IAWA Journal, Val. 20 (4),1999: 389-393 ON TUE OCCURRENCE OF WARTY STRUCTURES IN RATTAN by Jianhua Xu 1 & Walter Liese 2 SUMMARY A study on cellular details of rattan sterns by the resin casting method revealed the presence of wart-like structures as apposition on the cell wall of metaxylem vessels, protoxylem tracheids, fibres and also paren­ chyma. They were apparent for some species, but not observed in oth­ ers. Conventional SEM confirmed the presence of warts with a con­ siderable variation in occurrence. Therefore they have only limited taxonomic significance for the rattans. Key words: Warts, rattan, wood anatomy, resin casting method, scan­ ning electron microscopy. INTRODUCTION The occurrence ofwarty structures respectively vestures as an apposition on cell walls and pit chambers in tracheids, fibres and vessels of gymnosperms and angiosperms has been extensively reviewed by Jansen et al. (1998). In contrast, records for mono­ cotyledons are rare. In bamboo they were reported for Dendrocalamus (Liese 1957) and further investigated by Parameswaran and Liese (1977) in 34 species, of which about half exhibited wart-like structures in fibres, vessels and parenchyma cells. For pa1ms wart-1ike particles were identified in the parenchyma cells of Mauritiaflexuosa (Hong & Killmann 1992). Detailed investigations on the structure of numerous rattan palms did so far not reveal any such structures (Bhat et al. 1990, 1993, Weiner & Liese 1990; Weiner 1992). This lack of information does not necessarily indicate their absence, but may also be related to the material investigated. Warts are generally small particles on the tertiary wall/S3 layer. Their size for fibres and vessel members ofbamboo ranges between 150-300 nm. Structural details become clearly visible with TEM using the replica and thin section technique, or by SEM of cell wall surfaces. A study of rattan from China with the resin casting method by the first author indicated the presence of warts , which was confirrned by further studies in Hamburg. 1) Institute of Botany, Chinese Acaderny of Sciences, Beijing, 10093, China. 2) Institute for Wood Biology, University Hamburg, Leuschnerstr. 91, D-21031 Hamburg, Germany. Downloaded from Brill.com09/26/2021 10:07:43AM via free access 390 IAWA Journal, Vol. 20 (4), 1999 MATERIAL AND METHODS Altogether 19 rattan species were investigated by the resin casting method. Table 1 lists the species. The material was collected by Prof. Hu Yuxi (marked H.Y.) in Xishuangbanna, Yunnan Province, China and is stored at the first author's institution. For the SEM study sampies of four species were taken from the institute's collection at Hamburg (Weiner 1992), marked as Gw. The resin casting method has been rarely applied for wood anatomical studies (Stieber 1981; Fujii 1993; Andre 1998). Small dry blocks (c. 3-5 mm square and 10 mm high) from the middle part of the stern were immersed in styrene monomer with 1% benzoyl peroxide for several days and evacuated with a rotary pump for 5 min for better penetration of the resin mixture. The blocks were placed in small vials for polymerization at 60°C over 3 days and subsequently dissected in smaller pieces which were treated with a mixture of hydrogen peroxide and acetic acid (1 : 1) to remove the cell wall substances. The resin casts obtained were rinsed with water and dehydrated with ethanol. They were sputter-coated with gold and examined with a scanning electron microscope (SEM). For conventional SEM at Hamburg small segments (lOx lOx5 mm) were mounted on aluminium stubs and also sputter-coated with gold. Table 1. Rattan species investigated by the resin cast method, H.Y. sampies (* warts present), and by conventional SEM, GW sampIes (** warts present). Calamus australis Mart. (H.Y. 2) Calamus balansaeanus Becc. (H.Y. 5) Calamus bonianus Becc. (H.Y. 7) Calamus caryotoides A.Cunn. ex Mart. (H.Y. 21) Calamus dioicus LoUf. (H. Y. 4) Calamus erectus Roxb. (H.Y. 28) * Calamusflagellum Griff. (H.Y. 3) Calamus gracilis Becc. (H.Y. 17) * Calamus henryanus Becc. (H.Y. 18) Calamus melanoloma Mart. (H.Y. 25) Calamus multinervis Becc. (H. Y. 26) * Calamus nambariensis Becc. var. xishuangbannaensis l. S. Pei & S.Y. Chen (H.Y. 29) */** Calamus rhabdocladus Burret (H.Y. 15; GW 368b) * Calamus tetradactylus Hance (H.Y. 12) */** Calamus viminalis Willd. var,fasciculatus (Roxb.) Becc. (H.Y. 11; GW 372) * Calamus yunnanensis S.l. Pei & S.Y. Chen (H.Y. 1) * Daemonorops jenkinsiana (W. Griff.) Mart. (H.Y. 8) Daemonorops margarithae (Hance) Becc. (H.Y. 6; GW 46) Plectocomia microstachys Burret (H.Y. 24; GW 375) Downloaded from Brill.com09/26/2021 10:07:43AM via free access Xu & Liese - Warts in rattan 391 Fig. 1-6. Calamus viminalis, 1 & 2: resin cast; 3-6: conventional SEM. -1: Wart-like structures on vessel wall. - 2: Wart-like structures on cell wall and spirals of protoxylem tracheid. - 3 & 4: Warts on vessel wall in various density. - 5: Warts on spirals of a protoxylem tracheid. - 6: Warts in a parenchyma cel!. - Scale bars equal 20 lJlll for Fig. 1,2 & 6 and 5 lJlll for Fig. 3-5. Downloaded from Brill.com09/26/2021 10:07:43AM via free access 392 IAWA Journal, Vol. 20 (4), 1999 RESULTS AND CONCLUSION The resin cast produces a negative image of the structures, so that appositions such as warts and spiral thickenings appear as depressions. Figure 1 shows two metaxylem vessel members with the connecting scalariform plate and wart-like depressions in the vessel walls. In a protoxylem tracheid with spiral thickenings similar structures are located between the spirals as weIl as on top of them (Fig. 2). They were present in resin casts of eight species, whereas in the others no such structures were observed (see Table 1). Since the real nature of these structures appeared in the resin casts questionable and because of limited facilities at the first author' s institution to extend the resin cast investigation for convincing results about the wart-like structures, supplementary in­ formation was obtained with SEM on four species at the second institution. Two of them (Daemonorops margaritae and Plectocomia microstachys) did not reveal warts on their cell walls. However, in Calamus viminalis and C. rhabdocladus warts were clearly visible, confirming the earlier observations (see Table 1). They were present on the cell wall of metaxylem vessels, either sparsely or densely distributed (Fig. 3 & 4), protoxylem tracheids, between and on top of the spiral thickenings (Fig. 5), and also parenchyma cells (Fig. 6). The warts appeared as single particles directly on the inner cell wall without a covering membrane, as sometimes present for bamboo and also some dicotyledons. The warty structures occur rather irregularly, so that vessels with warts are neighbouring ones without. Even within one vessel member their density varies much as weIl as their size, with mean values between 250-400 nm, which corresponds to the values for bamboo (Parameswaran & Liese 1977). Thus, the presence of warty structures has been confirmed among the mono­ cotyledons also for the rattans belonging to the subfamily Calamoideae of the Palmae. Apparently warts do not occur in all species. Whereas in some they appeared mostly irregular and became obvious only after viewing larger tissue areas, in others they were not to be found at all in the sampies investigated. Their greatly varying distribu­ tion requires therefore an intensive screening before any conclusion can be made about their absence. The results indicate that for the rattans warty structures have only limited taxo­ nomic significance. The mystery about their ontogeny still remains, also in view of their irregular occurrence within cells and tissue, as outlined by Jansen et al. (1998). ACKNOWLEDGEMENT Thanks are expressed by J. X. to Prof. Ru Yuxi and Dr. Lin Jinxing for the material and their encouragement and by W.L. to Dr. Uwe Schmitt for his support. REFERENCES Andre, J. P. 1998. A study of the vascular organization of bamboos (Poaceae-Bambuseae) us­ ing a microcasting method. IAWA J. 19: 265-278. Downloaded from Brill.com09/26/2021 10:07:43AM via free access Xu & Liese - Warts in rattan 393 Bhat, K.M., W. Liese & U. Schmitt. 1990. Structural variability of vascular bundles and cell walls in rattan stern. Wood Sei. Technol. 24: 211-224. Bhat, K.M., K.M.Mohamed Nasser & P.K. Thulasidas. 1993. Anatomy and identification of South Indian rattan (Calamus species). IAWA J. 14: 63-76. Fujii, T. 1993. 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