Changes in polyamine concentration associated with aging in Pinus radiata and Prunus persica

Endogenous polyamine concentrations in apical buds of peach (Prunus persica (L.) Batsch cv. 'Hakuho') and monterey pine (Pinus radiata D. Don) seedlings, saplings and mature trees were analyzed by high performance liquid chromatography coupled with fluorescence detection to establish physiological correspondences and disparities between the species. Although there were many differences in polyamine metabolism between peach and monterey pine, several similarities were found. Specifically, in both species, the ratio between concentrations of free polyamines and low molecular-weight polyamine conjugates was greater than and less than unity in juvenile and adult plants, respectively. Free putrescine concentration decreased with age in both species.     

Endogenous polyamine concentrations in juvenile, adult and in vitro reinvigorated hazel

We investigated endogenous polyamine concentrations in leaves from juvenile and mature hazel (Corylus avellana L.) shoots, as well as leaves from shoots obtained by both forced outgrowth and micropropagation of adult tissues. To determine if the observed in vitro reinvigoration was associated with polyamine metabolism, we tested the effect of serial subcultures on polyamine concentrations. Polyamines, mostly free putrescine, were higher in juvenile tissues. Adult tissues micropropagated for 14 subcultures had polyamine concentrations characteristic of juvenile tissues. However, with additional subcultures, total polyamine concentrations decreased. The putrescine to spermidine plus spermine ratio was higher in juvenile and micropropagated tissues than in adult tissues, but decreased in micropropagated tissues after 20 subcultures. This ratio may reflect a balance between vegetative growth and reproductive processes. Thus, an analysis of polyamine concentrations may provide a simple assay for determining the juvenility of plant tissues and, hence, their suitability for micropropagation.     

Genomic DNA methylation-demethylation during aging and reinvigoration of Pinus radiata

In animals, DNA methylation is related to gene silencing during ontogenic development. Little is known about DNA methylation in plants, although occasional changes in the DNA methylation state of specific gene promoters have been reported in angiosperms during some developmental processes. We found large differences in the extent of DNA methylation between meristematic areas of juvenile and mature Pinus radiata D. Don. trees, whereas differences in the extent of DNA methylation between differentiated tissues of juvenile and mature trees were small. In meristematic areas, there was a gradual decrease in extent of DNA methylation as the degree of reinvigoration increased. The observed changes in extent of DNA methylation during aging and reinvigoration indicate that reinvigoration could be a consequence of epigenetic modifications opposite in direction to those that occur during aging.     

Evaluation of the Hitman PH330 acoustic assessment system for harvesters

Reductions in Pinus radiata D. Don. (radiata pine) clearfell age have increased the juvenile wood proportion in sawlogs, increasing the need to segregate low modulus of elasticity (MOE) material early in the supply chain to avoid the costly processing of low-value, non-structural boards. In Australian radiata pine plantations, variability in MOE is greater between trees than between stands, requiring tests of individual trees to identify those with low MOE. Time of flight of a sound wave in a tree or log is known to be well-correlated to its MOE. The trial examined the ability of a newly developed acoustic assessment tool, the Hitman PH330 (PH330) supplied by Fibre-gen Limited, fitted to a harvester head, to identify and segregate low MOE sawlogs during a cut-to-length harvesting operation in a radiata pine plantation. The impact of using the tool on the harvester’s productivity was also examined. There was a reduction in the mean productivity of the harvester when using the PH330 compared with normal operations not using the PH330 but it was not significant. Mechanical MOE testing showed that boards cut from sawlogs which the PH330 identified as structural, had significantly greater mean MOE than boards from non-structural sawlogs, demonstrating the PH330 was able to separate high and low MOE sawlogs.     

Effects of foliar potassium concentration on morphology, ultrastructure and polyamine concentrations of Scots pine needles

We examined the effects of three foliar potassium concentrations (high, intermediate and low) on the morphology, ultrastructure and polyamine concentrations of current-year and 1- and 2-year-old needles of 30-year-old Scots pine (Pinus sylvestris L.) trees. Foliar K concentration had only a slight effect on needle morphology. The sclerenchyma cell walls were thinner, the xylem area was larger, and the resin ducts were smaller in needles with a low K concentration than in needles with a high or intermediate K concentration. In addition, the bundle sheath cells were collapsed in needles having a low K concentration. The secondary growth of phloem tissue and the mesophyll area were greater in needles with a high or intermediate K concentration than in needles with a low K concentration, possibly indicating greater production of photoassimilates in these trees. At the ultrastructural level, mesophyll cells with enlarged central vacuoles and small vacuoles containing electron-dense material were common in needles having a low K concentration. Enlargement of the central vacuole coincided with an exponential increase in putrescine concentration in needles with a low K concentration, suggesting that the central vacuole may function as a storage site for putrescine.     

Role of polyamines in peach fruit development and storage

To investigate the role of polyamines in pre- and post-harvest fruit development of 'Akatsuki' peach (Prunus persica (L.) Batsch.) we measured polyamine concentrations, activities of polyamine biosynthetic enzymes and expression of genes encoding these enzymes. Concentrations of the free polyamines, putrescine (Put), spermidine (Spd) and spermine (Spm) in pre-harvest fruit peaked 16 days after full bloom (DAF) and then progressively decreased until harvest with the exception of Put, which showed a second peak at 94 DAF, just before the onset of ethylene production. In post-harvest fruit, minor changes in concentrations of Spd and Spm were observed, whereas Put concentration peaked on the harvest day, followed by an abrupt decrease and a subsequent 2-fold increase, which was opposite to the fluctuating pattern of ethylene production. Activities of arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) peaked during the first stage of fruit development and then decreased until 80 DAF, after which the activities were below detection limits, suggesting that Put is synthesized during the early stage of fruit development. Activity of S-adenosylmethionine decarboxylase (SAMDC) decreased progressively until the end of S2. Expression levels of five putative polyamine biosynthetic genes, ADC, ODC, SAMDC, spermidine synthase (SPDS) and spermine synthase (SPMS), in pre-harvest and post-harvest fruit did not coincide precisely with the observed changes in enzymatic activities and polyamine concentrations. The possible role of polyamines during peach fruit development and the relationship between polyamines and ethylene biosynthesis are discussed.     

Radial modulus of rupture in radiata pine measured by individual rings

New equipment was developed to measure the strength of individual annual rings in green wood under predominantly tensile stress. This equipment was then used to assess the variation of the radial modulus of rupture (rMOR) in thirty-six 25-year-old radiata pine trees taken from three sites in New Zealand. The rMOR for individual rings ranged from 4.2 to 12.7 MPa and was calculated on the assumption that during bending of the specimens fracture was caused by the tensile force in the radial direction (i.e., perpendicular to the tangential-longitudinal plane). No consistent trends were observed in rMOR from pith to bark; nor was there any evidence of differences between the three sites. However, there was substantial between-tree variability that manifested mainly in different average rMOR values for the trees rather than in variations from pith to bark. These results indicate that there are no concerns with respect to splitting resistance for the juvenile wood of radiata pine. It will be of interest to investigate whether splitting resistance is under genetic control.     

Free amino acid and protein levels,and γ‐glutamyltransferase activity in Pinus sylvestris apical buds and shoots during the growing season

Free amino acid and protein levels, and γ‐glutamyltransferase activity in apical buds and shoots of Scots pine during the growing season. The aim of the study was to obtain the basic information about nitrogen mobilization needed in carrying out studies on the optimal nitrate and ammonium ratios in the metabolism of Scots pine (Pinus sylvestris L.). Considerable seasonal changes in the concentrations of free amino acids and other ninhydrin‐positive low molecular‐weight compounds were observed in the buds and shoots of Scots pine. 43 different amino compounds were identified, the concentrations of arginine, glutamine, glutamic acid, γ‐aminobutyric acid, alanine and aspartic acid being highest at the break of dormancy. The amounts of certain amino compounds decreased during the growing season, those of arginine, ethanolamine and various ammonium compounds in particular. The amount of glutamic and aspartic acids, glycine, alanine and γ‐aminobutyric acid, however, remained relatively constant. The protein concentration and the specific activity of γ‐glutamyltransferase increased towards the end of the growing period. Slight differences were found between the fertilized trees and the control trees.     

Needle polyamine concentrations and potassium nutrition in Scots pine

The response of free polyamines (putrescine, spermidine and spermine) in needles of Scots pine (Pinus sylvestris L.) to varying needle potassium concentrations was investigated in two potassium fertilization experiments on drained peatlands. A significant negative correlation was observed between putrescine and potassium concentrations in needles. Putrescine responded more sensitively to decreasing needle K concentrations during the growing season than during the winter. Putrescine accumulation started when needle potassium concentrations were above 5.5 mg g(dw) (-1) in summer and above 5.0 mg g(dw) (-1) in winter. A decrease in needle potassium concentrations below 4.3 mg g(dw) (-1) in summer and below 3.5 mg g(dw) (-1) in winter resulted in an exponential increase in putrescine concentrations. Putrescine accumulation was initiated well above the needle potassium concentrations generally considered indicative of deficiency. The exponential increase in putrescine concentrations in winter occurred within the range of needle potassium concentrations that has been identified as indicating severe potassium deficiency.     

Effects of exogenous diamines on the interaction between ectomycorrhizal fungi and adventitious root formation in Scots pine in vitro

Production of free and conjugated polyamines by two ectomycorrhizal fungi, Pisolithus tinctorius (Pers.) Coker and Couch and Paxillus involutus (Batsch) Fr., was studied in vitro. Spermidine was the main polyamine in the mycelium of both fungi. Paxillus involutus also produced large amounts of the diamine putrescine, whereas Pisolithus tinctorius contained traces of the diamine cadaverine and released into the culture medium an unknown compound probably related to cadaverine or N-methylputrescine. Both fungi accelerated adventitious root formation and increased subsequent root growth of Scots pine (Pinus sylvestris L.) hypocotyl cuttings in vitro. Exogenous cadaverine enhanced rooting caused by Pisolithus tinctorius and also promoted mycorrhiza formation by the fungus. Putrescine and Paxillus involutus had a synergistic effect on root initiation, but not on subsequent root growth. We conclude that specific diamines may be involved in the interaction between ectomycorrhizal fungi and adventitious root formation in Scots pine, and that the effects of specific exogenous polyamines are dependent on the fungal strain and its ability to produce these compounds. The finding that Paxillus involutus enhanced rooting and root growth without mycorrhiza formation indicates that fungal-induced rooting is not necessarily related to visible mycorrhiza formation.     

Seasonal changes in amino acids, protein and total nitrogen in needles of fertilized Scots pine trees

Seasonal changes in amino acids, protein and total nitrogen in needles of 30-year-old, fertilized Scots pine (Pinus sylvestris L.) trees growing in Northern Sweden were investigated over two years in field experiments. The studied plots had been fertilized annually for 17 years with (i) a high level of N, (ii) a medium level of N, or (iii) a medium level of N, P and K. Trees growing on unfertilized plots served as controls. In control trees, glutamine, glutamic acid, gamma-aminobutyric acid, aspartic acid and proline represented 50-70% of the total free amino acids determined. Arginine was present only in low concentrations in control trees throughout the year, but it was usually the most abundant amino acid in fertilized trees. Glutamine concentrations were high during the spring and summer in both years of study, whereas proline concentrations were high in the spring but otherwise low throughout the year. In the first year of study, glutamic acid concentrations were high during the spring and summer, whereas gamma-aminobutyric acid was present in high concentrations during the winter months. This pattern was less pronounced in the second year of investigation. The concentrations of most amino acids, except glutamic acid, increased in response to fertilization. Nitrogen fertilization increased the foliar concentration of arginine from < 1 micromol g(dw) (-1) in control trees to a maximum of 110 micromol g(dw) (-1). Trees fertilized with nitrogen, phosphorus and potassium had significantly lower arginine concentrations than trees fertilized with the same amount of nitrogen only. Protein concentrations were similar in all fertilized trees but higher than those in control trees. For all treatments, protein concentrations were high in winter and at a minimum in early spring. In summer, the protein concentration remained almost constant except for a temporary decrease which coincided with the expansion of new shoots. Apart from arginine, the amino acid composition of proteins was similar in all treatments.     

Effectiveness of mycorrhizal inoculation in the nursery on growth and water relations of Pinus radiata in different water regimes

We compared the performance of mycorrhiza-inoculated and non-inoculated radiata pine (Pinus radiata D. Don) seedlings in two field studies. In the first study, above ground growth of 2-year-old container-grown trees was compared after planting in two areas that differed in water availability. Mycorrhizal inoculation significantly improved above ground growth in the 2 years after planting in both areas, especially at the drier site. In the second study, the influence of Rhizopogon roseolus (Corda ex Sturm) Th. Fries and Scleroderma citrinum Pers. on xylem water potential and hydraulic conductance at the soil-root interface of trees established at the same sites was assessed. Nursery inoculations with R. roseolus and S. citrinum improved tree growth during the first 2 years after field outplanting, particularly at the drier site.     

Juvenile radiata pine clonal seed orchard management in Galicia (NW Spain)

A juvenile radiata pine clonal seed orchard (Pinus radiata D. Don) in Sergude (northwestern Spain), comprising 57 clones, was evaluated for fertility, offspring diversity and genetic drift during 4 years. Flower and fruit production was used to asses clone fertility in the orchard. Fertility variation measured as “sibling coefficient” was found to be an average of 1.5, having high genetic diversity (0.99) and low coancestry (0.013). The clones varied in fertility from year to year. Effective population size in the orchard was between 35 and 40, indicating that between 60.30 and 69 %, the clones contributed effectively to seed yield. One way to improve seed yield in the orchard is by increasing the effective population size. Thinning and pruning highly reproductive clones of gibberellin application might be useful in increasing effective population size. The orchard’s parental balance showed consistent improvement over time. Cone and seed characteristics were also investigated. The results showed that significant genetic variation exists among clones for cone width and length; total, sound and empty seed number; as well as 100 seed weight. The seed orchard is still in a juvenile phase; moreover, the broad-sense heritability and variation data obtained in this study could be very valuable in the management practices of the existing radiata pine clonal seed orchard and can be also used for better planning of advanced generation of clonal seed orchards in Spain.     

多胺在植物抗逆中的生理机制

多胺（PAs）是一类低分子量、聚阳离子、脂肪族含氮物质,是植物对逆境响应的重要物质。国内外众多研究表明,在逆境胁迫下,植物体内不同类型的PAs,例如腐胺（Put）、亚精胺（Spd）、精胺（Spm）的含量会发生变化,外源PAs会对植物的抗逆性产生不同的影响。但多胺的研究对象多集中在农作物,对木本植物的研究较少。PAs对植物抗逆的作用机制较为复杂,不同种类的多胺对植物的抗逆影响不同,PAs的代谢与参与逆境胁迫的其他代谢密切相关。文中主要综述PAs在植物抗干旱、低氧、高温、低温、盐、重金属过程中的变化及生理作用机制,以期为开展PAs与抗逆林木研究、栽培与抗逆育种研究提供参考。     

Heat-shock response of Pinus and Picea seedlings

The effect of a short period of elevated temperature, or heat shock, on protein synthesis was investigated in 2-day-old seedlings of jack pine (Pinus banksiana Lamb.), loblolly pine (P. taeda L.), lodgepole pine (P. contorta Dougl.), black spruce (Picea mariana (Mill.) BSP), and white spruce (P. glauca (Moench) Voss.). In all species, heat shock led to increased [(35)S]methionine incorporation into heat-shock proteins (hsp's) with molecular masses of 83 and 72 kDA. Heat shock also induced synthesis of several low molecular weight proteins that were absent from control seedlings. The low molecular weight hsp's produced by pine seedlings had molecular masses of 27, 24.6, 20.5 and 17.5 kDa, whereas those produced by spruce seedlings had molecular masses of 27.2, 19.8, 18.4, 17.2 and 16.0 kDa. All of the low molecular weight hsp's showed isoelectric variants. Heat shock led to increased [(35)S]methionine incorporation into a group of low molecular weight hsp's that were also present in control seedlings.     

Polyamines in embryogenic cultures of Norway spruce (Picea abies) and red spruce (Picea rubens)

Embryogenic cultures of red spruce (Picea rubens Sarg.) and Norway spruce (Picea abies (L.) Karst.) were initiated from dissected mature zygotic embryos. The tissues were grown on either proliferation medium or maturation medium. On proliferation medium, the embryogenic tissue continued to produce early stage somatic embryos (organized meristems attached to elongated, suspensor-like cells), whereas on maturation medium fully mature embryos developed from the embryonic tissue. Analysis of polyamines in tissues grown on these two media showed that: (1) both putrescine and spermidine concentrations were always higher in cultures grown on proliferation medium than in cultures grown on maturation medium; (2) in both species, spermidine concentrations declined with time in the tissues grown on maturation medium; and (3) spermine was present in only minute quantities and showed only a small change with time. The presence of difluoromethylornithine in the culture medium had little effect on polyamine concentration, whereas the presence of difluoromethylarginine caused a decrease in putrescine concentrations in both red spruce and Norway spruce tissues grown on proliferation medium or maturation medium.     

Growth response of broom (<Emphasis Type="Italic">Cytisus scoparius</Emphasis>) growing with and without radiata pine (<Emphasis Type="Italic">Pinus radiata</Emphasis>) seedlings to different P levels in soils

A study was carried out to test the effects of three rates of TSP (triple superphosphate) (0, 50, and 100 mg·kg -1 P) on growth of broom with and without radiata pine seedlings and to determine the rela- tionships between P concentrations in the broom shoot and dry matter yields with soil plant-available P (Bray-2 P). A bulk sample of soil was collected from Kaweka forest at soil depth of 0 10 cm, in New Zealand on March 11, 2001. The forest area was not supplied with fertiliser at least 30 years. The results show that TSP application increased P avail- ability in the soil. The P availability concentration in soil of broom with radiata pine seedlings was higher than that in soil of broom alone. Bray-2 P concentrations had a significant logarithmic relationship with P con- centrations of broom shoot and an exponential relationship with dry matter weight of whole broom plant.     

Seasonal fluctuations of low‐molecular‐weight sugars,starch and nitrogen in sapwood of Pinus sylvestris L.

The content of water‐soluble substances and starch in the living tree stem at the time of felling influences wood durability during further utilization. The aim of the study was to describe the annual and seasonal fluctuations in the contents of stored carbohydrates and nitrogenous compounds. The contents of soluble sugars, starch, and nitrogen were measured in the outer sapwood (0–15 mm from cambium) of 65‐yr‐old Scots pine {Pinus sylvestris L.) trees during an annual cycle. To study the influence of growth conditions, samples were taken from different stands in Sweden, in one stand from a control and a fertilized block. The effect of the age of the trees on the content of stored substances was also considered by comparing young (10–15 yrs old) and older trees (40–65 yrs old). Determination of the carbohydrates was carried out using enzymatic analysis. The outer pine sapwood contained a higher content of low‐molecular weight sugars during autumn and winter than during spring and summer. Starch content rose at the beginning of the growth period and decreased in autumn. The content of soluble sugars increased towards the cambium on all sampling occasions. Fructose and glucose were dominant sugars in all the stands studied. Seasonal changes of sucrose were different from those of glucose and fructose, in that the sucrose content was already decreasing in February. The variations in the nitrogen content of the sapwood were far smaller than those of the soluble sugars. No significant differences were found between the stands with regard to glucose, fructose and the sum of all three sugars. The fertilized block showed low content of sucrose and nitrogen. It is concluded that seasonal fluctuations are more important with regard to the sugar content than the effect of growth conditions. Data indicate a lower content of soluble sugars and nitrogen in the outermost sapwood of young trees as compared with older trees.     

Effects of low-dose liming and nitrogen fertilization on stemwood growth and needle properties of Picea abies and Pinus sylvestris

Stemwood growth, needle weight and nutrient concentrations in needles after liming and nitrogen fertilization were studied in two randomized block trials. The treatments were a single application of 500 kg lime per hectare, 1000 kg limer per hectare, 150 kg N per hectare and combinations of the two compounds. The trials are situated in the southern part of Sweden on mesic mineral soils. One of the experiments was located in 32–55-year-old highly productive Picea abies stands and the other in a 31-year-old Pinus sylvestris stand.As calculated by growth-ring analysis, liming alone did not significantly affect the growth during a 10-year period following treatment. Nitrogen fertilization increased growth in pine, but not in spruce. Lime in combination with N gave about the same effect in pine as the pure N treatment, whereas lime and N interacted in spruce and resulted in increased stemwood growth.Current-year needles were sampled during the winter, weighed and analysed for nutrient concentrations. In the N-treated plots the N concentration increased in both tree species, whereas the needle weight increased only in pine. In two cases, lower concentrations were indicated. In the first, there was a tendency of decreased N concentrations in spruce needles after liming. In the second, the magnesium concentrations decreased in needles of both species, especially in the treatments that included nitrogen. The concentrations of the measured nutrients were never below levels considered to imply a severe deficiency.     

Differential effects of plant ontogeny and damage type on phloem and foliage monoterpenes in jack pine (Pinus banksiana)

Coniferous trees have both constitutive and inducible defences that deter or kill herbivores and pathogens. We investigated constitutive and induced monoterpene responses of jack pine (Pinus banksiana Lamb.) to a number of damage types: a fungal associate of the mountain pine beetle (Dendroctonus ponderosae Hopkins), Grosmannia clavigera (Robinson-Jeffrey & R.W. Davidson); two phytohormones, methyl jasmonate (MJ) and methyl salicylate (MS); simulated herbivory; and mechanical wounding. We only included the fungal, MJ and mechanical wounding treatments in the field experiments while all treatments were part of the greenhouse studies. We focused on both constitutive and induced responses between juvenile and mature jack pine trees and differences in defences between phloem and needles. We found that phytohormone applications and fungal inoculation resulted in the greatest increase in monoterpenes in both juvenile and mature trees. Additionally, damage types differentially affected the proportions of individual monoterpenes: MJ-treated mature trees had higher myrcene and β-pinene than fungal-inoculated mature trees, while needles of juveniles inoculated with the fungus contained higher limonene than MJ- or MS-treated juveniles. Although the constitutive monoterpenes were higher in the phloem of juveniles than mature jack pine trees, the phloem of mature trees had a much higher magnitude of induction. Further, induced monoterpene concentrations in juveniles were higher in phloem than in needles. There was no difference in monoterpene concentration between phytohormone applications and G. clavigera inoculation in mature trees, while in juvenile trees MJ was different from both G. clavigera and simulated herbivory in needle monoterpenes, but there was no difference between phytohormone applications and simulated herbivory in the phloem.