美乐多（Melodorum fruticosum Lour．）花粉形态观察

利用扫描电子显微镜（SEM）和透射电子显微镜（TEM）观察了美乐多（Melodorum fruticosum）的花粉形态特征。美乐多花粉为球形或扁圆形的单粒花粉,外壁纹饰为微褶皱状,有点状凹陷,无任何萌发孔或萌发沟。花粉外壁由外壁外层包括覆盖层（连续）、覆盖下层、基足层（1～3层薄片层结构,偶断裂或扭曲至6～10层）和外壁内层（连续）组成。其中,覆盖下层,其厚度为整个花粉外壁厚度的1／2,为混合型结构,即小柱状和颗粒状同时存在,但以颗粒状为主。花粉内壁分为内壁外层和内壁内层,其厚度逐渐变薄。美乐多的花粉特征（单粒、无萌发孔或沟、覆盖层连续、基足层为薄片层结构、花粉外壁内层薄等）与紫玉盘族其他类群一致。     

Beschorneria yuccoides and Asimina triloba (L.) Dun: Examples for proximal polar germinating pollen in angiosperms

Beschorneria yuccoides (Agavaceae) microspores are arranged mostly in planar tetrads. Later on, the pollen grains of the tetrad usually fall apart, but sometimes remain loosely connected by ektexine elements. The ektexine consists of a tectum, of short columellae, and of a thin, discontinuous foot layer. An endexine is absent. The bilayered intine is without any additional thickening that would usually indicate an aperture region. From this point of view the pollen grain might be considered as omniaperturate. The pollen ornamentation is reticulate with wide lumina and robust, smooth muri.

The pollen grains show an indistinct sulcus characterised by a loose reticulate ornamentation. The sulcus is not exactly at the distal pole, but shifted towards the equator. No pollen tubes are formed regularly at the sulcus. Instead, pollen tubes are normally formed at the proximal pollen face. The proximal area, indicating a large germination field, is morphologically and functionally clearly an aperture (a germination zone); however, it does not represent a sulcus. The proximal face of all pollen grains appears as ornamented, with some exine lumps.

Asimina triloba (Annonaceae) pollen is shed in permanent planar or decussate tetrads. The distal sides are microreticulate to foveolate, and do not show an aperture; the psilate proximal sides are the germination areas of A. triloba.

The presence of apertures placed at the proximal pole was reported for distinct taxa of several angiosperm families. For Drosera, Dionaea (Droseraceae) and most probably for the diaperturate Cuphea species (Lythraceae) the existence of polar germination areas can be excluded. However, in some Annonaceae taxa with permanent tetrads (Annona cherimola, Asimina triloba) a situation similar to Beschorneria might be present, and indeed a proximal polar pollen tube is formed. Beschorneria yuccoides, Annona cherimola and Asimina triloba are unequivocal examples of angiosperm pollen with an exactly proximal aperture (germination area).     

Palynology of the perigoniate Aroideae: Zamioculcas,Gonatopus and Stylochaeton (Araceae)

The pollen of the perigoniate Aroideae sensu Mayo et al. (1997) ( Zamioculcas Schott, Gonatopus Hook. f. ex Engl. and Stylochaeton Lepr.) differs ultrastructurally from that of the aperigoniate Aroideae in several important exine and aperture characters. The almost identical zona-aperturate pollen of Zamioculcas and Gonatopus has outside the aperture an elaborated, thick ectexine, while the aperture consists of a thin, but continuous ectexine and a thick, lamellate endexine. In contrast, the omniaperturate pollen of Stylochaeton has a thin, not clearly stratified ectexine and a thin, heterogeneous endexine below. However, the zona-aperturate pollen of Zamioculcas and Gonatopus deviates significantly from the superficially similar zona-aperturate pollen of the unrelated Monstereae (e. g., Monstera Adans., Amydrium Schott): in the apertures of Monstera or Amydrium both the thin, but continuous ectexine and the lamellate endexine, which are typical features for Zamioculcas and Gonatopus , are absent. The palynological data underline not only the present classification of Zamioculcas , Gonatopus and of Stylochaeton into two tribes (Zamioculcadeae and Stylochaetoneae) and the differences of both tribes from the other Aroideae, but show also significant deviations in the respective zona-aperturate condition in Monstereae (Monsteroideae) and Zamioculcadeae (Aroideae).     

大血藤科花粉形态及外壁超微结构的研究

对大血藤科及木通科的八月瓜属ＨｏｌｂｏｅｌｌｉａＷａｌｌ．和木通属ＡｋｅｂｉａＤｅｃｎｅ花粉进行了光镜及电子显微镜的观察研究。研究结果表明,其花粉形态具有较为明显的相似性,如花粉均为３沟,外壁表面具穴状纹饰,甚至大小也很近似。但从其外壁结构看,大血藤花粉的外壁内层为结均一的致密层组成     

A contribution to the ultrastructural knowledge of the pollen exine in subtribe Inulinae (Inuleae, Asteraceae)

To better understand the relationships within the Asteroideae and Inuleae, the structure of the pollen exine was investigated in seven genera and nine species of the subtribe Inulinae using LM, TEM and SEM. All taxa have a senecioid pattern of exine. The tectal complex consists of three main layers that differ in thickness and morphology: a tectum, a columellar layer, and a layer consisting of the basal region of the columellae. The absence or the vestigial condition of the foramina is considered as a plesiomorphy within the Asteroideae. All taxa have a complex apertural system that consists of an ecto-, a meso-, and an endoaperture. These apertures intersect respectively the tectal complex, the foot layer and the upper part of the endexine, and the inner layer of the endexine. A continuous transition among the different species of Inulinae was found for all the quantitative characters examined. This relative homogeneity of the pollen morphological characters enhances the naturality of the subtribe Inulinae.     

The Pollen Morphology and Exine Ultrastructure of Paeonia L in China

The pollen morphology of 9 species of Paeonia L. has been investigated with both light microscope and scanning electron microscope. In addition, the exine structure of pollen grains of Paeonia suffruticosa and P. lactiflora was examined by transmission electron microscope. Tricolporoidate aperture is an important character of the pollen grains of the Paeonia. The surface of the exine is characterized by reticulate, foveolate and irregularly tuberculate-foveolate sculpture under the SEM. Thin sections of the pollen of this genus shows that the layers of exine are complete i.e. a perforate rectum to semitectum, columellae and foot layers. The endexine is continuous, considerably thickened in the aperture areas and relatively thin or indistinct in the mesocolpia. Paeonia has been placed in Ranunculaceae. But since the beginning of this century many authors have suggested to separating Paeonia from Ranunculaceae. Pollen marphology supports such separation. In Ranunculaceae most pollen grains are tricolpate or have other types of aperture, and exine with spinules and perforations between them. In electron microscopy, the ektexine contains a foot layer, columellae, and perforate rectum, the columellar layer with two types of columellae; the endexine is generally thin. However, the columellar layer of Paeonia has only monomorphic columellae. Some authors considered that there is a close relationship between Paeonia and the Dilleniaceae, but these also differ in the characters of the pollen grains. In Paeonia the constriction of the colpus in equator is in some degree similar to that of Theaceae (Camellia sasanqua Thunb.), Guttiferae (Hypericum L.), Actinidiaceae and Rosaceae. But in the other respects they are quite different. In sum, the pollen morphology of Paeonia is unique. So the palynological information supports Takhtajan's view that Paeonia should be elevated to a family (Paeoniaceae) or order (Paeoniales).     

Pollen morphology and ultrastructure of selected species of Magnoliaceae

The pollen morphology and ultrastructure of 20 species, representing eight genera of the Magnoliaceae are described based on observations with light, scanning and transmission electron microscopy. The family represents a homogeneous group from a pollen morphological point of view. The pollen grains are boat-shaped with a single elongate aperture on the distal face. The tectum is usually microperforate, rarely slightly or coarsely rugulose. Columellae are often irregular, but well-developed columellae do occur in some taxa. The endexine is distinct in 14 species, but difficult to discern in the genera Parakmeria, Kmeria and Tsoongiodendron. Within the aperture zone the exine elements are reduced to a thin foot layer. The intine has three layers with many vesicular-fibrillar components and tubular extensions in intine 1. The symmetry of the pollen grains, shape, type of aperture and ultrastructure of the intine show a remarkable uniformity in the family. Nevertheless there is variety in pollen size, ornamentation and the ultrastructure of the exine. The pollen of Magnoliaceae is an example of an early trend of specialization, and supports the view that Magnoliaceae are not one of the earliest lines in the phylogeny of flowering plants.     

Studies on Pollen Morphology of Pulsatilla Mill.

Pollen grains of 18 species of Pulsatilla in Ranunculaceae distributed in Asia and Europe were examined by LM and SEM, and exine ultrastructure of tricolpate pollen grains of P. chinensis and of pantoporate pollen grains of P. campanella was examined by TEM. Pulsatilla pollen is divided into four major types based on the aperture character, i.e. tricolpate, di- and tricolpate, pantocolpate and pantoporate. The revolutionary trend of pollen types is as follows: tricolpate→pantocolpate→pantoporate. Surface spinulate and perforate. According to density and size of sptnulae and distribution of perforation, the pollen grains of the genus can be divided into two groups. Thin sections of P. chinensis and P. campanella show endexine thickened at colpi and ora. Ektexine consists of a foot layer, a collumellae layer and a continuous, perforate tectum. The columallae layer is thicker than foot layer and tectum. Pollen morphology of Pulsatilla is similar to that of Anemone, but different in the distribution of spinules and perforation. Pollen information supports Wang’s view about systematic arrangment of species of Pulsatilla in China.     

Pollen morphology supports the transfer of Wendlandia (Rubiaceae) out of Rondeletieae

Pollen morphology of 27 species, eight subspecies and one variety of Wendlandia was studied using scanning electron microscopy (SEM). Wendlandia pollen are monads, radiosymmetric, small in size, tricolporate (rarely tetracolporate or bicolporate) and spheroidal (rarely subprolate or suboblate) in equatorial view. The compound aperture consists of ectocolpus, mesoporus and endocolpus. In addition, reticulate sexine and granular nexine were observed. The pollen wall ultrastructure of two Wendlandia spp. was examined by transmission electron microscopy (TEM). The exine consists of the tectum, columellae, foot layer and endexine. The endexine is thickened into a costa around the aperture. The intine forms a protruding oncus at the aperture. The palynological characters show a remarkable uniformity among the Wendlandia spp. Differences with Rondeletia, the main genus of tribe Rondeletieae, exist in the exine pattern, the endoaperture and the pollen wall structure. Our observations indicated that the endoaperture type and the structure of the pollen wall of Wendlandia were similar to those of the Gardenieae–Pavetteae–Coffeeae–Octotropideae clade, which provided palynological evidence for a closer relationship of Wendlandia to subfamily Ixoroideae and the transfer of Wendlandia out of Rondeletieae. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 128–141.     

Caractères ultrastructuraux du pollen de quelques Podostémales. Affinités avec les Rosidae évoluées

The order Podostemales are two pantropical families of aquatic plants living in running water: Tristichaceae (five genera, ten species) and Podostemaceae (35 genera, 200 species). Pollen of the 26 genera and 62 species studied is characterized by: a granular infratectum in which the granules are sometimes organized as columellae like units, and a lamellar and/or granular endexine in all pollen types, single or in dyads. Most of the apertural characters and the ornamentation of the exine allow us to distinguish the previously established taxonomic groups: Weddellinoideae have tricolporate rugulo-areolate, pollen with a smooth apertural membrane; in Tristichoideae, pollen is periporate and the microspines of the tectum and of the apertural membrane are massive; in Podostemaceae, the tectal spines with their broad bulbous base are formed from numerous masses of sporopollenin, the endexine is microfibrillar at the base, the apertural membrane is constituted of structured ectexinous masses, and the endexine is granular at the aperture. Presence of the tricolporate pollen type associates the Podostemales with the higher eudicotyledons. Most of the pollen characters of Podostemales and their variations are found among advanced Rosidae (Hamamelidales, Polygalales, Santalales, Violales, Euphorbiaceae).     

四种番荔枝科植物花粉形态

利用扫描和透射电子显微镜,观察了番荔枝科(Annonaceae)4属4种植物的花粉形态与结构.刺果番荔枝(Annona muricata)和金钩花(Pseuduvaria trimera)为四合花粉,有四角形、偏菱形、T-型、十字形和四面体形.前者花粉表面具小穿孔,后者为皱波状纹饰.蕉木(Oncodostigma hainanense)和那大紫玉盘(Uvaria macclurei)为单花粉,前者表面为皱波状纹饰,后者为粗褶皱状纹饰.透射电子显微镜下,蕉木和那大紫玉盘覆盖层较厚、连续.蕉木覆盖下层较薄,偶尔可见颗粒状物质或不规则小柱,为过渡型覆盖下层;那大紫玉盘覆盖下层颗粒状.基层分为内外两层,外层较厚,平或呈波浪状,内层具有2～4片层结构.在不同属或同属不同种之间,花粉特征差异较大,多样性非常丰富.金钩花具有四合花粉、覆盖下层小柱状等进化特征,同时又具有花粉粒小、覆盖层无穿孔等较原始特征.     

Comparative exine development from the post-tetrad stage in the early-divergent lineages of Ranunculales: the genera <Emphasis Type="Italic">Euptelea</Emphasis> and <Emphasis Type="Italic">Pteridophyllum</Emphasis>

Studies of pollen wall development produce a great deal of morphological data that supplies useful information regarding taxonomy and systematics. We present the exine development of Euptelea and Pteridophyllum, two taxa whose pollen wall development has never previously been studied using transmission electron microscopy. Both genera are representatives of the two earliest-diverging families of the order Ranunculales and their pollen data are important for the diagnosis of the ancestral pollen features in eudicots. Our observations show these genera are defined by having microechinate microreticulate exine ornamentation, perforate tectum, columellate morphology of the infratectum and the existence of a foot layer and endexine. The presence of lamellations is detected during the early stages of development in the nexine of both genera, especially in the apertures. Euptelea presents remains of the primexine layer during the whole maturation process, a very thin foot layer, and a laminate exinous oncus in the apertural region formed by ectexine and endexine elements. Pteridophyllum has a thicker tectum than Euptelea, a continuous foot layer and a thicker endexine. In the apertures, the exinous oncus is formed by islets and granules of endexine, in contrast to the Euptelea apertures. The secretory tapetum produces orbicules in both genera, but they have different morphology and electron-density. Comparisons with pollen data from related orders and families confirm the ancestral states for the pollen of eudicots proposed in previous studies: reticulate and echinate surfaces, columellate infractectum and a thin foot layer relative to the thickness of the ectexine. According to our observations, we propose considering the possibility of a polymorphic state for the aperture number in the ancestor of Ranunculales, and suggest the development of orbicules as the ancestral state in this order.     

On some peculiarities of sporoderm structure in members of the Cycadales and Ginkgoales

The pollen morphology and ultrastructure of Cycas micholitzii, C. simplicipinna, Cycandra profusa, Ceratozamia mexicana, and Ginkgo biloba are studied. Pollen germination is also studied in C. mexicana and G. biloba. Although dehydrated pollen grains appear monosulcate, the study of hydrated pollen shows that the aperture occupies nearly half of the pollen surface and represents a pore rather than a sulcus. In the Ginkgoales, the inaperturate ectexine is characterized by a thick solid tectum, infratectum of columella-like elements or large granules, and distinct foot layer. On the contrary, in the Cycadales, the ectexine consists of a thin tectum, alveolar infratectum, and poorly discernable foot layer. Members of the Ginkgoales have a distinct distal aperture, which is constituted by an intine, endexine, and thin ectexine. In the modern Cycadales, an ectexine is well developed throughout the pollen perimeter; in the supposed aperture region the ectexine is not reduced in thickness, although it is characterized by a thinner tectum and thinner walls of infratectal alveoli. In Cycandra profusa, no unequivocal aperture region has been found. Thickened regions were observed in the intine of both the Cycadales and Ginkgoales.     

Pollen morphology in Campanulaceae IV

The exine structure has been studied in Campanulaceae s. lat. The results are combined with those in previous studies of shape, sculpturing and aperture conditions. Fifteen further species have been studied by SEM. Two main groups of pollen are found: (1) porate pollen with spinules and ridges/protrusions or a low relief reticulum, combined with an ektexine varying from simple to complex and a lamellated endexine; (2) 3–colpate/colporate pollen with a high relief reticulate/striate surface sculpturing, in general a homogeneous ektexine and an endexine lacking lamellae. The first group corresponds to Campanulaceae s. str., the second to Lobeliaceae s. str. Some genera like Cyananthus, Codonopsis and Parishella have unique characters which make them difficult to place in any of the two main groups.     

Ontogeny of the exine in pollen of Aristea (Iridaceae)

The ontogeny of the pollen wall was studied in four species of Aristea , from the vacuolated stage of the microspores, to observe the possible formation of an endexine. At this stage, the ectexine is completely formed (tectum, columellae, and structurally homogeneous foot layer), but its maturation is incomplete and variable depending on the species. In all cases, there are one or several tripartite lamellae with a white line under the foot layer, in the apertural and extra-apertural regions. In A. major , and A. pauciflora , the exintine is not yet present, whereas in A. macrocarpa and A. glauca , it has started to initiate. In mature pollen of the four species, the tripartite endexine lamellae of the vacuolated stage disappear and there is no trace of endexine. The tripartite intine is completely formed. Maturation of exine is complete and it appears homogeneous and of medium electron density, except in A. glauca , which has particularly fragile exine, where it remains incomplete with a granular and highly electron dense appearance, which contrasts with the usually mature exine. Despite the very clear presence of endexine lamellae at the vacuolated stage, it is thus very difficult to conclude that endexine exists in pollen of the genus Aristea .     

A unique pollen wall mutation in the family Compositae: ultrastructure and genetics

During a routine screening of pollen fertility in the n = 2 chromosome race of Haplopappus gracilis, a spineless pollen wall mutation was discovered that renders the otherwise functional pollen grains completely unrecognizable as Compositae pollen. Normal Haplopappus pollen is characterized by an outer layer, the ektexine, consisting of large spines supported by a roof (tectum), which in turn is supported by collumellae that are joined basally. A large cavity (cavea) stretches from aperture to aperture and separates columellae bases from the final ektexine unit, the foot layer. The spines, tectum, columellae, and columellae bases are filled with perforations (internal foramina), while the foot layer is without them. Immediately underlying the foot layer is a thickened, lamellate, disrupted, internal foramina-free second exine layer, the endexine. In contrast, the mutant pollen ektexine is a jumble of components with randomly dispersed spines as the only clearly definable unit. The endexine layer is similar to the endexine in normal pollen. The mutation apparently disrupts only the organization of ektexine units, and mutant pollen appears to be without the caveae and foot layer characteristic of normal pollen. In genetic tests, the mutant allele is recessive. There is a simple Mendelian pattern of inheritance of the mutant gene, and its phenotype is under sporophytic control.     

Microspore and tapetal development in Echinodorus cordifolìus (Alismaceae)

In the microspore tetrad period the exine begins as rods that originate from the plasma membrane. These rods are exine units that on further development become columellae as well as part of the tectum, foot layer and “transitory endexine”. The primexine matrix is very thin in the future sites of the pores. At these sites the plasma membrane and its surface coating (glycocalyx) are without exine units and adjacent to the callose envelope. The exine around the aperture margin is characterized by units of reduced height. After the exine units and primexine matrix have become ca 0.2 μm in height a fibrillar zone forms under the aperture margin. It is the exine units around the aperture that are templates for exine processes on apertures of mature pollen. Oblique sections of the early exine show that the tectum consists of the distal portions of close-packed exine units. The exine enlarges in the free microspore period but initially its substructure (tectum, columellae, foot layer and transitory endexine) is not homogeneous and unit structures are visible until after the vacuolate microspore period. There are indications of a commissural line/plane (junction plane) which separates the foot layer from the endexine during early development. Our observations of development in Echinodorus pollen extend a growing number of reports of “transitory endexines” in monocot pollen. The exine unit-structures become 0.2 μm or more in diameter and many columellae are composed of only one exine unit. Spinules become exceptionally tall, many protruding ca 0.7 μm above the level of the tectum as units only ca 0.1 μm in diameter. The outer portion of the tectum fills in around spinules and by maturity they are microechinate with their bases spread out to ca 1 μm or more. Unit structures can be seen with SEM in mature pollen following oxidation by plasma ashing and in the tapetum these units are arranged both radially, as in spinules, and parallel with the tapetal surfaces. There are clear indications of such an arrangement of units in untreated fresh pollen. Units comprising the basal part of the exine are not completely fused by sporopollenin accumulated during development. This would seem to be a characteristic feature, based on published work, of the alismacean pollen. Our use of a tracer shows, however, that there is considerable space within or between exine structure of mature Echinodorus pollen. Based upon the ca 0.1 μm size of exine-units formed early in development and exine components seen after oxidative treatment it seems that the early (primary) accumulated sporopollenin has greater resistance to oxidation than sporopollenin added, secondarily, around and between units later in development. Both primarily and secondarily accumulated sporopollenin are resistant to acetolysis but published work indicates that acetolysis alters exine material. At the microspore tetrad time and until the vacuolate stages tapetal cells are arranged as in secretory tapetums. During early microspore stages there are orbicules at the inner surface of tapetal cells. At free microspore period tapetal cells greatly elongate into the loculus and surround the microspores. By the end of the microspore vacuolate period tapetal cells release their cellular contents and microspores are for a time enveloped by tapetal organelles and translocation material.     

POLLEN APERTURE EVOLUTION AMONG THE SUBFAMILIES PERSOONIOIDEAE,SPHALMIOIDEAE, AND CARNARVONIOIDEAE (PROTEACEAE)

Pollen apertures were analyzed among the subfamilies Persoonioideae (seven genera; ca. 95 spp.), Sphalmioideae (one genus; one spp.), and Camarvonioideae (one genus; two spp.). Pollen was examined by light microscopy, cryosection, and transmission electron microscopy. Completed studies of pollen apertures among Grevilleoideae (ca. 40 genera; ca. 800 spp.), one of two major subfamilies in Proteaceae, provide a basis for comparison and analysis of aperture evolution among these subfamilies. Aperture characters within Persoonioideae are unique among Proteaceae examined to date. Five distinct aperture types occur among the three subfamilies, three of which (Placospermum, Persoonia, Bellendena) are restricted to Persoonioideae. Sphalmioideae and Camarvonioideae each exhibit a unique aperture organization. The most primitive aperture organization, and one unique to Placospermum, exhibits three main features: 1) a thin, granular endexine continuous around the grain; 2) a heterogeneous foot layer throughout the grain with increased disruptions at the aperture; and 3) only slight differences in exine characters between apertural and nonapertural regions. The Persoonia aperture type represents the next stage of aperture evolution which involves loss of endexine, restriction of a heterogeneous foot layer to the aperture, and marked differences in exine characters between apertural and nonapertural regions. The uniformly homogeneous ektexine in both nonapertural and aperture regions in Bellendena has developed independently. Sphalmium exhibits a primitively thin granular endexine though the restriction of endexine to the aperture is a derived condition. Carnarvonia exhibits several pollen characters also found among Grevilleoideae including: 1) a homogeneous nonapertural ektexine; 2) a slightly heterogeneous apertural ektexine; 3) a lamellate/granulate endexine organized into irregularly shaped “clumps” clustered around the aperture; and 4) a clear demarcation between apertural and nonapertural exine. These characters support the hypothesis that Carnarvonia may have diverged early from the pre-Grevilleoids.     

五列木科和肋果茶科花粉外壁超微结构及其与山茶科的系统学关系

借助光学显微镜、扫描电镜和透射电镜对五列木科Ｐｅｎｔａｐｈｙｌａｃａｃｅａｅ和肋果茶科Ｓｌａｄｅｎｉａｃｅａｅ花粉进行了观察,并与山茶科Ｔｈｅａｃｅａｅ若干属的花粉进行了详细的比较,同时参考了猕猴桃科Ａｃｔｉｎｉｄｉａｃｅａｅ的花粉特征。研究表明,肋果茶科的花粉与山茶科的花粉具有较多的相似性,如其形状和大小与山茶科中厚皮香亚科的几乎一致;而花粉的表面纹饰（粗糙至模糊的皱波状纹饰）则与山茶属,Ｆｒｅｚｉｅｒａ属和厚皮香亚科部分属的花粉纹饰相类似。从花粉外壁的结构看,肋果茶的花粉与石笔木属和山茶属的更接近,表现为：花粉外壁层次分化明显,复盖层和柱状层均较厚,外壁内层薄。而五列木科花粉除了形状和萌发孔类型与山茶科的相似外,其纹饰特征和外壁结构均与山茶科的差异较大,如五列木科花粉表面近光滑,外壁覆盖层较簿,柱状层很不发达,外壁内层相对较厚等。孢粉学上认为,肋果茶科与山茶科具有更为密切的关系,五列木科则与山茶科较疏远。支持把肋果茶科作为一个属置于山茶科内或作为山茶科的一个亚科