Manihot fallax M.J. Silva & L.S. Inocencio, 2017

Silva, Marcos Jose da, Inocencio, Lais de Souza, Sodre, Rodolfo Carneiro & Alonso, Alexandre Antonio, 2017, Morphological and anatomical evidence support a new wild cassava: Manihot fallax (Crotonoideae, Euphorbiaceae), from Mato Grosso, Brazil, PhytoKeys 91, pp. 139-156 : 140-143

Manihot fallax M.J. Silva & L.S. Inocencio sp. nov. Figs 1 , 2

Type:

BRAZIL. Mato Grosso: Município de Barra do Garça, BR-158, na altura do km 726, margem esquerda da estrada no sentido Nova Xavantina, campo cerrado em encosta, 15°17'9.7"S, 52°11'15.5"W, 385 m a.s.l., 26 Jan 2014, fl., L. S. Inocencio, A. O. Souza, L. L. C. Antunes, and C. C. Oliveira 293 (holotype: UFG; isotypes: K, MO, NY).

Diagnosis.

Shrubs slender and virgate, up to 1.9 m tall; leaves light green, entire, unlobed, with secondary veins perpendicular to the midvein. Stipules 1-3 × 0.2-0.3 mm, setaceous, entire, early caducous; racemes 2.5-6 cm long, solitary, subspicate, staminate buds obovoid, stamens with filaments pubescent, pistillate calyx dialisepalous and fruits light green, without wings.

Description.

Shrubs 1-1.9 m tall, slender and virgate, monoecious, glabrous. Stem solid in cross section, greenish to reddish, glossy and waxy in young parts; latex clear, abundant; roots fibrous. Stipules 1-3 × 0.2-0.3 mm, setaceous, margins entire, early caducous; petiole 0.3-0.7 mm long, angulate, greenish. Leaves alternate spiral, sparsely distributed along the branches, but more concentrated near apex, blades 8-14 × 1-2 cm, lanceolate, narrowly elliptic or linear, entire, unlobed, non-peltate, base obtuse, apex obtuse with a short mucro, firmly membranaceous to chartaceous, glabrous on both surfaces, adaxial surface dark green, abaxial surface glaucous, the latter with a smooth wax pattern, venation camptodromous-brochidodromous, primary and secondary veins impressed on both surfaces, the secondary veins perpendicularly arranged in relation to the midvein, all of them pinkish to yellowish. Racemes 2.5-6 cm long, staminate or bisexual, solitary, terminal or arising from dichotomy of the branches, glabrous, angulate, glaucous to cinereous, waxy. Staminate flowers: buds 5.8-6 × 3.9-4 mm, obovoid, yellowish-green, without purplish pigmentation; bracts 6-6.1 × 3.9-4 mm, widely elliptic, foliaceous, apex acuminate, persistent; bracteoles situated along the lower third up to half of the pedicel, 4-4.1 × 0.4-0.5 mm, lanceolate, foliaceous, persistent, subopposite; pedicels 0.5-0.7 mm long, cylindrical, glabrous, light green; calyx 13.2-14 × 5.9-6 mm, campanulate, yellowish, without purplish pigmentation, shortly tomentose internally, lobes widely triangular, ovate to oblong, apex obtuse, base truncate; stamens 10, in two whorls of five, filaments pubescent near apex, the longer 12.5-12.6 mm long, the shorter 8.4-8.5 mm long, both thickened; anthers 5-7 mm long, oblong, dorsifixed, bright yellow; disc 10-lobed, intrastaminal, dark yellow. Pistillate flowers: buds 6-9 × 4-6 mm, ovoid, green-yellowish, without purplish pigmentation; bracts 6.4-7 × 2.9-3 mm long, widely ovate, margin entire, glabrous; bracteoles 3.7-3.8 × 0.8-0.9 mm, lanceolate, foliaceous, persistent, margin entire, apex acuminate, opposite along the lower third of the pedicel, glabrous; pedicels 4-6 mm long, cylindrical-clavate, glabrous, green; sepals 10-12 × 5-7 mm, lanceolate, apex acute, shortly tomentose externally, yellowish, without purplish pigmentation; ovary 4-6 × 3-4 mm, globose to ovoid, glabrous, green, disc patelliform, lobed, yellow; styles 3, shortly united at the base, stigmatic surface 2-3 mm long, densely papillose. Capsules 0.9-1.5 × 0.8-1.2 cm, oblong, light green, smooth, glabrous, without wings, dehiscence septicidal and loculicidal; columella (carpophore) persistent, 0.9 × 2-2.2 mm (width at narrowest point in middle), narrowly alate. Seeds 0.7-1 × 0.39-0.4 cm, oblong-ellipsoid, dark grey, with black spots; caruncle triangular, prominent, apex bilobed, cream to yellowish.

Distribution and ecology.

Manihot fallax appears endemic to the state of Mato Grosso (Fig. 3 ), where it grows in Cerrado sensu stricto on flat or slope areas and also in grasslands, on clayey and sandy soils, between 385 m and 642 m elevation.

Phenology.

The species has been collected with flowers and fruits from October to March.

Etymology.

The specific Latin epithet “fallax” refers to deceptive and was chosen due to the false similarity of the new species to M. attenuata and M. weddelliana .

Conservation status.

According to the IUCN (2014), M. fallax can be considered preliminarily as an endangered species (EN-B2a), because it grows in disturbed areas subject to fires and human pressure and has an extent of occurrence of 175 km2.

Specimens Examined.

Brazil. Mato Grosso. Barra do Garças, Serra Azul, trilha as usina, próximo a sede da Moçonaria, 17 Mar 1990, fl., fr., L. Santos s.n. (UFMT/ICLMA 00856); próxima da cidade, nas imediações da antena do Cristo, 09 Mar 1991, fl., fr., L. Santos s.n. (UFMT/ICLMA 00866); Serra do Taquaral, Cerrado, 23 Nov 1997, fl., fr., L. C. Bernacci & G. Arborcz 2525 (UFMT, IAC); cerrado do Marcello, 15°50'50.9"S, 52°15'54.7"W, 14 Nov 2005, fl., fr., I. Faria & M. L. Mayer 339 (UFMT/ICLMA); gruta do pezinho, 15°50'29.6"S, 52°16'50"W, 28 Dec 2005, fl., I. Faria, M. L. Mayer & Moisés 517 (UFMT/ICLMA); Parque Estadual da Serra Azul, 15°51'S, 52°16'W, 21 Oct 2005, fl., M. Sanchez 2216 (UFMT/ICLMA); ib., 21 Feb 2006, fl., fr., I. Faria, M. L. Mayer & M. S. M. Ramos 787 (UFMT/ICLMA); ib., 15°52'S, 52°16'W, 04 Oct 2006, fl., R. Freitas & M. L. Mayer 145 (UFMT/ICLMA); ib., 13 Feb 2007, fl., R. Freitas & M. L. Mayer 404 (UFMT/ICLMA); ib., 1 Mar 2007, fl., fr., R. Freitas & M. L. Mayer 445 (UFMT/ICLMA); BR 158 na altura do km 726, margem esquerda, sentido Nova Xavantina, adjacências da Serra do Roncador, 15°17'21.8"S, 52°11'38.7"W, 389 m a.s.l., 28 Jan 2014, L. S. Inocencio, A. O. Souza & G. H. Silva 68, 69, 70, 71, 72 and 73 (UFG); ib., 15°17'9.7"S, 52°11'15.5"W, 385 m a.s.l., 26 Jan 2015, fl. fr., L. S. Inocencio, A. O. Souza, L. L. C. Antunes & C. C. Oliveira, 290, 291, 292 and 294 (UFG); BR 158, na altura do km 726, margem esquerda, sentido Nova Xavantina, 15°17'9.8"S, 52°11'22.3"W, 422 m a.s.l., 1 Feb 2015, fl. fr., L. S. Inocencio, A. O. Souza, L. L. C. Antunes & C. C. Oliveira 363, 364, 365, 366, 367, 368, 369, 370, 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, 385, 386, 387 and 388 (UFG); Serra do Roncador, ca. 60 km a norte da cidade pela BR-158 e 5 km a esquerda desta rodovia em direção a Xavantina a partir do povoado Vale dos Sonhos, 52°13'54"S, 15°20'54"W, 642 m a.s.l., 24 Mar 2016, R. C. Sodré, T. P. Mendes & J. A. Oliveira 2174 (UFG).

Discussion.

Manihot fallax stands out from the other species of the genus with entire and unlobed leaves ( Silva 2015) by its shrubby, slender, virgate habit up to 1.9 m tall, leaves ascendant and in a spiral arrangement along the branches. It morphologically resembles M. weddelliana and M. attenuata , especially the latter, in the aspect of the leaves, racemes conspicuously pedunculate, bracts of flowers of both sexes showy and foliaceous and calyx internally shortly tomentose. However, M. fallax differs from M. weddelliana in its shrubby, slender and virgate habit (vs. subshrub up to 0.5 cm tall in M. weddelliana ), leaves without repand margins (vs. leaves with repand margins) and bracts of both staminate and pistillate flowers ovate, with margins entire and apex acute or obtuse (vs. widely elliptic, with margins very serrated and apex conspicuously acuminate). The combination of the characters listed in table below serve to differentiate M. attenuata from M. fallax .

Regarding leaf anatomical features, M. fallax differs from M. attenuata in having the vascular cylinder with arch-shaped collateral vascular bundles surrounded by pericyclic fibres in the midvein (Fig. 4A ), uniseriate epidermis in the median portion of both surfaces of the leaf blade (Fig. 4B ), at the edge (Fig. 4C ) and petiole with collateral vascular bundles discontinuous in the vascular cylinder (Fig. 4N ). In M. attenuata , the vascular cylinder has collateral vascular bundles in a flattened arc, not surrounded by pericyclic fibres in the midvein (Fig. 4D ), epidermal cells without papillae in the median portion of the abaxial surface of the leaf blade (Fig. 4E ), but with druses in the protoplast (Fig. 4E, F ), as well as petiole with collateral vascular bundles continuous in the vascular cylinder (Fig. 4O ).

Both M. fallax and M. attenuata have midveins with angular collenchyma on both surfaces, ground parenchyma surrounding the vascular cylinder (Fig. 4A, D, H ), isobilateral mesophyll (Fig. 4B, E ), edges with annular collenchyma (Fig. 4C ), parenchymatic sheath surrounding the secondary veins towards the epidermal cells on both surfaces of the leaf blade (Fig. 4I ) and other veins without sheath (Fig. 4J ). Laticifers are also found in both species distributed along the phloem cells in the midvein, petiole and median portion of the leaf blade (Fig. 4G ). Additionally, the petiole has epidermal cells and cortex similar to those of the midvein (Fig. 4N, O ). The stomata are paracytic in both species (Fig. 4K ), evenly distributed on the abaxial surface of the leaf blade (Fig. 4L ) and in a parallel and continuous band on each side of the midrib (Fig. 4M ). Due to the stomatal pattern, both species have amphistomatic leaves.

Amongst the anatomical features that differ between M. fallax and M. attenuata , the presence the fibres in the vascular cylinder in the midvein, the papillae in the epidermal cells and the arrangement and number of collateral bundles in the petiole have been cited by Allem (1984), Cunha Neto et al. (2014) and Graciano-Ribeiro et al. (2016) as characters that help differentiate species in Manihot .

Figures

Figure 1. Manihot fallax. A Habit B Staminate bracts C Staminate bracteole D Staminate bud E Staminate flower F Staminate flower with calyx split and open G Inner surface of the staminate calyx showing the trichomes H Pistillate bracts I Pistillate bracteole J Pistillate flower K Inner surface of the pistillate calyx showing the trichomes L Fruit M Seed, ventral side N Seed, dorsal side. Drawn by Cristiano Gualberto from the holotype.

Figure 2. Manihot fallax. A Habit B Leaves; note the spiral phyllotaxy C Inflorescence; note the showy bracts D Staminate flower, frontal view E. Pistillate flowers in the inflorescence, lateral view; note the free sepals F Fruit.

Figure 3. Distribution map of Manihot fallax sp. nov and M. attenuata.

Figure 4. Leaf anatomy of species. A-J Cross section of the leaf blade. Manihot fallax (A-C): A Median portion of the midvein B Median portion of the leaf blade; abaxial epidermis papilose and stomata indicated by arrow C Edge. Manihot attenuata (D-J): D Median portion of the midvein E Median portion of the leaf blade; note stomata (arrow) and epidermal idioblast with druse (arrowhead) F Detail of epidermal idioblast with druse (arrowhead) G Laticifers in the midvein phloem (arrowheads) H Detail of the epidermis and collenchyma in the midvein I Vascular bundles with parenchymatical sheath in the median portion of the leaf blade (arrowheads correspond to laticiferous) J Vascular bundles in the median portion of the leaf blade (arrowheads correspond to laticifers) K-M Dissociated epidermis of both species. Manihot fallax. K. Paracytic stomata. Manihot attenuata (L-M): L Stomata distribution in the abaxial surface of the leaf blade M Stomata distribution in the adaxial surface of the leaf blade lateral to midvein N and O Schematic representation of the petiole in cross section N Manihot fallax O Manihot attenuata. CT: cortex; VC: vascular cylinder; co: collenchyma; ep: epidermis; pp: palisade parenchyma; sp: spongy parenchyma; pa: medullar parenchymatic.