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Pollen morphology of Pinus (Pinaceae) in northeastChinaUnsook Song a , Joonmoh Park b & Manman Song aa Institute of Agricultural Science & Technology, Chonbuk Nat. University , Jeonju ,561-756 , Republic of Koreab Jeollabuk-Do Forest Environment Research Institute , Jinan , 567-883 , Republic ofKoreaPublished online: 02 Nov 2012.

To cite this article: Unsook Song , Joonmoh Park & Manman Song (2012) Pollen morphology of Pinus (Pinaceae) innortheast China, Forest Science and Technology, 8:4, 179-186, DOI: 10.1080/21580103.2012.704973

To link to this article: http://dx.doi.org/10.1080/21580103.2012.704973

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Pollen morphology of Pinus (Pinaceae) in northeast China

Unsook Songa*, Joonmoh Parkb and Manman Songa

aInstitute of Agricultural Science & Technology, Chonbuk Nat. University, Jeonju 561-756, Republic of Korea; bJeollabuk-Do ForestEnvironment Research Institute, Jinan 567-883, Republic of Korea

(Received 30 December 2011; Accepted 16 May 2012)

The pollen morphology of eight taxa representing Pinus species of Pinaceae in northeast China was examined by lightmicroscopy and scanning electron microscopy. The pollen grains were bisaccate monads. A single elongate outlined(monosulcate) aperture was observed on the distal pole between the sacci (air sacs) and the sculpture pattern of thecorpus (pollen body) was verrucate or rugulate, while sacci were foveolate on either smooth or coarse surfaces. A keyto pollen types of Pinus in northeast China was developed based on whether the sacci outline in polar view wasdiscontinuous (diploxylonoid) or continuous (haploxylonoid) with the corpus outline, and on the exine sculpturepatterns on the corpi and sacci. The pollen types were Densiflora, Koraiensis, Sylvestris, and Tabulaeformis. Thepollen width with sacci was highly correlated with the corpus width.

Keywords: bisaccate; diploxylonoid; haploxylonoid; Pinus; pollen morphology; pollen type

Introduction

Pinus is the primary component of many forests in cooland cold regions of the northern hemisphere from nearthe northern limits of tree growth in North America,Europe, and Asia southward to northern Africa, AsiaMinor, Malaysia, and Sumatra (Critchfield and Little1966). Pinus is the largest genus (c. 100 spp.) inPinaceae, which are the largest and both economicallyand ecologically most important family of conifers.The genus also includes the longest-lived species oftree, intermountain bristlecone pine (P. longaevaD.K. Bailey), which lives over 5000 years (Judd et al.2008).

Pinus leaves are persistent and fascicled in groupsof 1 to 5. Pinus is monoecious, with microsporophyllsin microsporangiate strobili that are spirally arrangedand bilaterally symmetrical. Two microsporangia arepresent on the abaxial microsporophyll surface. Pollengrains have two sacci (air sacs) (Figures 2A, 2D, 2F,2H, 3A, 3E). Pinus has scales that are persistent andspirally arranged in cones that mature in two years.Each cone scale is apically thickened and often armedwith a prickle when it is mature. Two inverted(micropyle directed toward the cone axis) ovules areon the adaxial cone scale surface. A long terminal wingderived from tissue of the cone scale is attached to eachseed (Judd et al. 2008); however, the wing is reduced orabsent in pinyons such as Korean pine (P. koraiensisSieb. et Zucc.), Colorado pinyon (P. edulis Engelm.)and single leaf pine (P. monophylla Torr. & Frem.)(Hardin et al. 2001). There are 2–18 cotyledons in thestraight embryo (Judd et al. 2008).

Pinaceae are divided into two subfamilies, Abietoi-deae and Pinoideae, based on congruent structural andseed protein immunological data. The latter subfamilycontains two clades, Pseudotsuga þ Larix, and Cath-aya, Picea, þ Pinus. The genus Pinus has the longestfossil record of extant Pinaceae, extending back to theJurassic or early Cretaceous. By the late Cretaceous,two monophyletic subgenera (Pinus and Strobus) haddifferentiated. Members of the subgenus Pinus arereferred to as hard pines because their wood is harderthan that of members of the subgenus Strobus, whichare often called soft pines. The two subgenera differ inother wood anatomical features and the number ofvascular bundles in each leaf. There are two vascularbundles in hard pines, but one in soft pines (Hardinet al. 2001; Judd et al. 2008).

About 22 Pinus species grow throughout China.The representative Pinus taxa are primarily distributedin three provinces in northeast China (Zhou 1986), HeiLong Jiang, Ji Lin and Liao Ning. Major mountains inthe region include Daxing’an, Lesser Xing’an andChangbai (Zheng and Fu 1978). The region meets thenorthern limit at about 508 north. Pines grow from themiddle and eastward to Amur in river valleys on low,well-drained foothills and on relatively low mountainsat altitudes of 600–900 meters. Pinus koraiensis Sieb. etZucc. and P. sylvestris var. mongolica Litv. are con-sidered to be the most economically valuable trees inthe region.

It is acknowledged that pollen morphology is usefulfor recognition, identification, and interpretation of therelationships among plants at various taxonomic levels

*Corresponding author. Email: unsooksong@chonbuk.ac.kr

Forest Science and TechnologyVol. 8, No. 4, December 2012, 179–186

ISSN 2158-0103 print/ISSN 2158-0715 online

� 2012 Korean Forest Society

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(Chung and Lee 1995; Kim and Song 1998; Song andKim 1999; Park and Song 2010). Pollen morphologyhas effectively supported the amalgamation of familiesand contributed to assigning some misplaced genera tothe correct tribes (Graham and Barker 1981). Pollenmorphology has also contributed to the combinationof various genera into a single genus (Song 2007).The pollen morphology of Pinus has been studied byIkuse (1956), Erdtman (1969), Ueno (1978), andIwanami et al. (1988), most of whom observed severalspecies by light microscopy (LM). However, Ueno(1978) compared Pinus pollen with pollen from othergenera of Pinaceae by scanning electron microscopy(SEM) and Nilsson and Praglowski (1992) reanalyzedsome of the data reported by Erdtman (1969) basedon SEM.

Zhang (1989) investigated the pollen morphologyof Pinaceae in China and classified the family into thegenus level. Xiao and Chen (1990) investigated thepollen grain development of P. thunbergii Parl.However, there have been no morphological studiesof the pollen of Pinus distributed in northeast China.Therefore, in the present study, pollen from eightrepresentative Pinus taxa including five species andthree varieties were investigated and described basedon their morphological measurement and exine sculp-ture patterns.

The objectives of this study were to describemorphological characteristics of Pinus pollen in north-east China and to contribute to further taxonomic andpalynological studies of the genus.

Materials and methods

Pollen grains of eight taxa (five species and threevarieties) of Pinus were collected from Hei Long JiangProvincial Arboretum, Northeast Forestry Universityand Northeast Forestry Experimental Center inChina. Five different samples per taxon, giving atotal of 40 samples, were observed (Table 1). Thepollen specimens have been preserved in the herbar-ium of the Department of Forest Resources, ChonbukNat. University, Republic of Korea. All pollenspecimens were examined by light and scanningelectron microscopy.

Light microscopy study

Collected pollen grains were acetolysed and mountedin glycerol jelly. An Olympus B2011 microscope wasthen used to measure eight parameters, PL1 (pollenbody length), PL2 (pollen length with sacci), PW1(pollen width), PW2 (pollen width with saccus), AL(length of saccus), AW (width of saccus), ET (exinethickness) and FL (furrow length) in equatorial view(Figure 1) (Song and Kim 1999). Sculpture patterns ofpollen grains were also investigated. Fifty pollen grainsper taxon were measured (6400) using a lightmicroscope.

Microscopic study by SEM

For scanning electron microscopy (Harley and Daly1995; Harley et al. 2005), acetolysed pollen grains weretransferred through 50%, absolute, and 75% ethanol,and then pipetted onto aluminum stubs that hadpreviously been cleaned in acetone in an ultrasonicbath. The pollen suspensions on the stubs were coveredwith an inverted glass beaker and allowed to evaporateat room temperature. The stub preparations werecoated with c. 90 nm of platinum. Subsequent

Table 1. Pollen collection locality and date of the genus Pinus in northeast China.

Taxon Locality Date

P. banksiana Lindl. & Gord. Heilongjiang Provincial Arboretum 2 July 2001P. densiflora Sieb. et Zucc. Northeast Forestry Univ. Exper. Center 3 July 2001P. densiflora var. sylvestriformis Taken Northeast Forestry Univ. Exper. Center 23 May 2001P. koraiensis Sieb. et Zucc. Heilongjiang Provincial Arboretum 15 June 2001P. sylvestris var. mongolica Litv. Northeast Forestry Univ. campus 3 July 2001P. tabulaeformis Hort. ex K. Koch Heilongjiang Provincial Arboretum 22 May 2001P. tabulaeformis var. mukdensis Uyeki Northeast Forestry Univ. campus 3 July 2001P. ussuriensis Cheng et Y.W. Law Heilongjiang Provincial Arboretum 3 July 2001

Figure 1. Schematic representation of Pinus pollen grainindicating the positions of 8 parameters measured (PL1:pollen body length, PL2: pollen length with sacci, PW1:pollen width, PW2: pollen width with saccus, AL: length ofsaccus, AW: width of saccus, ET: exine thickness and FL:furrow length) in equatorial view.

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examinations of the pollen grain (61500–2000) in thepolar and equatorial views and exine pattern(610,000–20,000) of the corpus (pollen body) andsaccus were conducted using a scanning electronmicroscope (Hitachi S-47001).

Pollen morphological and statistical analyses

The pollen shapes and patterns observed by SEM wereanalyzed to make a pollen type key to Pinus innortheast China. Pearson Correlation Analysis wasrun to determine which parameters measured by LMwere correlated.

Pollen terminology

Terminology followed Punt et al. (2007).

Results

Size of pollen grain

The bisaccate monads (PL26PW2) ranged from42.00–97.006 28.00–81.50 mm (69.056 44.89 mm onaverage). Pinus tabulaeformis var. mukdensisUyeki hadthe largest monads (74.406 51.67 mm) while Pinusbanksiana Lindl. & Gord. had the smallest(56.746 34.19 mm). The corpus size (PL16PW1)was 28.50–71.506 21.50–55.50 mm (50.536 38.39 mmon average). The saccus size (AL6AW) was 18.00–61.006 18.00–54.50 mm (30.956 30.50 mm on aver-age). The exine was as thick as 0.80–5.50 mm (2.61 mmon average). The furrow size was 4.50–17.00 mm(8.93 mm on average). Pollen morphological data foreach taxon are given in Table 2. Pearson CorrelationAnalysis of eight parameters showed that the pollenwidth with sacci (PW2) and pollen width (PW1) hadthe highest correlation (0.80). The correlation betweenpollen width (PW1) and exine thickness (ET) wasnegative (70.37).

Pollen grain shape, aperture, and exine sculpturepattern

The equatorial corpus shapes (PL1/PW1) were eitherprolate or subprolate. The polar pollen shapes withtwo sacci were either haploxylonoid (P. koraiensis) ordiploxylonoid (all remaining taxa). The outline of thesacci in polar view was basically continuous with theoutline of the corpus, imparting haploxylonoid(Figure 3F) pollen grains with a generally smoothellipsoidal form. Conversely, the outline of the sacci inpolar view was discontinuous with the outline of thecorpus, indicating that the diploxylonoid (Figures 2B,3D) pollen grains had three distinct oval parts. A singleoutline (elongated monosulcate aperture) (Figure 2D)was observed on the distal pole between two sacci,which were formed by expansion of the exine of thepollen grain. The corpus exine sculpture patterns were T

able

2.

Pollen

morphologicaldata

ofPinusin

northeast

China.

Taxon

PL1

PL2

PW1

PW2

AL

AW

ET

FL

PS

PT

P.banksiana

39.11+4.34

56.74+5.94

28.77+3.13

34.19+3.22

25.95+2.86

25.80+3.99

3.06+0.79

9.48+2.56

PTabulaeform

is(28.50–51.00)

(42.00–70.50)

(23.00–35.50)

(28.00–45.75)

(18.00–29.50)

(18.00–32.00)

(1.50–5.50)

(5.50–17.00)

P.densiflora

46.65+7.44

66.78+6.10

35.68+6.52

41.79+4.39

29.35+4.29

27.03+3.82

2.56+0.55

8.33+1.66

SP

Densiflora

(28.50–60.50)

(51.00–83.00)

(21.50–46.50)

(33.50–49.50)

(21.50–48.50)

(21.50–40.50)

(1.50–3.50)

(5.50–12.00)

P.densiflora

var.sylvestriform

is49.68+5.65

62.62+6.55

36.87+5.46

41.44+5.51

28.25+4.25

26.14+4.64

2.53+0.44

8.25+1.58

PDensiflora

(38.50–58.00)

(46.50–81.00)

(25.92–49.50)

(32.00–58.00)

(18.00–39.00)

(19.00–44.50)

(1.50–3.00)

(6.00–13.50)

P.koraiensis

56.40+4.05

81.08+3.53

39.08+3.95

49.03+3.74

33.68+2.95

34.73+3.33

2.65+0.54

11.50+2.35

PKoraiensis

(51.00–67.00)

(74.00–97.00)

(33.00–44.50)

(39.00–56.00)

(28.00–39.50)

(29.50–42.00)

(2.00–3.50)

(8.00–17.00)

P.sylvestrisvar.mongolica

50.75+6.50

70.85+4.80

40.76+3.91

45.93+4.11

32.30+3.05

33.18+3.80

2.21+0.53

8.17+1.59

SP

Sylvestris

(44.00–63.00)

(59.00–85.50)

(28.80–49.00)

(38.00–54.50)

(25.50–40.50)

(25.00–40.50)

(1.00–3.00)

(4.50–13.50)

P.tabulaeform

is54.50+6.35

72.13+6.58

42.50+5.07

49.49+6.23

34.10+5.50

33.81+5.44

2.44+0.44

8.25+1.36

SP

Tabulaeform

is(40.50–74.50)

(54.50–94.00)

(26.50–53.00)

(34.50–69.00)

(22.00–61.00)

(24.00–54.50)

(1.50–3.00)

(6.50–12.00)

P.tabulaeform

isvar.mukdensis

53.46+3.80

74.40+10.31

43.70+4.55

51.67+5.21

35.21+4.54

35.79+3.88

1.99+0.54

9.64+2.37

SP

Tabulaeform

is(43.50–61.50)

(48.50–85.50)

(28.00–55.50)

(37.00–60.50)

(24.50–47.00)

(26.50–44.00)

(1.00–3.00)

(6.50–16.00)

P.ussuriensis

50.02+6.73

67.39+6.25

38.03+5.25

45.98+6.77

29.50+3.86

28.89+4.47

2.71+0.63

8.14+1.81

SP

Tabulaeform

is(41.00–71.25)

(57.00–90.50)

(28.50–48.50)

(35.50–81.50)

(21.00–46.00)

(20.50–42.00)

(1.50–4.00)

(4.50–15.50)

Notes:PL1(mm)¼

pollen

bodylength;PL2(mm)¼

pollen

length

withsacci;PW1(mm)¼

pollen

bodywidth;PW2(mm)¼

pollen

width

withsacci;AL

(mm)¼

saccuslength;AW

(mm)¼

saccuswidth;

ET(mm)¼

exinethickness;FL(mm)¼

furrow

length;PS¼

equatorialpollen

shape(PL1/PW1),(P¼

prolate,SP¼

subprolate);andPT¼

pollen

type.

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either verrucate (P. sylvestris var. mongolica) orrugulate (the rest of taxa). The saccus exine sculptureappeared to be reticulate upon LM, but either denselyfoveolate on coarse sacci (pollen type Densiflora) orsparsely foveolate on smooth sacci (pollen typeTabulaeformis).

Pollen morphological characteristics of each taxon

P. banksiana Lindl. & Gord. [Pollen typeTabulaeformis]The corpus is 39.116 28.77 mm, the pollen grain withtwo sacci is 56.746 34.19 mm, the saccus is25.956 25.80 mm, the exine thickness is 3.06 mm, and

Figure 2. LM images of Pinus pollen. Type Densiflora: (A) P. densiflora in equatorial view, (B) P. densiflora var. sylvestriformisin polar view, Type Koraiensis: (C) P. koraiensis in polar view, Type Sylvestris: (D) P. sylvestris var. mongolica in equatorial view,and Type Tabulaeformis: (E) P. banksiana in polar view, (F) P. tabulaeformis in equatorial view, (G) P. tabulaeformis var.mukdensis in polar view, (H) P. ussuriensis in equatorial view.

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the furrow length is 9.48 mm. The corpus shape withoutsacci is prolate in the equatorial view and the wholegrain with sacci is diploxylonoid (Figure 2E) in thepolar view. The exine patterns are rugulate (Figure 4A)on the corpus, but sparsely foveolate on smooth sacci(Figure 4B).

P. densiflora Siebold & Zucc. [Pollen type Densiflora]The corpus is 46.656 35.68 mm, the pollen grain withtwo sacci (Figures 2A and 3A) is 66.786 41.79 mm, thesaccus is 29.356 27.03 mm, the exine thickness is2.56 mm, and the furrow length is 8.33 mm. The corpusshape without sacci is subprolate in the equatorial view

Figure 3. SEM images of Pinus pollen types. Type Densiflora (A-D): A-C. P. densiflora. (A) a bisaccate pollen grain inequatorial view, (B) rugulate corpus exine, (C) densely foveolate exine on the coarse saccus. D. P. densiflora var. sylvestriformis.(D) a diploxylonoid pollen grain in polar view. Type Koraiensis (E-F): P. koraiensis. (E) a bisaccate pollen grain in equatorialview, (F) a haploxylonoid pollen grain in polar view. Type Sylvestris (G-H): P. sylvestris var. mongolica. (G) verrucate corpusexine, (H) sparsely foveolate exine on the smooth saccus.

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and the whole grain with sacci is diploxylonoid in thepolar view. The exine patterns are rugulate (Figure 3B)on the corpus, but densely foveolate on the coarse sacci(Figure 3C).

P. densiflora var. sylvestriformis Taken [Pollen typeDensiflora]The corpus is 49.686 36.87 mm, the pollen grain withtwo sacci is 62.626 41.44 mm, the saccus is28.256 26.14 mm, the exine thickness is 2.53 mm, andthe furrow length is 8.25 mm. The corpus shape withoutsacci is prolate in the equatorial view and the wholegrain with sacci is diploxylonoid (Figure 3D) in thepolar view. The exine patterns are rugulate on thecorpus, but densely foveolate on the coarse sacci.

P. koraiensis Siebold & Zucc. [Pollen typeKoraiensis]The corpus is 56.406 39.08 mm, the pollen grain withtwo sacci (Figure 3E) is 81.086 49.03 mm, the saccus is33.686 34.73 mm, the exine thickness is 2.65 mm, and

the furrow length is 11.50 mm. The corpus shapewithout sacci is prolate in the equatorial view and thewhole grain with sacci is haploxylonoid (Figure 3F) inthe polar view. The exine patterns are rugulate on thecorpus, but rarely foveolate on the smooth sacci.

P. sylvestris var. mongolica Litv. [Pollen typeSylvestris]The corpus is 50.756 40.76 mm, the pollen grain withtwo sacci (Figure 2D) is 70.856 45.93 mm, the saccus is32.306 33.18 mm, the exine thickness is 2.21 mm, andthe furrow length is 8.17 mm. The corpus shape withoutsacci is subprolate in the equatorial view and the wholegrain with sacci is diploxylonoid in the polar view. Theexine patterns are verrucate (Figure 3G) on the corpus,but sparsely foveolate on the smooth sacci (Figure 3H).

P. tabulaeformis Hort. ex K. Koch [Pollen typeTabulaeformis]The corpus is 54.506 42.50 mm, the pollen grain withtwo sacci (Figure 2F) is 72.136 49.49 mm, the saccus is

Figure 4. SEM images of Pinus pollen type Tabulaeformis. A–B. P. banksiana. C–D. P. tabulaeformis. E–F. P. ussuriensis. (A),(C), (E) rugulate corpus exine, (B), (D), (F) sparsely foveolate exine on the smooth saccus.

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34.106 33.81 mm, the exine thickness is 2.44 mm, andthe furrow length is 8.25 mm. The corpus shape withoutsacci is subprolate in the equatorial view and the wholegrain with sacci is diploxylonoid in the polar view. Theexine patterns are rugulate (Figure 4C) on the corpus,but sparsely foveolate on the smooth sacci (Figure 4D).

P. tabulaeformis var. mukdensis Uyeki [Pollen typeTabulaeformis]The corpus is 53.466 43.70 mm, the pollen grain withtwo sacci (Figure 2G) is 74.406 51.67 mm, the saccusis 35.216 35.79 mm, the exine thickness is 1.99 mm,and the furrow length is 9.64 mm. The corpus shapewithout sacci is subprolate in the equatorial view andthe whole grain with sacci is diploxylonoid in the polarview. The exine patterns are rugulate on the corpus,but sparsely foveolate on the smooth sacci.

P. ussuriensis Cheng et Y.W. Law [Pollen typeTabulaeformis]The corpus is 50.026 38.03 mm, the pollen grain withtwo sacci (Figure 2H) is 67.396 45.98 mm, the saccusis 29.506 28.89 mm, the exine thickness is 2.71 mm,and the furrow length is 8.14 mm. The corpus shapewithout sacci is subprolate in the equatorial view andthe whole grain with sacci is diploxylonoid in the polarview. The exine patterns are rugulate (Figure 4E) onthe corpus, but sparsely foveolate on the smooth sacci(Figure 4F).

Pollen type key to Pinus in northeast China

1. Haploxylonoid (the sacci outline in the polar view ismore or less continuous with the outline of the corpusso that the grains appear to have a generally smoothellipsoidal form) .................................Type Koraiensis1. Diploxylonoid (the sacci outline in polar view isdiscontinuous with the outline of the corpus so that thegrains seem to consist of three distinct, more or lessoval parts)

2. Verrucate corpus . . . . . . . . . . . . . . . Type Sylvestris2. Rugulate corpus

3. Densely foveolate on coarse sacci . . . . . . . . . .. . .. . . . . .. . . . . . . . . . . . . . .. . .. . .. . .Type Densiflora

3. Sparsely foveolate on smooth sacci . . . . . . . . . .Type Tabulaeformis

Pollen type Koraiensis includes P. koraiensis, pollentype Sylvestris includes P. sylvestris var. mongolica,pollen type Densiflora includes P. densiflora andP. densiflora var. sylvestriformis, and pollen typeTabulaeformis includes P. banksiana, P. tabulaeformis,P. tabulaeformis var. mukdensis and P. ussuriensis.

Discussion

The pollen morphological LM measurements, pollenshape and exine sculpture patterns varied among taxa.

However, the overall tendencies of the taxa towardspecialization and elaboration of the pollen morphol-ogy were used to construct a pollen type key to Pinusin northeast China. The Chinese P. koraiensis pollensizes (PL1 ¼ 56.40 mm) measured in the present studywere smaller than those in North America (PL167.20 mm) (Kim et al. 1995), but larger than those inKorea (PL1 ¼ 43.21 mm) (Choi 1998). However, thesize of two taxa, P. densiflora and P. banksiana, didnot differ between Korea (Choi 1998) and China.Some species such as P. strobus, P. rigida, andP. taeda in the USA (Kim et al. 1995) were 10–20 mm bigger than those in Korea (Choi 1998). Someof the size difference among studies might have beendue to the different growing environments, speciesvariation, and sampling ranges (Kurtz and Liverman1958). As Erdtman (1969) reported, the sacci(30.966 30.50 mm) were smaller than the corpi(50.536 38.39 mm). The average exine thickness was2.61 mm, and this size did not differ significantlyamong either taxa or pollen types. The furrow length(8.93 mm) was not consistent with that of otherstudies such as those conducted by Lee (1983) andChoi (1998). Thus, pollen size itself would not besufficient to classify Pinus taxa. Analysis of pollenmorphological measurements made by LM observa-tion demonstrated their limited taxonomic value;therefore, some other non-morphological character-istics such as the presence of pollen isozymes could beadded and useful in the systematic identification ofPinus (Kim et al. 1995).

Korean pine (P. koraiensis) was haploxylonoid.That is, the outline of the sacci in polar view wasgenerally continuous with the outline of the corpus, sothat the grains appeared to have a more or less smoothellipsoidal form. However, the others were diploxylo-noid, with the outline of the sacci in polar view beingdiscontinuous with the outline of the corpus so that thegrains seemed to consist of three distinct, more or lessoval parts (Punt et al. 2007).

When only corpi of the pollen grains wereobserved, the shapes were either prolate or sub-prolate, similar to those described by Lee (1983).The exine sculpture pattern in sacci appeared to bereticulate (Figures 2C and 2D) upon LM observa-tion, which agrees with the results of a study ofnine genera of Pinaceae in China by Zhang (1989).However, SEM observation revealed that the exinesculpture patterns were either verrucate or rugulatein corpi, and either densely (Figure 3C) or sparsely(Figures 4B, 4D, 4F) foveolate in sacci. Thesefindings imply that LM observation would not besufficiently accurate in terms of exine sculpturepatterns of pollen grains. The exine patternsobserved by SEM supported the results reportedby Lee (1983) and were valuable character statesthat enabled construction of a pollen type key toPinus in northeast China.

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Conclusion

Pinus pollen grains in northeast China were bisaccatemonads that were medium or large (42–97 mm) in size.Haploxylonoid Korean pine (P. koraiensis) was char-acterized based on other pines, which were diploxylo-noid. The saccus exine sculpture patterns appearedreticulate upon LM, but foveolate upon SEM. Pinuspollen grains were discerned by their corpus exinepatterns, which were either verrucate or rugulate. Akey to four different pollen types was constructedbased on how the corpus and the two sacci wereoutlined together and on their exine sculpture patterns.Pearson correlation analysis showed that the pollengrains with bisacci were large when the corpus waslarge.

Acknowledgements

We thank Prof. Chuan Ping Yang at Northeast ForestryUniversity in China and Yong Jie Niu at Hei Long JiangProvincial Arboretum in China for pollen materials.

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