| Northeast two vascular bundle pines are one of the most important members of the forest ecosystem in Northeast China. Its natural distribution area plays important roles in keep the balance and healthy of ecosystem in northeast of China. The natural forest of two-vascular bundle pines developed a discontinuous distribution in northeast of China. In the natural distribution area, geographical variations happened in many characteristics of the trees, such as morphologcal, anatomical, physiological, ephenological, and chemical composition of the plant, because of the natural environmental differences. The growth situation and adaptability of seedlings located in different geographic populations have closed relationship with their genetic, physiological characters, location, environment, and range of ecological adaptation. Our research targets are:(1) investigate the morphological, anatomical, and developmental characters of needles from Pinus densiflora, Pinus sylvestris var sylvestriformi, and Pinus sylvestnis var. mongolica in various geographic populations. Moreover, analyze the relationship of various populations revealed by characters of needles, seeds and seedlings, and the relationship of morphological character and genetic variation to provide the scientific basis for further investigation of two-vascular bundle pine species distribution, taxonomy, and genetic resource. (2) Based on the physiological analysis of seedlings under long term high temperature stress, reveals their characters of high temperature adaptability in various geographic populations, and provide the reference for investigation of their range of ecological adaptation, afforestation by better utilization of their spatial niches, reasonable utilization of forestry resources, and selection of optimal provenances with ability to adapt the climate warming. Further, it can provide the scientific basis for adaptive level and threshold, response and developmental tendency of northeast two-vascular bundle pine ecosystem to global climate changes.Our research results are as follows:1. The leave characters in northeast two-vascular bundle pines (Pinus densiflora, Pinus sylvestris var. sylvestriformis, Pinus sylvestnis var Mongolica) from various different geographical populations appeared difference.16 needles characteristics have obviously different among species, the same species from various populations, and indivadules in same population.The needle width(NW), ratio of needle thickness to width(TW), the number of stomatal lines (STR1, STR2), the number of endothelial cells (ENC) have higher variation levels(58-85%), which are important to separate species. The value of NW, STR, and ENC appeared Pinus sylvestnis var. mongolica> Pinus sylvestris var. sylvestriformis> Pinus densiflora, but the value of TW, SEN1/SEN2, and resin duct index (RDI) appeared object orders.2.The value of 1000-seed weight appeared Pinus densiflora> Pinus sylvestris var. sylvestriformis> Pinus sylvestnis var. mongolica. The seed germination rates of the three species are 87.45-92.53%, appeared no obviously different among species. However, the seed germination rates have significant different among populations. Mohe population and Heihe population of Pinus sylvestnis var. mongolica are higher than xingkai lake population. The germination pattern showed different among various species. Seed of Pinus sylvestnis var. mongolica appeared germinate earlier and quickly. Seed of Pinus densiflora from Korea germinated later but constitute long time. Moreover, the numbers and length of cotyledon, and height of primary seedling appeared different among species, populations and plant indivadues. The maximum is in Pinus densiflora. There is no obviously different between Pinus sylvestris var. sylvestriformis and Pinus sylvestnis var. mongolica. Xingkai lake population of Pinus densiflora has highest aforementioned value and the Jidong population has the lowest one. 3.The cluster analysis of characters of needles, seeds and seedlings from the species in nine different populations resulted three clusters. Three populations of Pinus sylvestnis var. mongolica belong to cluster one. The other cluster include three subclusters. The first subcluster comprised Xingkai lake population, Jidong population, and Erdaobaihe population, the second subcluster contained Dongning population and South Korea population, and the Antu population belongs to the third subcluster. Canonical discriminate analysis and principal components analysis of needles, seeds and seedlings from nine populations reflected that Pinus sylvestris var. sylvestriformis population interposed Pinus densiflora population and Pinus sylvestnis var. mongolica population, and closed to Pinus densiflora population.4.The northeast two-vascular bundle pine seedlings can survive under long term high temperature stress. The total biomass of seedlings of Pinus densiflora and Pinus sylvestnis var. mongolica has difference among various populations. The biomass of Pinus densiflora population was obviously higher than Pinus sylvestnis var. mongolica, except Antu population. The biomass of Xingkai lake population was five times higher than Mohe population.5. Analysis in species and population lavers respectively showed that under long term high temperature stress, the net photosynthetic rate, respiration rate (Rd), and apparent quantum yield (AQY) of species of Pinus densiflora, Pinus sylvestris var. sylvestriformis and Pinus sylvestnis var. mongolica have no obvious difference, but it is obviously different among populations.Among them, the Dongning and Xingkai population have the highest net photosynthetic rate and apparent quantum yield. AQY appeared difference among nine two-needle pine polulation. AQY of Xingkai lake population was 0.0845±0.0024 mol CO2·mol-1 photons and was the highest one. It was 13.10%-159.23% higher than others. AQY of Heihe population was the lowest. Rd of nine population also have significant difference (P<0.01). The Rd of Heihe and Xingkai lake population were highest, which was 1.62±0.18μmolCO2·m-2·s-1 and 1.52±0.30μmolCO2·m-2·S-1, respectively. The Rd of Antu and Dongning population were lowest, which were 0.40±0.01μmolCO2·m-2·S-1,0.34±0.03μmolCO2·m-2·S-1, respectively.6.Under long term high temperature stress, nonstructural carbohydrate (NSC) in seven geographical populations of Pinus densiflora and Pinus sylvestnis var. mongolica have obvious difference. The contents of soluble sugars and starch in the Pinus sylvestnis var. mongolica seedlings from three populations were obviously higher than those in four Pinus sylvestris populations. The contents of NSC of seedlings were different, which was higher in Pinus sylvestnis var. mongolica seedlings than in Pinus densiflora seedlings. In the three Pinus sylvestnis var. mongolica population, The contents of soluble sugars appeared: Heihe>Honghuaerji>Mohe. The highest contents were detected in main roots and lateral roots, and the maximum was detected in main root of Honghuaerji population. In the Pinus densiflora population, the lateral roots have high content of soluble sugars, and the highest one was 8.52%. The higher content of starch was detected in lateral roots of Pinus sylvestnis var. mongolica from Heihe and Mohe population. The content of starch in Pinus densiflora was the lowest. Except Xingkai lake population, the content of starch in the other three populations were only 2.28%-2.56%.7. Among different populations of Pinus sylvestnis var. mongolica and Pinus densiflora, the accumulation of NSC in unique plant has obviously different. The NSC in plants of Heihe and Xingkai lake population were the highest, in which the content of soluble sugars and starch were 0.68g/plant and 0.72/plant, respectively. The content of soluble sugars and starch in plants from Mohe and Antu populations were lowest, which was 0.2g/plant.8. The biomass and NSC contents among species and populations were decided by the stress conditions. The more serious stresses, the smaller biomasses, and the higher NSC content in plants. Overall, seedlings of Xingkaihu population showed strongest ability to adapt the high temperature stress in the 5 Pinus densiflora populations. Seedlings of Heihe population showed stronger ability to adapt the high temperature stress than another two populations of Pinus sylvestris var. mongolica.
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