Anatomical changes with needle length are correlated with leaf structural and physiological traits across five Pinus species

The genus Pinus has wide geographical range and includes species that are the most economically valued among forest trees worldwide. Pine needle length varies greatly among species, but the effects of needle length on anatomy, function, and coordination and trade‐offs among traits are poorly understood. We examined variation in leaf morphological, anatomical, mechanical, chemical, and physiological characteristics among five southern pine species: Pinus echinata, Pinus elliottii, Pinus palustris, Pinus taeda, and Pinus virginiana. We found that increasing needle length contributed to a trade‐off between the relative fractions of support versus photosynthetic tissue (mesophyll) across species. From the shortest (7 cm) to the longest (36 cm) needles, mechanical tissue fraction increased by 50%, whereas needle dry density decreased by 21%, revealing multiple adjustments to a greater need for mechanical support in longer needles. We also found a fourfold increase in leaf hydraulic conductance over the range of needle length across species, associated with weaker upward trends in stomatal conductance and photosynthetic capacity. Our results suggest that the leaf size strongly influences their anatomical traits, which, in turn, are reflected in leaf mechanical support and physiological capacity.     

Suitability of some southern and western pines as hosts for the pine shoot beetle, Tomicus piniperda (Coleoptera: Scolytidae)

The pine shoot beetle, Tomicus piniperda (L.), is an exotic pest that has become established in North America. Discovered in Ohio in 1992, it has since been found in at least 13 states and parts of Canada. The beetle can cause significant growth loss in pines, and it represents a potential threat to trees in areas where it has not yet become established. To evaluate this threat to native pines, field and laboratory tests were conducted on several common and important southern and western species to determine whether they are acceptable hosts for T. piniperda. Comparisons with Pinus sylvestris L., Scots pine, a preferred natural host for the beetle, were made where possible. Measurements of beetle attack success on southern pine billets showed that Pinus taeda L., Pinus echinata Miller, Pinus elliottii var. elliottii Engelmann, Pinus palustris Miller, and Pinus virginiana Miller (loblolly, shortleaf, slash, longleaf, and Virginia pine, respectively) and two western pines, Pinus ponderosa Lawson and Pinus contorta Douglas (ponderosa and lodgepole pine, respectively), were acceptable for breeding material, but brood production was highly variable. Among the southern pines, P. taeda and P. echinata were susceptible to shoot feeding by T. piniperda, whereas P. elliottii was highly resistant and P. palustris seemed to be virtually immune. Shoot feeding tests on the western pines were conducted only in the laboratory, but there was moderate-to-good survival of adults feeding on both species. It seems that if T. piniperda is introduced into the south and west it will likely establish and may cause some damage to native pines. P. taeda may be affected more than other southern pines because it is the most abundant species, it is readily attacked for brood production, which can result in moderately large broods, and the beetle survives well during maturation feeding on P. taeda shoots.     

湿地松林叶面积指数测算

对湿地松（Pinus elliotii）当年生和多年生两针一束、三针一束叶片的长度、宽度、厚度和重量分别进行量测,据此探讨不同类型叶片的叶形和比叶面积差异,并结合样地调查数据对中科院千烟洲试验站湿地松人工林的叶面积指数进行计算。结果表明：湿地松三针一束叶片合拢后横切面基本呈圆形,当年生叶和多年生叶的平均直径分别为1．688mm和1.706mm;两针一束叶片合拢后从统计学上讲横切面不是圆形,而是椭圆形,叶片厚度方向直径大于宽度方向（当年生叶厚度和宽度方向直径分别为1．580ram和1．422mm,多年生叶分别为1．568mm和1.410mm）,但如果把厚度和宽度方向直径的平均值近似成圆柱体直径计算时误差在3％以内;如果只用厚度或宽度方向直径代表平均直径计算结果会有2％。10％的误差;当年生叶和多年生叶、两针一束叶和三针一束叶之间比叶面积差别很大,计算的三种比叶面积（投影比叶面积、圆柱面比叶面积和比表面积）中,当年生叶的比叶面积明显大于多年生叶,三针一束叶片的投影比叶面积和比表面积都大于两针一束叶片,但圆柱面比叶面积恰好相反。湿地松林的叶面积指数若按投影叶面积算为3．61,按圆柱面的外表面算为5．12,按总表面积的一半算为4．52,比利用冠层分析仪测量的结果略大。     

Are needles of Pinus pinaster more vulnerable to xylem embolism than branches? New insights from X‐ray computed tomography

Plants can be highly segmented organisms with an independently redundant design of organs. In the context of plant hydraulics, leaves may be less embolism resistant than stems, allowing hydraulic failure to be restricted to distal organs that can be readily replaced. We quantified drought‐induced embolism in needles and stems of Pinus pinaster using high‐resolution computed tomography (HRCT). HRCT observations of needles were compared with the rehydration kinetics method to estimate the contribution of extra‐xylary pathways to declining hydraulic conductance. High‐resolution computed tomography images indicated that the pressure inducing 50% of embolized tracheids was similar between needle and stem xylem (P_{50 needle xylem} = ?3.62 MPa, P_{50 stem xylem} = ?3.88 MPa). Tracheids in both organs showed no difference in torus overlap of bordered pits. However, estimations of the pressure inducing 50% loss of hydraulic conductance at the whole needle level by the rehydration kinetics method were significantly higher (P_{50 needle} = ?1.71 MPa) than P_{50 needle xylem} derived from HRCT. The vulnerability segmentation hypothesis appears to be valid only when considering hydraulic failure at the entire needle level, including extra‐xylary pathways. Our findings suggest that native embolism in needles is limited and highlight the importance of imaging techniques for vulnerability curves.     

Structure of the Needles in the Early Phases of Development in Pinus ponderosa P. et C. Lawson with Special Reference to Plastids

Before they emerged from the fascicular sheath, the tissuesof young needles of Pinus ponderosa P. et C. Lawson alreadyshowed some characteristics typical of mature needles. The organelles,particularly the plastids, had undergone different development.The plastids in different types of cell varied in their ultrastructureand in association with the endoplasmic reticulum (ER). A sheathof ER was observed around the amoeboid plastids in epidermalcells, epithelial cells of resin ducts and maturing transfusiontracheids whereas there was no ER sheath around the young mesophyllchloroplasts, the fusiform chloroplasts in some transfusiontracheids and the proplastids in xylem and phloem cells. Thecontent of chlorophyll (a+b) was 0·85 g kg^-1 dry matterand chlorophyll a/b ratio was 2·70. The needles may becomephotosynthetically active whilst still within the fascicularsheaths.Copyright 1993, 1999 Academic Press Pinus ponderosa, ponderosa pine, needle structure, needle ontogeny, plastids, endoplasmic reticulum     

SECONDARY GROWTH IN NEEDLE LEAVES OF PINUS LONGAEVA (BRISTLECONE PINE) AND OTHER CONIFERS: QUANTITATIVE DATA

Needle leaves of Pinus longaeva can be accurately dated and remain alive on branches for 30 or more yrs, making this species ideal to study secondary growth in leaves. Field observations and regression analysis of needle age versus mean needle length both indicate primary (elongation) growth of needles is completed in the first year. Statistical analysis of cell counts for one- to 33-yr-old needles indicate production along the entire length of needles of 1.0-1.7 cell layers per year of secondary phloem, but no secondary xylem. Microscopic measurements and cell counts reveal that with advancing needle age phloem increases radially and transfusion tissue buckles, but the number of endodermal cells and xylem width do not change. Living phloem remains constant in amount (ca. 9 layers) with advancing needle age, indicating yearly replacement of old by new phloem. For comparison to P. longaeva, needle leaves were also studied for ten other conifer taxa with maximum needle longevities ranging from 3 to 19 yrs. In needles of each taxon no secondary xylem is produced, but secondary phloem production occurs throughout the post-elongation lifespan of the needles regardless of maximum needle longevity.     

Seasonality of Glutathione Dynamics in Scots Pine and Bilberry

Abstract: Seasonal changes in the glutathione status of Scots pine ( Pinus sylvestris L .) needles and bilberry ( Vaccinium myrtillus L.) stems and leaves were investigated during 1995 and 1997–1998, respectively. The glutathione concentration, the proportion of reduced glutathione (GSH%) and glutathione reductase (GR) activity were measured at monthly intervals throughout one year. The glutathione concentration and GSH% in current year's Scots pine needles were highest during late summer, but decreased during autumn. It is suggested that exchange reactions between free and protein-bound glutathione may be involved in this reduction. Both metabolites decreased towards summer in the previous year's needles. GR activity exhibited the lowest values in summer and the highest values in winter in both needle generations. In bilberry stems, glutathione peaked during midwinter, while GSH% remained high and relatively constant throughout the year. GR activity was highest in August, after which it gradually declined. In bilberry leaves, the total glutathione concentration was high in early summer. This peak was followed by a sharp decrease during midsummer. GR activity in the leaves was very low, but showed a clear increase towards autumn. Obviously, glutathione metabolism showed considerable seasonal variation in Scots pine needles and in bilberry leaves and stems, but the pattern of variation differed between the studied species and organs.     

Patterns of induced and constitutive monoterpene production in conifer needles in relation to insect herbivory

Studies were conducted to determine whether herbivore-induced synthesis of monoterpenes occurs in the needles of ponderosa pine (Pinus ponderosa Lawson), lodgepole pine (P. contorta Douglas var. latifolia Engelmann), white fir (Abies concolor Lindl. and Gordon) and Engelmann spruce [Picea engelmanii (Parry) Engelm.]. In the needles of all species except Engelmann spruce, simulated herbivory significantly induced the activity of monoterpene cyclases 4–8 days after wounding. In ponderosa pine, real herbivory by last-instar tiger moth larvae (Halisdota ingens Hy. Edwards: Lepidoptera) induced a significantly larger response (4.5-fold increase in monoterpene cyclase activity) than did simulated herbivory (2.5-fold increase). To our knowledge, this is the first report of herbivore-induced increases in monoterpene synthesis in needle tissue. Despite this increase in monoterpene synthesis, we observed no significant increase in total monoterpene pool size in wounded needles compared to controls. Large increases in the rate of monoterpene volatilization were observed in response to wounding. We conclude that the volatile losses caused by tissue damage compensate for herbivore-induced monoterpene synthesis, resulting in no change in pool size. Tiger moth larvae consume ponderosa pine needles in a pattern that begins at the tip and proceeds downward to midway along the needle, at which point they move to an undamaged needle. Constitutive monoterpene concentrations and monoterpene cyclase activities were highest in the lower half of ponderosa pine needles. The monoterpene profile also differed between the upper and lower needle halves, the lower half possessing an additional one to four monoterpene forms. We propose that the increasing gradient in monoterpene concentrations and number of monoterpenes along the needle from tip to base deters feeding beyond the midway point and provides time for the induction of increased cyclase activity and production of new monoterpenes. The induction of new monoterpene synthesis may have a role in replacing monoterpenes lost through damage-induced volatilization and preventing extreme compromise of the constitutive defense system. Received: 4 June 1997 / Accepted: 2 December 1997     

The effects of UV-B radiation on epidermal anatomy in loblolly pine (Pinus taeda L.) and Scots pine (Pinus sylvestris L.)

The effects of enhanced UV‐B radiation on the needle anatomy of loblolly pine (Pinus taeda L.) and Scots pine (Pinus sylvestris L.) were studied in the field under supplemental UV‐B radiation supplied by a modulated irradiation system. The supplemental UV‐B levels were designed to simulate either a 16 or 25% loss of stratospheric ozone over College Park, Maryland. Enhanced UV‐B radiation caused different responses in these two species. The needles of loblolly pine had larger amounts of tannin in the lumen of epidermal cells and more wall‐bound phenolics in the outer epidermal walls of UV‐B‐treated needles, whereas the most pronounced effect on Scots pine needles was increased cutinization. In both species, the outer epidermal cell walls thickened and the needle cross‐sectional and mesophyll areas decreased (statistically significantly only in Scots pine). This suggests that more carbon may have been allocated to the protection mechanisms at the expense of photosynthetic area. The difference in response between these species suggests that the response to UV‐B radiation is not mediated by a single mechanism and that no generalization with regard to the effects of UV‐B on conifers can be made.     

Nested polymerase chain reaction-based detection of Dothistroma septosporum, red band needle blight of pine, a tool in support of phytosanitary regimes

Red band needle blight is one of the most important foliar diseases of Pinus species and is of increasing international forest health and biosecurity concern. To provide a rapid identification technique for this pathogen in support of official control measures, a nested polymerase chain reaction-based diagnostic assay that employs species-specific primer sets has been developed. The assay is able to detect the presence of the pathogen direct from pine needles, irrespective of host species, to within 10 fg of target DNA, the equivalent of approximately 2-3 ascospores or hyphael cells.     

Morpho-anatomical traits of Pinus peuce needles from natural populations in Montenegro and Serbia

Variability of eight morpho-anatomical traits of two-year-old needles of the Macedonian pine (Pinus peuce Griseb.), collected from natural populations of Montenegro (Zeletin and Sjekirica) and Serbia (Mokra Gora), was investigated. The needles have two resin ducts of the external type (touching epidermis). The average values were as follows: 7.14 cm (needle length), 0.86 mm (needle width), 0.66 mm (needle thickness), 13.32 μm (cuticle+epidermis thickness), 16.24 μm (height of hypodermal cells), 1.45 (number of hypodermis layers), 2 (number of resin ducts) and 52.45 μm (resin duct diameter). The most variable characters were needle width and needle thickness. PCA visualizes overlapping of three populations. Cluster analysis suggests that the Sjekirica population is more similar to the Mokra Gora population than to the geographically nearest population of Zeletin. Given results are discussed in relation to our previous investigations of this species based on terpenes and n-alkanes, where the population from Mt. Zeletin also exhibited differences compared to the population from other Balkan localities.     

Water Potential and Leaf Elongation in Radiata Pine and Wheat

The rate of leaf elongation in radiata pine (Pinus radiata) and wheat seedlings was closely related to the osmotic potential of the rooting solution. Sudden stress application and removal treatments caused immediate changes in the leaf elongation rate and a new steady-state rate independent of the old was quickly established. The osmotic potential in the active elongation zones of a leaf differed from that of the remainder of the leaf and was considered more appropriate for deriving turgor pressure to be related to leaf elongation. Shifts in elongation rate were associated with corresponding shifts in total leaf water potential in both species and with corresponding shifts in turgor pressure in wheat. There was a linear correlation between the pitch of the helical thickenings in the protoxylem of radiata pine needles and their elongation rate. A record of elongation rate is, therefore, preserved in the needle. Developmental aspects of the deposition of the helix are discussed.     

Seasonal change in specific needle weight ofPinus thunbergii

To evaluate the reserve dynamics in pine needles, an index of specific needle weight (SNW; dry weight per unit length of needles) was provided. Developed needles ofPinus thunbergii did not show any additional elongation in their second year. Thus the seasonal change in SNW of developed needles was proved to indicate the dynamics of reserves in needles. SNW showed distinct seasonal change. It increased from autumn to carly spring, followed by a decrease by mid summer. This pattern of change was similar to the change in specific leaf weight (SLW) of evergreen broad leaves in temperate regions. It was concluded that the change in SNW indicated clearly the dynamics of reserves in needles, showing the accumulation in non-growth seasons and the consumption in subsequent growth seasons. The decrease in SNW during the growth season was 10–15% of the maximum found in early spring.     

Is the Lower Shade Tolerance of Scots Pine,Relative to Pedunculate Oak,Related to the Composition of Photosynthetic Pigments?

Foliage of Scots pine (Pinus sylvestris L.) and pedunculate oak (Quercus robur L.) was collected in a mixed pine/oak forest at canopy positions differing in radiation environment. In both species, chlorophyll (Chl) a/b ratios were higher in foliage of canopy positions exposed to higher irradiance as compared to more shaded crown layers. Throughout the growing season, pine needles exhibited significantly lower Chl a/b ratios than oak leaves acclimated to a similar photon availability. Hence, pine needles showed shade-type pigment characteristics relative to foliage of oak. At a given radiation environment, pine needles tended to contain more neoxanthin and lutein per unit of Chl than oak leaves. The differences in pigment composition between foliage of pine and oak can be explained by a higher ratio of outer antennae Chl to core complex Chl in needles of P. sylvestris which enhances the efficiency of photon capture under limiting irradiance. The shade-type pigment composition of pine relative to oak foliage could have been due to a reduced mesophyll internal photon exposure of chloroplasts in needles of Scots pine, resulting from their xeromorphic anatomy. Hence, the higher drought tolerance of pine needles could be achieved at the expense of shade tolerance.     

Desiccation of Pinus foliage induced by conifer sawfly oviposition: effect on egg viability

Abstract 1. Desiccation of needles following oviposition by Neodiprion lecontei in Pinus resinosa caused high egg mortality. Eight-five per cent of pine needles into which sawflies oviposited subsequently desiccated, compared with 2.5% of needles without eggs. No larval emergence occurred from desiccated needles.
2. Within affected shoots, the probability of desiccation increased with the extent of oviposition. In paired comparisons of needles, 41.2% of needle length was occupied by eggs in desiccated needles, compared with 24.0% of needles without desiccation.
3. Both density-dependent and density-independent factors may contribute to desiccation of egg-laden needles. The likelihood that needle vasculature will be severed by ovipositing females probably increases with population density. Drought, which was high during the observations, probably increases the incidence of needle desiccation following mechanical injury caused by oviposition.     

The hydraulic conductivity of the xylem in conifer needles (Picea abies and Pinus mugo)

Main resistances of the plant water transport system are situated in leaves. In contrast to angiosperm leaves, knowledge of conifer needle hydraulics and of the partitioning of resistances within needles is poor. A new technique was developed which enabled flow-meter measurements through needles embedded in paraffin and thus quantification of the specific hydraulic conductivity (K(s)) of the needle xylem. In Picea abies, xylem K(s) of needle and axes as well as in needles of different age were compared. In Pinus mugo, resistance partitioning within needles was estimated by measurements of xylem K(s) and leaf conductance (K(leaf), measured via 'rehydration kinetics'). Mean K(s) in P. abies needles was 3.5×10(-4) m(2) s(-1) MPa(-1) with a decrease in older needles, and over all similar to K(s) of corresponding axes xylem. In needles of P. mugo, K(s) was 0.9×10(-4) m(2) s(-1) MPa(-1), and 24% of total needle resistance was situated in the xylem. The results indicate species-specific differences in the hydraulic efficiency of conifer needle xylem. The vascular section of the water transport system is a minor but relevant resistance in needles.     

Alterations of chemical composition,construction cost and payback time in needles of Masson pine (Pinus massoniana L.) trees grown under pollution

Previous studies show that Masson pine (Pinus massoniana L.) stands grown at the industrially-polluted site have experienced unprecedented growth decline, but the causal mechanisms are poorly understood. In this study, to understand the mechanisms of growth decline of Mason pine strands under pollution stresses, we determined the reactive oxygen species levels and chemical composition of the current-year (C) and one-year-old (C + 1) needles, and calculated the needle construction costs (CC_mass) of Masson pine trees grown at an industrially-polluted site and an unpolluted remote site. Pine trees grown at the polluted site had significantly higher levels of hydroxyl radical and superoxide anion in their needles than those grown at the unpolluted site, and the former trees eventually exhibited needle early senescence. The contents of lipids, soluble phenolics and lignins in C and C + 1 needles were significantly higher at the polluted site than at the unpolluted site, but the total amounts of non-construction carbohydrates were lower in non-polluted needles than in polluted needles. Elevated levels of the reactive oxygen species and early senescence in polluted needles together led to significant increases in CC_mass and a longer payback time. We infer that the lengthened payback time and needle early senescence under pollution stress may reduce the Masson pine tree growth and consequently accelerate tree decline.     

A multitrophic interaction: consequences of grazing on decomposition of needles of <Emphasis Type="Italic">Pinus pinea</Emphasis> L. by <Emphasis Type="Italic">Ommatoiulus sabulosus</Emphasis> L.

The aim of this study was to assess how the physical (needle fragmentation by trampling) and chemical (nutritional enrichment from faeces) changes brought about by grazing influence the consumption of needles of Pinus pinea L. by Ommatoiulus sabulosus L. Adult individuals of O. sabulosus were introduced into trays with pine needles subjected to four treatments: (i) intact needles, (ii) trampled needles, (iii) intact needles fertilized with liquid manure, and (iv) trampled needles fertilized with liquid manure. After 30 days, litter decomposition was determined as a function of mass loss over time. Biometric and chemical characteristics of the needles were also measured. The pine needle decomposition rate was significantly higher in the presence of O. sabulosus (20–40%) than in its absence, presenting in addition a significantly higher rate in the treatments enriched with nitrogen. Average needle length was significantly shorter in the trampled treatments (6.89 ± 0.50 cm) than in those with intact needles (11.95 ± 0.69 cm). With regard to leaf mass per area and resistance to breakage, no significant differences were found. The fertilized treatments presented significantly higher N content (50% higher) than those in the non-fertilized ones with a significantly lower C:N ratio. The results of the present study indicate that goat grazing (which produces both trampling and fertilization) favoured the consumption of pine needles by O. sabulosus, which thus influences, along with the microbial community, the decomposition rate of these needles and thereby promotes incorporation of N into the system.     

Movement of Nutrients in Radiata Pine Needles in Relation to the Growth of Shoots

The pattern of needle growth and the movement of mineral nutrients(nitrogen, phosphorus, potassium and calcium) in needles ofradiata pine (Pinus radiata D. Don) were studied from needleinitiation to 2 years of age. During this period, very prominentcyclic patterns of nutrient accumulation, retranslocation andreplenishment were observed for nitrogen, phosphorus and potassium,which highlighted the potential role of needles as a nutrientreserve for growth. Significant retranslocation occurred from very young needlesabout 3 months after initiation. The phases of retranslocationcoincided with new flushes of shoot growth, and the growth ofnew shoots on a branch resulted in nutrient withdrawal frompre-existing needles, regardless of needle age and season. Suchwithdrawal occurred even in fertilized and irrigated trees onhigh quality sites and under environmental conditions conducivefor nutrient uptake. At all times, except for the short periodafter initiation when needles were actively growing, the nutrientsin the needle were readily available for retranslocation. Contraryto the general view, retranslocation of nutrients was not necessarilyrelated to senescence and ageing of needles. Because new shoots are the primary ‘sinks’ for retranslocatednutrients, an ongoing competition between different parts ofa branch for internal nutrients can be envisaged, preferencebeing for the youngest shoot in the hierarchy. The relevanceof these results to our understanding of ‘optimum nutrition’of pine trees is discussed. Pinus radiata D. Don, radiata pine, mineral nutrition, retranslocation, phosphorus, nitrogen, shoot growth     

马尾松受害诱导的化学物质滞后变化

通过接种马尾松毛虫Dendrolimus punctatus和人工剪叶,分析比较了不同受害方式对马尾松针叶内化学物质的影响。结果表明,害虫取食松针诱导的次生代谢物质(单宁、酚类物质)比人工剪叶处理略有增加,而营养物质-可溶性糖变化不大。对马尾松进行害虫取食为害、人工剪叶受害、未受害三种处理后,连续3年跟踪测定了松针叶内化学物质含量的变化。结果发现,无论是害虫取食为害,还是人工剪叶受害,针叶内次生代谢物质含量都减少,可溶性糖含量降低,直至一年后才恢复到原有的水平;蛋白质变化的趋势则始终是受害处理的含量比未受害处理的含量高,表明马尾松受害后诱导的化学物质变化具有滞后特性。