Tarenna idukkiana Robi & Balan

Jose, Robi Aloor, Balan, Anoop Puthuparambil & Ponnachan, Thomas Valukattil, 2024, A new species of Tarenna (Rubiaceae: Ixoroideae) from Kerala, India, Phytotaxa 661 (1), pp. 97-102 : 97-100

Tarenna idukkiana Robi & Balan sp. nov. ( Figures 1 & 2 )

Type:— INDIA. Kerala, Idukki, Elappara , ± 1189 m, 9°62’33.64” N 76°97’84.47” E, 07 January 2023, Robi A.J. & Anoop P. Balan 510 (holotype KFRI!; isotypes MH!, BAM!, CATH!) .

Tarenna idukkiana is similar to T. flava by means of habit, stipule, flower color, fruits and pollen shpe but can be distinguished by its terminal bud with white exudate (vs. yellow), lamina with caudate-acuminate apex (vs. acuminate apex); secondary veins with pubescent axillary domatia (vs. axillary domatia absent), calyx with funnel-shaped tube (vs. cup-shaped tube); corolla tube slightly protuded outside the calyx tube (vs. corolla tube concealed in the calyx tube), petals twisted (vs. straight); style sparsely pubescent at middle (vs. glabrous), fruit with cayx deciduous at maturity (vs. persistent at maturity), pollen grains aperture size is 3.8 µm (vs. 2.45 µm), ornamentation is microreticulate (vs. punctate), aspis is present (vs. absent) and margo present (vs. absent). More details are provided in Table 1 .

Description: Trees, up to 12 m tall. Branchlets glabrous, terete at base and 4-angled towards apex. Stipules interpetiolar, broadly ovate, 3–4 × 3.5–4 mm, apiculate at apex, margin undulate, green, glabrous. Stipules of the terminal bud with white exudate, globular in shape. Petioles 1–2 cm long, thick, green, glabrous; lamina elliptic, 9–11 × 3–4.5 cm, cuneate at base, caudate-acuminate (acumen ca. 1 cm long) at apex, margins flat, leathery, dark green, glabrous on both sides; midrib slightly raised above, prominent below, glabrous; secondary veins 8–10 pairs, impressed above, raised below, marginally looped, glabrous on both sides, axillary domatia with pubescence; tertiary veins scalariform-reticulate, faint abaxially. Inflorescence terminal, corymbose cymes; peduncle glabrous, 4–5 cm long, thick, basal branch 3–4 cm long, middle one 1–2 cm long; inflorescence-supporting leaf pairs elliptic, smaller than the vegetative leaves, 20–30 × 5–10 mm. Flowers hermaphrodite, 5-merous, homostylous, 13–15 mm long, white to creamy white, glabrous, pedicellate; pedicel terete, 1–2 mm long, shiny, glabrous. Calyx funnel-shaped, tube 3–4 mm long, prominently veined; lobes 5, ovate, 2.5–3 × 2.8–3 mm long, obtuse at apex, green, glabrous; calyx cup entirely encloses the corolla tube. Corolla campanulate, 10–12 mm long, white, glabrous outside; corolla tube 5–6 mm long; corolla throat and basal part of lobes are densely pubescent; lobes ovate, 6–7 × 2–3 mm, twisted, obtuse at apex. Stamens 5, exserted, attached to the mouth of corolla; filaments arising from corolla tube hair ring, minute, ca. 1 mm long; anthers oblong, 6–7 mm long, connective mucronate, produced above and bending outward; style 7–8 mm long, dilated at middle, sparsely pubescent at middle; stigma glabrous, wider than style, longitudinally furrowed, apex rounded, 5–6 mm long. Disc cylindrical, ovary inferior, bilocular with many ovules in each locule. Fruit berry, bilocular, globular, 9–10 × 5–6 mm, calyx persistent in young stage, deciduous or with short persistent calyx teeth during maturity, green; seeds 8–10, angular.

Phenology:—Flowering: October-January; Fruiting: January–March.

Distribution:— So far, known only from Cardamom Hills of Elappara, Idukki district of Kerala, India. It is growing as a tree in Cardamom Hill Reserves of Elappara at an altitude of ± 1200m.

Etymology:—The specific epithet “ idukkiana ” refers to its type locality including district name in Kerala, India.

Additional Specimens examined (Paratypes):— INDIA. Kerala, Idukki, Elappara , ± 1189 m, 9°62’33.64”N 76°97’84.47”E, 01 March 2022, Robi A.J. & Anoop P. Balan 335 (Immature fruits) (BAM!) ; ibid., 21 September 2022 Robi A.J. & Anoop P. Balan 449 (Mature fruits) (BAM!) .

Pollen morphology: —In Tarenna , pollen grains are monads, polar, triangular, obtuse convex, and tri-zono colporate. T. flava (P/E= 0.91±0.011) and T. idukkiana (P/E= 0.94 ±0.178) have oblate spheroidal shape ( Figure 3 ). The exine ornamentation in T. flava is punctate ( Maya 2023) but that of T. idukkiana is microreticulate. The aperture size (3.8 µm) is comparatively large in T. idukkiana . The presence of aspis around the pore, presence of margo and microreticulate exine ornamentations are distinguishing characters in T. idukkiana ( Table 1 ).

Figures

FIGURE 1. Tarenna idukkiana Robi & Balan sp.nov. A. Habit with flowers; B. Terminal bud; C. Leaves-adaxial view; D. Leavesabaxial view; E. Stipule; F. Domatia-enlarged; G. Immature fruit with persistent calyx; H. Infructescence; I. Fruits-enlarged (Photos by Robi A.J.).

FIGURE 2. Tarenna idukkiana Robi & Balan sp.nov. A. Twig with inflorescence; B. Flowers; C. Flower bud; D. Flower- enlarged; E. Calyx; F. Petal-twisted view; G. Anther; H. Style-Stigma complex; I. Style-enlarged; J. Calyx & Corolla tube; K. Fruits; L. Seeds (Photos by Robi A.J.).

FIGURE 3. Scanning Electron Microscopic images of pollen grains: T. flava; A. Polar view; B. Aperture; T. idukkiana; E. Polar view; F. Aperture (Photos by Robi A.J.).