Abstract Parasitic organisms are of interest in evolutionary biology, often displaying drastic modifications in morphology, physiology, genomes, and ecology. These properties, however, make them challenging from a systematics perspective. Mycoheterotrophy, in which plants become non-photosynthetic parasites on fungi, is an excellent example, and this unique life history has evolved numerous times in the orchid family. Here we focused on Stereosandra, a genus of mycoheterotrophic orchid comprising a single species, S. javanica, about which little is known. Stereosandra has been placed in the orchid tribe Nervilieae, along with the leafy, autotrophic Nervilia, and the leafless, mycoheterotrophic Epipogium. We characterized the first complete plastid genome for Stereosandra and used nuclear sequence capture to determine its relationships within Nervilieae. This study presents the first genetic data ever produced for Stereosandra. The plastid genome exhibits rampant gene losses, pseudogenes, and reduced size relative to Nervilia, but not to the extent seen in Epipogium. There is evidence of relaxed negative selection in six genes in Stereosandra, including matK, which functions in Group IIA intron removal of seven plastid genes, four of which have been lost or pseudogenized in this species. Applying mixture models, plastid genomes provided weak support for a sister position of Stereosandra to a clade of Epipogium + Nervilia. Nuclear phylogenomic analyses provided strong support for the same relationships. Ancestral state reconstruction revealed clear evidence that mycoheterotrophy evolved multiple times in the tribe from leafy ancestors. This study provides a previously unidentified, convergent instance of the evolution of full mycoheterotrophy in plants. We discuss the results in the context of proposed models of reductive plastid genome evolution and the genomic and evolutionary consequences of radical life history shifts in heterotrophic plants.

Extreme events (e.g. severe drought) can hinder the establishment of saplings in tropical forest plantations. To assess the resistance and recovery of three commercially important Amazonian tree species under drought conditions and to identify their key functional strategies for drought response, we conducted a controlled drought experiment exposing saplings of Bertholletia excelsa, Dipteryx odorata, and Tachigali vulgaris to water deficit followed by recovery. Tachigali vulgaris (fast-growing species) was more vulnerable to drought, as 80% of the drought-treated plants died. Nevertheless, the individuals who survived demonstrated a rapid recovery of physiological performance following rewatering. Bertholletia excelsa and D. odorata (slow-growing species) were more resistant to drought stress, as evidenced by lack of mortality in these species. Drought-stressed plants had the lowest growth rates, more biomass allocated to roots and less leaf biomass. The greater biomass allocation to roots in B. excelsa and D. odorata, together with their more conservative functional traits compared to T. vulgaris, appears to play an important role in their lower sensitivity to drought. These species exhibited strategies consistent with drought avoidance. Our results highlight the specific strategies of these species under water-deficit conditions and can help guide decisions on species selection and plantation management for reforestation under climate change scenarios.

Cytoplasmic male sterility (CMS) is a common biological phenomenon in chilli pepper hybrid production. Although several restorer-of-fertility (Rf) genes have been identified in pepper CMS lines, a regulatory network has yet to be constructed. Morphological characteristics of the sterile, maintainer, and restorer flower buds were studied at three different developmental stages. We conducted transcriptome analysis of the CMS/Rf system in pepper plants. Pentose and glucuronate interconversion pathways were particularly enriched in most comparison groups. In addition, differentially expressed genes among the different lines at flower bud stages 2 and 3 were generally enriched in amino sugar and nucleotide sugar metabolism pathways. In our study, the small auxin upregulated RNA (SAUR), A-ARR and GH3 genes in the plant hormone signal transduction pathway, Capana12g000348, CKX7 and cis-zeatin O-glucosyltransferase (CISZOG) genes in the zeatin biosynthesis pathway, and receptor-like protein kinase 2 (RLK2) in the germplasm development signal pathway showed gradual upregulation across developmental stages in the restorer line. However, expression of these genes was stable in the sterile and maintainer lines. qRT-PCR analysis showed that SAUR, A-ARR, GH3, Capana12g000348, CKX7, CISZOG, CRE1, AHP and TIR1 participate in CMS fertility regulation in chilli pepper. We constructed a regulatory network based on critical genes. Overall, our research provides a solid theoretical foundation for the development of CMS fertility studies on chilli pepper.

Pediocactus bradyi, a semi-globose cactus endemic to northern Arizona, displays a root-contraction mechanism to survive extreme drought: its roots contract, pulling the stem below ground during dry periods, re-emerging once rains return. To quantify how root contraction shapes population dynamics, we developed an integral projection model based on 31 years of demographic data from a P. bradyi population on the Navajo Nation Off-Reservation Trust Land. We explored two scenarios: one including root contraction and one excluding it. We found that, being ∼10% of the individuals and mostly confined to smaller individuals, root contraction did not have an effect on the long-term population growth [λ = 1.041 (1.039, 1.303) with contraction vs. λ = 1.044 (1.035, 1.289) without]. Also, we show that larger individuals have higher survival and reproductive rates, while growth declines beyond 35 mm in diameter. An elasticity analysis confirmed that survival and growth are the main vital rates affecting population growth, followed by root elongation after contraction. Thus, while root contraction may improve individual survival, elongation is in fact more important at the population level. Therefore, as with most cacti species, conservation efforts should focus on ensuring the survival of large individuals irrespective of their root contraction status.

Plants use chemicals to respond to their environments. Despite the impact of competition on plant productivity, few studies consider how plant–plant competition affects phytochemistry; most phytochemistry studies focus on plant–consumer interactions. It therefore remains unclear how plants chemically respond to changes in both competition and consumer pressure. We used 1H-NMR spectroscopy to characterize the phytochemistry (both primary and secondary metabolites) of a C4 grass (Andropogon gerardi) and a legume (Lespedeza capitata) in a field experiment. Both species were grown with intraspecific or interspecific neighbours (monoculture or 16-species polyculture) with or without a combined fungicide + insecticide treatment (consumers reduced vs. consumers present) in a factorial design. We measured species aboveground biomass, healthy plant cover (NDVI) and phytochemistry in the four treatments to determine whether plants alter their biomass, phytochemistry, or both in response to neighbours and herbivory. Phytochemistry of A. gerardi did not vary with neighbour identity or consumers, in contrast to A. gerardi biomass, which was higher under interspecific competition and when consumers were reduced. Phytochemistry of L. capitata was also unrelated to consumer reduction, though L. capitata had higher NDVI under reduced consumers. However, L. capitata had lower biomass and exhibited phytochemical signs of metabolic stress (lower sugars and higher amino acid production) when grown with interspecific neighbours. Theory and empirical work have focused on coevolution with consumers as driving phytochemical variation, but our results suggest that—at community scales—the competitive environment may be more important than consumer pressure in determining short-term phytochemical responses of some species.

Vessel scaling from tip to base in angiosperms has largely been studied based on vessel diameter. Here, we test if vessel anatomy and transport efficiency in a Fagus sylvatica L. sapling show axial scaling by maintaining a largely proportional ratio of lumen to end-wall resistivity to sap flow with tree height. Vessel diameter (D) of more than 50 000 vessels was measured based on wood sections, while mean vessel length (LV) was measured semi-automatically with a Pneumatron for 58 stem segments. Based on tip-to-base variation in D and LV, we estimated vessel lumen conductivity (KH) at the individual vessel level. We also estimated end-wall conductivity (KW) based on Darcy’s law, integrating pit membrane thickness (TPM) with scaling of D and total inter-vessel pit membrane area (AP) across the sapling. Axial variation in KW was evaluated against end-wall pressure difference (). In addition to a tip-to-base increase in D, we found an increase in LV and AP, illustrating basipetal vessel lengthening. These patterns were associated with proportional changes in KW and KH, which followed a 1:1 relationship with distance to the tip, each contributing to ∼ 50% of the whole-tree conductivity/resistivity. Our findings suggest that vessel dimensions and hydraulic functionality show axial scaling in angiosperm trees, suggesting that anatomy corresponds to the adjustment of hydraulic functionality with plant height. Proportional adjustment of KW and KH highlights the key role of vessel dimensions and inter-vessel pits in regulating transport efficiency and safety, potentially maintaining constant resistance per unit leaf area with height growth.

Clonal reproduction is often considered advantageous in stressful environments. While considerable research has explored how clonality supports plant survival in wet and cold conditions, its role in arid and semi-arid conditions remains underexplored. To address this gap, this study examines the distribution and diversity of clonality as a key component of belowground growth form (BGF) along aridity gradients across SW and Central Asia using the species-rich Lamiaceae family as a model. Data were collected from 281 species with a variety of BGFs occurring in a broad range of habitats. Data on BGFs were collected primarily in the field, with additional data from herbarium records and digital databases. BGFs were categorized into hypogeogenous rhizomes, epigeogenous rhizomes, stolons, and non-clonal types. Species distribution data were obtained from regional floras and the Global Biodiversity Information Facility (GBIF) and analysed using precipitation-related bioclimatic variables. Clonal species of the Lamiaceae family, particularly those with hypogeogenous and epigeogenous rhizomes, were more prevalent in extreme environments, both water-limited and moisture-rich, highlighting their adaptation to stressful conditions. They thrived in arid habitats like deserts and semi-deserts as well as wet habitats such as forests or wetlands. Non-clonal species were concentrated in the centre of the gradient, dominating montane steppe shrublands where water availability was moderate and seasonally variable. Clonal plants are not avoiding arid environment. This is particularly noteworthy for species with hypogeogenous rhizomes that have been shown to prefer wet conditions in temperate regions. The exact mechanisms that permit their specialization to wet or dry conditions is to be further studied experimentally. These findings highlight how climate change may differentially affect species based on their BGFs.

Hybridization, polyploidization, and apomixis are evolutionary forces that obscure genetic differentiation and boost morphological variability. These processes have shaped the family Rosaceae, particularly the genus Crataegus, which includes both diploid and polyploid species reproducing sexually or via apomixis. In Central Europe, C. monogyna and C. laevigata are predominantly diploid sexuals, while C. rhipidophylla is mainly a polyploid apomict. These species hybridize to form C. × media, C. × macrocarpa, and C. × subsphaerica. Our aim was to assess how hybridization, apomixis, and polyploidy shape Crataegus diversity by integrating genetic, morphological, and cytological data. Leaves and fruits were collected from ten natural populations where all three species coexist and hybridize. Species identification was performed with novel nuclear microsatellites, marking the first genetic-based Crataegus taxonomy in Central Europe. Ploidy levels were estimated by flow cytometry (FCM), including seed screening to infer reproductive modes. A combined morphological analysis of leaves and fruits was used to distinguish parental species and evaluate hybrid variability. Genotyping identified distinct genetic clusters for parental species and their hybrids, with geographic structuring within C. laevigata and C. rhipidophylla. Morphological data clearly separated genetically defined parental species, although hybrids can be difficult to distinguish from parents due to a big overlap in morphology. FCM indicated that C. × media is predominantly a diploid sexual hybrid like its diploid parents, while other tri- or tetraploid hybrids with polyploid C. rhipidophylla as a parent are apomictic. Ploidy rather than hybridization dictates the mode of reproduction.

Salinity is one of the most devastating abiotic stresses limiting crop productivity. Here, the salinity tolerance level and physiological changes in Echinochloa frumentacea in saline and alkaline soils were estimated by studying root morphology, quantifying ions (Ca2+, K+, Na+, Ca2+/Na+, and K+/Na+) in roots, and measuring antioxidant enzyme activities, malondialdehyde (MDA), proline, and soluble sugar contents. Echinochloa frumentacea was tested against four neutral and alkaline salts, NaCl: Na2SO4:NaHCO3:Na2CO3 in different proportions at 60, 120, 180, 240, and 300 mmol L−1 concentrations. Echinochloa frumentacea was evaluated and compared with plant species, which are commonly cultivated in non-saline and alkaline soils i.e. Echinochola crusgalli, Avena sativa, Salicornia europaea, Medicago sativa, and Glycyrrhiza uralensis. The results revealed an increase in root length, diameter, absorption area, fresh, and dry weight at 120 mmol L−1. However, a gradual decrease in these parameters was observed at higher salt concentrations. In contrast, an increase in superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) activities, and MDA and proline levels were observed with increasing salt concentration. The roots of E. frumentacea absorbed higher levels of ions than the other five forage plant species. Higher K+/Na+ and strong root structure in E. frumentacea indicate its better tolerance in saline soil than in alkaline soil. Our results demonstrate that E. frumentacea can tolerate up to 120 mmol L−1 salt in a saline–alkaline environment and is more suitable for growth in saline soil. In addition, the root system of E. frumentacea can be used to dechlorinate the chloride from soil and reduce its toxic effect on plants. It can also be used as a target species for selection and breeding programs to improve salt tolerance in future studies.

Plant–plant interactions play a crucial role in shaping the growth environment for crops, impacting their productivity and resilience to stress. Interactions between plants have been incorporated into breeding programmes by selecting new target traits that will advance plants’ abilities to produce in high densities. The study of plant–plant interactions belowground promises new pathways and traits for crop improvement. This study focuses on the developmental and physiological responses of sorghum (Sorghum bicolor L.) genotypes to neighbouring sorghum plants. In this study, we used two growing methods: (i) a focal plant surrounded by neighbouring plants in the same pot but without shading, and (ii) a focal plant grown either alone or surrounded by neighbours, irrigated with nutrient solution that was passed through pots (leachates) with or without plants. Our results show that the presence of neighbours in the same pot led to reduced dry weight, plant height, and leaf area of the focal plant. In addition, the presence of neighbours reduced stomatal conductance and photosystem II quantum yield. While the response direction was similar across tested genotypes, the magnitude varied. The results were repeated when neighbouring plants were not grown in the same pot, but a nutrient solution was passed through the root systems of other plants into a separate pot containing another plant. Furthermore, we saw a reduction in assimilation rate and stomatal conductance when plants were exposed to either the physical presence of neighbours or leachate. We did not find differences in root architecture in either treatment. These results show that plants change their growth in response to neighbours and that the signal is carried through the liquid phase of the soil. Our findings provide insights into sorghum plants’ responses to belowground signalling from neighbouring plants and lay the foundation for future studies enabling increased crop performance under high-density planting conditions.