稻族的系统发育及其研究进展

稻族Oryzeae是禾本科Poaceae中包含多种经济植物的重要类群, 现有大约12个属, 广布全球的热带和温带地区。由于其重要的经济价值和在理论研究上的代表性, 稻属Oryza及其近缘属的研究受到了广泛关注。虽然形态学和初步的分子证据表明稻族是一个单系类群, 但稻族内各属的分类处理和属间系统发育关系以及稻族的起源、地理分布式样和机制等方面仍存在许多悬而未决的问题。本文简要回顾了稻族系统学研究的历史, 包括稻族的建立及其在禾本科中的系统位置、稻族的族下划分、稻族各属的界定及其系统发育关系。目前已有的研究结果表明: 稻族是单系类群, 可分为两个主要分支, 相当于传统的两个亚族(Zizaniinae和Oryzinae), 但稻族单性花小穗是多次起源的, 不宜作为划分亚族的依据; 一些单型属(Hydrochloa、Porteresia和Prosphytochloa)的建立得不到分子证据的支持; 根据分子钟原理估计稻族两个主要分支(亚族)的分歧时间在大约2000万年前, 而稻属和近缘属假稻属Leersia的分歧时间为1400万年; 稻属内主要类群的分歧时间在900万年前左右。此外, 本文还对稻族的生物地理学问题进行了初步探讨, 对稻族系统发育和进化研究中存在的问题及未来研究方向进行了讨论。     

稻属叶表皮结构特征及其系统学意义

本文对稻属Oryza L. 23种植物叶片表皮的结构特征进行了观察和研究,结果表明:叶表皮的某 些性状,如在叶片脉带之间长细胞中乳突的大小和分布以及叶表皮气孔器上小乳突的数目和着生位置 在稻属的各种之间有着一定的变异规律,这在稻属各种的分类和其系统关系的研究中有一定的价值。 综合这些性状的变异特征,按照叶片下表皮脉间长细胞中乳突的大小和分布特征以及气孔器中小乳突 的数目和着生位置可将稻属这23个物种分为3组。第一组包括长颖野稻、马来野稻、疣粒野稻和颗粒 野稻,这些种的叶表皮脉间长细胞中没有大乳突和中乳突,仅偶见极稀疏分布的小乳突,气孔器中均无 小乳突。第二组包括短药野稻、二倍体和四倍体药用野稻、小粒野稻、紧穗野稻、斑点野稻、阔叶野稻、高 株野稻、大颖野稻、根茎野稻和澳洲野稻,这些种的叶表皮脉间长细胞中通常没有大、中乳突,但密布小 乳突,且大多数种的气孔器保卫细胞的近两端各有2个小乳突。第三组包括栽培稻、一年生普通野稻、 多年生普通野稻、长雄蕊野稻、展颖野稻、南方野稻、矮舌野稻、非洲栽培稻和希来特野稻,这些种的叶 表皮脉间的长细胞中常有大乳突、中乳突和小乳突,而气孔器保卫细胞的近两端各有2个明显的小乳 突,并同时常在气孔器副卫细胞的近内缘还有2～4个小乳突。     

The Structural Features of Leaf Epidermis in Oryza and Their Systematic Significance

The rice genus (Oryza L. ) belongs to the grass family(Poaceae) and contains 24 annual or perennial species, including two cultivated rice species, i.e., the Asian rice ( O. sativa L. ) and African rice (O. glaberrima Steud. ), and 22 wild species distributed throughout the tropics of the world. Species in this genus have been extensively studied by scientists with different approaches, including morphological characterization and cytological and molecular investigations. The leaf epidermis is an important morphological character which has been studied for taxonomic identification and studies on systematic relationships of species, particularly in grasses. In this study, morphological features of the leaf epidermis of 23 rice species were observed through light microscopy. The results showed that some characters of the rice leaf epidermis had significant diversity between species and these characters were valuable for the identifying Oryza species, and for assessing systematic relationships in the genus. For example, O.schlechteri, O.ridleyi, O.longiglumis, O.granulata, and O. rneyeriana had elliptic stomatal complexes, whereas the other species had rhombic stomatal complexes. In most cases, papillae on the surface of the epidermis were variable in size and distribution between species. The size of papillae varied from small ( 1.5～4.4µm in diameter), medium-sized (9～18µm), to large (21～30µm) , and the pattern of papillary size and distribution were very useful for identification of rice species. In addition, the number and location of the small papillae in stomatal complexes were particularly different between species. Based on the following combinations of leaf-epidermic characters, i.e., the size and distribution of papillae on the abaxial surface of the epidermis, the number and location of the small papillae in stomatal complexes, and the shape of stomatal complexes, the 23 studied Oryza species could be divided into three major groups. The first group comprises O.longiglumis, O.ridleyi, O.meyeriana, and O.granulata. In these species, neither large nor medium-sized papillae, in some cases extremely rare small papillae, were found on the surfaces of epidermis, and there were no small papillae found in stomatal complexes. All species in the first group had elliptic stomatal complexes. The second group consists of O.brachyantha, diploid and tetraploid O.officinalis, O.minuta, O.eichingeri, O. punctata, O.latifolia, O.alta, O.grandiglumis, O.rhizomatis, and O.australiensis. In these species usually no large papillae were observed, but medium-sized and densely populated small papillae were found to cover the surface of epidermis, and at least four small papillae were found in stomatal complexes (in guard cells) of most species. The third group contains O.sativa, O.nivara, O.rufipogon, O.longistaminata, O. glumaepatula, O.meridionalis, O.barthii, O.glaberrima and O. schlechteri. The abaxial leaf epidermis of these species was usually covered with large papillae, medium-sized, and small papillae. In addition, more than 4 (usually 6～8 ) small papillae were found in guard cells or/and subsidiary cells of the stomatal complexes. Most species in the second and third groups had rhombic stomatal complexes. These results agree mostly with previous re-ports on the biosystematic studies of rice species by applying other methodologies.     

稻属分类的现状及存在问题

稻属(Oryza L．是禾本科中重要的植物类群,该属含20余种,广泛分布于全球热带和亚热带地区。未来水稻育种的重大突破还将有赖于对稻属基因库中丰富种质资源,特别是野生稻资源的利用和开发。由于稻属植物在农业生产中的重要作用,引起了众多的植物分类学家、遗传学家、育种学家和分子生物学家的广泛研究。稻属自Linnaeus于1753年建立以来的200多年中,无论在物种的数量和分类系统上都产生了很大的变化。多位学者对稻属的属以下等级和种间的分类都做了详细的工作,对稻属现代分类系统的建立起到了重要的作用。Roschevicz(1931)对稻属全面深入的研究为后来的稻属系统分类奠定了基础。Sharma &; Shastry (1965) 建立的稻属分类系统在很大程度上受了 Roschevicz(1931)工作的影响,对属以下种以上的分类等级也处理得较合理,但是他们对稻属的分类定义较为广泛,包括了好几个如今已不放在稻属的物种。Vaughan(1989)对全球的稻属标本进行了较为全面的查证和研究,他建立的稻属系统不仅在属的界定上更为合理,而且对稻属中各物种的形态变异、地理分布和种间的关系,都有更清楚的描述。遗憾的是,Vaughan (1989)采用的属下等级——“复合体”(complex),不符合国际植物命名法规(ICBN)的规定。Lu(1999)在对前人大量工作的基础上,结合现代对稻属的研究成果并包括了近年来发表的一些新种,建立了稻属3组7系24种的分类系统。本文结合最新的研究成果对稻属作了进一步的修订,列出了以形态特征为基础的分种检索表,并对稻属分类中仍存在的一些问题进行了讨论。