Gastrodia indica M. Khanal, 2024

Khanal, Madhusudhan, Sarkar, Shuvadip, Sarkar, Kingsuk, Chhetri, Prakash, Rai, Santosh Kumar, Kumar, Devendra & Rawat, Sandeep, 2024, Gastrodia indica (Orchidaceae: Gastrodieae), a new completely cleistogamous holomycotrophic species from India, Phytotaxa 663 (1), pp. 26-32 : 27-30

Gastrodia indica M. Khanal , sp. nov. ( Figs. 1–2 )

Type:— INDIA . Sikkim: Gangtok, Pangthang , 2015 m, 21.09.202 3, 27°21’54.16’’ N, 88°34’06.07’’ E, M. Khanal 90345a [Holotype CAL] ; M. Khanal 90345b [Isotype BSHC] ; 23.09.202 3, M. Khanal 90346 [Paratype Sikkim University Herbarium] .

Description: Holomycotrophic terrestrial herb, 45 cm to more than 1 m tall. Rhizome 4.2–5.5 × 1–1.3 cm, horizontally placed, brownish, tuberous, fleshy, cylindrical, sparsely to densely pubescent with minute triangular scales with ciliate margins. Roots 1–1.1 mm dia., slender, filliform, few, arising from the base of the rhizome, glabrous. Inflorescence racemose, up to 94 cm tall, erect, glabrous; peduncle 35–60 cm tall, erect, stout, 4–7 nodded towards base, each node enclosed with single membranous sheathing bract, sheathing bracts 0.5–0.6 × 0.9–1 cm, glabrous, 7–10 veined; rachis 10–30 cm tall, with laxly arranged 7–22 flowers. Floral bracts 0.6–0.7 × 0.2–0.4 cm, brownish, ovate-lanceolate, apex acute, entire, slightly cymbiform, 3-veined, glabrous, caducous. Flowers 1.7–2.1 cm long, erect, completely cleistogamous, brownish, urceolate, sparsely verrucose throughout the outer surface, slightly recurved, foul smelling when dissected; sepals brownish, petals whitish-brown, labellum & column white. Pedicel and ovary 0.8–1.1 × 0.2– 0.25 cm, brownish, ovary portion slightly ribbed, pedicel not elongating during capsule maturation. Dorsal sepal 0.8–1.1 × 0.35–0.4 cm, obtuse, undulate to entire, slightly incurved and thickened, slightly verrucose, little broarder than the lateral sepals, connate 4/5 th to petals, glabrous. Lateral sepals 0.8–1.1 × 0.2–0.3 cm, obtuse, entire to undulate, connate with each other for more than 3/4 th of their length, slightly thickened, sparsely verrucose outside, glabrous. Petals ca. 0.1 × 0.1–0.2 cm, ovate to oblong with crisped margins, obtuse, membranous. Labellum 0.35–0.4 × 0.15–0.2 cm, ovate, obtuse, glabrous, margins crisped to irregularly denticulate and slightly reflexed inwards, 5-nerved, base with short stalk attached to the base of coulmn; disc with 4 keels, a pair of centrally placed whitish keel arising from the hypochile which raised abruptly towards apex and other pair of shorter adjacent keel placed laterally & base of the hypochile with a pair of whitish, globose subsessile calli. Column 0.4–0.45 × 0.1–0.12 cm, slightly bent, cymbiform, glabrous; columnar wings slightly broader at the middle gradually narrowing towards the truncate apex and slightly curved inwards terminating into a pair of shortly pointed stelidia which is parallel to the anther cap; column foot absent. Rostellum absent. Stigma glossy, placed at the base of the column. Anther cap 2-chambered, dome shaped, 0.6–0.7 × 0.5–0.6 mm. Pollinia 2, globose, mealy to granular, whitish. Capsule 0.8–1.3 × 0.4–0.5 cm, attached to a non-elongating pedicel.

Etymology: The new species is named after the country of discovery— India , as it is the first cleistogamous species of the genus Gastrodia discovered from India .

Phenology: Flowering and fruiting—September to October.

Distribution: India (Sikkim) [Endemic].

Habitat: Holomycotroph, found growing on dense rotten leaf litter in temperate deciduous oak forest associated with Magnolia doltsopa , Acer campbelli , Quercus lamellosa & Lithocarpus pachyphyllus ; elevation of 1950–2100 m above msl. (Fig-1).

Conservation status: Less than 100 individuals in flowering and fruiting stages were observed in the type habitat. As the type habitat is a long term ecological monitoring site, hence a limited anthropogenic disturbance probably resulted in a luxuriant growth of this extremely elusive species. Similar habitats in and around the type locality were surveyed but no population could be traced. It can be assumed that the new species being a holomycotroph is extremely sensitive to any anthropogenic pressure, hence any disturbance or changes in habitat could result in the loss of the species.

Species comparison: Gastrodia indica shows morphological affinities with G. exilis and G. dyeriana . Detailed comparisons between them have been provided in the table below to aid in easy identification.

Figures

FIGURE 1. A. Habit photograph of the plant in flowering stage; B. Close up photos of a single flower; C. Fruiting stages.

FIGURE 2. Photoplate of Gastrodia indica. A. Habit; B. Close up photo of rhizome; C–E. Flowers in different view; F. Floral bract; G1–G2. Opened up and spread perianth tube (Dorsal & ventral view); H1–H3. Labellum in different view; I1. Column with labellum (Different view); I2 –I3. Column (Front and side view); J1 –J2. Anther Cap (Dorsal & ventral view)