Electronic Journal of Biology

Keywords

Taxonomical and anatomical identification; Canscora diffusa; Canscora sanjappae; Canscora racemosa.

Introduction

The genus Canscora Lam. of the tribe Canscorinae is represented by 9 species in tropical Asia,Africa and Australia,of which 7 species are reported from India. Further floristic exploration of the biodiversity rich Mookambika Wildlife Sanctuary in the later years resulted in two more new species namely C. sanjappae Diwakar and R. Kr. Singh [1]. While carrying out floristic survey of Southern Kerala,the authors collected an interesting species of Canscora racemosa. On critical analysis,we confirmed as new species by both morphological and anatomical studies.

Description of new species

Stem 4-angular. Lower leaves 2 x 1.5 cm,elliptic,petiolate; upper ones ovate,sessile,3-ribbed,glabrous. Cymes terminal; bracts ovate. Flowers many; pedicel 1 cm long,filiform; calyx 6 mm long,wingless,5-toothed,glabrous; corolla white,9 mm long,tube cylindrical,lobes lanceolate,acute; two stamens fertile,two sterile. Capsule 5 mm long,linearoblong [2,3]. Profusely branched; quadrangular,wings upto 0.3 mm wide; 6–48 cm high. Irregular branching pattern. Lower cauline leaves deciduous; leaves coriaceous,glabrous; upper cauline leaves petiolate,elliptic lanceolate,12–39 × 7–27 mm,base attenuate to wedge-shaped,apex acute. Lax diffuse paniculate cymes. Flower-Pedicellate; pedicels 1.5– 15 mm long. Bract- Broadly ovate,1–4 × 0.1–1.2 mm.

The genus Canscora was first established by Lamarck (1785: 601) to include a single species,C. perfoliata Lamarck (1785: 601). The diagnostic characters as given by Lamarck include branched,angular stem,oval-pointed leaves,2–3-flowered inflorescence,rounded and perfoliate bracts,4 unequal petals (2 larger and 2 smaller),and 4 unequal stamens. Subsequently,a few more species were transferred to Canscora (viz.,C. heteroclita (Linnaeus) [4] (= Gentiana heteroclita Linnaeus [5],C. diffusa (Vahl) [6] (= Gentiana diffusa [7],C. alata (Roth) [8] (= Pladera decussata Roxburgh [9,10] divided the genus into three subgenera,namely,subgen. Canscora Lamarck (1785: 601) (as ‘Eucanscora’),Heterocanscora (Clarke) [10] and Phyllocyclus (Kurz) [10]. One more subgenus,viz.,subgenus Pentanthera [11] was subsequently recognized under this genus. The subgenus Canscora and Heterocanscora have typical zygomorphic corolla and anisomorphic stamens and belong to the present day circumscription of Canscora while subgen. Phyllocyclus is treated as a distinct genus and subgenus Pentanthera is placed under the synonymy of Duplipetala [12]. In his recent classification of the tribe Canscorinae,circumscribed Canscora as monophyletic,characterized by zygomorphic corolla and anisomorphic androecium,represented by 9 species and without any infrageneric taxa [2].

C. racemosa differs from C. diffusa by raceme type inflorescence,all stamen filaments were similar in size but 1 stamen inserted higher than other 3,solitary flowers,zygomorphic flowers. An anatomical variation also occurs between both species of Canscora. C. racemosa differs from C. diffusa by presence of trichomes,largest pith region and absence of vascular bundles in 4-angled stem region. By the above circumstance,we suggest this plant has a new species Canscora racemosa for the genus Canscora. The morphological and anatomical difference between C. diffusa and C. racemosa were clearly differentiated in table and photo plates.

Materials and Method

The plant specimens for the present study were collected from various parts of South India and the variations among these two plants were studied using fresh materials as well as herbarium specimens. The morphological and anatomical characters were recorded by examining several specimens of each species with the help of stereomicroscope and inverted phase-contrast microscope,respectively. Details about the distribution,habitat,local name and uses were taken from literatures,herbarium specimen data and field observations. Anatomical studies were conducted by hand sectioning and stained with safranin stain and glycerine.

Discussion

Systematic studies

Canscora diffusa

Herbs profusely branched; stems winged,green in colour; leaves few; present at the basal portion of the inflorescene; leaves linear-lanceolate; apex acuteacuminate,base flowered; each branch ends with 2-3 flowered; flower always zygomorphic; lobes 4,2+2; upper 2,equal oblong; lower lobed 2,based elliptic; stamen: anther 3+1 (white and longer orange),Filaments of the upper stamen broadened below the anther,Cymes dense; pedicels not thickened below the calyx; calyx without wings or striations

Canscora racemosa

Herbs sparsely branched; stem base winged,yellow in colour; leaves numerous; present at all the dichotomous stem branches; solitary flowers,petals 2+2-twisted,2-bilobed; flower zygomorphic or actinomorphic; calyx longer than corolla tube,gynoecium longer than stamens,3+1 stamens equal in size but 1-highly inserted persistent calyx.

Canscora diffusa

Canscora diffusa (Vahl) [6,10,12-15] Gentiana diffusa [7]. Exacum diffusum (Vahl) [13]. Erect,annual,glabrous herbs,4-65 cm tall. Stems 4-angular,winged (wings 1−2.5 mm broad) or 4-lineate,simplediffusely branched. Leaves subsessile-petiolate; petiole 26 mm long; blades of lower leaves broadly ovate or oblong-ovate; upper linear-lanceolate,15– 50 × 5–30 mm,3–5 nerved; apex acute-acuminate; base attenuate or cuneate. Cymes terminal or axillary,dense,dichasial 3–75-flowered; pedicels not thickened below the calyx,slender,5–10 mm long; bracts green,lanceolate or broadly ovate,foliaceous or subulate,1−6 × 0.7−4 mm; texture membraneous or mesophytic. Calyx green,slender,without wings or striations,persistent; lobes-4,lanceolate-linear,apex acuminate or acute,4−5 × 1−1.5 mm. Corolla often rose,rarely white or orange,tubular or funnel shaped; tube 47 mm long; lobes-4,orbicular,2 upper lobes equal,2−3 × 2.5−3 mm,lower lobes 3−4 × 1−2 mm,fused at the apex forming a deep slit in which one large stamen is lodged,sometimes with the lobes separated appearing as more or less equal lobes. Stamens 4,anisomorphic (1 large,3 small); upper stamen filament not broadened below the anther,1–1.8 mm long; lower stamens filament 0.5–0.9 mm long; upper stamen anther orange,lower yellowwhite,linear-oblong. Ovary green,cylindric,3–7 × 0.6–0.9 mm; style rose-white,filiform,exserted,2–4 mm long; stigma bilobed; lobes white,obovate,0.8– 7 × 0.4–7 mm. Capsule brown,oblong-subcylindric,4–6 × 1–2.5 mm. Seeds irregular,0.2–0.6 × 0.2–0.35 mm; testa brown,reticulate.

• Flowering and Fruiting: June–March.

• Habitat: River banks,grasslands and roadside earth cuttings.

• Distribution: Tropical Africa,Asia and Australia.

• Local name: Jeeraka-pullu (Malayalam).

• Uses: Used as a substitute for C. decussata [14].Canscora diffusa is the most widespread species of the genus in South India and shows considerable variation in habit size (4–65 cm tall),branching pattern (simple-compound diffusely branched),nature of wings (4-lineate or 4-angled-winged),and bracts texture (membraneous or mesophytic). The corollas are often rose,although sometimes might also be white or orange. [1] Described Canscora sanjappae from the Mookambika Wild life Sanctuary in Karnataka.

• 3.1.1.6 Diagnosis: They differentiated their species from C. diffusa by its apical branching and regular actinomorphic corolla. [2] Concluded that C. sanjappae and C. diffusa are synonymous. The branching of stem is neither confined to its apex nor is their flowers actinomorphic. The smaller corolla lobes are fused towards the apex,and sometimes are separated,giving the appearance of an actinomorphic corolla,which is common in C. diffusa. They found that both zygomorphic and what appear to be ‘actinomorphic flowers’ in the same plant. The length of the stamen also lies within the range of C. diffusa [2] (Figure 1A).

Figure 1: Habit of two species of Canscora.
A- A plant twig of Canscora diffusa showing cyme type of inflorecence [2].
B- A plant twig of Canscora racemosa showing raceme type of inflorescence [2].

Canscora racemosa

In new species of Canscora racemosa,differs by many characters such as raceme inflorescene,slightly bilobed for 2 petals,gynoecium is longer than stamens,persistent corolla,solitary flowers,calyx longer than corolla tube,longer ovary,yellow quadrangular stem and profusely branched stem. It endemic to Western Ghats especially restricted to Kerala.

• Flowering and Fruiting: December-Februry.

• Habitat: River banks,grasslands and wetlands.

• Distribution: Asia.

• Local name: Jeeraka-pullu

• Uses: Used as a substitute for C. diffusa

• Diagnosis: Canscora racemosa is closely allied to C. diffusa but differs in having limited dichotomous apical branching,and branches,farinaceous leaves,much reduction of leaves,pedicellate flowers,lanceolate bracts and two times longer filaments. A more detailed morphological comparison of these two species is given in Table 1.

Diwakar and Singh [1] described Canscora sanjappae from the Mookambika Wild life Sanctuary in Karnataka. They differentiated their species from C. diffusa by its apical branching and regular actinomorphic corolla. Shahina and Nampy [2] reported that C. diffusa shows considerable variation in habit size (4–65 cm tall),branching pattern (simplecompound diffusely branched),nature of wings (4-lineate or 4-angled-winged),and bracts texture (membraneous or mesophytic). The corollas are often rose,although sometimes might also be white or orange. They reported that the variation between both the species is due to the collections from the type locality and similar specimens from different areas lead us to the conclusion that C. sanjappae and C. diffusa are synonymous. The branching of stem is neither confined to its apex nor is their flowers actinomorphic. The smaller corolla lobes are fused towards the apex,and sometimes are separated,giving the appearance of an actinomorphic corolla,which is common in C. diffusa. They also observed that both zygomorphic and actinomorphic flowers appear in the same plant. The length of the stamen also lies within the range of C. diffusa.

In present study on new species C. racemosa,we observed variations in their branching type,leaves,inflorescence,anther size,gynoecium size,etc. (Figure 1B) (Table 1). Previous studies on C. diffusa,[2] reported that the variations are due to the type locality and similar specimens from different areas. We named the new species C. racemosa by raceme type of inflorescence. To confirm the new species C. racemosa,anatomical studies were carried between these two species of Canscora.

Anatomy of Canscora diffusa and Canscora racemosa

Canscora diffusa

• Stem: The T.S of the stem structure is round stem with 4-winged structure (Figure 2 A). The epidermis consists of single layered with no trichomes or outgrowth (Figure 2 B). The winged structure has single vascular bundle with some chlorenchymatous cell around it (Figure 2 C-2E). The cortex region has 3-4 layered parenchymatous membrane (Figure 2 A and 2B). Next region to cortex is vascular bundle which is largest layer of the stem. The primary xylem facing towards the pith and secondary xylem facing towards the periphery (Figure 2 F). The vascular bundle is largest region of the stem. The pith is centre region with parenchymatous cell.

Figure 2: Anatomical section of C. diffusa.
(A)T.S of stem (B)A sectioned enlarged (C)T.S of stem (D)Vascular bundle of winged portion of stem (E)Xylem and phloem of stem (F)T.S of leaf (G)T.S of root (H)A portion enlarged (J)Vascular bundle of root. Bar=100 μm.

• Leaves: The outermost layer is called as epidermis which is consisting of single layered structure with no trichomes (Figure 2 G). Next to the epidermis is 5-6 layered cortex consist of parenchymatous cells. Chlorenchymatous were seen at the both side of leaf region arising. Next to cortex is vascular bundle which separate from cortex by 1-2 layered linear parenchymatous cells.

• Root: The outermost layer is called epidermis which consists of single layered cells. The vascular bundle consists of xylem and phloem in which primary xylem facing towards the periphery and secondary xylem faces towards the pith (Figure 2 H-2J). The anatomical study reveals that C. diffusa and C. racemosa were two different species of the genus Canscora. The new species C. racemosa differs by the presence of trichomes,limited sclerenchymatous layers and larger pith region (Table 2).

Canscora racemosa

• Stem: The anatomy of the stem is irregular round shaped structure with 4-hand like projection from epidermis layer (Figure 3 A). The outermost layered is called epidermis. The epidermis consist of out-growth like structure is known as emergences type of trichomes which is a group of cell arising from the upper most layer of epidermis. The hand like projection is also consisting of finger like projection as trichomes present in the epidermis (Figure 3 B). Each finger like projections has 3 small vascular bundles (Figure 3 C). The cortex region is second layer of the stem which consists of 4-5 layered parenchymatous membrane. Next to the cortex region is the vascular bundle which consist of single layered parenchyma separate the xylem and phloem from the cortex region (Figure 3 D). The primary xylem is present towards the pith and secondary xylem towards the periphery. The centre region is the largest region which is fully occupied with large parenchymatous cells. The pith region is usually larger than the vascular bundle in size (Figure 3 A).

Figure 3: Anatomical section of C. racemosa.
(A) T.S of stem (B) Trichomes in epidermis and winged region of stem (C) Vascular bundle of stem with emergence type trichome (D) Enlarged vascular bundle (E) T.S of leaf (F) T.S of Root. Bar=100 μm

• Leaves: The outermost layer is called as epidermis which is consisting of single layered with spike like trichomes were present (Figure 3 E). Next to the epidermis is 5-6 layered cortex consist of parenchymatous cells. Chlorenchymatous were seen at the both side of leaf region arising. Next to cortex is vascular bundle which separate from cortex by 1-2 layered linear parenchymatous cells.

• Root: The outermost layer is called epidermis which consists of irregular mass of single or doubles layered cells. The vascular bundle consists of xylem and phloem in which primary xylem facing towards the periphery and secondary xylem faces towards the pith (Figure 3 F).

Conclusion

Shahina and Nampy [2] reported that C. racemosa is a variant form of Canscora diffusa. In present study,we observed that C. racemosa differ from C. diffusa by their limited branching and leave numbers,stem,raceme type of inflorescence,size and length of calyx and corolla and longer fruit size. Anatomical studies also confirmed the new species C. racemosa by presence of trichomes,limited sclerenchymatous layer,large pith size,etc. By this,we confirmed that C. racemosa is not a variation form of C. diffusa and it can be treated as a new species due to the presence of variation in both morphological and anatomical characteristic features.

Conflict of Interest Statement

We declare that we have no conflict of interest.

Acknowledgement

The authors would like to thank Bharathiar University for providing University Research Fellowship (URF).

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