Pinus Radiata Seedlings Research Articles

Frost hardening of Pinus radiata seedlings: effects of temperature on relative growth rate, carbon balance and carbohydrate concentration.

Pinus radiata (D. Don) seedlings were grown for 100 days at day/night temperatures of 10/1, 15/1, 20/1 and 25/1 degrees C, to determine whether temperatures above a threshold of 5 degrees C influence frost hardiness development. Relationships between hardening and relative growth rate, carbohydrate concentration and net carbon balance were also investigated. Seedlings hardened at a nearly constant rate in each treatment, although the rate of hardening was strongly temperature dependent. It increased as the temperature declined, but in a curvilinear fashion. Temperatures below 9.5 degrees C were effective in hardening the seedlings. During the daily temperature cycle, dehardening occurred at temperatures above the threshold, whereas hardening occurred at temperatures below the threshold. The net difference between the two processes determined the development of frost hardiness. The development of frost hardiness was negatively correlated with relative growth rate and positively correlated with the accumulation of starch and sugars. We conclude that frost hardening is a complex process that is causally linked to carbohydrate concentrations.

Do genetic improvements in radiata pine seedlings confound their use as indicators of change in soil quality?

In a glasshouse environment, and in field trials with trees up to four years of age, the effect of genetic improvement on the early nutrition and growth of radiata pine was examined. In the glasshouse trial, on a range of forest soils, there was no effect of genetic gain (expressed as growth and form rating) on either seedling biomass or nutrient content; in field experiments, correlations between genetic gain (breeding value and growth and form rating) and growth (height, root collar diameter, or both) became apparent from Age 2 years at both sites. It was concluded that the genetic improvement of radiata pine seedlings would not be needed to be taken into account if seedlings were to be used before the age of six months as `bio-assay' indicators of changes in soil quality.

Sequential Effects of Acidic Precipitation and Drought on Water Relations of Pinus radiata Seedlings

In this work we investigated the sequential effects of simulated acid rain and drought on water relations of radiata pine ( Pinus radiata D. Don) seedlings. Whole seedlings were firstly subjected during 1 month to acid rain, pH 3.0, applied 5 times a week at 3 mm precipitation equivalent per day. Afterwards, drought treatment was applied by withholding water for 20 days and subsequent rewatering for 6 days to analyze the sequential effect of acid precipitation and drought. Water status parameters were determined before the initiation of acid rain treatment and within 3 weeks after the end of treatment. Acid rain treatment in well-watered plants did not affect either water potential or relative water content, whereas a marked effect on electrolyte leakage from the needles and on instantaneous transpiration was recorded. Drought treatment had great effects on leaf water potential (-2.5 MPa), RWC (50 % diminution), membrane permeability (340 % increase) and transpiration rate (25 % inhibition). Interactions involving acid precipitation and drought led to much greater impacts on all of the parameters analyzed. We conclude that although acid rain had slight, if any, direct effects on the water relations of well-watered radiata pine, it altered the drought tolerance of this tree species. Under conditions of soil-water deficit, plants exposed previously to acid rain are more sensitive to drought and desiccation.

Effect of potassium phosphonate on root rot of Pinus radiata caused by Phytophthora cinnamomi

Seedlings of Pinus radiata transplanted into washed river sand or sand/peat potting mix pre-inoculated with Phytophthora cinnamomi developed severe wilt and root rot symptoms within 7 weeks, and died within 12 weeks. By contrast, direct inoculation of pathogen mycelium into stem wounds produced only restricted lesions. Soil incorporation of inoculum was subsequently used to assess the ability of potassium phosphonate to protect pine seedlings against wilt and root rot caused by P cinnamomi. Three concentrations of potassium phosphonate (0.1, 1.0 and 5.0 g/L), applied as either a single foliar spray or as a single root drench at transplanting into pots containing pathogen-infested sand or sand/peat, significantly reduced the incidence of root rot symptoms. At each concentration, soil drenches were more effective than foliar sprays in delaying and suppressing dieback symptoms in container-grown plants. Phosphonate applications were more effective in sand/peat potting mix than in washed river sand. Recovery of the pathogen from diseased plant roots and potting mix was lower in pots drenched with phosphonate than from pots treated by foliar sprays. Potassium phosphonate foliar sprays at a rate of 5.0 g/L were phytotoxic, causing burning of needles and temporary branch dieback.

Interval mapping of quantitative trait loci affecting NESTUR, a stem growth efficiency index of radiata pine seedlings

NESTUR (needle-to-stem unit rate) is a stem growth index of conifer seedlings that measures the efficiency of stemwood production per unit of needle growth, and is related to other seedling traits such as height, stem diameter, stem volume and needle volume. Quantitative trait loci (QTLs) affecting the expression of stem growth efficiency in radiata pine seedlings were investigated using a RAPD linkage map constructed from markers scored on haploid, megagametophytic DNA. Four putative QTLs were detected which accounted for 8.5–36.4% of the population variance. A search for evidence of epistasis, using both complete pairwise and conditional interactions, did not yield any statistically significant result. Over a 3-year period, seedlings with high-NESTUR marker alleles showed a superior growth performance of 17–40% for height, diameter and volume over those with low-NESTUR marker alleles.

Age-related changes in the expression of QTLs for growth in radiata pine seedlings

Haploid megagametophytes from a full-sib cross of Pinus radiata were used to construct a genetic linkage map for radiata pine based on random amplified polymorphic DNA (RAPD) markers. The map, which was made from 222 markers, was used to carry out a QTL analysis of growth using measurements made on seedlings from which these megagametophytes were collected at an early germination stage. Trends in the expression of QTLs for stem diameter, volume and height were compared using measurements made at 5 months of age, and at 1, 2 and 3 years of age. None of the observed trends showed complete stability, i.e. none of the putative QTL positions detected at any one age was strongly expressed at all of the four stages of measurement. However, 45% of the trends showed partial stability, i.e. putative QTLs significant at one age were also detected at a subsequent age. Trends in QTL expression with age followed one of three patterns: (1) putative QTLs at some locations showed a gradual linear increase in influence from 5 months of age and were highest at 3 years of age; (2) QTLs detected at 5 months of age gradually became less significant with age; and (3) some putative QTLs showed a curvilinear increase in effect from 5 months of age, reaching their peak expression at 1 to 2 years, and sometimes were still detected at 3 years of age.

Induction of phenylalanine ammonia lyase activity and control of Sphaeropsis sapinea infection in Pinus radiata by 5‐chlorosalicylic acid

SummaryPhenylalanine ammonia lyase (PAL) activity increased rapidly in Pinus radiata seedlings after treatment with 2 mm 5‐chlorosalicylic acid (5CSA) and peaked after 48 h at four‐times the level of the control. Elevation of PAF is often associated with the induction of host resistance mechanisms. Thus, effects of 5CSA on subsequent infection of P. radiata by Sphaeropsis sapinea was investigated. Only one out of 16 seedlings treated with 2 mm 5CSA, 4 days before inoculation, developed deadtop compared to 14 of the controls. The 5CSA was directly inhibitory at this concentration and reduced growth rate of S. sapinea on agar by 27%. However, antifungal activity does not fully account for the observed disease control afforded by 5CSA since 0.5 mm and 0.25 mm 5CSA, which did not inhibit growth of S. sapinea, significantly reduced the incidence of deadtop. Furthermore, 1 mm 5CSA protected seedlings against fresh inoculation challenge for up to 32 days after application. Such durable resistance is unlikely to be attributable to the direct effects of the applied compound and may suggest the involvement of inducible host resistance mechanisms.

A xyloglucan in etiolated seedlings of Pinus radiata

The changes in cell wall carbohydrates and starch were investigated in hypocotyls and cotyledons during growth of etiolated seedlings of Pinus radiata. Starch was depleted within two weeks with an accompanying rise in a hemicellulosic xyloglucan component. This was purified by fractional precipitation. Fractionation, methylation analysis, partial hydrolysis and chromium trioxide oxidation showed that this component was a fucogalactoxyloglucan of similar structure to those reported from dicots. It was the major hemicellulose in two-week-old hypocotyls and cotyledons. Other cell wall polysaccharides for which evidence was obtained by methylation analysis were a xylan, a glucomannan and an arabinan.

Effect of some common weed species on <i>Pinus radiata</i> growth at a dry South Island site

Reductions in radiata pine (Pinus radiata D.Don) growth caused by a range of common weed species were measured at a site where water availability was known to limit tree growth. Radiata pine seedlings were grown for 3 years on their own or with volunteer herbaceous broadleaves, broom, gorse or browntop. Water and nutrient levels were varied by factorial +/- irrigation and fertiliser treatments. Radiata pine stem volume was reduced in the presence of all four weed types. Herbaceous broadleaf weeds had the greatest effect on tree growth, gorse had the smallest effect, and broom and grass were intermediate. Water supply was thought to have a major effect in determining the influence of weeds on tree growth.

Linkage of RAPD markers to NESTUR, a stem growth index in radiata pine seedlings

Needle-to-stem unit rate (NESTUR) is a stem growth index of conifer seedlings that measures the efficiency of stemwood production per unit of foliage growth. The random amplified polymorphic DNA (RAPD) technique was applied to haploid DNA from the megagametophytes of a full-sib radiata pine cross to find markers linked to factors controlling the NESTUR trait. Using the bulked segregant analysis approach, 23 of 933 primers displayed putative linkage to factors controlling NESTUR. Based on the genotypic analysis of 174 individuals, two quantitative trait loci (QTLs) controlling NESTUR were identified at ANOVA P-levels of 0.01–0.001. The QTLs were identified by RAPD markers OPE-06450 and OPA-101200, which were linked to each other (r=7%), and UBC-333550, which was not linked to the other two. Linkage to components of NESTUR (increments in stem diameter and stem volume) was demonstrated for UBC-333550, while the others were not linked to NESTUR components.

Influence of radiata pine seedlings on chemical properties of some New Zealand montane grassland soils

Radiata pine (Pinus radiata) and cocksfoot grass (Dactylis glomerata) were grown in small pots containing grassland soils collected from seven sites in the South Island montane zone. After one year the overall mean dry matter yield of pine exceeded that of grass by a factor of 2.6, and uptake of all nutrients by pine was substantially greater. Mean soil pH was 0.3 units lower after pine growth than after grass. Organic carbon (C), total nitrogen (N), and organic phosphorus (P) levels were 15–19% lower after pine, while total P was 7% lower. Despite greater nutrient uptake by pine, mean mineralisable N and sulphate sulphur (S) levels in the soil were 500% and 200% higher respectively after pine growth than after grass. Inorganic and Bray-2 P levels were 10% and 20% higher respectively. Grass obtained almost all of its P from the inorganic pool, while pine obtained P from both inorganic and organic pools, though mostly from the latter. It is concluded that the differences observed in C, N, and P concentrations in soil indicate higher rates of mineralisation of soil organic matter in the presence of radiata pine than in the presence of cocksfoot grass. Possible implications for pastoral hill land use in New Zealand are discussed. It is suggested that pines incorporated into farming systems either on a rotational basis, or in wide-spaced agroforestry regimes, may be able to increase the rate of mineralisation of organic P, and also of N and S, and increase their availability to pasture species.

Simultaneous Effects of Foliar Nitrogen, Temperature, and Humidity on Gas Exchange in Pinus radiata

Seedlings of Pinus radiata were grown in a glasshouse in large pots with sand as the potting mix. They were kept well-watered and frequently supplied with nutrient solutions which contained different amounts of nitrogen for different treatments. Carbon assimilation and diffusive conductance of the foliage were measured under steady-state conditions at saturating light in all treatments. Experimental variables were leaf-air vapour pressure difference and leaf temperature at time of measurement. Data were fitted to a non-linear regression equation to examine responses of carbon assimilation, diffusive conductance, transpiration, assimilatory nitrogen-use efficiency, and assimilatory transpiration efficiency to foliar nitrogen concentration expressed on a leaf area basis ([N]), to leaf temperature, and to leaf-air vapour pressure (D). Parameters from the regression have been used to plot three-dimensional surfaces, so that simultaneous effects of experimental variables can be easily visualised. Carbon assimilation increased linearly with foliar [N], declined exponentially as D increased, and had a broad temperature optimum between c. 14 and 38�C. Diffusive conductance increased linearly with foliar [N], was related to the reciprocal of D, and declined as temperature increased. Using climatic vapour pressure deficit and air temperature data for Canberra, ACT, and for Mount Gambier, SA, and with the functions that had been fitted to experimental data, it was found that these regional climatic differences have potential for appreciably affecting carbon gain and water loss in the regions, which have P. radiata plantations. Predicted differences in carbon gain are of the order of reported differences in stem growth in the regions. This shows the need to take into account regional variation in climatic variables that strongly affect gas exchange when investigating regional differences in productivity.

Variations in response to induced stem bending in seedlings of Pinus radiata

The occurrence of stem deformation in Pinus radiata plantations has been examined previously in terms of the factors leading to the onset of bending symptoms. In this study the influence of seedling family and nitrogen availability on the ability of seedlings to recover from deformation was investigated under glasshouse conditions. Seedlings from four families ranging from resistant to susceptible to stem deformation were used. Stem deformation was induced by loading stems with a known weight and comparing bending moments and rates of recovery. Significant differences between families were found with more susceptible families exhibiting greater initial magnitudes of stem lean. Similarly these families also exhibited greater rates of apical elongation following bending despite the larger stem leans. This resulted in more exaggerated stem bends as a consequence of the recovery of the lower stem pushing the upper stem away from the vertical. The strength characteristics of the stems could not explain differences between families. Susceptibility to stem deformation was explained more by stem slenderness expressed as stem height to root collar diameter.

90Sr uptake by Pinus ponderosa and Pinus radiata seedlings inoculated with ectomycorrhizal fungi.

Strontium-90 ((90)Sr) is a radionuclide characteristic of fallout from nuclear reactor accidents and nuclear weapons testing. Prior studies have shown that Pinus ponderosa and P. radiata seedlings can remove appreciable quantities of (90)Sr from soil and store it in plant tissue. In this study, we inoculated P. ponderosa and P. radiata seedlings with one of five isolates of ectomycorrhizal fungi. Inoculated and noninoculated (control) seedlings were compared for their ability to remove (90)Sr from an organic growth medium. Seedlings were grown in a growth chamber in glass tubes containing 165 cm(3) of sphagnum peat moss and perlite (1 : 1 (v/v)) and, except in the controls, the fungal inoculum. After 3 months, 5978 Bq of (90)Sr in 1 ml of sterile, distilled, deionized water was added. Seedlings were grown for an additional month and then harvested. P. ponderosa seedlings with ectomycorrhizae accumulated 3.0-6.0% of the (90)Sr; bioconcentration ratios (Bq (90)Sr cm(-3) plant tissue/Bq (90)Sr cm(-3) growth medium) ranged from 98-162. Ectomycorrhizal P. radiata seedlings accumulated 6.0-6.9% of the (90)Sr; bioconcentration ratios ranged from 88-133. Nonmycorrhizal P. ponderosa and P. radiata seedlings accumulated only 0.6 and 0.7% of the (90)Sr and had bioconcentration ratios of 28 and 27, respectively. Ectomycorrhizal P. ponderosa and P. radiata seedlings are able to remove 3-5 times more (90)Sr from contaminated soil than seedlings without ectomycorrhizae.

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.

Relationships between stem structure and bending strength in Pinus radiata seedlings

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.

Effects of micronutrients on the growth form of two families of Pinus radiata (D.Don) seedlings

Micro-element deficiencies have been implicated in the development of poor stem form in Pinus radiata plantations. Cu, Mn and B have been implicated in previous studies as influencing tree form and/or the process of lignification in plants. Therefore an experiment was initiated to examine the individual and interactive effects exhibited by these trace elements on stem form and lignification. The investigation showed that Cu deficiency reduced both lignification and stem form in seedlings. Mn, competing with Cu for uptake, enhanced the symptoms of Cu deficiency. Boron addition did not alleviate the expression of deformity or increase levels of lignification. There was a clear family influence on the development of seedling stem form in response to variations in mineral nutrition.

Effects of propazine and chlorthal dimethyl on Phytophthora cinnamomi root disease of Pinus radiata seedlings and associated soil microflora

When propazine was used continuously for S years as a pre-emergent herbicide in a large Pinus radiata nursery at Benalla. where the soils were not believed to be conductive to Phytophthora cinnamomi root rot. disease appeared after ca 2 years and rapidly increased in intensity despite attempts to control it with fungicides. The disease and the fungus virtually disappeared, within one season, when chlorthal dimethyl replaced propazine. An explanation for these observations was sought by examining the effects of propazine and chlorthal dimethyl on soil, rhizosphere and rhizoplane bacteria. Actinomycetes and fungi and the effect of the herbicides on the resistance per se. of P. radiala seedlings to Ph. cinnamomi. These tests were carried out in a laboratory, phytotron and greenhouse. The nursery disease symptoms were reproduced in the phytotron when Ph. cinnamomi—free soils were inoculated and treated with both herbicides. Chlorthal dimethyl was found to strongly inhibit root disease and soil inoculum potentials of Ph. cinnamomi in 5 month-old seedlings while propazine had the opposite effect. When the stems of hcrbicidal-trcatcd seedlings growing in Ph. cinnamomi—free soils were inoculated with Ph. cinnamomi, there was evidence that propazine increased disease sensitivity considerably while the effect of chlorthal dimethyl was not consistent. Examination of the effects that both herbicides had, in phytotron tests, on soil, rhizosphcrc and rhizoplane microflora showed that chlorthal dimethyl reduced numbers of Gram-positive and -negative and spore forming bacteria ca 90% while propazine increased their numbers. In the rhizosphcrc and rhizoplane the inhibitory ctfcct of chlorthal dimethyl and the stimulatory influence of propazinc on bacteria was very variable which suggests that the root cxudatcs had a greater influence on microbial numbers than that of the herbicides. Examination of the effects various bacterial types on sporangial formation of Ph. cinnamomi showed that the spore-forming bacteria associated with propazine soil drenches strongly stimulated sporangial production. The evidence suggest that the disease outbreak at the Benalla nursery may have been due to an increase in numbers of soil bacteria that stimulated production of Ph. cinnamomi inoculum and a reduction in disease resistance. The disease reduction following applications of chlorthal dimethyl may have been due directly to fungitoxicity to Ph. cinnamomi and failure to stimulate soil microflora that may have increased inoculum levels. Its influence on disease resistance of P. radiala was possibly negligible.

Storage ofPinus radiataFoliage Prior To Determination of Water Potential

SYNOPSIS A procedure to sample and store foliage of Pinus radiata seedlings prior to determination of the water potential is described. The water potential of P. radiata fascicles sampled at pre-dawn can be maintained for seven hours by storing the foliage in humidified plastic bags on ice in a dark place.

Influence of phosphorus deficiency on the growth response of four families of Pinus radiata seedlings to CO 2-enriched atmospheres

Four half-sib families of Pinus radiata (D. Don) (20080, 20010, 20022 and 20062) were grown in pots under conditions where P was either deficient or adequate and water was supplied daily. Seedlings of all four families were exposed to 340 (ambient levels) or 660 μl CO 2l −1 in controlled-environment chambers for 16 weeks. Families 20010 and 20062 were grown at the same CO 2 concentrations for 22 weeks. A subset of plants grown in the chambers were subject to drought and their water potentials and relative water contents measured. In the glasshouse experiment, photosynthesis, conductance and elongation of needles were measured. The fresh and dry-weights of the tops of the plants were measured in both experiments. Elevated CO 2 concentrations increased shoot growth in all families, apparently through increases in photosynthesis. At 340 μl CO 2l −1, family 20062 accumulated the most dry-weight and 20010 the least. However, family 20010 responded so strongly to 660 μl CO 2l −1 that it produced as much dry-matter as 20062. Phosphorus deficiency generally diminished the response to high CO 2. Again, 20010 was outstanding in that its CO 2 response was least reduced by P deficiency. Carbon-dioxide enrichment did not increase the drought-tolerance of any of the four families, either by reducing conductance or by facilitating osmotic adjustment. These results provide strong indications that the higher levels of atmospheric CO 2 expected in the next century will increase the growth of P. radiata where P availability is adequate, but may reduce growth in areas where rainfall is low. Finally, the capacity to respond to CO 2 enrichment appears to be widely distributed among superior P. radiata genotypes selected by the Forestry Commission of New South Wales. However the magnitude of response varies considerably, particularly where P is deficient.