Exotic pine plantations and indigenous Lepidoptera in Australia

Temperate regions of Australia have extensive commercial plantations of Monterey pine, Pinus radiata D. Don. Replacement of indigenous forests by P. radiata is likely to have significant effects on assemblages of native Lepidoptera, and has been considered a major threat to native fauna through displacing native species. However, many species of Lepidoptera, including ennomine geometrid moths in the genus Chlenias Guenèe, have adopted P. radiata as a larval host. Comparisons were made of oviposition preferences and nutritional ecology of Chlenias auctaria Guenée on P. radiata and two native host plants [Acacia mearnsii De Wild. (Mimosaceae) and Eucalyptus obliqua LHérit (Myrtaceae)]. Females showed no significant oviposition preference for any of the three hosts. Growth of sixth instar larvae was significantly less on P. radiata than on the native hosts. Pupal weights were significantly lower, suggesting that the fitness of moths reared on P. radiata will be significantly reduced. The life history strategy of C. auctaria, which includes dispersal of first instar larvae by ballooning, may predispose this species to feed on poor quality hosts, and this may be common to other polyphagous species found feeding on P. radiata in southern hemisphere plantations. The impact of P. radiata may have a long term effect on lepidopteran communities, beyond the simple replacement of indigenous host plants leading to extirpations of feeding specialists.     

Inferring relatedness and heritability using molecular markers in radiata pine

A set of eight unlinked microsatellite markers was used to estimate relatedness among 355 individuals of a Pinus radiata breeding population. The average performance of open-pollinated progeny of each individual, for wood density, was considered to represent the phenotype of all 355 individuals. Marker-based estimates of relationship were compared with the pedigree-based coefficients of relationships. The phenotypic similarity among all pairs of individuals was regressed on marker-estimated relatedness to estimate the inheritance of wood density. The marker-based estimate of heritability was compared with that obtained using classical quantitative genetic methods. Overall, a low correlation (0.13) was observed between marker-based and pedigree-based estimates of relatedness. After discarding negative estimates of relatedness, the average coefficient of relationship among known groups of maternal half-sibs, full-sibs and unrelated individuals, increased from 0.24 to 0.29 (0.25 expected), from 0.43 to 0.48 (0.50 expected) and from –0.04 to 0.15 (0 expected), respectively. Marker-based and conventional estimates of heritability of wood density were 0.79 and 0.38, respectively. However, by using only marker loci with expected Hardy–Weinberg frequencies, marker-based estimate of heritability was 0.33, which is very similar to that obtained from conventional approaches. The use of molecular markers to understand quantitative genetic variation is discussed.     

Stem deformity inPinus radiata plantations in south-eastern Australia:

Visual symptoms of stem deformity similar to those of Cu deficiency are common inP. radiata established on fertile sites previously used for agricultural production in south-eastern Australia. In this study, Cu fertiliser was applied at rates of 0, 2, 5, 10, 20 and 50 kg ha⁻¹ to deformedP. radiata at ages 3 and 6 years. Available soil Cu and contents of Cu in the foliage increased significantly only in the younger plantation. Cu fertiliser did not affect growth nor did it improve stem form. Levels of N, Cu and Cu/N ratios in foliage of straight and deformed trees were similar. However, contents of Cu in apical buds were significantly lower in deformed trees. It was concluded that stem deformity inP. radiata as observed on these fertile pasture sites, cannot be corrected by application of Cu fertiliser. Differences in Cu levels in apical buds of straight and deformed trees suggest that Cu may still be involved in this syndrome. There was also no indication of other nutrient deficiencies that could be associated with the deformity.     

Pinus radiata D. Don in Chile. Fertilization trials with copper

Summary YoungPinus radiata D. Don were fertilized with copper oxychloride and copper sulfate on a random block basis with four replicates. Roots, needles, stems and shoot apices were analyzed separately for Cu, Fe, Mn and Zn contents at different times from fertilization. The results showed a rapid plant copper absorption, no effects being found on the Fe, Mn and Zn content. The dynamic internal distribution of copper among different plant parts is shown. The treatments applied did not cause any phenotypical alteration nor phytotoxicity in the plants, and no significant effect of the fertilizer chemicals on each other.     

The productivity of pine plantations in relation to previous land use

Summary The improved growth of pine plantations on pasture soils compared with that on soils which previously supported native eucalypt forest is primarily explained in terms of soil phosphorus. Pasture development has resulted in a decrease in the P adsorption maximum of about 300 g g^–1 soil, a figure which agrees with the increase in total P due to the application of superphosphate. P adsorption isotherms were used to calculate additions of P to give comparable levels of soil solution P in eucalypt and pasture soils. The growth of pine seedlings in soils thus amended showed a strong N×P interaction. When P was non-limiting, addition of N raised productivity of the eucalypt soil above that of the pasture soil. It is postulated that the different nature of the N×P interaction in eucalypt and pasture soils results from differences in the nitrogen cycle in the two soils.     

Non-morphogenic metabolism during shoot induction in radiata pine cotyledon explants

Summary The effects of excision, light and cytokinin (N⁶-benzyladenine) on¹⁴C-acetate metabolism in cotyledons ofPinus radiata (D. Don) were determined.¹⁴CO₂ was released and the distribution of radioactivity into lipids, sugars, organic acids and amino acids was determined. While light and cytokinin generally caused some increase in metabolism, the effect of excision, i.e., wounding, was most pronounced. Specific metabolites examined (citrate, malate, succinate, alanine, aspartate, glutamate and glutamine) were at least 50% greater in¹⁴C-labeling in excised cotyledons as compared to intact seedlings. This enhancement of wound metabolism would mask possible morphogenically-related changes occurring at that time. This research was supported by the Natural Sciences and Engineering Research Council of Canada Grant A-6467 to T.A. Thorpe.     

Identification of an agar constituent responsible for hydric control in micropropagation of radiata pine

Tissue cultured Pinus radiata grown on media containing agar as the gelling agent display toxic symptoms and poor long-term shoot survival, however it does have the attribute of hydric control, through a mechanism which, until now, has not been elucidated. Gelrite as an alternative gelling agent is clearly non-toxic but results in hyperhydric (vitrified) tissues. In an effort to overcome these problems, the controlling mechanism found in agar was examined. Hydric control was shown to be effected by a non-gelling, cold-water soluble constituent of a commercial agar, rather than by physical properties of the gel. It could be separated from low molecular weight components of the agar responsible for the toxic symptoms by dialysis. It was identified as being an agaroid-type xylogalactan bearing pyruvate and sulphate substituents. Improved management of gelling agents in culture medium has contributed substantially to a thirty fold increase in propagation rates.     

Short term effects of radiata pine and selected pasture species on soil organic phosphorus mineralisation

Silvopastoral systems comprise part of the continued expansion of conifer plantings on grassland in New Zealand. Greater understanding of the short term dynamics of soil organic P in such systems will further our knowledge about soil carbon and phosphorus relationships which will enable improved nutrient management in the field. A glasshouse experiment was carried out to examine the short-term effects (36 weeks) of combinations of radiata pine (Pinus radiata), lucerne (Medicago sativa L.) and perennial ryegrass (Lolium perenne L.) grown in the same soil type with a range of carbon (C) and phosphorus (P) levels on plant P uptake and the specific mineralisation rate (SMR). The SMR is defined as net mineralisation rate (i.e. gross mineralisation less microbial and geochemical uptake) and calculated from organic P decline as a percentage of organic P in the original soil before planting. This included an investigation of the effect of tree ectomycorrhizal (EM) hyphae on soil organic P. Plant P uptake was positively correlated with water soluble organic carbon (WSOC) and SMR, which in turn was closely related to soil C levels. The soils with high WSOC and C levels (which also contained high levels of labile inorganic and organic P) enabled high P uptake. Although P uptake was the greatest under radiata pine, the trees tended to deplete inorganic P to a lesser extent than the forages. When tree and forage species were combined, P uptake by forages was similar to when the forages were grown alone. The various soil and plant treatments significantly affected SMR. The two low C soils, showed the greatest organic P mineralisation while a high C soil, which contained significant levels of bicarbonate extracted inorganic P at planting and was under a long established undisturbed pasture, showed the least mineralisation. Trees grown alone showed the greatest SMR, EM hyphae and trees with lucerne were slightly lower than trees alone, while the forages showed the lowest SMR. The findings of this study showed that changes in organic P are strongly influenced by interactions between plant species (radiata pine, lucerne, ryegrass) and soil properties as determined by land use and management.     

Testing for linkage disequilibrium in the New Zealand radiata pine breeding population

Linkage analysis is commonly used to find marker-trait associations within the full-sib families of forest tree and other species. Study of marker-trait associations at the population level is termed linkage-disequilibrium (LD) mapping. A female-tester design comprising 200 full-sib families generated by crossing 40 pollen parents with five female parents was used to assess the relationship between the marker-allele frequency classes obtained from parental genotypes at SSR marker loci and the full-sib family performance (average predicted breeding value of two parents) in radiata pine (Pinus radiata D. Don). For alleles (at a marker locus) that showed significant association, the copy number of that allele in the parents was significantly correlated, either positively or negatively, with the full-sib family performance for various economic traits. Regression of parental breeding value on its genotype at marker loci revealed that most of the markers that showed significant association with full-sib family performance were not significantly associated with the parental breeding values. This suggests that over-representation of the female parents in our sample of 200 full-sib families could have biased the process of detecting marker-trait associations. The evidence for the existence of marker-trait LD in the population studied is rather weak and would require further testing. The exact test for genotypic disequilibrium between pairs of linked or unlinked marker loci revealed non-significant LD. Observed genotypic frequencies at several marker loci were significantly different from the expected Hardy-Weinberg equilibrium. The possibilities of utilising marker-trait associations for early selection, among-family selection and selecting parents for the next generation of breeding are also discussed.     

Boron deficiency inPinus radiata D. Don and the effect of applied boron on height growth and nutrient uptake

Summary Severe dieback observed inP. radiata D. Don plantations during dry years in Southeastern Australia was found to be due to boron deficiency. Borax applied in spring (August 1982) at rates of 50, 100 and 150 kg ha^–1 resulted in a marked increase in foliar B and an alleviation of B deficiency symptoms. During the dry summer following the application of borax no further dieback was observed and height growth of fertilized trees was significantly improved. Correction of B deficiency enhanced the uptake of P by the trees.     

Molecular control of early cone development inPinus radiata

Summary A family of genes expressed during early stages of shoot development were isolated fromPinus radiata. A homologue of theLEAFY/FLORICAULA flower meristem-identity genes,NEEDLY (NLY), and three MADS-box genes,PrMADS1, PrMADS2 andPrMADS3 (Pinus radiata MADS-box genes), were expressed at early stages of initiation and differentiation of reproductive (male and female) cone buds, as well as vegetative buds. Expression ofNLY in transgenicArabidopsis thaliana promoted floral fate, demonstrating that it encodes a functional ortholog of theFLORICAUL A/LEAFY genes of angiosperms.Abbreviations DSB dwarf shoot bud - LSTB long-shoot terminal bud - PCB pollen cone bud - SCB seed cone bud - LD long day - SD short day     

Competitive processes in a monoculture of Pinus radiata D. Don

Summary The changes between 9 and 40 years of age of the frequency distribution of tree diameters were studied in an experiment in a plantation of Pinus radiata D. Don in South Australia in which the spacing between trees at planting varied. Empirical functions were developed to relate tree diameter to growth rate in diameter, variance of growth rate in diameter and mortality rate. These functions were used in solving a forward diffusion equation to predict future diameter distributions. The contributions from each of the terms in the diffusion equation were examined and it was found that the drift (growth rate in diameter) term made the greatest contribution to the solution, whilst the diffusion (variance in growth rate) term had neglible effect. This implied that competition between individual trees for light was the dominant competitive process operating in this plantation, rather than below ground competition for soil resources. The ramifications of this finding to forest growth modelling are discussed.     

A method for extraction of total RNA fromPinus radiata and other conifers

Carbohydrates, polyphenolic compounds, terpenoids and tannins interfere with the extraction of intact, uncontaminated total RNA from conifers. A method for extraction of total RNA fromPinus radiata is described. This method uses cesium trifluoroacetate in the ultracentrifugal separation of RNA to overcome the problems of co-purification of contaminating secondary metabolites.     

Testing for unequal paternal contributions using nuclear and chloroplast SSR markers in polycross families of radiata pine

The lack of male pedigree control is the major limitation of an otherwise very useful and cost effective mating design, namely, the polycross. This study was conducted to investigate the relative contribution of different pollen parents to the sound-seeds stage, and also in a field progeny trial. Pollen from 15 radiata pine (Pinus radiata D. Don) parents was mixed in equal volume and applied to the same 15 parents, potentially allowing selfing. Samples of 8-year-old offspring were genotyped from five polycross families, and available seed from three of these five families was tested for unequal paternal contributions. The total paternal exclusion probability of five chloroplast markers and four microsatellite markers in our study was 99.1%. Overall, 81% of the offspring (both seeds and 8-year-old offspring) were assigned to 1 out of the 15 potential male parents, but a surprisingly high proportion (about 13%) was evidently fathered by pollen not included in the pollen-mix. Inconclusive evidence of unequal paternal contribution was observed in some families, but it did not influence the general combining ability (GCA) estimates appreciably, as evident from a high degree of correspondence between GCA estimates obtained from polycross and female-tester mating designs. A non-significant negative correlation was observed between the relative reproductive success (across polycross families) and predicted breeding values for diameter growth.     

Effects of aluminium on growth and cation uptake in seedlings of Eucalyptus mannifera and Pinus radiata

This experiment was designed to examine the effects of aluminium (Al) on the growth of Pinus radiata (D. Don) and Eucalyptus mannifera subsp. mannifera (Mudie) seedlings in culture solutions in a glasshouse to help explain the failure of radiata pine trees on some acid, low fertility soils in Australia on which the native eucalypts flourish. Aluminium (Al) in culture solution increased the growth of roots and shoots of seedlings of both species but while growth of the eucalypt continued to increase with increases in Al to 2.222 μM, growth of the pine was largest at 370 μM Al. In addition to total root length, specific root length (length per unit dry weight), a measure of fineness of the root, increased in the eucalypt seedlings as the substrate Al increased. Growth of the shoots and roots of the pine in the absence of any added Al was extremely poor suggesting that Al, in low concentrations, may be an essential element or ameliorate some other factors in solution culture at low pH. Root and shoot concentrations of K increased with increasing Al, whilst Ca and Mg Concentrations decreased and Mn concentrations were unaffected in both species. Tissue Ca and Mg concentrations were 2 to 3 times higher in the eucalypt seedlings than the pine at all levels of added Al due to greater uptake of these elements by the eucalypt. In contrast, at the highest concentration of Al in the medium, shoot Al concentrations were lower in the cucalypt than in the pine due to a greater proportion of Al being retained in the eucalypt roots. These differences between the seedlings in terms of root growth and tissue cation concentrations may help explain the ability of eucalypt species to maintain vigorous growth on acid soils high in Al and low in Ca and P, where growth of the pines failed.     

Water potential and gas exchange did not reflect performance of Pinus radiata D. Don in an agroforestry system under conditions of soil-water deficit in a temperate environment

In order to understand how radiata pines respond to declining supply of soil-water in agroforestry systems, we monitored water potential in xylem (ψ _x ), osmotic potential (ψ) and relative water content (q) for fascicles at pre-dawn and at mid-day for 3-year-old trees that were raised from either seedlings (Seedling) or from tissue culture (TC3 and TC4), and grown either alone (Control) or over lucerne (Medicago sativa) pasture (Lucerne). Water relations at dawn were mostly similar for all the pines, except late in the season when ψ was lower, bulk turgor pressure (P), deduced as the difference between ψ _x and ψ, was higher, for TC3 than for the other two pines. At mid-day, Seedling often had higher ψ _x and ψ, but because of its poor osmotic adjustment (OA) had lower P, than either TC3 or TC4. The cell walls were more elastic in Seedling with modulus of elasticity (e) of 6.5 MPa compared with 8.1 MPa for both TC3 and TC4, while loss of turgor was estimated to occur at ψ _x of −1.45 MPa for Seedling, −1.38 MPa for TC3 and −1.35 MPa for TC4. All trees irrespective of their origin had higher ψ _x , P, CO₂ assimilation (A), and stomatal conductance (g _s ), but lower ψ, in Control than in Lucerne in which the soil profile was consistently drier. The trends in ψ _x , ψ, q and A did not reflect the known differences in dry weight of trees, P was in the order TC3 > TC4 > Seedling, consistent with previously reported tree weights. Both TC3 and TC4 had higher P, due to their larger OA, than Seedling, although the latter had higher A. Thus ψ _x and A that are routinely measured may not always adequately explain differences in growth amongst pines; it is advisable that ψ be determined to allow deductions of P be made when using water relations to analyse plant growth.     

植物根毛的发生、发育及养分吸收

根毛是植物吸收养分的重要器官,认识根毛的发生、发育规律及其与养分吸收的关系,可为植物养分吸收效率的遗传改良提供依据.介绍了植物根毛的形态特性、发生和发育过程及其调控机制,并结合本实验室的工作,讨论了根毛对养分吸收的贡献、根毛受养分有效性的调节及其与其他根系形态构型性状间的关系,阐述了根毛中养分转运等植物营养过程及其生理和分子生物学基础.最后提出了关于根毛研究中的一些问题和研究前景.     

The origin and genetic diversity of Pinus radiata in Australia

Summary Despite the fact that forest trees are in early stages of domestication there has been little direct evaluation of either the origin of, or genetic diversity within the breeding material in tree improvement programs. Allozyme variation was used to compare the total genetic diversity in the breeding programs of P. radiata within Australia and the five wild populations in North America. The current breeding populations were very similar genetically and were essentially homogenous with only 1.8% of the variation among programs. The total genetic diversity in the species was 0.12, which is a low estimate compared to most conifers. Overall in the Australian material the genetic diversity was somewhat less. The comparison of allelic frequencies in the five native populations with the Australian material indicates that the Monterey and Año Nuevo populations were probably the major source of the original introductions and that a substantial portion of the genetic diversity in the two populations has been captured in current breeding programs. The three southern populations do not appear to be currently represented in the breeding programs. The implications for future breeding strategies are discussed.     

Relationships between stem structure and bending strength in Pinus radiata seedlings

Summary Seedlings from nine families of Pinus radiata were grown in a glasshouse under conditions of high and low nitrate nitrogen availability to investigate effects on anatomical and strength characteristics of stems. Families were classified into groups dependent upon their previously determined susceptibility to stem deformation prevalent in plantations established on fertile ex-pasture. Nitrogen treatments significantly affected seedling form in terms of both branch production and stem slenderness. The high N treatment resulted in shorter seedlings, a proportion of which were obviously stunted. Stem strength of seedlings, physically supported throughout the experiment, was assessed as stem lean at harvest as well as the bending strength of the fresh stem at 50% stem height. These two variables were found not to be correlated. Stem lean at harvest was greatest in families known to be susceptible to stem deformation. These families produced stems that were also more slender than families of low susceptibility. Increased stem lean was associated mostly with increased stem slenderness while elasticity was more influenced by pith diameter, stem density and wood radius.     

Gene silencing studies in the gymnosperm species Pinus radiata

A biolistic transformation procedure was used to transform embryogenic Pinus radiata tissue with constructs containing the Zea mays UBI1 (ubiquitin)-promoter followed by the P. radiata CAD (cinnamyl alcohol dehydrogenase) cDNA in sense or anti-sense orientation or in the form of an inverted-repeat. The effect of the different constructs on silencing the endogenous CAD gene was monitored in embryogenic tissue and somatic seedlings of 28 P. radiata transclones. Quantitative CAD measurements demonstrated that the construct containing an inverted-repeat of the CAD cDNA was most efficient in triggering gene silencing in P. radiata. Northern hybridization experiments with silenced transclones revealed that reduced CAD activities were the result of reduced steady state levels of the targeted CAD mRNA. Monitoring of the activity of the UBI1-promoter in the P. radiata transclones and heat-shock experiments with transgenic somatic P. radiata seedlings indicated that gene silencing is positively correlated with the expression level of the transgene. The obtained data are also consistent with a role for the expression level of the endogenous CAD gene in gene silencing.