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CYPSELAR ANATOMY OF FIVE SPECIES OF THE TRIBE CALENDULEAE, FAMILY ASTERACEAE

Detailed anatomical features of cypselas of five species (Calendula arvensis L., Calendula maderensis DC., Calendula stellata Cav., Calendula suffruticosa Vahl ssp. suffruticosa and Osteospermum vaillantii (Decne.) Norl.) of the tribe Calenduleae have been studied to observe the variation pattern among them. Among the five cypselas, in case of C. stellata, mesocarpic region is made up of only parenchyma cells, containing pits. In remaining four cypselas, mesocarpic region is made up of both parenchyma and sclerenchyma cells. In the cypsela of O. vaillantii, vallecular cavity is present in mesocarpic region. This cavity is absent in remaining four cypselas. In the cypsela of C. arvensis and C. suffruticosa, secretory duct exists in mesocarpic region, which is absent in remaining three cypselas. In the cypsela of C. arvensis and C. maderensis, six vascular traces are present in mesocarpic region, whereas in O. vaillantii, eight vascular traces; in C. stellata, five vascular traces; in C. suffruticosa, four vascular traces are present in mesocarpic region. Based on the above mentioned anatomical features, an artificial key to the species has been constructed.


INTRODUCTION
The tribe Calenduleae is considered as probably the most complex tribe in the Asteraceae (Nordenstam 1977) on the basis of morphological observation. The tribe consists of 12 genera and approximately 120 species (Jeffrey 2007). The name of this tribe was first recognised by Cassini (1821) as a natural group. Later, it was recognized as a distinct tribe by Bentham (1873). According to Norlindh (1943) this tribe is fairly well understood at the species level. The cypselar features of this tribe is interesting to taxonomists. Cypselas are generally homomorphic-polymorphic, terete, may be either winged or wingless, and may be either straight or slightly curved, provided with beak or without beak etc. (Kadereit and Jeffrey 2007). Different types of secondary metabolites, such as calendic acid, dimorphecolic acid etc. are present in some members (Calendula, Dimorphotheca etc.) of this tribe (Smith et al. 1960, Barclay andEarle 1965). The tribe Calenduleae as a whole shows a very uniform embryological character, but the members, differ in cypselar characters (Ahlastrand 1985). The work regarding the cypselar characters has been undertaken by several authors, such as Jana et al. (2013), Mukherjee andSarkar (1999), Nordenstam (1977) and Norlindh (1943). The present paper deals with the detailed anatomical features of cypselas of five species of the tribe Calenduleae.

MATERIALS AND METHODS
Mature, identified cypselas were procured from different foreign herbaria of the world. The name of the taxa and their sources were given in the Table 1.

Botanischer Garten der Universitat Zurich
For the study, cross sections were taken with the help of a sharp, razor blade through the middle region of cypselas. Sections were stained by immersing in 0.2% acquous saffarin solution. Good sections were placed under compound microscope with (5  6, 5  20, 5  45 and 6  45) magnification to observe different anatomical regions.

RESULTS AND DISCUSSION
Anatomically the studied cypselas are triangular -quadrangular -elliptic in outline. Epicarp is made up of uni-seriately arranged parenchyma cells. Internal to the epicarpic region, mesocarp is present. In the cypsela of C. stellata, mesocarp is made up of only parenchyma cells with vascular trace just below the ribs, whereas in remaining four studied cypselas, mesocarpic region is made up of both parenchyma and sclerenchyma cells.
Osteospermum vaillantii (Fig. 2 F In case of C. officinalis, mesocarpic region is also made up of both parenchyma and sclerenchyma cells (Mukherjee and Sarker 1999). In the cypsela of C. suffruticosa and C. arvensis, secretory ducts are present in mesocarpic region, than remaining three studied cypselas, where secretory ducts are absent. In the cypsela of O. vaillantii, vallecular cavity exists in mesocarpic region. The function of this cavity is still unknown.
In the cypsela of C. maderensis, C. stellata and C. suffruticosa, testal layer is uniseriately arranged and is made up of parenchyma cells. According to Reese (1989), taxa having well organized testa epidermis has been considered as primitive one in comparison to advanced taxa, which have disorganized testal epidermis i.e. testal epidermal cells lack sclerification and wall thickening. So, according to the observation of Reese, C. maderensis, C. stellata and C. suffruticosa are most primitive, as they are containing well organized testal layer. In this connection, Jana and Mukherjee (2014) have done a contribution regarding the testal structure in some species of Compositae and also have provided a classification on the basis of 82 studied taxa. Internal to the testal layer, endosperm layer is present. In the cypsela of C. suffruticosa, endosperm layer is uni-seriate, made up of parenchyma cells, whereas in remaining studied cypselas, endosperm layer is absent.