Characterization and density of trichomes on three common bean cultivars

Trichomes have been implicated as a mechanism which can confer resistance to both plant pests and drought. A study was conducted to provide information regarding genetic variability for trichome distribution and density among three diverse dry bean (Phaseolus vulgaris L.) cultivars, and to characterize the types of trichomes present among the cultivars. Trichomes on the leaf surfaces were micrographed with a scanning electron microscope (SEM) and counted using a stereomicroscope on both the abaxial and adaxial leaf surfaces of the cultivars ‘Bill Z’, ‘Pompadour Checa’ and ‘Diacol Calima’. Straight, hooked, and glandular trichomes were observed on the leaf surfaces of each cultivar. SEM micrographs are presented for the leaf surfaces of each cultivar and trichome type. The abaxial leaf surface had more straight trichomes than the adaxial leaf surface for ‘Pompadour Checa’ and ‘Diacol Calima’, however ‘Bill Z’ had more on the adaxial surface. The opposite relationship existed among the cultivars and leaf surfaces for the hooked trichomes.     

Comparative Epidermal Ultrastructure of Cotton (Gossypium hirsutum L.) Leaf, Bract and Capsule Wall

Cotton leaves are more physiologically active than the bractand the capsule wall of the fruiting structures. To elucidatethe disparities in their physiological behaviour, epidermalcell density, stomatal index, stomatal size, trichome densityand type, and epicuticular wax ultrastructure of cotton leaf,bract and capsule wall were delineated using scanning electronmicroscopy (SEM). The epidermal cells of the outer periclinalwalls on both surfaces of the leaf and bract were raised andconvex. Conversely, the capsule wall epidermal cells were polygonalwith flat outer periclinal walls. The stomatal complex in theleaf and bract was paracytic, whereas in the capsule wall thestomatal complex was anomocytic. The adaxial and abaxial stomataof the leaf were coplanar to the epidermal surface, as opposedto the raised adaxial stomata on the bract. On the contrary,the stomata on the capsule wall surface appeared to be slightlysunken. Furthermore, the capsule wall stomata were larger thanthe stomata on either surface of both the leaf and the bract.The stomatal index was greater on the abaxial surfaces of theleaf and the bract (18.4 and 9.4, respectively) than their correspondingadaxial surfaces (14.4 and 4.7, respectively). Leaves had thehighest stomatal index followed by the bract and the capsulewall. The indumentum consisted of glandular and nonglandulartrichomes, the density of which was greater on the abaxial surfacesthan on the adaxial surfaces of the leaf and bract. The capsulewall indumentum lacked nonglandular trichomes. Epicuticularwax occurred in the form of striations. However, the striationpattern varied among the organs. This study clearly illustratesmorphological disparities in the epidermal features of leaf,bract and capsule wall, helping to explain their physiologicaldivergence. Copyright 2000 Annals of Botany Company Gossypium hirsutum, epicuticular wax, raised stomata, scanning electron microscopy, stomatal index, trichomes     

Variable responses of tuber moth to the leaf trichomes of wild potatoes

This study examines the response of tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), during the initial stages of attack, to variability in trichome density and composition on foliage of Solanum berthaultii (Hawkes) and Solanum tarijense (Hawkes) (Solanaceae). Solanum berthaultii bears two types of glandular trichome (type A and type B) that together reduced oviposition by the moth. Females were often completely deterred from ovipositing on foliage with >300 trichomes per cm². In contrast, neonate establishment on S. berthaultii was generally positively related to trichome densities, indicating that trichomes may be a poor defense against P. operculella when the moth oviposits in soil and neonate larvae select the host plant. Solanum tarijense has only one type of glandular trichome (type A) and eglandular hairs. Most eggs were deposited on the adaxial leaf surfaces that had lower trichome densities. Although the density of type A trichomes was negatively related to oviposition, high densities of hairs on the abaxial and adaxial leaf surfaces appeared to stimulate oviposition, leading to stronger positive relations between hair densities and oviposition. Larvae generally established on the abaxial surface where hair densities were greatest. Relationships between the abaxial densities of leaf hairs and neonate establishment on S. tarijense were positive. The results indicate that the responses by P. operculella to the types and density of trichomes are complex. Whereas type A and type B trichomes may act synergistically to reduce oviposition by the moth, leaf hairs do not defend against oviposition and neither leaf hairs nor type A and B trichomes reduce neonate establishment by this herbivore species.     

西安市常见绿化植物叶片润湿性能及其影响因素

利用接触角测定仪测定了西安市21种常见绿化植物叶片表面的接触角,探讨了叶片表面特性如蜡质、绒毛、气孔对接触角的影响。结果表明,植物叶片正背面、物种间的接触角差异均显著,叶片正面和背面接触角大小在40°～140°。接触角大小与变异系数呈负相关,可能由于接触角小的润湿叶片在不同的生境和位置下,受到环境条件的影响较大而出现大的变异;接触角较大的非润湿性叶片,环境物质持留时间较短,对叶片形态和组成影响较小,因而出现小的变异。植物叶片表面的接触角随蜡质含量的升高而增大。表皮蜡质去除后大部分叶片接触角明显降低,尤其是疏水性较强的银杏(Ginkgo biloba)、月季(Ro-sa chinensis)和紫叶小檗(Berberis thunbergii)。女贞(Ligustrum lucidum)正背面、加杨(Popu-lus canadensis)背面等亲水型的叶片蜡质去除后接触角反而增大。叶片绒毛的多少及其形态、分布方式对接触角具有重要的影响,不同的作用方式表现出润湿和不润湿的特征,人为将其去除可以增加叶片的润湿性。背面气孔密度与气孔长度、保卫细胞长度呈负相关;接触角则与气孔密度呈负相关,与气孔长度呈正相关。     

6-Benzylaminopurine treatment induces increased pubescence on wheat leaves

The epidermis of wheat (Triticum aestivum L.) leaves contains trichomes that contribute to resistance to insect pests and drought tolerance. In the present study, we examined the effects of 6-benzylaminopurine (BA) and methyl jasmonate (MeJA) treatment on trichome development on the leaves of wheat cv. Norin 61 seedlings. Without phytohormone treatment, trichomes on the adaxial leaf surface were short (90 μm) and their density was low (3.6 trichomes/mm²). Both BA and MeJA treatments significantly increased the density of trichomes, and there were no significant differences between the phytohormone treatments. BA treatment increased trichome length to five times as long as that in the control, whereas MeJA treatment did not significantly affect trichome length. Since BA treatment concurrently increased the DNA content of the nuclei in trichome cells, endoreduplication of the nuclei is probably involved in trichome enlargement. These results indicate that even wheat cultivars with short trichomes retain the mechanisms for trichome enlargement and stimuli such as BA application can induce increased pubescence on wheat leaves.     

Leaf morphological and ultrastructural performance of eggplant (Solanum melongena L.) in response to water stress

The effects of water stress on leaf surface morphology (stomatal density, size, and trichome density of both adaxial and abaxial surfaces) and leaf ultrastructure (chloroplasts, mitochondria, and cell nuclei) of eggplant (Solanum melongena L.) were investigated in this study. Higher stomata and trichome densities were observed on abaxial surface compared with the adaxial surface. Compared with well watered (WW) plants, the stomata and trichome density of the abaxial surface increased by 20.39% and 26.23% under water-stress condition, respectively. The number of chloroplasts per cell profile was lesser, the chloroplasts became round in a shape with more damaged structure of membranes, the number of osmiophilic granules increased, and the number of starch grains decreased. The cristae in mitochondria were disintegrated. The cell nuclei were smaller and the agglomerated nucleoli were bigger than those of WW plants. Our results indicated that the morphological and anatomical responses enhanced the capability of plants to survive and grow during stress periods.     

Water Stress Induced Changes in Anatomy of Tomato Leaf Epidermes

Anatomical changes of leaf epidermes of tomato plants (Lycopersicon esculentum Mill. cv. INCA 9) submitted to water stress in the preflowering stage were studied. 20 d after germination, plants were subjected to three treatments: 1) 100 % of evapotranspired water was applied every day, 2) from 100 up to 10 % of evapotranspired water was applied every day, and 3) water supply was completely suppressed. Trichome density was similar in apical, middle and basal zones, and adaxial and abaxial leaf surfaces. Stomatal density and length, and epidermal cell length and width had similar values on the same leaf surface, but the values were higher on the abaxial than on the adaxial leaf surface. The water deficit had little effect on number of trichomes, length and width of epidermal cells and length of stomata, and decreased the stomatal density especially on adaxial surface.     

Micromorphology of the leaf epidermis in taxa of the Agropyron-Elymus complex (Poaceae)

WEBB, M. E. & ALMEIDA, M. T., 1990. Micromorphology of the leaf epidermis in taxa of the Agropyron-Elymus complex (Poaceae). A comparative analysis by scanning electron microscopy was carried out on both leaf epidermes (adaxial and abaxial) of Elymus pychnanthus (Godr.) Meld, and Agropyron glaucum Roemer & Schultes.
The adaxial epidermes of E.pychnanthus and A. glaucum are similar in the position and the shape of the long cells, silica bodies and costal and papillate prickles. They differ in the higher number of silica cells in E. pychnanthus and in the presence of intercostal hooks in A. glaucum.
The abaxial epidermes of both species are similar in the shape of interstomatal cells, silica bodies and papillate prickles. They differ in the distribution of the stomata and in the contact zones of the long cells. Elymus pychnanthus and A. glaucum differ also in the trichomes situated along the margins of the leaf blade.
These micromorphological differences, especially those of the abaxial epidermis, are useful taxonomic features.     

PATTERNS OF VARIATION IN FOLIAR TRICHOMES OF EASTERN NORTH AMERICAN QUERCUS

Scanning electron microscopy of leaf trichomes of the forty two native species of oaks in eastern North America indicates five patterns of variability: 1) Eight trichome types are evident among the species and each species possesses a definite complement of trichome types. Certain trichomes are restricted to particular subgenera and series. 2) An obvious seasonal loss of trichomes occurs during leaf maturation. This loss may be both quantitative in terms of trichome density and qualitative in terms of trichome type. 3) There is an obvious difference between the adaxial and abaxial surfaces. The adaxial side of most oak leaves is dark green, lustrous, and glabrous or glabrate. The abaxial surface either remains pubescent, becomes glabrate or glabrous, or maintains trichomes along the midrib or in the axils of major secondary veins. There are also initial quantitative and qualitative trichome differences between the two sides. 4) Geographical and ecological variations are due in part to non-genetic ecophenic modifications, ecotypic differentiation, and random genetic differences not necessarily correlated with environmental conditions. Trichome types are considered to be less affected by environment than is trichome density. 5) Hybridization and introgression within a subgenus leads to localized variability. Trichomes of hybrids are usually a combination of the parental types. These five patterns of variation are predictable and appear to be held within rather narrow limits. The complement of foliar trichomes, therefore, is a reliable character in the taxonomy of the oaks.     

Differential regulation of trichome formation on the adaxial and abaxial leaf surfaces by gibberellins and photoperiod in Arabidopsis thaliana (L.) Heynh.

In wild-type (WT) Columbia and Landsberg erecta ecotypes of Arabidopsis thaliana (L.) Heynh., trichomes are present on the adaxial surfaces of all rosette leaves but are absent from the abaxial surfaces of the first-formed leaves. We have determined that both long-day (LD) photoperiod and gibberellin (GA) stimulate trichome formation. WT plants grown in LD conditions produce the first abaxial trichome on earlier leaves than plants grown in short-day (SD) conditions. Photoperiod sensitivity of abaxial trichome formation on WT plants develops gradually over time, reaching the maximum sensitivity about 24 d after germination. Application of gibberellic acid to WT plants growing in SD conditions accelerates the onset of abaxial trichomes. Conversely, application of 20 to 80 mg L-1 paclobutrazol, a GA biosynthesis inhibitor, to wild-type plants suppresses trichome initiation on the abaxial epidermis. The GA-deficient mutants ga1-5 and ga4-1 and the GA-insensitive mutant gai-1 exhibit delayed onset of abaxial trichomes when grown in LD conditions. The null mutant ga1-3 produces completely glabrous leaves when grown in SD conditions. Application of gibberellic acid to glabrous ga1-3 plants consistently induces earlier formation of trichomes on the adaxial epidermis than on the abaxial epidermis, demonstrating a difference between the adaxial and abaxial surfaces in their response to GA with regard to trichome formation.     

Surface morphology, leaf and cuticle thickness of four dwarf shrubs from a sub-Arctic heath following long-term exposure to enhanced levels of UV-B

In 1991 a field experiment was established in subarctic heathland at Abisko (68°35'N, 18°82'E), northern Sweden, to investigate the effects of enhanced UV-B (280–315 nm) radiation, simulating 15% ozone depletion, on plants in their natural environment. Leaves of the four dominant dwarf shrubs, the deciduous Vaccinium myrtillus L. and V. uliginosum L. and the evergreen V. vitis-idaea L. and Empetrum hermaphroditum Hagerup were examined after 7 years of UV-B treatment. SEM and ESEM were used to visualize surface features and to determine trichome density. Multiphoton laser scanning microscopy showed that UV-B absorbing compounds were localized in the trichomes of all species. Trichomes varied in size, number and distribution between the species. Enhanced UV-B reduced adaxial trichome density significantly (by approximately 25%) in only one species, V. uliginosum . This effect could be of importance for the UV-B absorbing potential of the adaxial epidermis of V. uliginosum . Epicuticular wax structures were found only on the abaxial surface of V. uliginosum and were unaffected by enhanced UV-B. The cuticular surfaces of all other species were smooth and featureless. Leaf thickness, adaxial and abaxial cuticle thickness varied between the species although there was no apparent effect of enhanced UV-B. It is concluded that long-term enhancement of UV-B has an effect on adaxial trichome density in V. uliginosum , but that there is no general effect on leaf morphology of the other species.     

A new quantitative classification of ecological types in the bromeliad genus Tillandsia (Bromeliaceae) based on trichomes

Using collection specimens, we measured the density and wing area of trichomes in 37 species of the bromeliad genus Tillandsia, specifically the abaxial proximal, abaxial distal, adaxial proximal and adaxial distal parts of the leaf. The product of the trichome "wing" area by the number of trichomes (means) produced a pure number (T) that was correlated to ecological features. The correlation was positive with respect to arid environments (xeric Tillands) and negative with respect to humid environments (mesic Tillands). Bulbous, and particularly myrmecophytic species and species with tanks, represented particular categories. Other intermediate types were identified based on the T number, totalling five ecological types. In comparison with other systems of ecological typification for Tillands and other Bromeliaceae, the present system offers measurable data whose analysis is reproducible.     

The foliar trichomes of Hypoestes aristata (Vahl) Sol. ex Roem. & Schult var aristata (Acanthaceae) a widespread medicinal plant species in tropical sub-Saharan Africa: with comments on its possible phylogenetic significance

The micromorphology of foliar trichomes of Hypoestes aristata var. aristata was studied using stereo, light and scanning microscopy (SEM). This genus belongs to the advanced angiosperm family Acanthaceae, for which few micromorphological leaf studies exist. Results revealed both glandular and non-glandular trichomes, the latter being more abundant on leaf veins, particularly on the abaxial surface of very young leaves. With leaf maturity, the density of non-glandular trichomes decreased. Glandular trichomes were rare and of two types: long-stalked capitate and globose-like peltate trichomes. Capitate trichomes were observed only on the abaxial leaf surface, while peltate trichomes were distributed on both adaxial and abaxial leaf surfaces.     

地黄叶和茎的解剖学及组织化学研究

采用解剖学和组织化学方法对地黄叶和茎的显微结构以及梓醇、多糖的分布进行观察研究,以明确梓醇和多糖在地黄叶和茎中的分布特征。结果显示:(1)地黄叶的上、下表皮均分布有腺毛和非腺毛,腺毛都属于头状腺毛,包括长柄和短柄的头状腺毛,两类腺毛的分泌物化学成分主要是黄酮和多糖;叶的上、下表皮上都分布有无规则型气孔,下表皮的气孔密度比上表皮的大,但气孔指数相差不大;栅栏组织由2～3层薄壁细胞构成,排列紧密,海绵组织薄壁细胞形状无规则,细胞间隙大。(2)组织化学研究表明,海绵组织中黄斑样的薄壁细胞是梓醇和多糖的贮存场所,这类薄壁细胞在叶片边缘的齿末端处最为集中,茎的皮层、韧皮部和木质部的薄壁细胞也都是梓醇和多糖的贮存场所。     

Hydrophobic trichome layers and epicuticular wax powders in Bromeliaceae

The distinctive foliar trichome of Bromeliaceae has promoted the evolution of an epiphytic habit in certain taxa by allowing the shoot to assume a significant role in the uptake of water and mineral nutrients. Despite the profound ecophysiological and taxonomic importance of this epidermal structure, the functions of nonabsorbent trichomes in remaining Bromeliaceae are not fully understood. The hypothesis that light reflection from these trichome layers provides photoprotection was not supported by spectroradiometry and fluorimetry in the present study; the mean reflectance of visible light from trichome layers did not exceed 6.4% on the adaxial surfaces of species representing a range of ecophysiological types nor was significant photoprotection provided by their presence. Several reports suggesting water repellency in some terrestrial Bromeliaceae were investigated. Scanning electron microscopy (SEM) and a new technique-fluorographic dimensional imaging (FDI)-were used to assess the interaction between aqueous droplets and the leaf surfaces of 86 species from 25 genera. In the majority of cases a dense layer of overlapping, stellate or peltate trichomes held water off the leaf epidermis proper. In the case of hydrophobic tank-forming tillandsioideae, a powdery epicuticular wax layer provided water repellency. The irregular architecture of these indumenta resulted in relatively little contact with water droplets. Most mesic terrestrial Pitcairnioideae examined either possessed glabrous leaf blades or hydrophobic layers of confluent trichomes on the abaxial surface. Thus, the present study indicates that an important ancestral function of the foliar trichome in Bromeliaceae was water repellency. The ecophysiological consequences of hydrophobia are discussed.     

An investigation of the foliar trichomes of Tetradenia riparia (Hochst.) Codd [Lamiaceae]: An important medicinal plant of Southern Africa

The morphology and distribution of leaf trichomes of Tetradenia riparia were studied using light and scanning microscopy. Three morphologically distinct types of trichomes were observed on T. riparia leaf surfaces: glandular capitate (short and long stalked), peltate and non-glandular. The glandular and non-glandular trichomes were present in abundance on both the adaxial and abaxial surfaces. Young leaves were densely covered with trichomes; however, the density of trichomes decreases progressively with leaf maturity. This suggests that the trichomes are established early in leaf differentiation and their density decreases with leaf development and age.     

A Developmental Study of Silicification in the Trichomes and Associated Epidermal Structures of the Inflorescence Bracts of the Grass, Phalaris canariensis L

Silicon accumulation is greatest in the abaxial epidermis ofthe inflorescence bracts of Phalaris canariensis L. It occursinitially in glumes 1 week before emergence, at low levels inthe trichomes and long cells, but at high levels in the papillae.Accumulation in long cells remains low throughout, althoughit increases with time. Papillae and prickle hair silicon countsconsiderably exceed values for other epidermal structures. Siliconis also deposited in glume macrohairs before emergence, andat maturity reaches intermediate levels. Little silicon is present in the macrohairs and long cells ofthe abaxial epidermis of the fertile lemma prior to emergence.After emergence, however, silicon is rapidly accumulated inthese structures, and at maturity they have the highest siliconlevels of all the mature bract tissues. Silicon accumulation in the lemma lags behind that of the glumeuntil emergence, when it increases more rapidly, and by maturityexceeds that of the glume in macrohairs and long cells. Thesignificance of the results is discussed in relation to wallthickening, bract anatomy and panicle emergence. Phalaris canariensis, L, canary grass, inflorescence bracts, silicification, trichome, glume, lemma     

中华补血草盐腺发育的解剖学研究

采用叶表皮印痕、扫描电镜以及石蜡切片法对中华补血草的叶片进行解剖研究,观察其成熟盐腺的结构、盐腺的发育与盐腺的密度。结果表明:(1)上表皮的盐腺密度比下表皮的略小。(2)成熟的盐腺由20个细胞构成,中央有4个分泌细胞,每一个分泌细胞外侧又伴有一个长方形的毗邻细胞;向外由2层杯状细胞包围,每一层分别有4个杯状细胞,使盐腺呈近似圆形;盐腺内部靠近叶肉细胞处有4个收集细胞;中央4个分泌细胞顶端的角质层各有一小孔,是盐分泌出的通道。(3)中华补血草盐腺是由一个单独的表皮细胞发育而成,分别经历单细胞时期、2细胞时期、4细胞时期、8细胞时期、16细胞时期和20细胞时期的不同发育阶段。     

冬凌草腺毛的形态学及组织化学研究

利用光学显微镜对药用植物冬凌草地上部分腺毛的形态、分布和组织化学进行了研究。结果表明:(1)冬凌草的叶表皮有3种形态显著不同的毛,即非腺毛、盾状腺毛和头状腺毛;盾状腺毛和头状腺毛均具1个基细胞、1个柄细胞和头部;成熟的盾状腺毛的头部一般由4个分泌细胞组成,而头状腺毛头部由2个分泌细胞组成。(2)组织化学鉴定结果显示:2种腺毛中均含有黄酮类成分,盾状腺毛中还含有单萜、倍半萜等萜类成分;冬凌草甲素可能只存在于盾状腺毛中,但需要更直接的证据证明。研究认为,高密度的盾状腺毛可以作为筛选冬凌草高甲素含量品种的一项重要依据。     

Leaf epidermis of Quercus subgen. Cyclobalanopsis (Oerst.) Schneid. (Fagaceae)

The characters of leaf epidermis (mainly epidermal cells, stomata, trichomes) have been examined in 48 species of Quercus subgen. Cyclobalanopsis of the Fagaceae. The adaxial leaf epidermis was investigated under light microscope. The epidermal cells of this surface are of two types in terms of the outline of their anticlinal wall. One type is characterized by having straight wall, and this type has been observed in most of the species studied, while the other is characterized by having sinuate or sinuolate wall, and this type has been found only in eight species, such as Q. blakei and Q. hui. There exist two types of trichome-bases on this surface: in one type the bases are singlecelled, and this type has been found in most of the species studied, such as Q. oxyodon and Q. augustinii; while in the other the bases consist of a group of cells, and this type has been found only in nine species, such as Q. thorelii and Q. chungii. The abaxial leaf epidermis was investigated under light microscope and scanning electron microscope. The epidermal cells and the trichome-bases on this surface under LM are in morphology essentially similar to those on the adaxial surface. The stomata under LM include three types: cyclocytic, subcyclocytic and anomocytic. The stomatal density is of some diagnostic value to distinguish between closely related species, e.g. the stomatal density in Q. glauca is higher than that in Q. schottkyana. Under SEM the stomata are elliptical or roundish. The most noteworthy feature of the adaxial leaf epidermis is the trichomes. Eight types of trichomes have been observed under SEM: simple-uniseriate, solitary, papillae, stellate, fused-stellate, stipitate-fasciculate, multiradiate and jellyfish-like. The first type, i.e. the simple-uniseriate trichome, is glandular, other six types, i.e. the solitary, papillae, stellate, fused-stellate, stipitate-fasciculate and multiradiate trichomes, are non-glandular, and the last one, i.e. the jellyfish-like trichome, may represent an intermediate type in structure between the glandular and the non-glandular trichomes. Papillae are very common in subgen. Cyclobalanopsis although in the Fagaceae they were previously reported only in a few species of Lithocarpus. The jellyfish-like trichome, observed only in Q. sichouensis, is reported in the Fagaceae for the first time. The evolutionary trends of trichomes are discussed. The trichomes seem to evolve toward the direction of increasing complexity in structure. Papillae are considered as the pedomorphism of trichomes. From papillae the solitary trichomes and then the stellate ones have evolved. The complicated trichome types with more arms may be produced from relatively simple ones with fewer arms by means of varions fusion: several stellate trichomes are fused to form the fused-stellate ones by basal fusion, and by the same way the fused-stellate ones to form the stipitate-fasciculate ones; the multiradiate trichomes are formed by the stellate ones, in which the arms emerge in a variety of seemingly random directions from a typically rounded common base. Based on the above results, it is considered that the trichome features are of important significance for a better understanding of the infrageneric division of Quercus and the phylogenetic relationships between this genus and the other genera in the Fagaceae. The very common presence of papillae in Quercus subgen. Cyclobalanopsis and in a few species of Lithocarpus may indicate that subgen. Cyclobalanopsis is a quite natural group on the one hand, and may have close relationship with Lithocarpus on the other hand. The thin-walled, jellyfish-like trichomes found in Q. sichouensis are in structure similar to the “glandular” peltate trichomes in Trigonobalanus, a genus generally regarded as the most primitive in subfam. Quercoideae, indicating that the affinity between subgen. Cyclobalanopsis and Trigonobalanus may becloser than that between subgen. Quercus and Trigonobalanus.