Ischaemum sunilii Jabeena, Nithya, K.M.P. Kumar & Maya, 2022

Jabeena, Manjakulam Khadhersha, Nithya, Vadassery Madhanan, Prabhukumar, Konickal Mambetta, Athira, Subramanian, Hareesh, Vadakkoot Sankaran & Maya, Chandrasekharan Nair, 2022, A novel taxon of the genus Ischaemum (Poaceae: Andropogoneae: Ischaeminae) from southern Western Ghats, Kerala, India, Phytotaxa 556 (2), pp. 178-184 : 179-183

Ischaemum sunilii Jabeena, Nithya, K.M.P. Kumar & Maya sp. nov. ( Figs.1 & 2 )

Type:— INDIA: Kerala: Palakkad district, Nelliyampathy hills, Govindamala , 10°33’14”N, 76°40’28”E, 1033 m, 20 November 2020, Jabeena M. K. & Maya C. Nair 4469 (holotype: MH; isotypes: CALI, LWG) .

Diagnosis:— The new species Ischaemum sunilii is morphologically similar to I. rangacharianum ( Fig. 3 ) in its distinctly petiolate lower leaves, round or cordate based upper leaves and lower glume of pedicelled spikelet broadly winged on one margin, but differs in having sparsely villous node (vs. glabrous), short stout raceme with prominently inflated and bulbous pilose peduncle (vs. slender, non-inflated and glabrous), inflated joints of pedicel (vs. non-inflated), smooth lower glume of sessile spikelets, rarely with 2–3 interconnected nodules and keeled margins (vs. nodulated lower glume with winged margin), upper glume with acuminate apex (vs. acute apex), lower glume of pedicelled spikelets without nodules (vs. with 2–3 nodules on one margin) and oblong-elliptic caryopsis (vs. narrowly oblong). The delineation of the taxon is given in Table 1 .

Description:— Annuals. Culms decumbent, upto 30 cm tall; nodes sparsely villous. Leaves all along the culm, lower ones gradually tapering into a 2–3 cm long pseudopetiole, upper ones rounded or cordate at base and sessile; sheath 2– 7 cm long, keeled on the back, bulbous based hairy; ligule 1–2 mm long, keeled on both sides, retuse or wavy at apex, bulbous based hairy abaxially; blade 2–9 × 0.5–1.6 cm, linear-lanceolate to lanceolate, margins wavy on one side, acute at apex, bulbous based hairy. Inflorescence terminal, long exerted; racemes two, 2–4 cm long, paired, adpressed together and appears as solitary, purplish-red, sparsely hairy; peduncle prominently inflated towards apex and bulbous pilose; joints of rachis 4–5.5 mm long, turbinate, trigonous, ciliate on outer angle, minutely tuberculate, crustaceous, inflated. Sessile spikelet 7.5–8 × 2–2.3 mm, oblong, awned; callus 1–1.5 mm long, inflated, hairy. Lower glume 7–7.5 × 2–2.3 mm, oblong, rarely constricted at the middle, crustaceous and tuberculate in the lower two third and coriaceous in the upper one-third, generally smooth without nodules or rarely with 3–4 interconnecting side nodules below the middle, glabrous or sparsely hairy towards the retuse apex, 13–15 nerved, margins keeled and ciliate in the upper half, usually not winged rarely narrowly winged on margins above one third, the wings scaberulous. Upper glume 7–7.5 × 1.3–1.5 mm (when folded), boat- shaped, oblong-lanceolate when spread, sub-coriaceous, keeled on the back with scabrous keel, acuminate at apex, minutely tuberculate on abaxial surface, margins hyaline and ciliate along the upper half, 7-nerved. Lower florets male and upper florets bisexual. Lower lemma 6.7–7.2 × 1–1.2 mm, elliptic-lanceolate, acute at apex, hyaline, 3-nerved, glabrous. Lower palea 6.6–7 × 1–1.2 mm, oblong-elliptic, margins infolded, obtuse at apex, hyaline, 2-keeled, 2-nerved, glabrous. Upper lemma 5.9–6.3 × 1.5–2 mm, oblong, cleft upto two-third with acute lobes, glabrous, hyaline, 3-veined and awned from the sinus; awn 20–24 mm long with a column 10–12 mm long. Upper palea 5–6 × 0.6–1 mm, linear-oblong, obtuse at apex, glabrous, hyaline, 2-veined. Pedicelled spikelet 7–7.5 mm long, oblong-elliptic, acute at apex, shortly awned or awn less; pedicel 1–2.3 mm long or upto 3 mm long at the base of the raceme, turbinate, trigonous, crustaceous, inflated, ciliate on dorsal angles and at the apex. Lower glume 6.7–7 × 2.2–2.5 mm, slightly oblique, oblong-elliptic, glabrous or sparsely hairy towards apex, minutely tuberculate, nonnodulated, broadly winged on one margin and narrowly winged on the other margin towards apex or wingless, apex shortly clefted, 9–11-nerved. Upper glume 6.7–7 × ca. 1.5 mm (when folded), boat-shaped, oblong-lanceolate when spread, keeled along upper half and rounded along the lower half, acuminate at apex, densely tuberculate abaxially, margins ciliate in the upper half, otherwise glabrous, sub-coriaceous 5–7-nerved. Lower florets male and upper florets bisexual. Lower lemma 6.3–6.5 × 1–1.5 mm, lanceolate, acute at apex, hyaline, 3-nervedmargins ciliate towards upper half. Lower palea 6.1–6.3 × 1–1.3 mm, lanceolate, acute at apex, margins infolded, hyaline, 2-keeled, 2-nerved, nerves scabrid. Upper lemma 5–5.2 × 0.9–1 mm, oblong, deeply cleft to one third below at apex with obtuse to acute lobes, margins sparsely ciliate, 3-veined and awned from the sinus, hyaline; awn 10–13 mm long. Upper palea 4.9–5 mm long, ovate-lanceolate, obtuse at apex, 2-nerved, 2-keeled, hyaline. Lodicules 2, 1–1.1 mm long. Stamens 3; anthers 3–3.5 mm long, oblong, yellow. Ovary sub-globose, 0.6–0.8 mm long, glabrous; style 1.9–2.3 mm long, glabrous; stigma 2.5–3.1 mm long, feathery, purple. Caryopsis 2.5–3 × 1–1.1 mm, oblong-elliptic.

Phenology:— September–December.

Etymology:— The new species is named after Dr. C.N. Sunil, Associate Professor (Rtd.), S.N.M. College, Maliankara for his immense contributions to the field of angiosperm taxonomy specifically for sedges and grasses in India.

Distribution:— The new species was collected only from the type locality Govindamala, in Nelliyampathy range of southern Western Ghats at an elevation of 900–1100 m. Ischaemum sunilii was found growing in open montane grasslands along with Arundinella ciliata Nees ex Miquel (1851: 30) , Alysicarpus heyneanus Wight & Arnott (1834: 234) and Canscora roxburghii Arnott ex Miquel (1852: 11) .

Taxonomic affinity: Though the smooth non-nodulated nature of lower glumes of both sessile and pedicelled spikelets, petiolate lower leaf blades and the general morphology brings the taxa near to I. commutatum Hackel (1889: 209) , the taxon shows differences in sparsely villous node (vs. glabrous), bulbous based hairs on leaf sheath and ligules (vs. glabrous), inflated peduncle as well as joints of rachis, callus and pedicel (vs. not inflated), 7–7.5 mm long lower glume of sessile spikelet (vs. 5–6 mm long), 7–7.5 mm long, tuberculate, 7-nerved upper glume of sessile spikelet (vs. 5–6 mm long, non-tuberculate, 3-nerved), 20–24 mm long awn of upper lemma of sessile spikelet (vs. 10–15 mm long), short pedicel of length 1–2.3 mm of pedicelled spikelet (vs. 3– 4 mm long pedicel) and awned upper lemma of pedicelled spikelet (vs. awnless).

Apart from the diagnostic differentiating traits with I. rangacharianum , there were more distinct differences in the quantitative measurements viz. sessile spikelet including 6.7–7.2 mm long lower lemma (vs. 4.5–6 mm long), 6.6–7 mm long lower palea (vs. 4.4–6 mm long), 5.9–6.3 mm long upper lemma (vs. 4–5.5 long), 5–6 mm long upper palea (vs. 3.5–4 mm long) and 20–24 mm long awn of sessile spikelet (vs. 10–17 mm long).

Figures

FIGURE 2. Ischaemum sunilii. A. Raceme showing spikelet pairs. B. Spikelet pair. (C–F) Parts of sessile spikelet. C. Abaxial view of lower glume. D. Adaxial view of lower glume. E. Upper glume. F. Lower lemma. G. Lower palea. H. Upper lemma. I. Upper palea. (J–P) Parts of Pedicelled spikelet. J. Abaxial view of lower glume. K. Adaxial view of lower glume. L. Upper glume. M. Lower lemma. N. Lower palea. O. Upper lemma. P. Upper palea. Q. Joints of rachis. R. Anther. S. Pistil. T. Caryopsis. (Photos: Nithya V.M. based on Jabeena M.K. & Maya C. Nair 4469)

FIGURE 3. Ischaemum rangacharianum Fischer A. Habit. B. Culm at nodal region C. Ligule D.–G. Parts of sessile floret D.–E. Lower glume D.Abaxial surface E.Adaxial surface. F. Upper glume G. Upper lemma. H.–M. Parts of pedicelled floret. H. Lower glume. I. Upper glume. J. Lower lemma K. Lower palea L. Upper lemma M. Upper palea N. Stamen. O. Pistil P. Caryopsis (Photos: Nithya M. & Jabeena M.K.)

FIGURE. 1. Ischaemum sunilii. A. Habit. B. Inflated peduncle. C. C.S. of peduncle. D. Leaf apex. E. Pseudopetiole of lower leaf. F. Culm at nodal region. G. Ligule bearing bulbous based hairs. H. Leaf sheath bearing bulbous based hairs. (Photos: Nithya V.M. based on Jabeena M.K. & Maya C. Nair 4469)