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植物研究雑誌 J. J. Jpn. Bot. 66: 66: 319-351 (1991) Anatomical Structure of Fruits and Evolution of the Tribe Sorbeae in the Subfamily Maloideae (Rosaceae) 1 Hiroyuki IKETANI ) and Hiroyoshi OHASHI Biological Biological Institute ，Faculty of Science ，Tohoku University ， Sendai ，980 ，JAP AN パラ科ナシ亜科ナナカマド連における果実の解剖学的構造と進化 池谷祐幸 1) ，大橋広好 東北大学理学部生物学教室 980 仙台市青葉区荒巻字青葉 (Received (Received on July 6， 1991) Structures Structures of fruits of 61 species of 17 genera of the tribe Sorbeae (Rosaceae-Maloideae) 訂 e anatomically anatomically examined. Structure of the pulp is different at the generic level in Sorbeae. Nearly half of of the genera examined have a homogeneous pulp structure consisting of parenchyma and few or no stone stone cells. In contrast ， the other genera have several kinds of heterogeneous pulp structure consisting of of parenchyma ， stone cells ， and pigment cells. The inner epidermis does not be sclerified in most of genera ， but in some genera it becomes sclerenchymatous. Hypothetical Hypothetical evolutionary trends of the structure of the fruits in Maloideae are proposed. The fruit fruit of Crataegeae is inferred as more primitive than that of Sorbeae. Pulp structure of Sorbeae may have have been evolved through loss of sclerenchymatous cells and/or through specialized distributional pattem pattem of sclerenchymatous cells and pigment cells ，e. g. ，clusters of stone cells in the center of the flesh flesh (Pourthiaea) ，clusters of large sized pigment cells and/or stone cells in the whole part of the flesh (Micromeles (Micromeles and subgenera Aria and Chamaemespilus of Sorbus) ， and clusters of stone cells in the inner inner flesh (subgenus Torminalia of Sorbus). Phylogenetic relationships of the genera of Sorbeae are inferred inferred based on these evolutionary trends. Introduction Introduction Decaisne (1874) first recognized the diversity of The subfamily Maloideae is divided into two pulp structure in Sorbeae. He discovered the tribes ， Crataegeae and Sorbeae ， based on heterogenωus nature of the pulp with normal-sized characters characters of the fruit (Koehne 1890 ，Schluze 回 Menz parenchyma and large cells in Pourthiaea ， 1964 ，Kovanda 1965 ，Phipps et al. 1990). In Micromeles ， and subgenus Aria (including Crataegeae almost all parts of the carpel become Chamaemespilus) of Sorbus. This was not bony in the mature fruit and the fruit becomes evaluated as a taxonomic character until the middle drupe-like. drupe-like. This does not occur in the fruits of the of this century. Gabrielian (l958) and Kovanda tribe tribe Sorbeae. (1 961) re-examined anatomical characters of fruits -319 一 320 320 植物研究雑誌第66 巻第6 号 平成 3 年12 月 of of European species of Sorbus and concluded that distribution of stone cells ，and structure of the pulp pulp structure is very useful for distinguishing the inner epidermis and neighboring cells of the frui t. subgenera subgenera of Sorbus. However ，since they did not Based on these data we w i1l attempt a systematic investigate investigate Pourthiaea ，Micromeles ， and the As iatic evaluation of these characters in this tribe. species species of Sorbus ，it was not clear whether the pulp structure structure is truly distinctive 町nong the subgenera Materials and methods of of Sorbus or not ，and whether the heterogeneous Seventy-three species belonging to 24 genera of nature nature of the pulp of these three taxa is homo- the Maloideae ， of which 61 species of 17 genera logous logous or no t. in the tribe Sorbeae and 12 species of 7 genera in It It is well known that the degree of density of the tribe Crataegeae ， were studied. Fruits examined stone stone cells in the pulp is a useful character for were either fresh or dried ， or from herbarium distinguishing distinguishing some genera of Sorbeae. For specimens. Sources of materials and voucher example ，there are many stone cells in the pulp of specimens are listed in the appendix. Pyrus ， but only a few or no stone cells in that of Fresh 仕凶 ts we 児 fixed inFAAσive parts stock M alus ， with the exception of sections Docyniopsis fOFmalin; five parts glacial acetic acid; 90 parts and Eriolobus 侭ehder 1940). Structures of the 70 0/ 0 ethanol). Dried fruits were softened with a innermost innermost part of the fruit flesh have also been solution containing equal volumes of glycerol and recognized recognized as different 出 nong genera. It has been 10% aerosol-OT for about a week at room described described as cartilaginous ， membranous ， or temperature. After these treatments all materials leathery leathery (e.g. ， Hutchinson 1964 ， Robertson et al. from fresh or dried fruits were softened with 15% 1991). 1991). However ， except for some species with hydrofluoric acid for about two weeks at room edible edible fruits ， these characters have not been well temperature. Then they were washed with running investigated. investigated. water and dehydrated through 担任buthanol series As mentioned above ，anatomical characters of and embedded in paraplast (melting point the the fruit of Sorbeae have been recognized as useful 57-58 0 C) for microtoming. Some exceptionally taxonomic taxonomic characters for distinguishing genera hard or large specimens were dehydrated with an since since the last century ， but they have not been well ethanol 凶 ethyl ether series and embedded in investigated. investigated. Al most all anatomical studies of the celloidin ， or double embedded in celloidin- fruit fruit have been performed in Malus domestica paraplast (Johansen 1940). Paraplast sections and Borkh. Borkh. (e.g. ，MacArthur and Wetmore 1939 ， double embedded sections cut 15-20μm in MacDaniels MacDaniels 1940 ，Tukey and Young 1942 ，Roth thickness were either triple stained with Heiden- 1977) 1977) and Pyrus communis L. (e.g. ， MacDaniels hain's Hematoxylin ， Safranin 0 and Fastgreen 1940 ，Sterling 1954 ，Roth 1977). Except for FCF ， or double stained with Safranin 0 and Gabrielian's Gabrielian's (1 958) and Kovanda's (1 961) works Fastgreen FCF. Celloidin sections cut 50-100μm in in Sorbus ，no anatomical works on the fruits of in thickness were stained with Safranin 0 and Sorbeae Sorbeae have been performed from a systematic Fastgreen FCF. All stained sections were mounted point point of view. in Entellan New (Merck Co. Ltd ふ In In this study ， we report the anatomical Prepared specimens were observed with a characters characters of the fruit of the genera of Sorbeae ， normal optical microscope. Specimens were also with with special attention to the structure of the pulp ， observed in crossed polarized light for the presence Decernber Decernber 1991 Journal of Japanese Botany Vo l. 66 No. 6 321 of of sclerenchymatous cells. Results Results Terminology The so-called fruit of the sub- f出 nily Maloideae is a fal 田 fruit called a pome that consists consists of carpels and a fleshy enlarged hypan- thium (somet 卸les called calyx tube) surrounding 10 or or fused to them (F ig. 1). Bony p紅白 in the mature 9 fruit fruit of the tribe Crataegeae are sometimes recognized recognized as the endocarp ，and the fruit is called a drupe or pyrene (Lindley 1821 ，Kovanda 1965 ， Fig. Fig. 1. Explanatory scherne of the general structure Kalkman 1973). Actually ，however ， not only the of the fruit of Sorbeae. 1: style. 2: apical part of innermost innermost part of the carpel (true endocarp) but the inner flesh. 3: sepal. 4: a portion of free hypanthiurn. hypanthiurn. 5: inner epiderrnis. 6: dorsal bundle also also almost the other part of carpel becomes bony of the carpe l. 7: innerrnost prorninent bundle of as as described by Sterling (1964) ，and the hypan- the hypanthiurn. 8: epiderrnis. 9: inner flesh. 10: outer outer flesh. Broken line indicates the border thium becomes fleshy (F igs. 2-6). So ，this kind of between the part derived frorn the carpel (inner fruit fruit is not the same as that of true drupe ， as in 目白 h) and that derived frorn the hypanthiurn (out 釘 flesh). flesh). Prunus. Prunus. In the tribe Sorbeae generally both parts of of the fruit derived from the carpel and the hypan- thium become completely fleshy and cannot be separated separated histologically. Fahn (1 990) recognized the the border betw 民 n the dorsal bundles of the carpel and the innermost prominent bundles of the hypanthium. We follow him and we called the outer outer part of this border “ outer flesh" and the Fig. Fig. 2. Schernatic drawing of the fruit structure of inner inner part “ inner flesh" as used by Olson and Crataegeae Crataegeae and Prunus. A: Crataegeae ， B: Prunus. Steeves Steeves (1982). Hy: part derived frorn the hypanthiurn. C: part derived derived frorn the carpe l. L: locule. The dotted part In In true fruits ，exocarp ，mesocarp ，and endocarp represents sclerenchyrnatous tissue. are are often distinguished in the pericarp. In many fruits fruits of Sorbeae ，it is impossible to distinguish pattem varies in the genera. The shape of sclereids mesocarp and exocarp ， because these two parts are isodiametric (= stone cells) in the most part of become fleshy as outer flesh. Moreover ， these three flesh ， but in the inner epidermis and neighboring terms terms are sometimes confused in the fruits of cells it is sometimes radially elongated. In many Maloideae ，and ， in some cases ，mesocarp is used cas 邸 the apical pa 此 of the inner flesh and the inner as as the whole fleshy part of the pome (Camefort epidermis and neighboring cells have some and Boue 1980). So ， in this study ，we don't use different pulp structure from the other part of these these three terms. frui t. Therefore ，we describe these parts separately. Description Description of the structure of the fruit Degree Hence ，a fruit is divided into the following six of of density of sclereids and pi 伊 lent cells in the flesh p 紅 ts; inner epidermis and neighboring cells ， inner differs differs in genera of Sorbeae.

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