Juvenile Needles Research Articles

Variation of Essential Oil Composition, Antioxidant and Anticholinesterase Activities between Pinus halepensis Mill. Plant Organs

: The essential oils extracted from different organs of Pinus halepensis were analyzed by GC-FID and GC-MS and evaluated for their antioxidant and anti-acetylcholinesterase and anti-butyrylcholinesterase activities. The composition and biological activities of essential oils extracted from immature cones, juvenile needles and male inflorescences were analyzed for the first time. The common compounds of the investigated essential oils were α-pinene (6.4 to 46.1 %), β-myrcene (5.5 to 28.3 %), β-caryophyllene (1.3 to 32.8 %), β-caryophyllene oxide (2.7 to 66.6 %) and α-humulene (2.4 to 5.8 %). Significant variations of essential oil composition were detected between the investigated plant parts. The analyzed essential oils exhibited antioxidant and anticholinesterase activities. These activities varied significantly among organs. The essential oil of needles showed the highest antiradical activity with DPPH assay (0.31 mg eq Trolox/g EO). However, for ABTS radical scavenging assay, juvenile needles showed the uppermost antioxidant activity (2.52 mg eq Trolox/g EO). Male inflorescences possessed the most important chelating activity (267.43 mg eq EDTA/g EO). Essential oils of juvenile needles exhibited the highest antiacetylcholinesterase activity (1.37 mg eq dopenzil/g EO). Male inflorescences revealed the most important activity against butyrylcholinesterase (57.442 mg eq dopenzil/g EO).

Rising [CO2] effect on leaf drought-induced metabolome in Pinus pinaster Aiton: Ontogenetic- and genotypic-specific response exhibit different metabolic strategies

Rising atmospheric CO2 concentrations ([CO2]) together with water deficit can influence ecological interactions of trees through an array of chemically driven changes in plant leaves. In four drought stressed Pinus pinaster genotypes, grown under two levels of atmospheric [CO2] (ambient (aCO2) and enriched (eCO2)) the metabolome of adult and juvenile needles was analyzed to know if the metabolic responses to this environmental situation could be genotype-dependent and vary according to the stage of needle ontogeny. Drought had the highest incidence, followed by needle ontogeny, being lower the eCO2 effect. The eCO2 reduced, eliminated or countered the 50 (adult needles) – 44% (juvenile) of the drought-induced changes, suggesting that CO2-enriched plants could perceived less oxidative stress under drought, and proving that together, these two abiotic factors triggered a metabolic response different from that under single factors. Genotype drought tolerance and ontogenetic stage determined the level of metabolite accumulation and the plasticity to eCO2 under drought, which was mainly reflected in antioxidant levels and tree chemical defense. At re-watering, previously water stressed plants showed both, reduced C and N metabolism, and a “drought memory effect”, favoring antioxidants and osmolyte storage. This effect showed variations regarding genotype drought-tolerance, needle ontogeny and [CO2], with remarkable contribution of terpenoids. Chemical defense and drought tolerance were somehow linked, increasing chemical defense during recovery in the most drought-sensitive individuals. The better adaptation of trees to drought under eCO2, as well as their ability to recover better from water stress, are essential for the survival of forest trees.

The foliar characters in Callitris (Callitroideae, Cupressaceae s. str.) and their evolutionary and ecological significance

The foliar shift from juvenile needle leaves to the mature scale leaves was investigated in five Callitris species. Their habitats range from rainforest to the semi‐arid. In C. macleayana from the most mesic environment the change from needle to scale leaves is variable and juvenile leave are even retained on mature trees. In the other four species there is a rapid change in size and structure to scale leaves. Anatomically the photosynthetic tissue is condensed and stomatal area is limited compared to species with conventional leaves. A hypodermis is most prominent on the abaxial side of the leaves and may play a role in protection from high solar radiation as most species grow in high light areas. While stomata in the four taxa from wet or moderate rainfall areas are freely exposed, those of C. gracilis from semi‐arid habitats are well protected in longitudinal furrows between the decurrent leaves. The reduced leaf area of all species allows close association between the water‐conducting xylem and the stomata that will facilitate rapid leaf conductance. This links with the anisohydric physiology of the genus and the shallow rooting that can take advantage of brief rainfall events for species in arid climates.

Does climate-related in situ variability of Scots pine (Pinus sylvestris L.) needles have a genetic basis? Evidence from common garden experiments.

The correlations of phenotypic traits with environmental drivers suggest that variability of these traits is a result of natural selection, especially if such trait correlations are based on genetic variability. We hypothesized that in situ correlations of structural needle traits of Scots pine (Pinus sylvestris L) with minimal winter temperature (Tmin) reported previously from a temperate/boreal transect would be conserved when plants are cultivated under common conditions. We tested this hypothesis by analyzing needles from two common gardens located in the temperate zone, one including adult trees and the other juvenile seedlings. The majority of adult needle traits for which correlations with Tmin were found in the field turned out to be under environmental influence. In contrast, the majority of traits studied in juvenile needles were correlated with the original Tmin suggesting the role of past natural selection in shaping their variability. Juvenile needles thus appeared to be inherently less plastic than adult needles, perhaps reflecting the stronger selective pressure acting during juvenile, as compared with adult, ontogenetic stage. Genetically based cold-climate adaptation in either juvenile or adult needles, or both, involved an increase in leaf mass per area and leaf density, decrease in needle length, reduction in the amount of xylem and phloem, increase in thickness of epidermis, decrease in tracheid diameter and increase in tracheid density, and increase in diameter and volume fraction of resin ducts. We also show that at least some traits, such as transverse xylem and phloem areas and number of fibers, scale with needle length, suggesting that climate-related trait variation may also be mediated by changes in needle length. Moreover, slopes of these allometric relationships may themselves be plastically modified. The phenotypic syndrome typical of needles from cold environments may thus be under environmental, genetic and allometric control.

Metabolic response to elevated CO2 levels in Pinus pinaster Aiton needles in an ontogenetic and genotypic-dependent way

Global climate changes involve elevated atmospheric [CO2], fostering the carbon allocation to tree sink tissues, partitioning it into metabolic pathways. We use metabolomics analysis in adult and juvenile needles of four Pinus pinaster genotypes exposed to two levels of growth [CO2]: ambient (400 μmol mol−1) and enriched (800 μmol mol−1), to know if the metabolic responses are genotype-dependent and vary according to the stage of needle ontogeny. The eCO2-induced changes in the needle metabolomes are more significant in secondary metabolism pathways and especially meaningful in juvenile needles. The heteroblasty has important consequences in the expression of the metabolome, and on the plasticity to CO2, determining the level of specific metabolite accumulation, showing an interdependence between adult and juvenile needles. The P. pinaster needle metabolomes also show clear quantitative differences linked to genotype, as well as regarding the metabolic response to eCO2, showing both, common and genotype-specific biochemical responses. Thus, the changes in flavonol levels are mainly genotype-independent, while those in terpenoid and free fatty acids are mainly genotype-dependent, ratifying the importance of genotype to determine the metabolic response to eCO2. To understand the adaptation mechanisms that tree species can develop to cope with eCO2 it is necessary to know the genetically distinct responses within a species to recognize the CO2-induced changes from the divergent approaches, what can facilitate knowing also the possible interrelation of the physiological and metabolic responses. That could explain the controversial effects of eCO2 on the carbon-based metabolite in conifers, at the inter- and intra-specific level.

Permafrost Regime Affects the Nutritional Status and Productivity of Larches in Central Siberia

Permafrost exerts strong controls on forest development through nutrient availability. The key question of this study was to assess the effect of site conditions on macroelement concentration and stable isotope (δ13C and δ15N) dynamics during the growing season, and nutrient stoichiometry and resorption efficiency in the foliage of two common larch species in Siberia. Foliar nutrient (N, P and K) concentrations of larches grown on permafrost soils were exceptionally high in juvenile needles compared to those from a permafrost-free region (+50% and 130% for P and K), but were two-fold lower at needle maturation. Within permafrost terrain trees, sites with a warmer and deeper soil active layer had 15–60% greater nutrient concentrations and higher δ15N in their needles compared to shallower, colder soils. Larch of permafrost-free sites demonstrated an enrichment of foliage in 15N (+1.4% to +2.4‰) in comparison to permafrost terrain (−2.0% to −6.9‰). At all sites, foliar δ13C decreased from June to August, which very likely results from an increasing contribution of current photoassimilates to build foliar biomass. With senescence, nutrient concentrations in larch needles decreased significantly by 60–90%. This strong ability of larch to retain nutrients through resorption is the essential mechanism that maintains tree growth early in the growing season when soil remains frozen. The high resorptive efficiency found for K and P for larches established on permafrost suggests nutrient limitation of tree growth within the Central Siberian Plateau not only by N, as previously reported, but also by P and K. The increasing nutrient concentrations and a 15N enrichment of foliage towards warmer sites was paralleled by an up to 50-fold increase in biomass production, strongly suggesting that accelerated nutrient cycling with permafrost degradation contributes to an increased productivity of Siberian larch forests.

Structural controls on photosynthetic capacity through juvenile‐to‐adult transition and needle ageing in Mediterranean pines

AbstractNeedle photosynthetic potentials strongly vary among primary (juvenile) and secondary (adult) needles (heteroblasty) inPinusspecies, but there is limited understanding of the underlying structural, diffusional and chemical controls.We studied differences in needle photosynthetic characteristics among current‐year juvenile and adult needles and among different‐aged adult needles in Mediterranean pinesPinus halepensisMill.,P. pineaL. andP. nigraJ. F. Arnold subsp.salzmannii(Dunal) Franco, hypothesizing that needle anatomical modifications upon juvenile‐to‐adult transition lead to reduced photosynthetic capacity due to greater limitation of photosynthesis by mesophyll conductance and due to an increase in the share of support tissues at the expense of photosynthetic tissues. We also hypothesized that such alterations occur with needle ageing, but to a lower degree.Photosynthetic capacity per dry mass was 2.4‐ to 2.7‐fold higher in juvenile needles, and this was associated with 3.4‐ to 3.7‐fold greater mesophyll diffusion conductance, 2‐ to 2.5‐fold greater maximum carboxylase activity of Rubisco (Vcmax) and 2.2‐ to 3‐fold greater capacity for photosynthetic electron transport (Jmax). The latter differences were driven by modifications in mesophyll volume fraction and changes in the share of nitrogen between structural and photosynthetic functions. Analogous changes in photosynthetic characteristics occurred with needle ageing, but their extent was less.These results indicate that conifer foliage photosynthetic machinery undergoes a profound change from a fast return strategy in juveniles to slow return stress‐resistant strategy in adults and that this strategy shift is driven by modifications in foliage biomass investments in support and photosynthetic functions as well as by varying mesophyll diffusional controls on photosynthesis. Changes in needle morphophysiotype during tree and needle ageing need consideration in predicting changes in tree photosynthetic potentials through tree ontogeny and during and among growing seasons.Aplain language summaryis available for this article.

A major trade-off between structural and photosynthetic investments operative across plant and needle ages in three Mediterranean pines.

Pine (Pinus) species exhibit extensive variation in needle shape and size between juvenile (primary) and adult (secondary) needles (heteroblasty), but few studies have quantified the changes in needle morphological, anatomical and chemical traits upon juvenile-to-adult transition. Mediterranean pines keep juvenile needles longer than most other pines, implying that juvenile needles play a particularly significant role in seedling and sapling establishment in this environment. We studied needle anatomical, morphological and chemical characteristics in juvenile and different-aged adult needles in Mediterranean pines Pinus halepensis Mill., Pinus pinea L. and Pinus nigra J. F. Arnold subsp. salzmannii (Dunal) Franco hypothesizing that needle anatomical modifications upon juvenile-to-adult transition lead to a trade-off between investments in support and photosynthetic tissues, and that analogous changes occur with needle aging albeit to a lower degree. Compared with adult needles, juvenile needles of all species were narrower with 1.6- to 2.4-fold lower leaf dry mass per unit area, and had ~1.4-fold thinner cell walls, but needle nitrogen content per dry mass was similar among plant ages. Juvenile needles also had ~1.5-fold greater mesophyll volume fraction, ~3-fold greater chloroplast volume fraction and ~1.7-fold greater chloroplast exposed to mesophyll exposed surface area ratio, suggesting overall greater photosynthetic activity. Changes in needle traits were similar in aging adult needles, but the magnitude was generally less than the changes upon juvenile to adult transition. In adult needles, the fraction in support tissues scaled positively with known ranking of species tolerance of drought (P. halepensis > P. pinea > P. nigra). Across all species, and needle and plant ages, a negative correlation between volume fractions of mesophyll and structural tissues was observed, manifesting a trade-off between biomass investments in different needle functions. These results demonstrate that within the broad trade-off, juvenile and adult needle morphophysiotypes are separated by varying investments in support and photosynthetic functions. We suggest that the ecological advantage of the juvenile morphophysiotype is maximization of carbon gain of establishing saplings, while adult needle physiognomy enhances environmental stress tolerance of established plants.

Leaf metabolic response to water deficit in Pinus pinaster Ait. relies upon ontogeny and genotype

Pinus pimaster Aiton displays marked heteroblasty during its vegetative phase, showing complex interactions between developmental processes and environmental adaptation, with a patent differentiation in functional performance according to leaf type resulting from heteroblasty. In this work, untargeted quantitative metabolic profiling in adult and juvenile needles of four water-deficit stressed P. pinaster genotypes was investigated to know if metabolic responses to drought are genotype-dependent and vary according to the stage of needle ontogeny.Among the changes in metabolome, it highlights the increase of osmotically active substances, as well as the overproduction of antioxidant compounds by up-regulating ascorbate, shikimate/phenylalanine and phenylpropanoid metabolic pathways. Moreover, significant inter-clonal quantitative variations were also found at different levels, in both primary and secondary metabolism pathways, although terpenoids and specially flavonoids showed the highest significance. A surprising result was the ontogenetic changes in metabolic profiles. Juvenile needles contain significant higher levels of UV screener and antioxidant flavonoids. The level of drought tolerance of a genotype and the ontogenetic stage were important factors in determining the drought-induced level of flavonoid increase in needles of a given genotype. Regarding terpenoids, the significant drought-induced accumulation of neutral diterpenes in juvenile needles, and mono- and sesquiterpenes in adults, was genotype dependent regardless its degree of drought tolerance.These results point to flavonoids as very versatile metabolites in maritime pine needle, acting like important compounds modulating not only drought acclimation but also changes in needle metabolism associated with developmental processes such as heteroblasty.

Organ-specific metabolic responses to drought in Pinus pinaster Ait.

Drought is an important driver of plant survival, growth, and distribution. Water deficit affects different pathways of metabolism, depending on plant organ. While previous studies have mainly focused on the metabolic drought response of a single organ, analysis of metabolic differences between organs is essential to achieve an integrated understanding of the whole plant response. In this work, untargeted metabolic profiling was used to examine the response of roots, stems, adult and juvenile needles from Pinus pinaster Ait. full-sib individuals, subjected to a moderate and long lasting drought period. Cyclitols content showed a significant alteration, in response to drought in all organs examined, but other metabolites increased or decreased differentially depending on the analyzed organ. While a high number of flavonoids were only detected in aerial organs, an induction of the glutathione pathway was mainly detected in roots. This result may reflect different antioxidant mechanisms activated in aerial organs and roots. Metabolic changes were more remarkable in roots than in the other organs, highlighting its prominent role in the response to water stress. Significant changes in flavonoids and ascorbate metabolism were also observed between adult and juvenile needles, consistent with previously proven differential functional responses between the two developmental stages. Genetic polymorphisms in candidate genes coding for a Myb1 transcription factor and a malate dehydrogenase (EC 1.1.1.37) were associated with different concentration of phenylalanine, phenylpropanoids and malate, respectively. The results obtained will support further research on metabolites and genes potentially involved in functional mechanisms related to drought tolerance in trees.

Morpho-anatomical studies on the change in the foliage of two imbricate-leaved New Zealand podocarps: Dacrycarpus dacrydioides and Dacrydium cupressinum

Many extant gymnosperms have strongly reduced leaves. While this is usually treated as adaptation to drought, other habitat factors must also be involved. This subject and the related change from juvenile needle leaves to adult imbricate leaves are poorly understood. Here we explore these topics by describing the leaf morphology and leaf anatomy of seedlings and adult plants of Dacrydium cupressinum and Dacrycarpus dacrydioides. In both species, the cotyledons, primary leaves, and juvenile leaves are needle like. Then D. dacrydioides foliage becomes partly imbricate. In D. cupressinum, the needle leaves gradually become smaller and more close-set, with some fully imbricate leaves appearing on old trees. It follows from very high rainfall and low soil phosphorus of the habitat that their very small leaf size is likely to be a scleromorphic character, not a xeromorphic one. Confusion in the literature in the use of scleromorphy and xeromorphy is pointed out and clarified.

Among-population variation and plasticity to drought of Atlantic, Mediterranean, and interprovenance hybrid populations of maritime pine

Maritime pine grows naturally under a wide range of climatic conditions, from strongly Atlantic to strongly Mediterranean. Aiming to improve our understanding of the genetic structure and inheritance of drought resistance strategies in the species, we conducted an environmentally controlled experiment to assess the genetic variation and plasticity to drought of Atlantic and Mediterranean populations, and the interprovenance hybrids between them. Hybridization could also help to provide new genetic material for use in transitional areas between the two regions, for which reproductive materials of good quality are generally lacking. Plastic responses to water stress appeared to be highly conserved among populations, with a common conservative isohydric strategy based on promoting growth when water was abundant, and stopping it when water became limiting. We found, however, a strong intraspecific variation in biomass allocation patterns. The Atlantic populations showed a risky growth-based strategy with a larger amount of juvenile needles, whereas Mediterranean populations showed a more conservative strategy, minimizing aerial growth and increasing the proportion of adult needles that is more resistant to water loss. Hybrid populations performed more similarly to the Mediterranean parent, suggesting a dominance of the Mediterranean-like characteristics. Some of the tested hybrid populations, however, combined high growth with traits of drought adaptation, and thus represent potentially interesting materials for use in transitional regions between the two climate zones.

Leaf dimorphism in Thuja plicata and Platycladus orientalis (thujoid Cupressaceae s. str., Coniferales): the changes in morphology and anatomy from juvenile needle leaves to mature scale leaves

Thuja plicata and Platycladus orientalis initially produce only bifacial needle leaves. When the first lateral shoots develop, the leaf morphology and anatomy changes dramatically. Subsequently, only greatly reduced, bifacial scale leaves are developed. A new kind of “superimposed bifaciality” occurs with the change from juvenile needle leaves to mature scale leaves. Anatomical dorsiventrality affects not only the individual leaf, but also the complete plagiotropic lateral shoots of Thuja, which have a sun- and shade-exposed side. The upper light-exposed median leaves show adaxial leaf anatomy, contrary to the lower shaded median leaves showing abaxial leaf anatomy. Due to their mixed exposure, the lateral leaves show a lateral differentiation. At vertical lateral shoots of Platycladus, a predominant light-exposed side is absent. Thus, the anatomical dorsiventrality does not affect the complete shoot. Here the morphological abaxial side of a scale leaf becomes functionally and physiologically adaxial by reorientation of the palisade parenchyma and stomata. In juvenile needle leaves, the palisade parenchyma is located adaxial, with the majority of stomata being located abaxial. Conversely, in mature scale leaves, the palisade parenchyma is abaxial and the majority of stomata are adaxial.

Reorientation Strategies in leaning stems of young maritime pine (Pinus Pinaster) and Loblolly Pine (Pinus Taeda)

To test for different stem reorientation strategies in leaning seedlings of maritime pine (Pinus pinaster Ait.) and loblolly pine (Pinus taeda L.), we inclined dormant plants at 0°, 45° and 90° for 35 days in optimal growthconditions. Stem angle to the vertical was measured at regular intervals. After 22 and 35 days, bending tests were carried out to determine stem elasticity and stiffness. The quantity of compression wood (CW) formed was also measured. Results showed that after 24 h, the apices of leaning maritime pine stems had completely reoriented to the vertical, whereas no such primary tropic response was observed in loblolly pine. After 22 days, the significantly stiffer loblolly pines had begun straightening up from the stem base, but not maritime pine. After 35 days, the overall secondary reorientation process was more efficient in loblolly pine, with significantly more CW produced. In both species, CW had formed immediately on tilting stems, i.e. no early wood cells had formed. As maritime pine originates from a dry to semi-arid region, having less CW will mean that water uptake will be greater for the same xylem area compared to loblolly pine which possesses more CW. In establishing maritime pine seedlings, rapid apical orientation with regard to light and gravity will compensate for a slower straightening up mechanism in the more lignified parts of the stem. Therefore, juvenile needle exposure to patches of light will be maximised at all times.

Difference in cuticular transpiration and sclerophylly in juvenile and adult pine needles relates to the species-specific rates of development

Pinus species show remarkable ontogenetic differences in needle morphology (heterophylly) between juvenile and adult vegetative phases. This developmental shift may play an adaptative role in their success under diverse habitats. As a first step to know the functional differences between each vegetative phase, we compared water loss through the cuticles of juvenile and adult needles of 21-month-old nursery-grown seedlings of nine hard pine species. Cuticular transpiration (CT), calculated after complete stomatal closure, was obtained by leaf-drying curves, and was related to leaf, ontogenetic and climatic parameters. The rate of cuticular transpiration (RCT) between juvenile and adult needles differed across pine species, and in particular segregated the Mediterranean species Pinus canariensis and P. halepensis, from the Eurasian P. uncinata and introduced species P. radiata. For these species, RCT was always higher in juvenile needles. The different leaf and ontogenic parameters studied were correlated with the variation in RCT among the nine pine species. We discuss this relationship in the light of the species ecology. Besides their possible adaptive interpretation, these results suggest an underlying need to consider the ontogenetic heterophylly when assessing functional traits in hard pine seedlings, in particular those traits that govern water relations.

Nutrients, buffer capacity, iminoacids and phenolic compounds as chemical parameters to indicate fire damages in Pinus pinaster trees

Changes in the level of some chemical parameters are researched in needles, juvenile needles and roots of P. pinaster trees caused by fire impact of three fire front linear intensities: 146 Kw.m-1 (QII), 357 (QI), and 423 (QIII) Kw.m-1, in Pontevedra, Galicia, NW of Spain. The most important variations are observed in needles. The free protocatechuic acid is a very sensitive parameter; it decreases to 48 p. 100 in QII, 40 p. 100 in QI and 68 p. 100 in QIII in relation to the control plot. Other good indicator is the free p-hidroxybenzoic acid, that falls in QII andQI to 61 p. 100 and 78 p. 100 respectively, and increases to 96% in the most intensity burned plot, QIII. The phosphorus level decreases in QII and QIII a 26 and 47 p. 100 respectively. The highest intensity fire (QIII) induces changes in a lot of parameters, other different from those in needles. The values of potassium, zinc and buffer capacity decrease and the values of calcium, copper, iron, astringency, total polyphenols, condensed tannins, free L-proline, free gallic acid, esterified protocatechuic and syringic acid increase. In roots, zinc is a good indicator. It descends in all cases researched. The level of total polyphenols falls in QII and QIII and free protocatechuic acid increases in QIII. In juvenile needles, except buffer capacity that decreases in QIII, we do not observe significative changes in other parameters.

Characterisation of Phenolic Constituents from Juvenile and Mature Needles of Norway Spruce by Means of High Performance Liquid Chromatography-Mass Spectrometry

The novel flavonol laricitrin 3-O-(6″-acetyl)-glucoside has been characterized in needles of Norway spruce (Picea abies) together with quercetin 3-O-(6″-acetyl)-glucoside, the 3-O-glucoside and 3-O-rutinoside of syringetin, and 3′-O-caffeoyl-quinic acid, all detected for the first time from this species. Further, taxifolin, coniferin and Z-astringin are unreported together with 24 other phenolics of different classes. Juvenile needles contain significant levels of several flavonols, whereas stilbenes and simple phenolics are predominant in mature needles. Only gallocatechin, catechin, p-hydroxyacetophenone and taxifolin appear without sugar units. Characterization of the compounds was performed using high performance liquid chromatographic retention times, masses from thermospray ionisation, and ultraviolet spectral data.

Reproductive Behavior of the Specialist Predator Elatophilus hebraicus (Hemiptera: Anthocoridae)

The reproductive biology of Elatophilus hebraicus Pericart, the principal predator of Matsucoccus josephi Bodenheimer & Harpaz (Homoptera: Matsucoccidae), was investigated. Oviposition is usually through a stoma. Eggs were laid on both adaxial and abaxial sides along the needle. In the forest usually a few eggs were inserted in a straight line through the adaxial side; additional eggs were observed in needles collected from the north-facing, inner parts of the crown. Females of E. hebraicus were exposed separately to 28 plant species. Adult needles of each of the 17 pine species employed, which consisted of both Haloxylon and Dilpoxylon, served for oviposition and successful neonate hatching. No oviposition took place in juvenile needles of tested pines. Oviposition did not occur in conifer needles other than pine or in needlelike assimilating organs of broad-leaved plants. A possible explanation of the ability of E. hebraicus to recognize pines and reject other plants is discussed. The preoviposition period ranged from 3.8 to 5.1 d. Significant differences were found in length of oviposition periods and life span under different temperature regimes. The highest mean number of eggs per female (202.7) was achieved when development and oviposition occurred at 26°C. At constant 20°C, or 18-28°C outdoors, an average female lived ≈3 mo; oviposition lasted ≈2 mo; and a female's life span was reduced to 5 and 2 wk at constant 26 and 30°C, respectively.

Fumigation with β-pinene disrupts turgor of juvenile Picea abies needle tips

Needles from seedlings of Picea abies grown in controlled temperature and photoenvironment, and from 3 m tall trees grown out-of-doors, were subjected to a short term (12 h) fumigation treatment with β-pinene. The water relations of needle tips and bases were measured at 4-h intervals during the fumigation period, using thermocouple psychrometers. Turgor of young needle tips declined significantly with fumigation. Fumigation did not decrease the turgor of needle bases or of mature needle tips. The response observed in this study may be related to membrane disruption under the influence of β-pinene. Juvenile needle tips appear to be more sensitive to β-pinene toxicity than mature needle tips or needle bases.

15N]urea foliar application effect on allocation of overwinter reserves for Pinusradiata seedling growth

Urea labelled with 15N was applied to the foliage of Pinusradiata D. Don seedlings growing outdoors in a nursery during winter. Thereafter seedlings were either left outdoors or kept under controlled-environment conditions simulating winter (6 weeks) followed by spring (6 weeks). The fate of urea N was followed by analysis of 15N. All 15N was taken up within 6 h and existed initially in the aqueous acetone soluble fraction. Nitrogen enrichment was highest in glutamine, arginine, proline, 4-aminobutyric acid, glutamic acid, and pipecolic acid. Within 1 week, amino acid and soluble-15N enrichment declined in the needles. This was more rapid in the faster growing seedlings kept outdoors. Concurrent increases of 15N in the insoluble fraction were observed in all seedlings. Subsequently, a decline in 15N enrichment predominantly from the amino acids (glutamine and arginine) was apparent. Nitrogen extracted from the insoluble-N fraction was used to sustain seedling growth. Foliar N concentration, which in this experiment was almost entirely dependent upon stored reserves, declined from 2.1 to 1.1% N over the 12-week period. Trends in foliar starch concentrations were not affected by growth conditions. Starch concentrations in needles declined during the 1st week after [15N]urea application but thereafter increased during winter and declined in spring. These results confirmed the importance of reserve N in juvenile needles for shoot expansion during spring.