Sunday 13 March 2022

Plagiostachys subsessiliflora & Plagiostachys longipetiolata: Two new species of Ginger from Mindanao Island, Philippines.

Gingers, Zingiberaceae, are a large group of flowering perennial herbs with creeping rhizomes or tuberous roots, found throughout tropical Africa, Asia, and the Americas. The group includes a number of species grown commercially for as foods, spices or medicines, notably Bananas and Plantains, Turmeric, Ginger, Javanese Ginger, and Galangal. The genus Plagiostachys contains about 30 species of Gingers from Southeast Asia, with inflorescences that emerge laterally from leaf sheaths, either just above the ground, in the middle, or very close to the terminal of the leaf shoots.

In a paper published in the journal Taiwania on 2 March 2022, Kean Mazo of the College of Forestry and Environmental Science at Central Mindanao University describes two new species of Plagiostachys from the Zamboanga Peninsula of Mindanao Island in the Philippines.

The first new species is named Plagiostachys subsessiliflora, in reference to the short stem of its flowers. The species is described from four clumps of plants, each containing 5-10 individuals, found near the Molina River in Barangay Tinuyop in Zamboanga del Norte Province. 

Plagiostachys subsessiliflora is a perennial terrestrial herb growing in loose clumps, with subterranean short creeping rhizome. It's leaf shoots reach 3.0–4.5 m tall with 7–9 leaves. The leaf sheaths are brownish-green, the petioles (leaf stems) mid green and covered in hairs, the leaves are a paler green, with a waxy upper surface and a hairy underside. The inflorescence is borne 13–16 cm above the base of the leafy shoot. It is 13–20 cm long, and produces dense clumps of hair-covered red flowers, which give way to globose to subglobose fruit measuring 16–25 × 18–22 mm, that are red-to-maroon when growing, but ripen to green. 

 
Plagiostachys subsessiliflora. (A) Habit; (B) Petiolate lamina showing inequilateral base; (C) Ligule; (D) Inflorescence, side view; (E) Inflorescence, front view; (F) Flower; (G) Flower, calyx and bracteole removed; (H) Longitudinal view of corolla tube showing epigynous glands, style, lateral staminodes and anther; (I) Bracteole; (J) Calyx; (K) Corolla lobes; (L) Dorsal corolla lobes; (M) Labellum; (N) Infructescence showing reddish to maroon immature fruits; (O) Mature fruits. Mazo (2022).

Plagiostachys subsessiliflora is known only from a single location, and a search of the surrounding areas found no additional populations. The area where it was found it threatened by illegal logging, mining activities, and land conversion, with freshly illegally-cut trees were found about 10–30 metres away from the plants. For this reason, Mazo recommends that the species be treated as Critically Endangered under the terms of the International Union for Conservation of Nature Red List of Threatened Species.

The second new species described is named Plagiostachys longipetiolata, in reference to the long petioles of its leaf blades. The species is described from a single Plant found growing close to the Sapalola River in Barangay Tinuyop in Zamboanga del Norte Province.

Plagiostachys longipetiolata is a perennial terrestrial herb growing in loose clumps, with subterranean creeping rhizome. It produces leafy shoots 1.5–2.5 m tall with 6–8 leaves. The leaf sheaf, petiole, and blades are all a similar shade of green. The leave are waxy on their upper surfaces and hairy on their undersides. Inflorescences are borne 1.2–1.5 m above the base of the leafy shoot. These are 14–16 cm long, cone-shaped, and unbranched, producing numerous tube-shaped red flowers. 

 
Plagiostachys longipetiolata. (A) Habit; (B) Terminal portion of the leafy shoot showing undulate leaves; (C) Leaf adaxial view showing slender petioles; (D) Ligule (E) Inflorescence, inset front view of the flower; (F) Flower; (G) Flower, calyx and bracteole removed; (H) Epigynous gland, style and stamen; (I) Calyx; (J) Dorsal corolla lobes; (K) Corolla lobes; (L) Labellum; (M) Stamen, front and side view (preserved in ethanol). Mazo (2022).

Because only a single specimen of this Plant was found, Mazo recommends that it be treated as Data Deficient under the terms of the International Union for Conservation of Nature Red List of Threatened Species.

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