Dyckia sulcata Guarçoni, 2014

Guarçoni, Elidio A. E., Azevedo, Aristéa Alves & Costa, Andrea Ferreira Da, 2014, Dyckia sulcata (Bromeliaceae), a new species from Minas Gerais, Brazil, with notes on leaf anatomy, Phytotaxa 188 (3), pp. 169-175 : 170-174

Dyckia sulcata Guarçoni , sp. nov. ( Fig. 1 , A–K, 2 , A–C)

The new species differs from Dyckia brachyphylla in having larger asymmetric rosettes (vs. symmetric), strongly succulent leaf blades that are flat to slightly canaliculated and strongly ribbed (vs. slightly so), with patent to slightly retrorse spines (vs. antrorse), floral bracts long-acuminate (vs. acute), flowers slightly reflexed or rarely patent (vs. patent), anthers elliptic (vs. linear). It differs from D. saxatilis by having an asymmetric rosette (vs. symmetric), leaf blades strongly succulent (vs. succulent), strongly ribbed on the abaxial surface (vs. slightly ribbed), with shorter spines (0.7–1.4 mm vs. 1.5–2.3 mm), except for the entire apical third, upper peduncle bracts ovate (vs. elliptic to oblong), filaments free above the common tube with the petals (vs. connate), and having a shorter style (0.6–0.7 vs. 1–2 mm).

Type: — BRAZIL. Minas Gerais: Municipality of Serro, Province of Pedro Lessa, Serro –Diamantina Highway, near the source of the Jequitinhonha river , 1066 m elevation, 18º 34’ 20” S, 43º 29’ 07” W, 24 May 2011, E. A. E . Guarçoni 1663 & B . Paixão (holotype VIC!) .

Plants terrestrial, flowering (24.7) 40.6–63.3 (75.6) cm tall. Leaves 10–27, rigid, fleshy coriaceous, spreading-arcuate (basal leaves) to erect (upper leaves), forming an asymmetric rosette of 8.8–15.4 cm tall, 20.3–42.7 cm in diameter; sheaths suborbicular, 1.5–4.3 × 2.3–6.7 cm, white to cream colored, abaxially brown when dry, white lepidote in the upper third of the abaxial surface, inconspicuously aculeate in the upper third, thorns brown; blades very narrowly triangular, 9.9–17.8 × 0.9–1.4 cm, flat to slightly canaliculate, strongly succulent, green or rarely vinaceous on the basal half of the adaxial surface, strongly ribbed abaxially, densely white lepidote at the base, with trichomes concentrated between the ribs and not obscuring the leaf color, adaxially sparsely white lepidote in basal half, and glabrous towards the apex, apex acute, pungent, margins glabrous, spinose except for the apical third; spines patent to slightly retrorse, dark brown, 0.7–1.4 mm long, 0.5 mm wide at base, 10.1–20.1 (26.1) mm apart. Inflorescence simple, erect, (23.9) 38– 62.4 (70.8) cm tall; peduncle erect, terete, 15.8–47.7 cm long, 1.7–5.3 mm in diameter, green to brown, white lepidote, with internodes 28.2–63 mm long; peduncle bracts shorter than internodes, ovate, long-acuminate, ending in a spine, green except for the slightly vinaceous apex or stramineous with orange base, carinate, white tomentose abaxially, the basal ones inconspicuously spinulose at base, 0.8–6.1 × 0.1–0.9 cm, the upper ones entire, ovate, 6.1–14 × 4.2–8.6 mm; rachis orange, white to cinereous tomentose, becoming glabrous soon; floral bracts reaching the midpoint of the sepals, orange to stramineous, with green base, convex, carinate, white tomentose abaxially, ovate-triangular, longacuminate, ending in a spine, 3.8–7.8 × 2.8–5.9 mm, fimbriate. Flowers 5–18, lax, slightly reflexed or rarely patent at anthesis, 1.4–1.9 cm long; pedicels orange, 2.4–6.4 mm long, 3.1–3.2 mm in diameter, white lepidote; sepals reaching the midpoint of the petals, 5.9–8.9 × 4.4–6.9 mm, triangular to ovate, obtuse to acute, orange, imbricate, fleshy, white lepidote abaxially, convex, margins with fimbriate trichomes; petals orange, obovate to slightly obtrullate, obtuse to slightly emarginate, 9.7–13.1 × 6.7–10.6 mm, imbricate, crenulate and sometimes bearing inconspicuous fimbriate trichomes on the apical half; stamens included; filaments yellow, oblong to triangular, complanate, 7–9.5 × 0.9–1.2 mm, fleshy, connate at base for 1.6–3.3 mm and forming a common tube with the petals, free above it; anthers elliptic, 3.4–4.4 mm long, acute, yellow, dorsifixed near the base; ovary oblong, orange, 5.3–10.3 mm long; style orange, 0.9– 2.1 mm long; stigma conduplicate-spiral, 0.6–0.7 mm long, yellow. Fruits ovoid, dark brown, 11.4–13.7 × 9.2–10.3 mm.

Distribution and habitat:––This new species has been observed only in the Espinhaço Mountain Range, in the municipality of Serro, Minas Gerais State, in southeastern Brazil. It was found as a terrestrial plant, growing on quartzitic rocky outcrops, in sandy soil.

Phenology:––The flowering period of Dyckia sulcata is between February and June.

Conservation status: — Dyckia sulcata is considered to be critically endangered (CR) because its area of occurrence is estimated to be less than 100 Km² and it has been reported from only a single location (along Federal Highway BR-259 that connects Serro to Diamantina in Minas Gerais State).

Etymology: —The specific epithet refers to the deep grooves present on the abaxial leaf surface, which differentiate this species from its closest relatives ( Fig. 3A ).

Additional specimen examined (paratypes): –– BRAZIL, Minas Gerais: Serro, Pedro Lessa, Serro-Diamantina Highway , 1066 m elevation, 18º 34’ 20” S, 43º 29’ 07” W, 24 May 2011, fl., E. A. E . Guarçoni 1662 & B . Paixão ( RB!) ; idem, 20 May 2012, fl., E. A. E. Guarçoni 1879 ( VIC!) ; idem, E. A. E. Guarçoni 1880, 1882, 1884 ( R!) ; idem, EA. E. Guarçoni 1881, 1885, 1886, 1887 ( VIC!) ; idem, E. A. E. Guarçoni 1883, 1888 ( RB!) .

Discussion:–– This new species is closely related to D. brachyphylla L. B. Smith (1970: 282) and D. saxatilis , differences are given in Table 1.

The main features of D. sulcata are the asymmetrical rosette with leaves arising more on one side, the leaf blades strongly succulent, flat to slightly canaliculate, and strongly ribbed abaxially.

Leaf anatomy:— The leaf anatomy of D. sulcata follows patterns common to the genus ( Tomlinson 1969; Santos- Silva et al. 2013). Other features observed (such as a thick cuticular layer, well-developed aquiferous parenchyma, and high densities of trichomes) can be viewed as adaptations to a xeric life style, as observed in other Dyckia species ( Lobo 2007; Santos-Silva et al. 2013).

Dyckia sulcata D. brachyphylla D. saxatilis

Rosette form asymmetrical symmetrical symmetrical

Rosette size (cm) 8.8–15.4 × 20–43 5–9 × 8.4 6–24 × 13–46

Apical third of leaf blades entire aculeate aculeate

Canaliculate leaf blades flat to slightly canaliculate wide canaliculate flat to slightly canaliculate Leaf sulcate abaxially Strongly ribbed Slightly ribbed Slightly ribbed

Spines posture patent to slightly retrorse antrorse-uncinate antrorse

Spine lenght (mm) 0.7–1.4 0.8–1.1 1.5–2.3

Distance between spines (mm) 10–20 (26) 3–10 19–30

Upper peduncle bracts ovate ovate elliptic to oblong

Shape of the floral bracs apex long-acuminate acute acuminate

Filaments above the common tube with the Petals free free connate

Anthers shape elliptic linear elliptic

Style length (mm) 0.6–0.7 0.7 1–2

Cross-sections of the leaf blades of D. sulcata show an approximately flat adaxial surface and a homogeneous epidermis above the upper third. The abaxial surface in contrast, is distinctly ribbed, with protruding costal zones. There are only ordinary epidermal cells in the costal zones, while stomata and trichomes are observed in the intercostal zones ( Fig. 3A ).

membrane, ZC = costal zone, ZI = intercostal zone; scale bars = 100 μm.

D. sulcata has a uniseriate epidermis on both surfaces. The epidermal cells tend to be rounded, with reduced lumens, and their walls are anticlinal and inner periclinal thickened but not lignified, while the outer periclinal is thin and covered with a thick cuticular membrane ( Fig. 3B ). Silica bodies can often be seen in the epidermal cells of the leaf blades.

The peltate trichomes are attached to the epidermis by a pedicle composed of two cells. These trichomes cover both surfaces, although only on the proximal half of the adaxial surface. The peripheral shield of the scale is short (not exceeding the costal zone) and cup-shaped ( Fig. 3C ). Due to the high density of scales in the abaxial zone, they cover the stomata.

The leaves are hypostomatic, with the stomata raised above the epidermal surface ( Fig. 3D ). The guard cells have thickened walls, forming crests.

Under the epidermis, on both sides of the leaf blade, there is a sclerophyllous hypoderm composed of fibers. The cells of this hypoderm have strongly thickened walls with evident pits. The fibers make up about three to four continuous layers on the adaxial surface, while fibers are restricted to costal zones on the abaxial surface, in five to six layers. These fibers are characterized by elongated cells, with tapering edges and transverse septa.

The next layer on both sides of the leaf is composed of aquiferous parenchyma (hydrenchyma). This parenchyma is continuous on the adaxial surface, with small, rounded peripheral cells. The cells gradually become more elongated in an anticlinal direction, becoming chlorophyll-free, with thin and siphoned walls and wide lumens. The parenchyma is interrupted in the intercostal zone on the abaxial surface by the aerenchyma. These cells are rounded to slightly anticlinally elongated, with or without chlorophyll.

The transition between the aquiferous parenchyma and the chlorophyllous parenchyma (chlorenchyma) is continuous and gradual. The chlorenchyma is more concentrated near the vascular bundles (in some points adaxially entered in the direction of the hydrenchyma) and is characterized by juxtaposed cells, approximately isodiametric, and densely chlorophyllous.

Interspersed with the vascular bundles towards the intercostal areas, there are longitudinal columns of cellfree spaces in the aerenchyma, which is composed of braciform cells with short arms, but with low intercellular lacunosity.

The vascular tissues are arranged in lateral bundles, in a single series. Larger diameter bundles alternate with smaller diameter bundles ( Fig. 3E ). Fibers surround these bundles and can be observed between the xylem and phloem. The larger bundles have fiber caps only at their ends. The smaller vascular bundles often have short extensions of fibers near the abaxial surface.

Idioblasts containing raphides were observed in the bottom third of both faces of the leaf blade, and only on the adaxial surface beyond this point.

Considering the features of the leaf anatomy of Dyckia reported in the literature, especially by Santos-Silva et al. (2013), it is clear that the leaves of D. sulcata have characteristics common to other species of Dyckia . However, detailed descriptions of specific structural elements (such as presence of peltate scales in the initial third of the adaxial epidermis, three to four layers or five to six layers of cells in the adaxial and abaxial sclerenchymatous hypodermal layers respectively, sclerenchymatous hypodermal cells with very thick cell walls, and sheath sclerenchyma fibers in the larger vascular bundles forming caps) contribute decisively to the identification of this species ( Tab. 2).

Figures

FIGURE 1. Dyckia sulcata (E.A.E. Guarçoni 1663 & B. Paixão). A. Habit. B. Leaf. C. Detail of a leaf blade in cross section. D. Detail of a spine of the leaf blade. E. Basal peduncle bract. F. Upper peduncle bract. G. Floral Bract. H. Flower. I. Sepal. J. Petal and stamens. K. Stigma. Illustration by Reinaldo Pinto Monteiro.

FIGURE 2. Dyckia sulcata. A. General view of the species habitat. B. Asymmetrical rosette. C. Detail of the strongly pronounced nerves on the abaxial side of the leaf blades. D. Habit. (Photos: E.A.E. Guarçoni).

FIGURE 3. Photomicrograph of a cross section of the leaf of D. sulcata. A. Abaxial surface showing the costal and intercostal zones; mechanical hypodermis with five layers of cells in the costal zone. B. Adaxial surface with uniseriate epidermis (arrow) and mechanical hypodermis with three layers of cells. C. Cup-shaped scale. D. Stomata extending above the epidermal surface. E. Large vascular bundles (arrow) alternating with smaller bundles (star). AH = aquiferous parenchyma, CL = chlorenchyma, ES = sclerenchyma, MC = cuticular