OBV (obscure vein), a C2H2 zinc finger transcription factor, positively regulates chloroplast development and bundle sheath extension formation in tomato (Solanum lycopersicum) leaf veins

Leaf veins play an important role in plant growth and development, and the bundle sheath (BS) is believed to greatly improve the photosynthetic efficiency of C4 plants. The OBV mutation in tomato (Solanum lycopersicum) results in dark veins and has been used widely in processing tomato varieties. However, physiological performance has difficulty explaining fitness in production. In this study, we confirmed that this mutation was caused by both the increased chlorophyll content and the absence of bundle sheath extension (BSE) in the veins. Using genome-wide association analysis and map-based cloning, we revealed that OBV encoded a C2H2L domain class transcription factor. It was localized in the nucleus and presented cell type-specific gene expression in the leaf veins. Furthermore, we verified the gene function by generating CRISPR/Cas9 knockout and overexpression mutants of the tomato gene. RNA sequencing analysis revealed that OBV was involved in regulating chloroplast development and photosynthesis, which greatly supported the change in chlorophyll content by mutation. Taken together, these findings demonstrated that OBV affected the growth and development of tomato by regulating chloroplast development in leaf veins. This study also provides a solid foundation to further decipher the mechanism of BSEs and to understand the evolution of photosynthesis in land plants.

Elevation of Symplocos macrophylla subsp. namboodiriana (Symplocaceae) to the species rank

In a comprehensive taxonomic revision of the Old World species of Symplocos (Symplocaceae) many infraspecific taxa were recognized within S. macrophylla, but subsequently most of these have been either moved to other species or recognized at the species rank. Following this trend, we provide herewith morphological evidence to warrant the elevation of S. macrophylla subsp. namboodiriana to the species rank. Symplocos namboodiriana comb. & stat. nov. differs from the other subspecies of S. macrophylla in its 1-flowered inflorescences (versus multi-flowered), shorter bracts, and 4 to 6 secondary leaf veins (versus longer bracts and 6 to 13 secondary veins). We provide an updated description of the species along with photographic images of live specimens and a conservation threat assessment.

A new species of Phyllagathis (Melastomataceae, Sonerileae) from Guangxi, China

Phyllagathis impressinervia (Melastomataceae, Sonerileae), a new species from northwestern Guangxi, China and previously misidentified as P. cavaleriei in Chinese herbaria, is illustrated and described. The new species closely resembles P. cavaleriei in leaf shape, inflorescence type, and morphology of stamens and capsule, but can be easily distinguished by the leaf veins strongly sunken adaxially, hypanthium pubescent with ca. 1 mm long, spreading glandular hairs, creamy white anthers, and conspicuous ovary crown at anthesis.

Involucrella lithophila (Rubiaceae: Spermacoceae): A new species from Guangxi, China

Involucrella lithophila from the limestone area of Guangxi, China, is described and illustrated here. It is most similar to Hedyotis kurzii and Involucrella chereevensis in having tetragonal stems, slender pedicels and loculicidally dehiscent capsules, but it differs from the former by its 3–5 (–7)-lobed stipules, heterostylous and white flowers and depressed seeds, and from the latter by its 2–4 secondary leaf veins and heterostylous flowers. The molecular phylogenetic analysis revealed that this new species was embedded in the Involucrella clade and closely related to I. chereevensis. It is evaluated as Least Concern according to IUCN Red List Categories and Criteria.

Difference between emergent aquatic and terrestrial monocotyledonous herbs in relation to the coordination of leaf stomata with vein traits

Emergent aquatic plants mostly occur in shallow waters and root in bottom substrates, but their leaves emerge from the water surface and are thus exposed to air, similar to the leaves of terrestrial plants. Previous studies have found coordination between leaf water supply and demand in terrestrial plants; however, whether such a coordination exists in emergent aquatic plants remains unknown. In this study, we analysed leaf veins and stomatal characteristics of 14 emergent aquatic and 13 terrestrial monocotyledonous herb species (EMH and TMH), with 5 EMH and 8 TMH belonging to Poaceae. We found that EMH had significantly higher mean leaf area, leaf thickness, stomatal density, stomatal number per vein length and major vein diameter, but lower mean major vein length per area (VLA) and total VLA than TMH. There was no significant difference in stomatal length, minor VLA and minor vein diameter between the two groups. Stomatal density and total VLA were positively correlated among the EMH, TMH, as well as the 8 Poaceae TMH species, but this correlation became non-significant when data from both the groups were pooled. Our results showed that the differences in water supply between emergent aquatic and terrestrial plants modify the coordination of their leaf veins and stomatal traits.

Dendrochilum ignisiflorum (Coelogyninae, Arethuseae, Orchidaceae), a new species from Luzon Island, Philippines

Dendrochilum ignisiflorum is hereby described and illustrated as a new species of orchid endemic to Luzon Island, Philippines. The species resembles D. vanoverberghii by having petiolate leaves, channelled petioles, labellum of the same size, and the erect to suberect incurved column but distinct by the sub-globose or broadly ellipsoid pseudobulb, 3 distinct leaf veins, barely spreading flowers, lanceolate and revolute dorsal sepal, and the absence of callus in the labellum.