IAWA Bulletin n.s., Vol. 4 (4),1983 255

ISOLATED SIEVE TUBE(S)/ELEMENTS IN THE BARKS OF SOME ANGIOSPERMS

by

R.R. Chavan*, J.J. Shah and K.R. Patei" Department of Biosciences, Sardar Patel University, Vallabh Vidyanagar, 388 120, Gujarat, India

Summary The occurrence of solitary or groups of iso­ tures, information on naturally occurring iso­ lated tube element(s) in the interfascicular re­ lated sieve tube elements is meagre and data on gion of Aristolochia indica L., Datura innoxia their development, histochemistry and dimen­ Mil!., Lecanthus wightii Wedd. and Xanthium sional details are sparse in comparison with strumarium L. and in the secondary phloem other aspects of phloem research. The present rays of Strychnos nux-vomica L., Boehmeria study augments information in this direction. nivea Gaudieh., Leucosceptrum cannum Sm., Dahlia imperialis Roezl., Gynura angulosa DC., Materials and Methods Vernonia divergens (Roxb.) Edgew. and Verno­ The materials for the investigation were col­ nia volkameriaefolia De., encountered during lected from Central, Northeastern, Southern an investigation of the barks of 125 dicotyle­ and Western parts of India (Chavan, 1981). dons belonging to 43 families, has been record­ Five to ten sam pies of bark from the main ed. The salient developmental features of iso­ trunk at 1.5 m height of arborescent members lated sieve tube elements in the last three taxa and of internodal regions at mid-height of her­ are described involving histochemical tests and baceous members were collected from various their dimensional details. A comparative analy­ localities to randomise them and avoid specific, sis of secondary phloem of members of Com­ c1imatic and edaphic effects. They were fixed positae with and without isolated sieve tube on the spot in formalin acetic alcohol (Sass, elements indicates that taxa with a high fre­ 1958) and processed for mierotomy by conven­ quency of isolated sieve tube elements show a tional methods (Berlyn & Miksche, 1976). high incidence of compound sieve plates on Transverse, radial and tangential longitudinal predominantly very oblique end walls and also sections of 8-10 J..I.ITl thiekness were stained possess a system of broad rays. The possible with tannic acid-ferric chloride-resorcin blue signifieance of isolated sieve tube elements is combination (Cheadle et al. , 1953), safranine' discussed. '0' (Sass, 1958) and toluidine blue '0' (O'Brien Key words: Histochemistry, phloem rays, inter­ et al., 1964). Unembedded bark sampies were fascicular region, Compositae, Solanaceae, cut on a sliding microtome. Histochemical tests Loganiaceae, Urtieaceae. for total proteins, total nucleic acids, DNA, starch (Jensen, 1962) and histones (Black & Introduction Ansley, 1964) were performed. Dimensional Fischer's report on the occurrence and dis­ details were obtained with a Carl Zeiss projec­ tribution of isolated sieve tube elements and tion disc microscope and Kelner's eye piece. isolated phloem bundles in members ofCucur­ Photomicrographs were taken on a Carl Zeiss bitaceae (1884, cited in Esau, 1969) was fol­ photomicroscope with planapochromatic ob­ lowed by only a few, as in Vicia. Conium and jectives using ORWO NP-15, Kodak mono­ Aristolochia (von Guttenberg, 1943), in the chrome SO 410,35 mm black and white films. mesocarpie and endocarpie regions of Citrullus lanatus. Coccinia grandis. Luffa cylindrica and Results L. acutangula (Thanki, 1978; Shah et al., 1983) Isolated sieve tube element(s) (ISTEs) occur and in internodal regions of seven cucurbita­ either solitary or in groups, in the interfascicu­ ceous species (Karnik, 1981). Though Metcalfe lar region of Aristolochia indica. Datura inno­ and Chalk in their monumental work (1950, xia. Lecanthus wightii and Xanthium struma­ 1979) covered major aspects of anatomie al fea- rium (Figs. I & 2). In Strychnos nux-vomica.

* Present address: Department of Botany, D.V.S. College of Arts and Science, Shimoga 577 201, Karnataka, India. *·Present address: School of Forestry & Environmental studies, Yale University, New Haven, Con­ necticut 06511, U.S.A.

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Dahlia imperialis, Gynura angulosa, Vernonia tiation of ISTEs occurs at random in the ray volkameriaefolia, Boehmeria nivea and Leuco­ (Figs. 21, 22) frequently towards its margin sceptrum cannum solitary or isolated groups of (Figs. 8, 10). The initial of an ISTE is histologi­ sieve tube elements occur in secondary phloem cally and histochemically different from the rays (Figs. 3, 4-12, 18, 19). neighbouring cells, showing dense cytoplasm Among the Compositae Dahlia imperialis, and a prominent nucleus with higher amounts Gynura angulosa and Vernonia volkameriaefo­ of total protein, total nucleic acids, DNA, and lia, ISTEs are frequent in the wide rays show­ arginine rich histones as evidenced by mercuric ing tangentially horizontal or diagonal disposi­ bromophenol blue, azur B, Feulgen and ammo­ tions (Figs. 3-10, 14, 15, 18, 19). They may niacal silver nitrate reactions. The initial divides be solitary and isolated from the main strand parallel to its longest axis in D. imperialis and (Figs. 2, 3) or in groups of two or more, either V. volkameriaefolia (Figs. 23-28), and at right interconnected end to end to bridge adjacent angles in G. angulosa (Fig. 21) and further the main secondary phloem strands (Figs. 5, 10, 11, derivatives enlarge and elongate. One of them 13) or superimposed (Fig. 6). Sometimes they becomes the ISTE mother cell which divides end blindly (Figs. 9, 12, 19), when they are unequally into two cells. The larger differentia­ away from main phloem strands. The number tes as an ISTE, the smaller one into a compan­ of ISTEs increases with distance from the vas­ ion cell (Figs. 29, 30). PAS positive spherical cular cambium. bodies appear in the developing ISTE (Fig. 32). ISTEs differentiate from the phloem ray pa­ The necrosis of the ISTE nucleus includes the renchyma cells in D. imperialis, G. angulosa change of a spherical nucleus to a spindle-shaped and V. volkameriaefolia and from interfascicu­ one (Figs. 28, 29), a marked decrease in stain­ lar parenchyma cells in Xanthium strumarium. ability of the nucIeus with Feulgen reagent and The salient developmental features have been traced in the former three taxa. The differen- (text continued on page 262)

General explanation of Figures 1-32. All the seetions are of bark. Fig. 1-3, 28-32. Transverse sections. Fig. 14-17. Radial longitudinal sections. Fig. 4-9, 10-13, 18-20,21-27. Tangential longitudinal sections. Hollow arrow indicates isolated sieve tube element(s): ISTE(s); curved arrow indicates sieve plate and dart indicates companion cell.

Fig. 1-9. I: Interfascicular region of Aristolochia indic4, x 158. - 2: Interfascicular region of Xan­ thium strumarium, x 349. - 3: Secondary phloem ray in Vernonia volkameriaefolia, x 502. - 4: Solitary ISTE in nonfunctional secondary phloem of V. volkameriaefolia, x 500. - 5: ISTE bridge in V. volkameriaefolia, x 500. - 6: Superimposed ISTEs in V. volkameriaefolia, x 500. - 7: Irregu­ lar arrangement of ISTE group in V. volkameriaefolia, x 500. - 8: ISTE at the corner of a ray in nonfunctional secondary phloem of V. volkameriaefolia, x 457. - 9: Blind ending of an ISTE in Dahlia imperialis, x 55.

Fig. 10-20. 10: ISTE bridge at the corner of a ray in functional secondary phloem of Dahlia impe­ rialis, x 143. - 11: ISTE group in ray of functional secondary phloem of D. imperialis, x 46. - 12: ISTE group in nonfunctional secondary phloem of Strychnos nux-vomica, x 400. - 13: ISTE in nonfunctional secondary phloem of Gynura angulosa, x 414. - 14: ISTE cut transversely in Verno­ nia volkameriaefolia, x 580. - 15-17: Compound sieve plates of ISTE in V. volkameriaefolia (sa: sieve area, sp: sieve pore), 15, x 628; 16, x 549; 17, x 594. - 18-19: Blind endingofISTEin V. volkameriaefolia and D. imperialis; 18, x 914; 19, x 300. - 20: ISTE with L type of companion cell in D. imperialis, x 414.

Fig.21-32. 21: Initials of isolated sieve tube element (zig-zag arrow) in Gynura angulosa, x 534. - 22: Differentiating ISTE in Dahlia imperialis, x 126. - 23: ISTE initial in D. imperialis, x 571. - 24-25: NucIear division of ISTE initial in D. imperialis (n: nucIeus); 24, x 526; 25, x 777. - 26: Nuclear division of ISTE initial in G. angulosa, x 457. - 27: Cytokinesis in ISTE initial of D. impe­ rialis, x 517. - 28: Arginine rich histone in ISTE initial and derivatives in D. imperialis, x 594. - 29: Necrosis of ISTE nucIeus (note change in shape) in D. imperialis (nn: necrotic nucIeus), x 722. - 30: EnucIeate ISTE having companion cell with DNA rich nucIeus in D. imperialis, x 830. - 31: Development of ISTE after two longitudinal divisions in Vernonia volkameriaefolia, x 342. - 32: PAS positive bodies (PB) in developing ISTE of D. imperialis, x 960.

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<">co 0-- (4),1983 (4),1983 4 Vol. n.s., Bulletin Bulletin IAWA IAWA t0 Table I. Dimensional details of isolated sieve tube elements. 0\ 0

Plant name STELin J..Ill1 STEWinJ..lll1 L/W No. of LSA / STE MINLSADinJ..lll1 MLSADinJ..lll1 SPPD inJ..lll1 LSAPDinJ..lll1 SPPD/ LSAPD Mean & SD Mean&SD Mean & SD Mean & SD Mean & SD Mean & SD Mean & SD

Vemonia volkameriaefolia 87.4 ±31.2 26.9 ± 5.6 3.2 11.0 ± 5.8 1.4 ± 0.4 5.7 ± 2.3 1.4 ± 0.1 1.1 ± 0.2 1.2 Gynura angulosa 128.0 ± 51.0 21.0 ± 4.4 6.0 13.0 ± 11.8 1.2 ± 0.5 3.3 ± 1.7 1.5 ± 0.2 1.0 ± 0.1 1.3 Dahlia imperialis 48.8 ± 26.9 23.3 ± 3.3 2.0 4.0 ± 2.25 2.6 ± 1.5 5.5 ± 2.3 1.6 ± 0.3 1.1 ± 0.2 1.3

STEL = Sieve tube element length; STEW = Sieve tube element width; L/W = Sienderness ratio; LSA = Lateral sieve area; STE =Sieve tube element; MIN LSAD = Minimum diameter of lateral sieve area; MLSAD = Maximum diameter of lateral sieve area; SPPD = Sieve plate pore diameter; LSAPD = Lateral sieve area pore diameter; SD = Standard deviation.

Table 2. Dimensional details of isolated sieve tube elements.

Frequencies in percentage Type of Range of Companion cell CSP SA on Frequent Plant name FSSP FCSP FTEW FSOEW FVOEW CSP SPL in J..Ill1 Length in J..Ill1 Width in pm type s;: ::;::

Downloaded fromBrill.com09/29/2021 04:06:16AM SC RE Mean & SD Mean & SD Mean & SD E S R L ;J> I;t) Vemonia E. volkameriaefolia 37 63 24 15 61 + 2-4 33.9 ± 9.1 73.0 ± 24.2 11.0 ± 3.3 + + E [ Gynura 5' angulosa 48 33 19 + 2-4 136.0 ± 30.1 9.9 ± 2.4 + + + E&S ~ Dahlia <: imperiaIis 74 26 53 36 11 + 2-4 25.4 :r. 5.4 49.7 ± 10.1 6.5 ± 1.1 E + + + ?- ~ FSSP =Frequency of simple sieve plate; FCSP = Frequency of compound sieve plate; FTEW = Frequency of transverse end wall; FSOEW = Frequency of slightly oblique end wall; FVOEW = Frequency of very oblique end wall; CSP = Compound sieve plate; SC = Scalariform; RE = Reticulate; SPL = Sieve plate length; E = Companion cell as long ~ via freeaccess as its sieve tube element; S = Companion cell shorter than its sieve tube element; R = Companion ceHs in a row or astrand; L =Companion cellionger than its sieve tube \D 00 element; SD = Standard deviation. w ;; ~ > t:xi E.. ~ Table 3. Details of secondary phloem parameters of some Asteraceae. 5' ::l in Frequencies in percentage Type ofCSP Mean & SO inf.l1T1 -< Plant name Occurrence Number of SPPO/ ~ of ISTE FSSP FCSP FTEW FSOEW FVOEW SA on CSP SC RE LSAPO SPL SSPL CSPL "'" ~ \0 Vernonia volkameriaefolia + 19 81 6 3 91 2-10 + + J.5 48.7 ±19.7 26.8 B.6 54.5 ±17.7 00 w Vernonia divergens + 42 58 12 87 2-7 + 2.0 40.3 ±13.8 31.9 B.O 47.5 ±15.3 Gynura angulosa + 60 40 15 17 68 2-8 + + 1.6 32.1 ±14.3 25.0 B.6 44.8 ±17.3 (~G.cusimbua)

Dahlia imperialis + 81 19 28 11 61 2-5 + + J.3 34.4 ±IOA 30.4 ±4.0 47.1 ±14.1 Xanthium strumarium + 84 16 4 19 77 2-6 + 1.5 31.0 :1-13.1 26.6 ±4A 54.5 :1-18.5 Tridax procumbens 96 4 42 28 30 2-3 + 1.7 15.8 ±2.1 15.7 ±2.1 18.3 ±2A Vicoa indica 96 4 37 29 34 2-6 + 1.8 16.6 ±4.8 15.7 ±2.1 37.3 ±6.2 Blumea eriantha 97 3 38 27 35 2-3 + 1.8 21.2 ±S.8 19.9 ±2.1 37.3 ±12.2 Ozrysanthemum cariantum 95 5 33 30 37 2-4 + 1.8 16.2 BA 15.6 ±1.7 26.8 :1-.9.1 Downloaded fromBrill.com09/29/2021 04:06:16AM

ISTE ~ Isolated sieve tube element; + ~ Present; - ~ Absent; FSSP ~ Frequency of simple sieve plate; FCSP ~ Frequency of compound sieve plate; FTEW ~ Frequency of

transverse end wall; FSOEW ~ Frequency of slightly oblique end wall; FVOEW = Frequency ofvery oblique end wall; SA = Sieve area; CSP = Compound sieve plate; SC = Scalariform type; RE = Reticulate type; SPPO/LSAPO = Ratio ofsieve plate pore diameter to lateral sieve area pore diameter; SPL = Sieve plate length; SSPL = Simple sieve plate length; CSPL = Compound sieve plate length; SO = Standard deviation. via freeaccess IV 0\ 262 IAWA Bulletin n.s., Vol. 4 (4),1983 depletion of the arginine fraction concomitant Comparative dimensional analysis of normal with dominance of the lysine fraction (Figs. sieve tube elements and isolated sieve tube ele­ 28-30). But the companion cell nuc1eus retains ments indicates that the latter are smaller. a high amount of arginine rich histones and to­ They show predominance of transverse end tal nuc1eic acids indicating its functional nature walls with a high frequency of simple sieve (Figs. 29, 30). Rarely the ISTE mother cell plates compared with normal sieve tube ele­ may undergo two longitudinal divisions (Fig. ments (Tables 2, 3). Similarly, the compound 31) resulting in an ISTE flanked by companion sieve plates of the ISTE are predominantly sca­ cells on either side (Figs. 18, 19). lariform with a reduced number of sieve areas. A mature ISTE simulates the normal sieve This indicates that even sieve plates of ISTE tube element but for its dimensional values, de­ show specialisation in utilising the maximum tails of which are presented in Tables land 2. area on the sieve plate (Shah & Chavan, 1980). The lateral sieve area is of the aggregate scatter­ The ratio of sieve plate pore diameter to lateral ed type (Chavan, 1981). Scalariform compound sieve area pore diameter is comparatively low sieve plates are common (Figs. 16, 17). E and S (Table I). This is because of the occurrence of types of companion cells (Chavan, 1981) are fairly big lateral sieve area pores (in relation to frequent (Figs. 4, 7, 19). In G. angulosa type L sieve plate pore diameter). This probably indi­ is present (Fig. 20). In V. volkameriaefolia each cates that isolated sieve tube elements are in­ of the two companion cells flank on either side volved in exchange of material with the ray of the ISTE, where both may be type E (Fig. parenchyma cells. Whenever they occur in 18). In D. imperialis one of the two companion groups, they tend to interconnect with the cells is type E while the other is type S (Fig. main phloem strands, indicating their role in 19). See also Table 2 for explanation of the dif­ lateral transport across the rays. The fact that ferent types. the frequency of isolated sieve tube elements increases in wide rays and away from the cam­ Discussion bium presumably indicates that they develop as Among 125 taxa surveyed, eleven species be­ additional translocatory paths to cope with the longing to the families Compositae, Solanaceae, normal conduction, as in cucurbitaceous fruits Loganiaceae and Urticaceae showed solitary or (Thanki, 1978; Shah et al., 1983) and fast grouped sieve tube elements either associated growing cucurbits (Karnik, 1981). Their con­ with the interfascicular region or with second­ stant association with companion cells marks ary phloem rays. The incidence of ISTEs is low the functional nature and further the flanked in Datura innoxia, Lecanthus wightii, Strychnos arrangement of companion cells showing in­ nux-vomica, Vernonia divergens and Xanthium creased con tact area seem to reflect their spe­ strumarium. It is high in some Compositae like cialised nature (Esau, 1969; Chavan, 1981). But Dahlia imperialis, Gynura angulosa and Verno­ the occurrence of totally sec1uded and blind nia volkameriaefolia. A comparative analysis of ending isolated sieve tube elements obscures secondary phloem in members of Compositae the whole picture. Though a comparison of with and without the isolated sieve tube ele­ some parameters of isolated sieve tube elements ments is interesting. From Table 3 it is evident is made to indicate their specialised features, an that taxa possessing frequent isolated sieve attempt to assess their overall degree of specia­ tube elements show a very high incidence of lisation with the proposed mathematical model compound sieve plates along with the predomi­ (Chavan, 1981) will be improper, because they nant occurrence of very oblique end walls, owe their origin to phloem parenchyma while while the reverse is true among others. The de­ the secondary phloem elements are derived gree of compoundness is high among them as from the vascular cambium. indicated by the presence of reticulate com­ The differentiation of either solitary or pound sieve plates which are otherwise absent grouped sieve tube elements in response to in­ from taxa without isolated sieve tube elements. jury or chemicals, especially growth hormones The mean values of sieve plate length and simple have been shown by many students of phloem and compound sieve plate lengths show signifi­ (Eschrich, 1953; La Motte & Jacobs, 1962 & cantly higher values among members with iso­ 1963; Digby & Wareing, 1966a & b; Aloni, lated sieve tube elements than the others. All the 1980). The consistent occurrence of isolated species with isolated sieve tube elements show sieve tube elements in all the sampies collected reduced values for the ratio of sieve plate pore from different areas in the diverse taxa indi­ diameter to lateral sieve area pore diameter cates that they are not necessarily the result of (Table 3) and have maximum frequencies of extraneous factors. Though the taxonomic value phloem parenchyma and very wide multiseriate of a typical endomorphic feature as internal rays occupying a larger area of bark. phloem, included phloem and isolated sieve

Downloaded from Brill.com09/29/2021 04:06:16AM via free access IAWA Bulletin n.s., Vo!. 4 (4),1983 263 tube elements is weil known (Radford et a!., Guttenberg, H. von. 1943. Die physiologischen 1974), the limitation of taxa in this investiga­ Scheiden in Handbuch der Pflanzenanato­ tion prevents attribution of any phylogenetic mie (ed. K. Linsbauer). Band 8. 42. importance to the occurrence of isolated sieve Jensen, W.A. 1962. Botanical histochemistry, tube elements. principles & practice. W.H. Freemann, San Francisco. Acknowledgements Karnik, S. L. 1981. Systematic anatomy of sec­ The authors are thankful to Prof. K. Esau and ondary phloem in dicots. Ph.D. Thesis. Sar­ Prof. V.!. Cheadle for their valuable sugges­ dar Patel Univ., Vallabh Vidyanagar, Guja­ tions. The award of a teacher fellowship by the rat, India. University Grants Commission, New Delhi, to La Motte, C.E. & W.P. Jacobs. 1962. Quantita­ R. R. Chavan is gratefully recorded. tive estirnation of phloem regeneration in Coleus internodes. Stain Techno!. 37: 63- References 73. Aloni, R. 1980. Role of auxin and sucrose in - & - 1963. A role of auxin in phloem re­ the differentiation of sieve and tracheary generation in Coleus internodes. Developm. elements in plant tissue cultures. Planta Bio!. 8: 80-98. 150: 255-263. Metcalfe, C. R. & L. Chalk. 1950. Anatomy of Berlyn, G.P. & J.P. Miksche. 1976. Botanical Dicotyledons. Vois. I, 11, Ist Ed. Clarendon microtechnique and cytochemistry. Iowa Press, Oxford. State Univ. Press, Arnes. - & - 1979. Anatomy of Dicotyledons. 2nd Black, M.M. & H.R. Ansley. 1964. Histone Ed. Clarendon Press, Oxford. staining with arnmoniacal silver. Science O'Brien, T.P., N. Feder & M.E. McCully. 1964. 143: 693-695. Polychromatic staining of plant cell walls Chavan, R. R. 1981. Systematic anatomy of sec­ by toluidine blue O. Protoplasma 59: 367- ondary phloem in dicots. Vois. 1& II. Ph.D. 373. Thesis. Sardar Patel Univ., Vallabh Vidya­ Radford, A.E., W.C. Dickison, J.R. Massey & nagar, Gujarat, India. C. Ritchie Bell. 1974. Vascular plant syste­ Cheadle, V.I., E.M. Gifford Jr & K. Esau. 1953. matics. Harper & Row, London. A staining combination for phloem and Sass, J .E. 1958. Botanical microtechnique. Iowa contiguous tissues. Stain Techno!. 28: 49- State College Press, Ames. 53. Shah, J.J. & R.R. Chavan. 1980. Analysis of Digby, J. & P.F. Wareing. 1966a. The effect of dimensional interrelationships of sieve plates applied growth hormones on carnbial divi­ in some members of Asteraceae (Abstract). sion and the differentiation of carnbial deri­ All India Symp. on Current Res. in Plant vatives. Ann. Bot. 30: 539-548. Sciences, Chandigarh. - & - 1966b. The relationship between en­ - , G.M. Nair, Y.J. Thanki & l.L. Kothari. dogenous hormone levels in plant and sea­ 1983. Isolated sieve tubes in the fruit of sonal aspects of carnbial activity. Ann. Bot. Coccinia gran dis (L.) Voight (Cucurbita­ 30: 607-622. ceae). Ann. Bot. 51: 251-253. Esau, K. 1969. The phloem. Handbuch der Pflan­ Thanki, Y.J. 1978. Development and structure zenanatomie. Vo!. 5. Gebr. Borntraeger, of some cucurbitaceous fruits. Ph.D. Thesis. Berlin. Sardar Patel Univ., Vallabh Vidyanagar, Eschrich, W. 1953. Beiträge zur Kenntniss der Gujarat, India. Wundsiebrohrenentwicklung bei Impatiens holstü. Planta 43: 37-74.

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