopy techniques. Scanning electron microscopy confirmed that checking was as an intercell failure that usually occurs at the cm1/S1 boundary. A comparative study was also conducted to see if the checked wood had some inherent properties that made it more susceptible to checking. It was found that checking could be influenced by tracheid geometry and cell wall thickness. If the wood had large tracheids with thin walls, it was more likely to develop checks during drying. Lignin distribution in the cell wall layers was also seen to play an important role in checking. Lower lignin levels and disruption in the pattern of lignification of the cell wall layers increased the tendency of the wood to develop checks. Similarly, it the tracheids have larger pits then their tendency to check increases. Structural features that disrupt the uniformity of the interlocking pattern of the tracheid such as rays and resin canals could also play a role in checking. Checked wood tends to have more surface area occupied by ray tissue. However, resin canals do not seem to be directly involved in checking, though their arrangement could indicate disturbances during xylogenesis. The second step was to understand the process of xylogenesis in Pinus radiata especially with respect to the influence of auxin and boron on it. Nutrient and organ culture methods were manipulated and successfully used to study xylogenesis. An exhaustive comparative study was carried out to observe and measure selected wood properties. Microscopy and image analysis revealed that auxin and boron changes in the medium led to the alterations in the cell division, expansion and lignification. However, the analysis of the measurements and the observations displayed complex 'between-tree' and 'within-culture variations'. Clear trends did not emerge from the analysis hence, a confident conclusion on the association between auxin, boron and lignification could not be drawn from this organ culture study. The study has added to the knowledge about checking and wood properties associated with it. A new tool of organ culture had been established that can hlep future research on the process of xylogenesis in Pinus radiata.

Ectomycorrhizal colonisation potential of Pinus radiata seedlings inoculated with the commercially available Trichoderma species bio-inoculant, Arbor-Guard™, was investigated in a commercial containerised nursery setting and in a separate glasshouse experiment, which included the co-inoculation of specific ectomycorrhizal fungi. Application of Arbor-Guard™ to Pinus radiata seedlings in a containerised commercial nursery had no significant effect on the ability of the naturally occurring ectomycorrhizal (ECM) fungi to colonise the seedlings. Thelephora terrestris was the dominant ectomycorrhizal species colonising the P. radiata root tips and has been described as a species able to rapidly outcompete other ECM species colonisation, particularly in high organic matter media like that used at the containerised commercial nursery investigated. In a similar experiment run to augment the commercial experiment, specific ECM fungi identified as Rhizopogon roseolus, Suillus luteus, and Rhizopogon villosulus were co-inoculated with Arbor-Guard™ to investigate the effect on the colonisation potential of the respective ECM species in combination with Trichoderma. The treatment effect of the addition of Arbor-Guard™ did not negatively impinge on the ECM species found, or the abundance of ECM root tips colonising the P. radiata seedlings. Ectomycorrhizal species in the Thelephoraceae family were the dominant species found colonising the P. radiata root tips. Of the inoculated ECM, S. luteus was the only detected species colonising the P. radiata root tips but was only found in low abundance. Non-conducive abiotic factors for optimum ECM colonisation were considered the most likely reason for the low colonisation of the inoculated ECM species. Any effect of the unintentional co-inoculation of the wood decaying fungi Hypholoma fasciculare and Lentinula edodes, due to misidentification, with the inoculated ECM species was unable to be resolved in this study. However, it was speculated that H. fasciculare may have had a negative effect on the inoculated ECM species colonisation. In vitro dual culture assays were initiated to investigate the specific interactions between each of the candidate ECM fungi inoculated in the glasshouse experiment when challenged with each of the six Trichoderma isolates in Arbor-Guard™. Both competition for nutrients and/ or space were concluded to be the main antagonistic mechanisms potentially used by five of the Trichoderma isolates against all co-inoculated ECM species and L. edodes. Hypholoma fasciculare was not inhibited by the five Trichoderma isolates, however, one Trichoderma isolate (LU 663) competitively antagonised all inoculated ectomycorrhizal/ saprophytic species before the mycelial fronts converged. Agar diffusible secondary metabolites were speculated to be potential mechanism of antagonism expressed by LU 663 over volatile antibiotics such as 6-pentyl-α-pyrone. No direct correlation could be dervived from the in vitro dual culture assays and what was observed in the containerised in planta results. Overall the results indicated no negative impact of the Trichoderma bio-inoculant Arbor-Guard™ on ectomycorrhizal colonisation of Pinus radiata seedlings in a containerised nursery system.

Thesis (Ph.D.)--University of Western Australia, 2006.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references. Also available on the World Wide Web.