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| Curcuma borealis Saensouk, P.Saensouk & Boonma, in P. Saensouk, S. Saensouk, Maknoi et Boonma, 2024. |
Abstract
This study introduces Curcuma borealis Saensouk, P.Saensouk, and Boonma and C. retrocalcaria Saensouk, P.Saensouk, and Boonma, two newly discovered species within the Curcuma genus of the Zingiberaceae family, found in the Mae Hong Son and Chiang Mai Provinces of Northern Thailand, respectively. This research aims to clarify the taxonomic identity of these species, which were initially confused with C. ecomata Craib and C. chantaranothaii Boonma and Saensouk due to similarities in flower coloration and some morphological characteristics, respectively. Detailed morphological analysis was conducted to distinguish these species. Curcuma borealis is differentiated by its unique anthers lacking appendages or projections at the base of the spurs, in contrast to the appendages or projections present in C. ecomata, while C. retrocalcaria is characterized by anther spurs folding or curving backward under the anther base and with two purple patches at the base of the labellum, distinguishing it from C. chantaranothaii. The findings highlight distinct morphological traits that set C. borealis and C. retrocalcaria apart from existing Curcuma species. The pollen morphology of the two new taxa was also studied here for the first time. This research emphasizes the importance of thorough taxonomic scrutiny for accurate species identification and contributes to our understanding of the diversity within the Curcuma genus. Accurate identification of these species is crucial for conservation efforts, underscoring the need to protect their habitats and maintain biodiversity in the region.
Keywords: Curcuma; Ecomata; new species; Thailand; Zingiberales; Zingiberaceae; Zingibereae
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| Curcuma borealis Saensouk, P.Saensouk, and Boonma sp. nov.: (a) inflorescence with flowers; (b) semi-side view of flower showing the anther spurs without prominent appendages or projections; (c–e) color variation in bracts and flowers; (f) natural habitat; (g) habits. Photographs by Thawatphong Boonma and Payungsak Joipradit. |
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| Curcuma borealis Saensouk, P.Saensouk, and Boonma sp. nov.: (a) side and front view of anther; (b) habit; (c) dorsal corolla lobe; (d) lateral corolla lobes; (e) lateral staminodes; (f) labellum; (g) epigynous glands with ovary; (h) inflorescence with flowers, and new shoot with curling leaf. Drawn by Thawatphong Boonma. |
Curcuma borealis Saensouk, P.Saensouk, and Boonma sp. nov.
Diagnosis: A new species is similar to Curcuma ecomata Craib but differentiated by its very pale yellowish-white rhizome (vs. pale brown); elliptic lamina measuring 29–43 × 13–17 cm, with a glabrous surface except for hair along the veins (vs. oblanceolate, 15–45 × 5–12 cm, finely hairy); lateral inflorescences (vs. both terminal and lateral); broadly obovate and pubescent fertile bracts (vs. ovate and glabrous); sparsely hairy corolla lobes (vs. glabrous); elliptic-rhomboid staminodes, 1.7–1.9 × 0.8–0.9 cm (vs. obliquely ovate, 1.3–1.6 × 0.6–0.9 cm); pubescent labellum (vs. glabrous with glandular hair); filament 5.5–6 mm long and c. 4 mm wide (vs. 5–7 mm long and 2.5–3 mm wide); anther spurs do not produce mucilage and lack prominent appendages or projections (vs. anther spurs mucilage-producing with prominent appendages or projections); and epigynous glands 8–8.5 mm long (vs. 7–8 mm).
Etymology: The specific epithet “borealis” is derived from the Latin word “borealis”, meaning “northern”. This name was chosen to reflect the species’ distribution exclusively in the northern regions of Thailand.
Vernacular name: “Thep Apsorn”, this name is derived from the name of Apsara, the most beautiful celestial maiden in Hindu and Buddhist mythology. The name reflects the striking beauty of the species’ inflorescences and flowers, particularly when they bloom simultaneously from the lower fertile bracts. This blooming pattern, with the upper bracts still without flowers, resembles the traditional depiction of an Apsara, who is often portrayed with a flowing dress that leaves her upper body uncovered.
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| Curcuma retrocalcaria Saensouk, P.Saensouk, and Boonma sp. nov.: (a) front view of flower; (b) dorsal corolla lobe; (c) lateral corolla lobes; (d) side view of the anther; (e) dissection of the floral tube showing the epigynous glands; (f) side view of flower; (g) lateral staminodes with filament and anther; (h) labellum (i) dissection of calyx showing apex’s lobes; (j) side view of inflorescence with flower; (k) habit. Photographs by Thawatphong Boonma. |
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| Curcuma retrocalcaria Saensouk, P.Saensouk, and Boonma sp. nov.: (a) habit; (b) side view of inflorescence with flower; (c) side view of anther; (d) side view of flower; (e) dorsal corolla lobe; (f) lateral corolla lobes; (g) dissection of calyx; (h) lateral staminodes; (i) Labellum; (j) dissection of the floral tube showing the epigynous glands, and semi-front view of anther. Drawn by Thawatphong Boonma. |
Curcuma retrocalcaria Saensouk, P.Saensouk, and Boonma sp. nov.
Diagnosis: A new species closely resembles Curcuma chantaranothaii Boonma and Saensouk but can be distinguished by the following characteristics: ligule—3.5–5 mm long, apex rounded (vs. C. chantaranothaii with ligule 7–8 mm long, apex acute); staminodes—asymmetrical ovate, apex obtuse, white with a yellow dot at the base and a darker reddish spot inside (vs. rhomboid, apex acute, white with a yellow patch along the center); labellum obovate—white with a yellow band extending from the apex down to about half their length. At the base of the labellum, there are two yellow dots with a darker reddish spot inside, positioned on the side closer to the staminode. Adjacent to these dots, there are two pale purple patches (vs. labellum broadly obovate, white with an embossed yellow median band extending from tip to base, diverging at the base in a Y-shape, with two paler yellow crescent patches from the apex on each side to the half of the length); anther thecae—c. 4 mm long (vs. c. 6 mm long); anther crest—2.5–2.8 mm long, apex slightly retuse (vs. c. 0.8 mm long, apex rounded); anther spurs—c. 1 mm long, folding or curving backward under the anther base (vs. spurs c. 0.5 mm long, not folding, pointing downwards).
Etymology: The specific epithet “retrocalcaria” derives from Latin roots. The “retro” denotes “backward”, indicating the characteristic of the spurs folding or curving backward; “calcaria” is the plural form of “calcar”, meaning “spurs”. Together, “retrocalcaria” describes the unique anatomical feature of this new Curcuma species, where the spurs fold backward under the base of the anther (Figure 6 and Figure 7).
Vernacular name: “Sri Sunthon”, this name is derived from the esteemed Mr. Sunthon Aiamwilai, who introduced this undescribed species of Curcuma to the third author in 2021. Subsequently, specimens of the plant were gathered in the years that followed. In honor of Mr. Sunthon Aiamwilai’s pivotal role in the discovery of this species, it was named after him, with the prefix “Sri” conveying respect and admiration in this context. Additionally, the word “Sunthon” in Thai means “beautiful”, which is fitting as it is associated with the beauty of this species.
Piyaporn Saensouk, Surapon Saensouk, Charun Maknoi and Thawatphong Boonma. 2024. Curcuma borealis sp. nov. and C. retrocalcaria sp. nov. (Zingiberaceae): Two Novel Taxa from Northern Thailand. Horticulturae. 10(8), 787. DOI: doi.org/10.3390/horticulturae10080787
