Tarenna charlesii S. Maya & Sunilk.

Maya, Sukumaran Nair, Pillai, Sunilkumar Thrivikraman & Antony, Valiiyaveettil Thomas, 2024, Tarenna charlesii, a new species of Tarenna (Rubiaceae) from southern Western Ghats, Phytotaxa 660 (2), pp. 191-197 : 192-195

Tarenna charlesii S. Maya & Sunilk. sp. nov. ( Figs. 1 & 2 )

Diagnosis: Tarenna charlesii shows similarity with Tarenna flava Alston (1931: 150) by the presence of waxy exudate, glabrous stem and leaves, secondary veins 8–11, flower bud covered with wax, calyx encloses corolla tube completely, infundibuliform corolla with hairs at throat and fruit with persistent calyx lobes. The new species differs from T. flava by its under shrubby habit, 1.5–2 m high (vs. large shrub-tree, 4–12 m high), white to creamy white exudate (vs. yellow to yellowish-white), spreading, light green leaves (vs. porrect, dark green), limited 10–15 flowers per inflorescence (vs. many, 24–30), 9–11 mm long large calyx (vs. small, 4–5 mm long), calyx cup encloses corolla tube completely and lobes partially (vs. calyx encloses corolla tube only), filament conspicuous (vs. inconspicuous), anther connective curved inwardly (vs. outwardly curved), fruiting calyx 6.3–6.6 mm long (vs. 1.2–1.4 mm long) and prominent groove on both sides of stigma (vs. groove absent) [ Table 1 ].

Type: India. Kerala: Palakkad district, Nelliyampathi hills, Kesavanpara , 10 o 52’47.875” N, 76 o 66’78.594” E, 1200 m, 9 December 2019, Maya S. Nair 5220 (Holotype NBRI; isotype KUBH) .

Description

Erect shrub with a bushy appearance, up to 2 m high. Stem branched, woody, angular, green, glabrous; internodes 1.5–2 cm long, stipulate. Stipules interpetiolar, linear, 4–6 × 5–6 mm, base broad, margin entire, apex acute, young green, turns brown at maturity, glabrous. Apical bud covered with white to creamy-white coloured exudate. Leaves spreading, petiolate; petioles 0.7–1.1 cm long, thick, green, glabrous; lamina obovate, 9.5–14 × 5–6 cm, base attenuate, margins entire, apex acuminate, light green, turns brown on drying, glabrous on both sides; midrib slightly protruding on both surface, secondary veins 8–11 pairs, glabrous. Inflorescence terminal, corymbose cyme, 10–15 flowers; peduncle glabrous, 1.3–2 cm long, thick, bracteolate; bracteole 1–2 mm long, glabrous. The central flower in each subunit of cyme sessile to sub-sessile, lateral flowers pedicellate; pedicel 4–7 mm long, shiny, glabrous. Flowers fragrant, hermaphrodite, pentamerous, homostylous, 1.7–1.9 cm long, creamy white turns brown post- fertilization, glabrous; flower bud covered with waxy coating. Calyx large, cup shaped; lobes 5, spreading, lanceolate, 9–11 mm long, tube-lobe ratio 1:1, apex acute, margin entire, green, glabrous. Corolla funnel-shaped, 0.9–1.2 cm, tube-lobe ratio 2:3, corolla tube and a part of corolla lobe enclosed within calyx cup, lobes ovate, 0.7–0.8 × 0.3–0.4 cm, throat densely pubescent with a ring of hairs, the base of the lobes slightly pubescent; creamy-white. Stamens 5, epipetalous, exserted; filaments conspicuous, ca. 1.5–2 mm long; anthers oblong, 3.5–4.2 mm long, connective mucron reflexed inwardly with extended protrusion. Style stout, 6–6.2 mm long, slightly bulging in the middle, green, puberulous, stigma club-shaped with prominent longitudinal grooves on both sides, 5.9–6 mm long, disc cylindrical, ca. 0.2 mm, glabrous; ovary 2-celled with 4 ovules in each cell, glabrous. Fruit berry, bilocular, globular, 7.7–7.9 × 7.5–7.7 mm, with 6.3–6.6 mm long persistent calyx, green, glabrous. Seeds 4–8, variously shaped, brown at maturity.

Phenology: Flowering November–February; fruiting January–March.

Habitat &Distribution: Tarenna charlesii is grown in rocky areas of Kesavanpara forest regions in Nelliyampathy hills, Palakkad district, Kerala.

Etymology:—The species is named after Charles Antony, the son of the third author (Prof. V.T. Antony), who passed away recently in 2019. Charles Antony assisted and supported Prof. V.T. Antony for the completion of his book ‘Flora of Kottayam district’ and many other botanical exploration surveys.

Pollen morphology:— The pollen grains are monads, medium sized (polar axis: 18–19.8µm, equatorial axis: 20.7–21.8 µm), polar, triangular, obtuse convex, and tri-zono colporate. T. flava and T. charlesii had oblate spheroidal (P/E= 0.91±0.011 & 0.895±0.301 respectively) morphology, but T. asiatica was suboblate (P/E= 0.88±0.028). The exine ornamentation in T. flava and T. charlesii are punctate, but that of T. asiatica is microreticulate punctate. In all three species the pollen showed ectocolpate and endoporate condition, but the presence of aspis around the pore of T. charlesii was a distinct characteristic ( Figure 3 .).

Notes: Tarenna charlesii exhibiting some affinities with T. flava and T. asiatica , but it can be easily distinguished from others by many attributes. A detailed comparison of these species are given in Table 1 .

Figures

FIGURE 1. Habit of Tarenna spp. of A. T. flava; B. T. charlesii sp. nov.; C. T. asiatica (Photos A & C @ Maya S. Nair, B @ Sukesh).

FIGURE 2. Tarenna charlesii sp. nov.A. Inflorescence; B. Inflorescence showing sub-sessile mid-flower; C. Infructescence; D. Flower; E. Calyx; F. Corolla spilt-open showing stamens; G. Style and stigma; H. Ovary C.S.; I. Fruit showing persistent calyx; J. L. S. of fruit; K. Seeds (Photos @ Maya S. Nair)

FIGURE 3. SEM images of pollen grains: T. flava; A) Polar view; B) Aperture; T. asiatica C) Polar view; D) Aperture; T. charlesii; E) Polar view; F) Aperture.