The Cretaceous–Paleogene (K–Pg) mass extinction was geologically instantaneous, causing the most drastic extinction rates in Earth’s History. The rapid species losses and environmental destruction from the Chicxulub impact at 66.02 Ma made the K–Pg the most comparable past event to today’s projected “sixth” mass extinction. The extinction famously eliminated major clades of animals and plankton. However, for land plants, losses primarily occurred among species observed in regional studies but left no global trace at the family or major-clade level, leading to questions about whether there was a significant K–Pg plant extinction. We review emerging paleobotanical data from the Americas and argue that the evidence strongly favors profound (generally >50%), geographically heterogeneous species losses and recovery consistent with mass extinction. The heterogeneity appears to reflect several factors, including distance from the impact site and marine and latitudinal buffering of the impact winter. The ensuing transformations have affected all land life, including true angiosperm dominance in the world’s forests, the birth of the hyperdiverse Neotropical rainforest biome, and evolutionary radiations leading to many crown angiosperm clades. Although the worst outcomes are still preventable, the sixth mass extinction could mirror the K–Pg event by eliminating comparable numbers of plant species in a geologic instant, impoverishing and eventually transforming terrestrial ecosystems while having little effect on global plant-family diversity.

Seeds show important variation as plant regenerative units among species, but their evolutionary co-variations with other plant characteristics are still poorly understood. Whilst a positive association of seed mass with genome size (GS) and life forms has already been documented, a broad-scale quantification of their evolutionary correlation and adaptive selection has never been conducted. Here, we tested for correlated evolution of seed mass and GS towards distinct selective regimes related to life form in angiosperms. In particular, we tested the hypothesis that the selection toward lighter seeds and smaller genomes is stronger for annual plants, ensuring high regenerative potential. Using multivariate evolutionary models over a dataset containing 3242 species, we showed an overall positive correlated evolution of seed mass and GS deviating from a pure drift process. Instead, evolutionary changes in seed and genome sizes were driven by adaptive selection towards optimal values differing among life forms. Specifically, the evolutionary optima towards which the seed and genome sizes evolve show a covariation toward small values in annuals, intermediate values in perennial herbs and a trade-off between seed mass and GS in woody plants. Moreover, the evolutionary correlation between seed mass and GS is strongest in annuals as an adaption to complete their life cycle in a short time window, when environmental conditions are favourable for regeneration and development to maturity. The asymmetry in the correlated evolution acting on seed and genome sizes due to life form could explain how life-history traits interplay with functional traits and how plants have evolved diverse successful life-history strategies.

Thirty angiosperm species in 20 families, collected in Nam Kading National Protected Area, are recorded in Laos for the first time. Because the flora of Nam Kading is rich in endemic species, the area represents one of the core sites of plant biodiversity in Laos. To elucidate the plant diversity accurately, further intensive floristic surveys are required.

The feature distinguishing typical angiosperms from gymnosperms is that their ovules are enclosed before pollination. Bennettitales were formerly related to angiosperms because of the flower-like organisation of the former's reproductive organs. There is little information on how the naked ovules of Bennettitales became enclosed in angiosperms because fossil evidence for such a transition, if it exists, has not been described. Here, we report a reproductive organ, Zhangwuia gen. nov., from the Middle Jurassic of Inner Mongolia, China. Like many Bennettitales, the arrangement of the foliar parts around the female part in Zhangwuia demonstrates a resemblance to typical angiosperm flowers. It is noteworthy that the ovule is secluded from the exterior space in Zhangwuia, therefore implying the existence of angio-ovuly. Although Bennettitales have been related to angiosperms for more than a hundred years, their way of ovule-enclosing was not previously revealed. The discovery of Zhangwuia prompts a rethinking of the relationship between Bennettitales and angiosperms, as well as of the origin of angiosperms.

The genus Donella Pierre ex Baill. is here reinstated and Austrogambeya Aubrév. is, for the first time, placed in synonymy based on the findings of recent combined molecular and morphological studies. Seventeen species are recognised, two of which, Donella ranirisonii L.Gaut. & Mackinder and D. humbertii Capuron ex Mackinder & L.Gaut., from Madagascar, are described here for the first time. The flowers of Donella ambrensis and D. delphinensis are described here for the first time, as are the fruits of D. guereliana. Two keys, to the species of Madagascar and tropical Africa, respectively, are presented. Ten species are endemic to Madagascar, six species are endemic to tropical Africa and one, Donella lanceolata, occurs from Madagascar to the Solomon Islands. For each species, the accepted name with synonymy is given, followed by a morphological description. Geographical range and details of habitat are provided, with taxonomic and/or nomenclatural notes as appropriate. Distribution maps are presented for all species, and preliminary conservation assessments are made. Five species qualify for a category of Threat, and three further species are assessed as Near Threatened. An index to species and a list of exsiccatae are included.

A synopsis of the native and naturalised species of Senna (Leguminosae: Caesalpinioideae) in the Arabian Peninsula is provided. Nine species are recognised. A key to the species is presented. For each species the accepted name with selected synonymy is given, followed by a diagnostic morphological description, the geographical distribution, details of habitat preference, and citation of specimens studied. Preliminary regional conservation assessments are given for all species.

Medicago truncatula, soybean (Glycine max), Arabidopsis thaliana and rice (Oryza sativa) all belong to the core angiosperm group of plants. Seed-specific genes are important for seed formation and development in these angiosperms. The identification of genes specifically expressed in angiosperm seeds and the comparison of the expression patterns of homologous genes among different angiosperm species can provide novel insights into the functions of genes that control seed development and the evolution of angiosperms. We downloaded the sequences and expression data from the relevant databases, and the seed-specific expression of genes was identified with cut-offs of a gene expression level ratio ≥ 5 and a Z-score ≥ 6. The genes were analysed using local BLAST software with an E-value ≤ 1.0E − 505. A total of 605, 581, 778 and 722 genes showed specific expression in the seeds of Medicago, soybean, Arabidopsis and rice, respectively. Additionally, we compared the expression patterns of seed-specific genes from each species with their homologues in the other three species, and found that the degree of variation in the expression patterns of homologous genes was low among closely related species but higher among more distantly related ones. The discrepancy between the homologous gene expression patterns may be caused by the different characteristics of the cis-elements in the promoter regions of the homologous genes.

New records in the Flora of Laos are presented, along with a short history of botanical collection in the country. The records are given in two lists, one relating to the Flore du Cambodge, du Laos et du Viêtnam and the other relating to the older Flore générale de l'Indochine.