Journal of Plant Research最新文献

Cassava (Manihot esculenta Crantz) is a prioritized crop for food security for nearly one billion people worldwide. We examined the genetic structure and diversity in a panel of 176 cassava cultivars from diverse biogeographic regions of Colombia using a total of 57,410 SNP markers obtained by Genotyping-by-Sequencing (GBS). A moderately high total diversity, heterozygotes deficit and inbreeding were found. Furthermore, we find three distinct genetic clusters (GC1, GC2 and GC3) with clear geographic correspondence to Amazonian, Andean, and Caribbean Colombian regions, a substantial phenotypic correlation with root bitterness and a greater differentiation between clusters than typically found in global scale studies. Each genetic cluster exhibits distinctive selection signatures reflecting region specific adaptations. GPI-anchor biosynthesis and chitin catabolism in Amazonian bitter cassava (defense against pathogens), oxidative stress response in Andean cassava (adaptation to highland conditions) and trehalose biosynthesis, cyano-amino acid metabolism and tuberization accumulation in Caribbean sweet cassava (drought tolerance, altered cyanogen processing and tuberization characteristics). These signatures align with phenotypic differentiation between bitter and sweet cultivars. These analyses highlight Colombia as a unique diversification core where environmental challenges and cultural practices have structured cassava diversity, underscoring the importance of integrated conservation strategies that preserve both genetic resources and the traditional knowledge systems that sustain them.

Invasion by alien woody plants strongly affects plant-animal interactions, often reducing invertebrate and bird abundance, thereby altering pollination and ultimately influencing plant reproduction. However, it remains unclear whether invasive alien trees also affect interactions typically considered antagonistic, such as nectar robbing. This study investigates the effects of invasive alien trees on insect communities and how these, in turn, affect the occurrence and frequency of nectar robbing in bird-pollinated Erica discolor and Erica unicolor. Floral-visitor observations were recorded at 27 uninvaded and 31 invaded fynbos (a Mediterranean-type shrubland) sites along the southern Cape coastal mountains, South Africa, from April to June 2023. We assessed factors affecting (1) nectar-robbing insect abundance, (2) the rate of nectar robbing, and (3) the impact of nectar robbing on pollination rate. Although overall robbing rates did not differ between invaded and uninvaded sites, the species composition of nectar robbers shifted. The Cape honey bee (Apis mellifera capensis) dominated robbing in uninvaded sites, whereas small solitary bees dominated robbing in invaded sites. Robbing appeared to have no effect on bird pollination rates in either Erica species. This study is the first to directly compare the widely used cumulative measure of robbing rate with observed robbing rate, revealing a significant positive relationship between the two. Together, these findings offer insights into how invasive alien trees can alter fynbos ecosystems and emphasise the critical role of insect communities in shaping plant-animal interactions.

Medakamo hakoo is an ultrasmall green alga with a simplified cellular structure, offering potential as a new model organism. To explore the genetic basis of cell morphology and its physiological implications, we applied carbon-ion beam irradiation to induce mutations in M. hakoo and successfully isolated two mutants: LRG (Large) and TTR (Tetra). LRG exhibited significantly enlarged cell size and increased chlorophyll content, but lower photosynthetic efficiency compared to the wild-type. Proteomic analysis of LRG revealed upregulation of photosynthesis-related proteins, stress response proteins, and ribosomal proteins, suggesting a link between increased cell size and disrupted photosynthetic homeostasis. TTR showed a higher proportion of dividing cells throughout the light-dark cycle and exhibited cell aggregation. Proteomic profiling revealed increased abundance of dynein and cell wall-modifying enzymes such as expansin and mannosidases, indicating that TTR may undergo cell cycle delay or dysregulation of cytoplasmic and cell wall dynamics. TTR also displayed decreased levels of photosynthetic proteins and reduced photosynthetic activity. Both mutants demonstrated slower growth compared to the wild-type. These findings highlight the close relationship between cell size and cell cycle/cell wall dynamics with photosynthetic activity, providing new insights into the cellular regulatory mechanisms of photosynthetic microalgae. Our study also demonstrates the utility of heavy-ion mutagenesis in dissecting microalgal physiology in species for which genetic transformation systems have not yet been developed.

Deceptive pollination exploits pollinator perceptual biases while offering no reward. Arisaema (Araceae) employs an extreme form of this strategy, in which fungus gnats are lured into a slippery floral tube that often proves fatal. However, the key factors governing attraction and capture remain poorly understood, partly due to the typically low frequency of floral visitation. Preliminary observations revealed that Arisaema serratum exhibits a relatively high visitation rate of fungus gnats. We therefore conducted direct behavioral observations of pollinators associated with A. serratum in a controlled field plot, combining video monitoring with morphometric analyses. Over two years, we recorded 2459 visits by male Cordyla sixi (Mycetophilidae) during 64 hours of observation, confirming a highly specialized interaction. Visit frequency declined only after floral senescence, with no progressive decrease observed within daily sessions, indicating negligible learning-based avoidance. Morphometric analyses suggested a positive correlation between thicker appendices and increased visitation, as well as between larger spathes and increased visitation, but a negative correlation between higher inflorescence placement and visitation, likely reflecting the low flight path of fungus gnats. Behavioral observations revealed frequent genital displays, wing-fanning, and exploratory walking on the appendix. Simultaneous visits by multiple males prolonged residence time and facilitated the arrival of additional individuals. Together, these findings support a scenario in which floral scent mimics sexual or aggregation pheromones, attracting dense male assemblies and enhancing pollination success. This study provides the first detailed ethogram of fungus gnat behavior associated with Arisaema, thereby offering novel insights into the mechanistic basis of this highly exploitative pollination system.

Succulent plants, characterized by the presence of water-storage tissues, often exhibit distinctive leaf morphology. However, their developmental mechanisms remain largely unknown, partly due to the lack of an appropriate model plant. In this study, we evaluated the potential of Asteraceae species as a model system for investigating the mechanisms underlying leaf succulence. First, we analyzed the leaf anatomical and cellular characteristics of succulent plants in the genera Caputia, Crassothonna, Curio, Othonna, and Senecio. To explore a potential mechanism involved in succulent leaf development, we focused on endoreduplication-genome replication without mitosis-and measured the ploidy levels of leaf cells in each species using flow cytometry (FCM) to assess the relationship between leaf succulence and endoreduplication. The FCM data indicated that succulent leaves of Caputia, Curio, Senecio, and Othonna were not associated with endoreduplication. In contrast, endoreduplication was detected in enlarged leaf cells of Crassothonna capensis, while no endoreduplication was observed in the peduncles, which did not appear succulent, or in ligules, which are the lateral organs homologous to leaves. These results suggest that unknown mechanisms other than endoreduplication contribute to leaf succulence in certain genera, and that endoreduplication is regulated in an organ-specific manner in Cr. capensis. Additionally, even if endoreduplication is involved in leaf succulence, it may serve as a supplementary mechanism for cell enlargement. Collectively, these findings highlight Crassothonna and its related genera in Asteraceae as a promising group for studying the mechanisms of leaf succulence.

Alexa grandiflora Ducke is a papilionoid legume tree native to the Brazilian Amazon Forest. It belongs to the early-diverging Angylocalyx clade within the subfamily Papilionoideae, which is characterized by keel flowers, with some genera having flowers other than typical papilionaceous ones. This study describes the floral organography, organogenesis, and secretory structures of A. grandiflora and compares its floral morphology with that of three species from different genera within the Angylocalyx clade to deepen the understanding of the clade's floral structure and, by extension, the broader Papilionoideae subfamily. To conduct the study, floral buds and flowers from A. grandiflora were collected and processed for surface and anatomical studies, and flowers from herbarium specimens of Castanospermum australe, Xanthocercis madagascariensis and Angylocalyx oligophyllus to elucidate the clade's floral evolution and its implications for Papilionoideae diversity. Floral buds and flowers of A. grandiflora were analyzed using surface and anatomical techniques, while herbarium specimens of the comparative taxa were examined via scanning electron microscopy. In A. grandiflora, the apical meristem of the racemose inflorescence primary axis produces first-order bracts acropetally in a helical order. Sepal initiation is unidirectional, petal initiation is simultaneous, with the adaxial petal growing faster than the others. Antesepalous stamens appear simultaneously and concurrently with the carpel, while antepetalous stamens emerge simultaneously. Floral secretion of nectar, terpenes, and oleoresin supports phyllostomid bat pollination in Alexa species, consistent with the previously proposed association between intense nectar and terpene production and chiropterophily in the genus. Comparative analysis reveals that the Angylocalyx clade shares key floral traits, including a gamosepalous calyx, an enlarged adaxial petal, and similarly shaped lateral and abaxial petals. However, variations are observed in the type of inflorescence and in the level of insertion of the filament in the anther, highlighting the floral diversity within the clade.

The Stress Gradient Hypothesis (SGH) predicts that the net effects of competition and facilitation among plants are determined by the interactions with environmental stressors. Juniperus virginiana is a stress-tolerant species that is native to the eastern United States but expanding into novel habitats, which may interact with changes in plant density as invasion proceeds to shape the course of species establishment. We tested this hypothesis by examining three sites along a complex latitudinal gradient shaped by historical glaciation and varying in snowfall, temperature, precipitation, and soil nutrients. We examined the impact of intraspecific competition (zero, one, two, and four competitors) on J. virginiana sapling growth metrics (relative growth rate, total biomass, and nitrogen concentration), physiological traits (midday water potential, assimilation rate, transpiration rate, and stomatal conductance), and water status. We found that abiotic conditions impacted plants in a non-linear fashion along a complex stress gradient, with the highest performance at high and low latitude sites. Intraspecific competition had limited effects overall, though some evidence suggests that negative impacts would develop over time at the highest density. Our study testing the expectations of SGH using this stress-tolerant species demonstrates how the theory can be applied to inform invasion management plans by showing that (1) intraspecific competition alone is unlikely to impact J. virginiana performance except at high plant densities, (2) environmental complexity, including the combined effect of temperature, precipitation, soil nutrient content, and competition, is a more likely driver of productivity and establishment, however (3) warmer, drier sites with higher soil nitrogen are expected to support higher growth rates, making them more vulnerable to J. virginiana invasion.