Comparative Petiole and Midrib Anatomical Characters in Selected Species of Coelostegia (Bombacaceae) in Malaysia
A comprehensive study on the petiole and midrib anatomical characters was conducted on three species of Coelostegia (Bombacaceae). Results from this study showed that common characteristics in all three species include the midrib outline, in the presence of mucilaginuous cells, solitary crystals and as well as the presence of sclerenchyma phloem in the medullary vascular bundles. The outline of petiole can be used for distinguishing species such as in Coelostegia borneensis and C. chartacea. The type of vascular bundles system and the presence of sclerenchyma cells around the vascular bundles in the midrib are also have systematic significant. Results in this study has shown that the anatomical characters have taxonomic value at genus and spesies level in Bombacaceae.
Bombacaceae is a small family in Malaysia and consisting of 26 genera with 250 species out of species world wide (Bose et al. 1998). The family is divided into five tribes, Durioneae, Hampeae, Matiseae, Catostemateae, Adansoneae and Ceibeae (Hutchinson 1967). Tribe Durioneae consists of five genera, namely Coelostegia, Durio, Kostermansia, Neesia and Bombax (Keng 1986). Coelostegia consists of seven species, C. borneensis Becc., C. griffithii Benth., C. chartacea Soeg. Reksod., C. kostermansii Soeg. Reksod., C. neesiocarpa Soeg. Reksod., C. montana Sidiyasa and C. sumatrana Becc., distributed in Peninsular Malaysia and Borneo except C. sumatrana which is found in Indonesia (Hinsley 2006). Leaf anatomical study in Bombacaceae is meagre (Metcalfe & Chalk 1950) and among the most prominent features that has long been employed by systematists is the petiole and midrib anatomical characters for classification and identification purposes (Noraini et al. 2005).
DISCUSSION AND CONCLUSIONS
Mucilaginous cells were found to be present in all species studied either in midrib or petiole indicating that this character is common to Coelostegia species. In the petiole cross section, the presence of clustered sclerenchyma cells surrounding the vascular bundle is common in all species studied (Fig. 1d – 1f). Phloem sclerenchyma cells is also present in the medulla vascular bundles in all species studied (Fig.1i). The presence of clusters and phloem sclerenchyma in all species examined may be characteristic of Bombacaceae species. The petiole outline is almost similar in all species observed, however C. chartacea can be distinguished by having almost rectangulate abaxial (Fig.1d). Therefore, the results of this study showed that petiole outline can be used to differentiate species.
The presence of sclerenchyma cells surrounding the midrib vascular bundles can be used for distinguishing species. Incomplete layers of sclerenchyma cells surrounding the vascular present in C. borneensis (Fig.1a), whereas complete in C. grifithii (Fig.1b), and C. chartacea (Fig.1c). Closed system of vascular bundles, present in C. chartacea (Fig.1c), whereas an opened system of vascular bundles with abaxial and adaxial vascular bundles, present in C. borneensis (Fig.1a) and C. grifithii (Fig.1b). Thererefore these two anatomical characters can be useful for identification of these three Coelostegia species.
Complex peltate scale-like hairs (Fig.1h) present from very sparsely to sparsely scattered in all species studied giving a good character for the genus. This study proved that the trichome evidence has systematic significance in the Coelostegia species.
As a conclusion, this study has shown that the combination of anatomical characters can be useful for grouping and distinguishing species.
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