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Uu Donghua1 and Gao Xinzeng2 Materials and Methods Sieve

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Uu Donghua1 and Gao Xinzeng2 Materials and Methods Sieve IAWA Journal, Vol. 14 (3), 1993: 289-298 COMPARATIVE ANATOMY OF THE SECONDARY PHLOEM OF TEN SPECIES OF ROSACEAE by Uu Donghua1 and Gao Xinzeng2 Summary Materials and Methods The anatomy of the secondary phloem of The barks used for this investigation were species belonging to four genera in Rosaceae obtained from the trees grown on the campus is described. The three genera of the Maloi­ of Peking University, Peking, China. The deae studied are more or less similar in their collection of materials began September 15, phloem anatomy; tangential bands of fibre­ 1991. All the sampies were taken from trunks sclereids alternate with bands of sieve ele­ (3 trees each species) at 1 m height of appar­ ments, companion cells and parenchyma ently healthy trees over 10 years in age. Sci­ cells; superficially, the nonconducting and entific names of the trees studied are shown conducting phloem are not distinct from one in Table 1. another; sieve plates are compound and there Small pieces of about 5 mm 3 were re­ are conspicuous sieve areas on lateral walls; moved from bark sampies (15 mm3 ), fixed rays are uniseriate and multiseriate, and homo­ in FAA, and then embedded in paraffin. From cellular. In the five species of Prunus (Prun­ representative bark of each specimen, trans­ oideae) studied, there are no fibre-sclereids in verse, radial and tangential seetions of 10-12 the conducting phloem, end walls bearing sim­ 11m thickness were obtained with a sliding ple sieve plates are oblique to nearly horizon­ microtome. The seetions were stained with tal; and rays are uniseriate and multiseriate, safranine and fast green. homocellular. Macerations were obtained with a solution of 1 part 10% chromic acid and 1 part 10% Key words: Rosaceae, secondary phloem, nitric acid, and then stained with star blue. sieve elements, rays, phloem anatomy, Quantitative data were obtained from 30 cells crystals, fibre-sclereids. of each species. Introduction Results From an anatomical point of view, both The results show that the genera of Maloi­ phloem and xylem are considered important deae are similar to each other in the structure and useful for identification and evaluating of their secondary phloem and that there are the taxonomie position of plant species. Many differences between Prunus and the genera of studies have been published on phloem anat­ Maloideae (Figs. 1-6). omy (e.g., Esau 1939, 1950, 1979; Evert 1960, 1961, 1963a, b; Davis & Evert 1968, Sieve elements and companion cells 1970; Derr & Evert 1967; Furuno 1990). Sieve plates are divided into two types, This study is aimed at increasing our un­ compound sieve plates and simple sieve derstanding of the anatomical features of the plates, according to the degree of specialisa­ secondary phloem in ten species in four gen­ tion of the end walls of sieve elements. The era of the Rosaceae. three genera of the Maloideae show the fol- 1) Departrnent of Biology, Tianjin Normal University, Tianjin 300 074, People's Republic of China. 2) Department of Biology, Peking University, Peking 100 871, People's Republic of China. Downloaded from Brill.com09/27/2021 08:11:32PM via free access IV'0 Table 1. Anatomical characters ofthe secondary phloem of 10 species ofthe family Rosaceae from China. 0 Sieve elements Ray parenchyma cells Parenchyma cells Sclerenchyma I I I I cells Uniseriate rays Multiseriate rays Fibre-sclereids 11 S- ~ .:; 'il ~ E I S- -;;- oS .:; -a ~ ,,~ ~ .:; I ~ I !l 1l I I ] j !l > .., .., '" ~ ~ oS -a " ~ .!I .... -5 -5 ...." (;' co .~ 0 .~ " !;j .;"f~ :9 0 e ~ ::~ & .0 ~ Jj '6 " ..c:~ ci Ii o " S 1 JJ " '6 a'. a'. ~8 ! ~ " .~ '"~ :2 " .ll.~ .., " 1l ~ ~ .*" ~ e'O ~ -5 " I ~ " :l ~ e ~ ~ s : ~ "~ " ~ ~ "0 § .E ~ ~ .~ . ] ~ " .!2 1 I0 > "> 0 > ~ .t:: > .( .( CI) .( .( .( u iE. < :I: <s < ~ 1:I: :I: " 8 P'l a 8 < (/)" '" "" Prunoideae Prunus armeniaca L. 272 35 + 144 2-12 11 670 5-62 67 2-6 + + 7.3 + + + 862 15 Prunus cerasifera Ehrh. var. pissardii Koehn. 461 26 + 153 2-16 12 638 7-78 63 2-5 + 9.8 + + + 714 16 Prunus davidiana Franch. 262 24 + 138 2-17 15 599 8-80 53 2-6 + + 8.3 + + + 1097 16 ..... Prunus persica Batch. 243 33 + 159 2-17 20 562 5-60 101 2-7 + + 5.6 + + + 740 24 > Downloaded fromBrill.com09/27/2021 08:11:32PM var. rubro-plena Schneid. 268 24 + 145 1- 9 18 579 6-55 111 2-4 + 5.4 + 845 16 + + ~ ..... 0 Maloideae $::: ::I Malus pumiUa Mill. 409 23 + 12.2 90 1- 8 12 189 3-21 27 2-3 + 10.8 + + 419 18 ~ Malus spectabilis Borkh. 476 25 + 12.5 84 2-12 17 208 4-37 32 2-3 + 9.3 + + 812 17 <: ~ Pyrus betulaefolia Bunge 470 20 + 12.5 128 2-17 12 184 4-24 21 2-3 + 10.3 + + 460 19 + ...... ./>0. Pyrus bretschneideri Rehd. 424 30 + 12.2 147 2-25 16 299 4-31 32 2-3 + 10.7 + + 621 22 ,-... ~ Crataegus pinnatifida Bunge 316 24 + 11.4 123 2-18 14 244 8-40 28 2-3 + 12.5 + + 290 19 + via freeaccess I~ Liu Donghua & Gao Xinzeng - Phloem of Rosaceae 291 lowing features: the length of sieve elements parenchyma cells occur in more or less regu­ is over 316 Jlm on average (Table 1); the end lar tangential bands one celllayer in depth, walls, which bear compound sieve plates, are altemating with uniseriate layers of sieve ele­ extremely inclined and can hardly be distin­ ments and their companion cells (Fig. 5). The guished from lateral walls so that the cells are parenchyma cells in Prunus are irregular in truly fusiform; the sieve plates bear many arrangement (Fig. 9). sieve areas, ranging from 11.4 to 12.5 Jlm on With the cessation of function of the sieve average (Table 1); the lateral sieve areas are elements and the companion cells, the paren­ conspicuous, rounded or elliptical in appear­ chyma cells continue to increase in size both ance, and scalariformly arranged (Fig. 7); and radially and tangentially in nonconducting the sieve elements of the conducting phloem phloem. Some parenchyma cells develop into are squarish or nearly rounded in transection fibre-scJereids. In the species of Maloideae, (Figs. 2, 4, 5), while those of the noncon­ the parenchyma cells and the rays form a net­ ducting phloem become irregular in outline as like pattern in transection (Fig. 5). their radial walls gradually collapse (Fig. 4). Crystal-conraining cells - Crystal-con­ The sieve elements in the Prunus species taining cells were found in all the sampies in­ are mostly cylindrical and the end walls, which vestigated. There are some regularities in their bear simple sieve plates, are oblique to nearly morphology, arrangement and distribution. horizontal, and rare compound sieve plates Prismatic and styloid crystal-containing cells are found in P. cerasifera var. pissardii and occur in the three Maloideae genera, but druse P. persica. The lateral sieve areas are incon­ crystal-containing cells characterise the Pru­ spicuous (Fig. 8). The average length of sieve nus species. The prismatic and styloid crystal­ elements is much shorter than that of the sieve containing cells are distributed in two ways: elements of the species of Maloideae, except I) linked in strands where each chamber con­ that of P. cerasifera var. pissardii (Table 1). tains a solitary prismatic crystal which is The sieve elements of the conducting phloem slightly longer than wide and parallel to the appear almost rounded in transection (Fig. 9). sieve elements in arrangement, as seen in ra­ The sieve tubes of the nonconducting phloem dial section (Fig. 10); 2) spatially associated collapse and are obliterated soon after becom­ with the tangential bands of phloem fibre­ ing nonfunctional and the nonconducting scJereids (Fig. 11). The druse crystal-con­ phloem contains large intercellular spaces taining cells appear scattered in transection. (Figs. 6, 9). Ray parenchyma cells - Phloem rays are The companion cells are shorter than the mostly uniseriate and multiseriate and homo­ sieve elements in all species examined. They cellular in all species investigated. There are appear nearly triangular in transection and are differences in height and width of rays among located on one side of the sieve elements. the genera (Figs. 12, 13). Multiseriate rays in Generally , each sieve element has one to two the three genera of Maloideae range from 21 companion cells in species of the Maloideae, Jlm to 32 Jlm in width (2- or 3-seriate) and or two to three companion cells are arranged 184 Jlm to 299 Jlffi (21 to 40 cells) in height, in strands in Prunus. The companion cells but those in the Prunus species are much die when the sieve element protoplasts are larger (Table 1). Uniseriate rays in Prunus disorganised and the walls common to both are composed of procumbent cells. Druse cells collapse. crystal-containing cells were found only in the multiseriate rays of Prunus. In addition, Parenchyma in Pyrus some ray parenchyma cells adjacent Axial parenchyma cells - In the three gen­ to the fibre bands are sclerified Pits are clear­ era of Maloideae the phloem parenchyma cells ly discernible in the thickened cell walls. The in the conducting phloem appear rounded in rays do not become dilated in the nonconduct­ transection. The phloem parenchyma cells ing phloem, but rather become curved to that are relatively dark in appearance occur in varying degrees. The rays of the Maloideae the late phloem, and those with relatively light curve slightly (Fig. 4) and those of Prunus contents are located in the early phloem. The strongly (Fig. 6). Downloaded from Brill.com09/27/2021 08:11:32PM via free access 292 IAWA Journal, Vol.
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