Zeylanidium manasiae R.Krishnan, P.Khanduri & R.Tandon, 2019

Krishnan, Remya, Khanduri, Priyanka & Tandon, Rajesh, 2019, Zeylanidium manasiae, a new species of Podostemaceae based on molecular and morphological data from Kerala, India, PhytoKeys 124, pp. 23-38 : 28-30

Zeylanidium manasiae R.Krishnan, P.Khanduri & R.Tandon sp. nov. Figs 2 , 3 , 4

Diagnosis.

It can be distinguished from the closely related Z. lichenoides by the position of floriferous shoots along the margins of thallus, two bracts per floriferous shoot, unequal stigmatic lobes, larger fruits, ellipsoidal capsule and larger seeds.

Type.

INDIA. Kerala: Idduki district, Thommenkuthu Waterfalls, River Kaliyar, 9°57'21.59"N 76°50'01.87"E, 64 m alt., 31 Dec 2015, R. Krishnan & P. Khanduri 8010 (holotype: DUH accession no. 14378!; isotypes: CALI accession no. 7000!, DUH accession no. 14379!)

Description.

Herbs rheophtytic, annual. Thallus 3.79 ± 0.44 mm wide, green to yellow, ribbon-shaped, dorsiventrally flattened, dichotomously branched, attached to the substrate by disc-shaped haptera, 1.14 ± 0.92 mm diam. Leaves produced at the margins and sinuses/branch points of the thallus, in pairs, caducous; blades 2.5-6.75 × 0.26 ± 0.03 mm, subulate, flattened, lacking a midrib. Floriferous shoots produced both marginally and at the branch points of the thallus, solitary, horizontally appressed to the thallus, composed of 2 subulate bracts subtending a single flower, successive shoots 3.56 ± 0.87 mm apart; bracts 2.25-8.20 mm long, caducous, with long caducous apices. Spathella 1.98 ± 0.30 mm long, obovoid, membranous, non-vascularised, persistent, enveloping the flower at pre-anthesis, rupturing longitudinally or irregularly at anthesis. Flowers green, bisexual, zygomorphic, achlamydeous, erect; pedicel measuring 8.32 ± 2.32 mm long in a mature flower; tepals 2, one on either side of the andropodium, 0.83 ± 0.21 mm long, filiform; stamens 2, borne on an andropodium, 0.74 ± 0.15 mm long at anthesis, elongating to 3.67 ± 0.74 mm long at post-anthesis, branched approximately ¼ from the apex, each branch measuring 0.13 ± 0.04 mm long at anthesis, elongating to 0.80 ± 0.10 mm long at post-anthesis, anthers 0.50 ± 0.06 × 0.37 ± 0.12 mm, quadrangular, base bilobed, lobes subequal, dehiscence introrsely rimose; 4273 ± 941 pollen dyads per flower, 30.25 ± 2.42 × 19.62 ± 1.99 µm, tricolpate, microechinate; gynoecium bicarpellate, syncarpic, ovary 2.07 ± 0.28 mm long, ellipsoidal, anisolobous, membranous septum separating two unequal locules, ovules 78 ± 14, anatropous, borne on a swollen axile placenta, style absent, stigma bifid, stigmatic lobes unequal, subconical, the longer 0.48 ± 0.06 × 0.10 ± 0.01 mm, the shorter 0.42 ± 0.06 × 0.08 ± 0.01 mm. Capsule dehiscent, loculicidal capsule measuring 1.96 ± 0.25 × 0.84 ± 0.10 mm and pedicel elongates to 15.55 ± 2.21 mm, bivalved, brown, ellipsoidal, longitudinally ridged, ridges 6, 3 on each valve, one valve persistent, the other deciduous. Seeds 60 ± 15.50 per capsule, 248.75 ± 12.70 × 136 ± 8.90 µm, spermoderm reticulate, cells rectangular with wavy striations.

Anatomy.

Floral parts of Z. manasiae were anatomically investigated. The spathella is non-vascularised and consists of thick-walled polygonal cells. The anthers are of bithecous type, have secretory tapetum and each locule contains pollen dyads. The ovary is pluriovulate and divided into two unequal locules by an apical septum. The ovules are anatropous, bitegmic and tenuinucellate that are borne on a bulbous axile placenta (Fig. 2H ).

Palynology.

The dyads of Z. manasiae are of the acalymmate type and measure 30.25 ± 2.41 µm in length and 19.62 ± 1.99 µm in width. Individual pollen grains are sub-prolate in shape with tricolpate aperture. The exine wall has microechinate ornamentation. The echinations on the apertural surface are larger than those on the non-apertural surface (Fig. 3B ).

Additional specimens seen (paratypes).

INDIA. Kerala: Idduki district, Thommenkuthu Waterfalls, River Kaliyar, 9°54'00"N 76°46'00"E, 64 m alt., 23 Dec 2016, R. Krishnan 8080, (DUH accession no. 14380!). The same locality, 25 Dec 2016, R. Krishnan 8081 (DUH accession no.14381!).

Etymology.

The specific epithet ‘manasiae’ ' honours the late Dr. Manasi Ram née Ghosh for her contributions to the study of embryology and systematics of Santalaceae ( Ghosh 1956) and Trapa L. ( Lythraceae ; Ghosh 1954).

Distribution and ecology.

Zeylanidium manasiae is highly endemic and is known from only one location so far, i.e. Thommenkuthu waterfalls (Figs 1 and 3A ). According to a previous report, rocks of this waterfall are hornblende biotite gneiss type ( Girija 2008). According to Mathew and Satheesh (1996), water in Kaliyar River is well-oxygenated hard water with low chloride content. Zeylanidium manasiae grows along with Z. lichenoides and Z. sessile . Diatoms ( Cymbella C.Agardh species) were also observed forming colonies on the spathella of some of the plants.

Conservation status.

This species is currently known to occur from a single location in Kerala and, hence, we suggest its placement in the Data Deficient category of IUCN (2017).

Phenology.

Flowering and fruiting occurs from December to January when the water level recedes to partly expose the rocks.

Figures

Figure 1. Distribution map of Zeylandium manasiae (red dot). Thommenkuthu Waterfalls, Idukki, Kerala (Map constructed using ArcGIS 9.2 software).

Figure 2. Zeylandium manasiae A habit showing mature fruits B floral bud enclosed in spathella and subtended by two bracts C flower showing andropodium, tepals and unequal stigmatic lobes D longitudinal section of the ovary, showing unequal locules E capsule. Illustration by Rajesh Tandon.

Figure 3. Zeylandium manasiae A habitat and habit showing plants on exposed rock surface (arrows) B habit of the plant showing solitary horizontally appressed flowering shoots C ventral surface of the thalli with haptera (arrows) D thalli bearing floriferous shoots on margins and point of branching E a young flower bud covered by bracts F floriferous shoot with flower subtended by two bracts. A pair of leaves can also be seen (arrows) G flower with spathella removed showing an anther and two tepals (arrows) H longitudinal section of floral bud enclosed in a spathella (sp). The ovary is bilocular and divided into two unequal halves by an apical septum (arrows). Numerous anatropous ovules (ov) are borne on a swollen placenta (p). One of the anthers in section shows a copious amount of dyad pollen I forked andropodium with two anthers J a mature capsule K a dehisced capsule showing persistent valve L comparative fruit morphology of congenerics. (Left to right) Z. maheshwarii, Z. lichenoides, Z. olivaceum and Z. manasiae M Comparative morphology of stigma. (Left to right) Z. maheshwarii, Z. lichenoides, Z. olivaceum and Z. manasiae. Scale bars: 2 mm (B); 3 mm (C); 2 mm (D); 1 mm (E); 2 mm (F); 0.5 mm (G); 0.2 mm (H); 0.5 mm (I); 1 mm (J); 1 mm (K); 5 mm (L).

Figure 4. Scanning electron micrographs A seed with reticulate spermoderm pattern B dyad pollen with micro-echinate ornamentation over the apertural (ap) and non apertural regions (np). Scale bars: 50 μm (A); 5 μm (B).