《中国植物志》|| 杜鹃花科 ERICACEAE ||杜鹃花亚科 RHODODENDROIDEAE Drude ||杜鹃属 Rhododendron L.

4．杜鹃属 Rhododendron L.
L. Sp. Pl. 392. 1753; Benth. et Hook. f. Gen. P1 2 (2): 599. 1876; Drude in Engler u. Plantl, Nat. Pflanzenfam. 4(1): 35. 1889; Sleumer in Bot. Jahrb. Syst. 74(4): 511-553. 1949; Cullen et Chamb. in Not. Bot. Gard. Edinb. 36: 105-126. 1978 et 37: 327-338. 1979; Cullen in ibid. 39: 1-207. 1980; Chamb. In ibid. 39: 209-486. 1982.
灌木或乔木，有时矮小成垫状，地生或附生；植株无毛或被各式毛被或被鳞片。叶常绿或落叶、半落叶，互生，全缘，稀有不明显的小齿。花芽被多数形态大小有变异的芽鳞。花显著，形小至大，通常排列成伞形总状或短总状花序，稀单花，通常顶生，少有腋生；花萼5（-6-8）裂或环状无明显裂片，宿存；花冠漏斗状、钟状、管状或高脚碟状，整齐或略两则对称，5（-6-8）裂，裂片在芽内覆瓦状；雄蕊5-10，通常10，稀15-20（-27），着生花冠基部，花药无附属物，顶孔开裂或为略微偏斜的孔裂；花盘多少增厚而显著，5-10（-14）裂；子房通常5室，少有6-20室，花柱细长劲直或粗短而弯弓状，宿存。蒴果自顶部向下室间开裂，果瓣木质，少有质薄者开裂后果瓣多少扭曲。种子多数，细小，纺锤形，具膜质薄翅，或种子两端有明显或不明显的鳍状翅，或无翅但两端具狭长或尾状附属物。
属的模式种：Rhododendron ferrugineum L.
约960种，广泛分布于欧洲、亚洲、北美洲、主产东亚和东南亚，形成本属的两个分布中心，2种分布至北极地区，1种产大洋洲，非洲和南美洲不产。我国约542种（不包括种下等级），除新疆、宁夏外，各地均有，但集中产于西南、华南。
本属是杜鹃花科中最大的属，也是中国和喜马拉雅植物区系中的大属之一。本属植物在园艺学上占有重要的位置，自19世纪中期，J. D. Hooker从锡金发现并引回英国30种杜鹃开始，至20世纪 G. Forrest、俞德浚等人在中国西南的采集活动以来，杜鹃属植物大量被发现，被引种栽培的杜鹃已不下600种，遍及世界许多国家。由于杜鹃属植物在自然界杂交现象普遍，栽培条件下亦易于杂交变异，大量的杂交种不断被育出，且观赏价值胜于野生种。
由H. F. Tagg. J. Hutchinson, A. Rehder三人合作做出、经英国杜鹃协会于1930年出版的《The Species of Rhododendron》，首次汇编了已知的世界杜鹃属850余种，但全书划分45个系（series）的编排尚不能反映本属的分类系统。H. Sleumer于1949年提出世界杜鹃属分为8个亚属及亚属下分组、亚组的全面的分类系统。J. Cullen和D．F. Chamberlain（1978）在此基础上略有修订，即将有鳞的3个亚属（Subgen. Pseu-dazalea, Subgen. Pseudorhodorastrum, Subgen. Rhodorastrum）归并到杜鹃亚属作亚组等级，提出5个亚属的观点。随后W. R. Philipson（1980）在前两者的基础上将原置于马银花亚属Azaleastrum的2个组：Sect. Candidastrum（产北美），Sect. Mumeazalea（产日本）分别独立成亚属，并按A. Gray（1878）将云间杜鹃属 Therorhodion （Maxim.）Gray作为本属的一个亚属，提出又一8个亚属的系统。本志采纳的是H. Sleumer的系统概念和A. Gray的观点，将国有杜鹃种类分为9个亚属。

《Flora of China》|| Apiaceae || ||杜鹃属 Rhododendron

12. Rhododendron Linnaeus, Sp. Pl. 1: 392. 1753.

杜鹃属 du juan shu

Fang Mingyuan (方明渊), Fang Ruizheng (方瑞征 Fang Rhui-cheng), He Mingyou (何明友), Hu Linzhen (胡琳贞 Hu Ling-cheng), Yang Hanbi (杨汉碧 Yang Han-pi); David F. Chamberlain

Rhododendron aganniphum var. schizopeplum Credit: Harvard University Herbaria

《云南植物志》|| 杜鹃花科 Ericaceae nom. conserv. ||杜鹃花科 Ericaceae nom. conserv. ||杜鹃属 Rhododendron L.

1．杜鹃属 Rhododendron L.
灌木或乔木，有时矮小成垫状，陆生或附生；植株无毛或有各式毛被，或枝、叶、花的部分被鳞片。叶常绿或落叶，具叶柄，稀无柄，互生或数片聚生近似轮生，革质或少数落叶种类叶片纸质，全缘，极少有浅而小的齿。花芽被多数形态大小有变异的芽鳞。花大而显著，通常排列成伞形或短总状花序，稀单花，花序通常顶生，有时腋生；花萼各式，5裂稀6—8裂，或环状不裂，宿存；花冠漏斗状、钟状、管状或高脚碟状，整齐或有时略两侧对称，通常5裂，少有6—8裂，裂片在芽内覆瓦状，直立或开展；雄蕊5—10，稀达25(—27)，着生花冠基部，或多或少不等长，花丝无毛或下部有柔毛，花药背着，无附属物，顶孔开裂或为多少偏斜、椭圆形而近侧生的孔裂；花粉粘结；花盘多少增厚而显著，5—10(—14)裂；子房5—7(—20)室，花柱与雄蕊等长，或长于少有短于雄蕊，细长劲直或粗短而弯弓状。蒴果自顶部向下室间开裂，果瓣木质少有质薄。种子极多，锯屑状，常有狭翅，有时两端有尾状附属物。
本属约850种，广布于欧、亚、北美，主产于东亚和东南亚，仅1种延至热带澳大利亚。我国约470种，主要集中分布在西藏东南、云南西北和四川西南部。云南有227种。
H.Sleumer(1949)，(1980)在前人的分类工作基础上将本属分为8个亚属；J. Cullen & D.F. Chamberlain(1978)则分为5个亚属。本书基本采用的是H.Sleumer分类系统的概念。
除迎红亚属(Subg.Rhodorastrum)产亚洲东北至日本(我国东北也有)外，其余7个亚属云南均有。

《Flora of North America》|| Ericaceae || || Rhododendron

23. Rhododendron Linnaeus, Sp. Pl. 1: 392. 1753; Gen. Pl. ed. 5, 185. 1754.

Azalea [Greek rhodon, rose and dendron, tree]

Walter S. Judd, Kathleen A. Kron

Anthodendron Reichenbach; Azaleastrum (Planchon ex Maximowicz) Rydberg; Biltia Small; Hymenanthes Blume; Ledum Linnaeus; Rhodora Linnaeus; Tsusiophyllum Maximowicz; Tsutsusi Adanson

Subshrubs, shrubs, or trees, (rhizomatous or not). Stems erect (and/or creeping, prostrate in R. groenlandicum, R. lapponicum, R. tomentosum); twigs hairy or glabrous, (older twigs without peglike projections). Leaves persistent or deciduous, alternate; petiole present; blade coriaceous to membranous, (base cuneate, rounded, or obtuse), margins entire, (sometimes ciliate, plane to revolute, abaxial surface 1/3+ visible except sometimes in bud, surfaces hairy and/or scaled, midvein hairy or not, adaxial surface sometimes impressed; venation usually brochidodromous). ( Winter buds usually large, with imbricate scales; floral buds usually larger than vegetative buds.) Inflorescences terminal (axillary in R. albiflorum, short, corymbiform or rounded racemes (fasciculate racemes in R. canadense, R. lapponicum; fasciculate in R. albiflorum), 3-35-flowered (1-2-flowered in R. albiflorum); perulae brownish, scalelike, dry. ( Pedicels horizontal to erect (recurved); bracteoles 2, brownish, scalelike, basal.) Flowers bisexual, weakly bilaterally symmetric (radially symmetric in R. columbianum, R. groenlandicum, R. tomentosum, scented or not); sepals 5[-9], slightly connate; petals 5[-9], strongly to only slightly connate (sometimes nearly distinct), corolla deciduous, rotate to campanulate or funnelform; stamens 5-12[-20], included to long-exserted; (filaments usually unequal, usually unicellular-hairy, glabrous in R. vaseyi, glabrous or proximally unicellular-hairy in R. groenlandicum, R. lapponicum); anthers without awns, dehiscent by terminal pores; ovary 5[-18]-locular; style inserted in slight depression at ovary apex or smoothly intergrading, (usually curved, long, slender); stigma capitate. Fruits capsular, elongate, usually ovoid to cylindric, dehiscence usually basipetally septicidal (acropetally septicidal in R. columbianum, R. groenlandicum, R. tomentosum). Seeds (10-)100+, flattened-ellipsoidal to fusiform, often tailed, ± winged; testa smooth. x = 13.

Species ca. 1000 (25 in the flora): North America, Europe, Asia, Australia.

R. Good (1974) provided an excellent discussion of the phytogeography of Rhododendron, which occurs in arctic to tropical montane regions of North America, Europe, and Asia, extending southward to northeastern Australia. Its main centers of diversity are in the mountains of southern China and bordering countries, with a secondary center in New Guinea; eastern North America is a third center of diversity.

The species of Rhododendron are divided into subgenera (see references and discussion under various representative species). The subgenera are occasionally segregated; see, for example, H. F. Copeland (1943). The name Azalea Linnaeus often has been used for species with deciduous leaves; such use is misapplied.

Therorhodion has usually been included within Rhododendron, and these species are then placed in subg. Therorhodion (Maximowicz) A. Gray (W. R. Philipson and M. N. Philipson 1986). Here, Therorhodion is recognized as a genus distinct from Rhododendron (see K. A. Kron and W. S. Judd 1990; Kron 1997; Kron et al. 2002) because of its foliaceous perulae and base chromosome number of 12. Therorhodion probably is sister to the remaining genera of Rhodoreae (most of which belong within Rhododendron). Rhododendron is closely related to Menziesia, and the recognition of the latter may render Rhododendron paraphyletic (Kron 1997).

Numerous non-native species are grown for their beautiful flowers, and some of these, e.g., Rhododendron molle (Blume) G. Don, R. luteum Sweet, R. simsii Planchon, and R. obtusum (Lindley) Planchon, sometimes persist after cultivation. Probably, all species are poisonous due to the presence of andromedotoxin, a resinoid (M. D. McGee 1973).

SELECTED REFERENCES Chamberlain, D. F. 1982. A revision of Rhododendron II. Subgenus Hymenanthes. Notes Roy. Bot. Gard. Edinburgh 39: 209-486. Chamberlain, D. F. et al. 1996. The Genus Rhododendron: Its Classification and Synonymy. Oxford. Chamberlain, D. F. and S. J. Rae. 1990. A revision of Rhododendron IV. Subgenus Tsutsusi. Edinburgh J. Bot. 47: 89-200. Cullen, J. 1980. A revision of Rhododendron. 1. Subgenus Rhododendron sections Rhododendron and Pogonanthum. Notes Roy. Bot. Gard. Edinburgh 39: 1-207. Goetsch, L., A. J. Eckert, and B. D. Hall. 2005. The molecular systematics of Rhododendron (Ericaceae): A phylogeny based upon RPB2 gene sequences. Syst. Bot. 30: 616-626. Harmaja, H. 1991. Taxonomic notes on Rhododendron subsection Ledum (Ledum, Ericaceae), with a key to its species. Ann. Bot. Fenn. 28: 171-173. Judd, W. S. and K. A. Kron. 1995. A revision of Rhododendron VI. Subgenus Pentanthera (sections Sciadorhodion, Rhodora, and Viscidula). Edinburgh J. Bot. 52: 1-54. Kron, K. A. 1993. A revision of Rhododendron section Pentanthera. Edinburgh J. Bot. 50: 249-364. Kurashige, Y. et al. 2001. Sectional relationships in the genus Rhododendron (Ericaceae): Evidence from matK and trnK intron sequences. Pl. Syst. Evol. 228: 1-14. Philipson, W. R. and M. N. Philipson. 1986. A revision of Rhododendron III. Subgenera Azaleastrum, Mumeazalea, Candidastrum and Therorhodion. Notes Roy. Bot. Gard. Edinburgh 44: 1-23. Sleumer, H. 1980. A system of the genus Rhododendron L. In: J. L. Luteyn and M. E. O’Brien, eds. 1980. Contributions toward a Classification of Rhododendron: Proceedings, International Rhododendron Conference...May 15-17, 1978.... Bronx. Pp. 1-18.