Impatiens maolanensis (Balsaminaceae), a new species of Impatiens in a tiankeng from Guizhou, China

<i>Impatiensmaolanensis</i> Z.B.Xiong & Q.Y.Wen (Balsaminaceae), a new species of Impatienssubg.Clavicarpa from Maolan National Nature Reserve, Guizhou, China, is described. The new species grows in a tiankeng (a large, naturally formed pit) connected to a dried-up underground river. <i>I.maolanensis</i> is similar to <i>I.auriculata</i> Chang Y. Xia & S. X. Yu, <i>I.liboensis</i> K. M. Liu & R. P. Kuang and <i>I.tianlinensis</i> S. X. Yu & L. J. Zhang, but differs from the latter three species in terms of orange-red flowers, roots, stems, bracts, dorsal petals, lateral sepals, lower sepals, pollen grains and seeds micromorphology. The micromorphological characteristics and surface patterning of pollen grains and seeds of the new species were examined using scanning electron microscopy (SEM). Pollen grains of <i>I.maolanensis</i> are triangular-round in polar view and elliptical in equatorial view. The pollen exine has an irregular and relatively smooth reticulate ornamentation, and under high magnification, granular protrusions can be observed. Seeds of <i>I.maolanensis</i> are black and narrowly ellipsoid. The seed coat has reticulate ornamentation with slightly sunken meshes, folded base, and granular protrusions within the meshes. Morphological and micromorphology evidence support the establishment of the new species. Our study provides detailed information on the new species, including morphological characteristics, phenology, photographs, palynology, seed micromorphology, etymology, habitat and distribution, and conservation assessment.