温-压热降解实验中松粉的演变特征

松粉温-压模拟实验研究表明,热演变过程中随颜色加深,花粉个体大小收缩率可达40％以上,并且气囊比本体收缩率更高。因此,在孢粉化石鉴定时应考虑热演变程度对孢粉形态的影响。花粉热变指数、H／C、O／C原子比及镜质体反射率都是良好的热成熟度指标,前者在未熟-低熟阶段反映演变程度更为敏感,后者进入成熟阶段以后,能更详尽地描述热演变程度。花粉属于Ⅱ1型干酪根,含有大量的类脂组分,是一类良好的生油母质,其生烃能力与浮游藻类接近。     

Specific Features of Development of Male Generative Organs in Clones of the Siberian Stone Pine (Pinus sibirica De Tour) of Different Origins in the Krasnoyarsk Forest-Steppe

The development of male generative organs of the Siberian stone pine clones of different origin was analyzed in the Krasnoyarsk forest-steppe for many years. Geographical and individual variability was described as concerns the number of microstrobils and pollen variability. The beginning of flowering, abundance of microstrobils, and their regular formation were shown to markedly vary and, all other conditions being equal, be determined by the presence of clones, their hereditary features, and environmental conditions, as well by the influence of stock.     

Cell structural changes in the needles of Norway spruce exposed to long-term ozone and drought

Effects of ozone and/or drought on Norway spruce needles werestudied using light microscopy and electron microscopy. Saplingswere exposed to ozone in open-top chambers during 1992–1995and also to drought in the late summers of 1993–1995.Samples from current and previous year needles were collectedfive times during 1995. Ozone increased the numbers of peroxisomesand mitochondria, which suggests that defence mechanisms againstoxidative stress were active. The results from peroxisomes suggestthat the oxidative stress was more pronounced in the upper sideof the needles, and those from mitochondria that defence wasmore active in the younger needle generation. Possibly due tothe good nitrogen status and the active defence, no ozone-specificchloroplast alterations were seen. At the end of the season,older needles from ozone treatments had smaller central vacuolescompared with other needles. Cytoplasmic vacuoles around thenucleus were increased by ozone in the beginning of the experiment,and did not increase towards the end of the season as in thecontrols. These results from vacuoles may indicate that ozoneaffected the osmotic properties of the cells. Decreased numberand underdevelopment of sclerenchyma cells and proliferationof tonoplast were related to nutrient imbalance, which was enhancedby drought. Larger vascular cylinders and more effective starchaccumulation before and after the drought periods compensatedfor the reduced water status. Numbers of peroxisomes and mitochondriawere increased in the drought-exposed needles before the onsetof drought treatments of the study year, i.e. these changeswere memory effects. Interactions between ozone and droughtwere few.     

Seasonal variation in respiration of 1-year-old shoots of scots pine exposed to elevated carbon dioxide and temperature for 4 years

Sixteen 20-year-old Scots pine (Pinus sylvestris L.) trees growing in the field were enclosed for 4 years in environment-controlled chambers that maintained: (1) ambient conditions (CON); (2) elevated atmospheric CO2 concentration (ambient + 350 micro mol mol-1; EC); (3) elevated temperature (ambient +2-6 degrees C; ET); or (4) elevated CO2 and elevated temperature (ECT). The dark respiration rates of 1-year-old shoots, from which needles had been partly removed, were measured over the growing season in the fourth year. In all treatments, the temperature coefficient of respiration, Q10, changed with season, being smaller during the growing season than at other times. Respiration rate varied diurnally and seasonally with temperature, being highest around mid-summer and declining gradually thereafter. When measurements were made at the temperature of the chamber, respiration rates were reduced by the EC treatment relative to CON, but were increased by ET and ECT treatments. However, respiration rates at a reference temperature of 15 degrees C were reduced by ET and ECT treatments, reflecting a decreased capacity for respiration at warmer temperatures (negative acclimation). The interaction between season and treatment was not significant. Growth respiration did not differ between treatments, but maintenance respiration did, and the differences in mean daily respiration rate between the treatments were attributable to the maintenance component. We conclude that maintenance respiration should be considered when modelling respiratory responses to elevated CO2 and elevated temperature, and that increased atmospheric temperature is more important than increasing CO2 when assessing the carbon budget of pine forests under conditions of climate change.     

Light and water-use efficiencies of pine shoots exposed to elevated carbon dioxide and temperature

An automatic gas exchange system was used to continuously measure water and carbon fluxes of attached shoots of Scots pine trees (Pinus sylvestris L.) grown in environment-controlled chambers for a 3-year period (1998-2000) and exposed to either normal ambient conditions (CON), elevated CO2 (+350 micro mol mol-1; EC), elevated temperature (+2-6 degrees C; ET) or a combination of EC and ET (ECT). EC treatment enhanced the mean daily total carbon flux per unit projected needle area (Fc.d) by 17-21 %, depending on the year. This corresponds to a 16-24 % increase in light-use efficiency (LUE) based on incident photosynthetically active radiation. The EC treatment reduced the mean daily total water flux (Fw.d) by 1-12 %, corresponding to a 13-35 % increase in water-use efficiency (WUE). The ET treatment increased Fc.d by 10-18 %, resulting in an 8-19 % increase in LUE, and Fw.d by 48-74 %, resulting in a reduction of WUE by 19-34 %. There was no interaction between CO2 and temperature elevation in connection with either carbon or water fluxes, as the carbon flux responded similarly in both ECT and EC, while the water flux in the ECT treatment was similar to that in ET. Regressions indicated that the increase in maximum LUE was greater with increasing air temperature, whereas changes in WUE were related only to high vapour pressure deficit. Furthermore, changes in LUE and WUE caused by ECT treatment displayed strong diurnal and seasonal variation.     

cDNA isolation,functional expression,and characterization of (+)-alpha-pinene synthase and (-)-alpha-pinene synthase from loblolly pine (Pinus taeda): stereocontrol in pinene biosynthesis

The complex mixture of monoterpenes, sesquiterpenes, and diterpenes that comprises oleoresin provides the primary defense of conifers against bark beetles and their associated fungal pathogens. Monoterpene synthases produce the turpentine fraction of oleoresin, which allows mobilization of the diterpene resin acid component (rosin) and is also toxic toward invading insects; this is particularly the case for alpha-pinene, a prominent bicyclic monoterpene of pine turpentine. The stereochemistry of alpha-pinene is a critical determinant of host defense capability and has implications for host selection, insect pheromone biosynthesis, and tritrophic-level interactions. Pines produce both enantiomers of alpha-pinene, which appear to arise through antipodal reaction mechanisms by distinct enzymes. Using a cDNA library constructed with mRNA from flushing needles of loblolly pine (Pinus taeda), we employed a homology-based cloning strategy to isolate, and confirm by functional expression, the genes encoding (+)-(3R:5R)-alpha-pinene synthase, (-)-(3S:5S)-alpha-pinene synthase, and several other terpene synthases. The pinene synthases, which produce mirror-image products, share only 66% amino acid identity (72% similarity) but are similar in general properties to other monoterpene synthases of gymnosperms. The stereochemical control of monoterpene cyclization reactions, the evolution of "antipodal" enzymes, and the implications of turpentine composition in ecological interactions are discussed.     

Diurnal changes in needle gas exchange in alpine Pinus pumila during snow-melting and summer seasons

Pinus pumila (Pallas) Regel. is a dominant dwarf tree in alpine regions of Japan. The possible factors limiting the net photosynthetic rate (P_n) of the needles of P. pumila were examined in the snow-melting (May) and the summer (August) seasons. In August, in situ maximum P_n was 20 mol kg^–1 needle s^–1 in the current-year needles and 25 mol kg^–1 needle s^–1 in the 1-year-old needles. Diurnal trends of P_n in August were positively related to fluctuations in photosynthetic photon flux density (PPFD) and no midday depression of P_n was found, indicating that a decrease in PPFD rather than an increase in needle-to-air vapor pressure deficit (W) might cause the reduction of P_n. Both stomatal conductance (g_s) and P_n were lower in May than in August. In May, P_n and g_s were almost zero in the morning, but gradually increased with decreasing W, reaching maximum P_n values (4 mol kg^–1 needle s^–1) and g_s (60 mmol kg^–1 needle s^–1) at 16.00 hours. The daytime P_n in May was positively related to g_s. Relative water content in the exposed needles above the snow in May was 83%, which was far above the lethal level. This indicates that the water flow from stems or soils to needles was enough to compensate for a small amount of water loss due to the low g_s in May, although the water supplied to needles would be impeded by the low temperatures. Thus, the reduced g_s in May would be important for avoiding needle desiccation, and would result in a reduced P_n.     

Genetic differentiation in the winter pine processionary moth (Thaumetopoea pityocampa--wilkinsoni complex), inferred by AFLP and mitochondrial DNA markers

The winter pine processionary moth has become an important pine pest in the last century, as a consequence of the spread of pine cultivation in the Mediterranean region. The pattern of genetic differentiation of this group, that includes two sibling species (Thaumetopoea pityocampa and Th. wilkinsoni), has been studied in nine populations using amplified fragment length polymorphism (AFLP) and single strand conformation polymorphism-sequence analysis (SSCP) of the mitochondrial cytochrome oxidase 1 (COI) and cytochrome oxydase 2 (COII). Results indicate the existence of strong genetic differentiation between the two species that became separated before the Quaternary ice ages. Moreover data indicate that Th. pityocampa has a strong geographical structure, particularly evident at the nuclear level, where all pairwise phiST resulted to be highly significant and individuals from the same population resulted to be strongly clustered when an individual tree was reconstructed. The estimates of the absolute number of migrants between populations (Nm), obtained from mitochondrial and nuclear DNA markers, suggest that gene flow is low and that a gender-related dispersal could occur in this species. The males appear to disperse more than females, contributing to the genetic diversity of populations on a relatively wide range, reducing the risks of inbreeding and the genetic loss associated with bottlenecks occurring in isolated populations.     

The effect of cold temperature exposure and long-day photoperiod on the termination of the reproductive diapause of newly emerged female Pissodes strobi (Coleoptera: Curculionidae)

Abstract

• 1 There is confusion in the literature concerning a possible reproductive diapause in the adult white pine weevil Pissodes strobi.
• 2 We evaluated the effects of temperature, photoperiod, feeding substrate and mating status on the sexual maturation and oviposition of female white pine weevils.
• 3 Less than 30% of female P. strobi became sexually mature and laid eggs without experiencing dormancy under a temperature regime of 2 °C for 4 weeks.
• 4 Among the females that experienced a cold temperature treatment after emergence, 80% laid eggs after dormancy when exposed to a long‐day (LD 16 : 8 h) photoperiod and 17.6% laid eggs when exposed to a short‐day (LD 8 : 16 h) photoperiod.
• 5 Significantly more eggs were laid by all the females (with and without a cold treatment) when subjected to a long‐day photoperiod compared with a short‐day photoperiod.
• 6 A period of cold temperature followed by exposure to a long‐day photoperiod with warmer temperatures is required to break reproductive diapause and to obtain a good oviposition response in female P. strobi.
• 7 This study reveals the existence of much intraspecific variation in the response of the white pine weevil to temperature and photoperiod with respect to the induction and termination of reproductive diapause.

     

X-ray microanalytical studies of mineral localization in the needles of white pine (Pinus strobus L.)

Eastern white pine (Pinus strobus L.) shoots from mature trees were collected from two sites of contrasting soil pH: the Glendon campus of York University in Toronto, Ontario (pH 6.7 at 40 cm); and Muskoka near Huntsville, Ontario (pH 4.2 at 40 cm). Needles of ages 1-3 years were removed from the shoots, and the percentage of ash and silica was determined for all ages. Other needles were frozen in liquid nitrogen and kept in a cryo-biological storage system before x-ray microanalysis. Percentages of ash and silica were higher in the needles from Muskoka. Ash and silica increased with needle age for trees from the Muskoka site, but less so at the Toronto site. Of the 13 elements (Na, Mg, Al, Si, P, S, Cl, K, Ca, Mn, Fe, Cu and Zn) detected by microanalysis, Mn, Fe, Cu and Zn were detected in small amounts in the epidermis, endodermis and transfusion tissue (the layer of tracheids and parenchyma immediately surrounding the vascular bundles), and K, P, S and Cl were almost ubiquitous in distribution. Sodium was occasionally detected in the transfusion tissue, and magnesium was concentrated in the endodermal cells. The epidermal walls, transfusion tissue and endodermis were major sites of calcium localization. Silicon was concentrated in the extreme tips of the needles in all tissues, but particularly in the transfusion tissue, and more so in the Muskoka samples. Microanalysis revealed a higher Al content in the Muskoka needles, that Al was concentrated in the needle tips and that the transfusion tissues were major sites of accumulation.