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Premise Geophytes—plants that typically possess a bulb, corm, tuber, and/or rhizome—have long captured the attention of hobbyists and researchers. However, despite the economic and evolutionary importance of these traits, the potential drivers of their morphological diversity remain unknown. Using a comprehensive phylogeny of monocots, we test for correlations between climate and geophyte growth form to better understand why we observe such a diversity of underground traits in geophytes. Understanding the evolutionary factors promoting independent origins of these potentially adaptive organs will lend insights into how plants adapt to environmental hardships. Methods Using a comprehensive phylogeny incorporated with global occurrence and climate data for the monocots, we investigated whether climatic patterns could explain differences between geophytes and non‐geophytes, as well as differences among bulbous, cormous, tuberous, rhizomatous, and non‐geophytic taxa. We used phylogenetically‐informed ANOVAs, MANOVAs, and PCAs to test differences in climatic variables between the different growth forms. Results Geophytes inhabit cooler, drier, and more thermally variable climates compared to non‐geophytes. Although some underground traits (i.e., bulb, corm, and tuber) appear to inhabit particular niches, a result supported by strong phylogenetic signal, our data has limited evidence for an overall role of climate in the evolution of these traits. However, temperature may be a driving force in rhizome evolution, as well as the evolution of taxa which we considered here as non‐geophytic (e.g., trees, epiphytes, etc.). Conclusions While precipitation patterns have played a role in the evolution of geophytism, our results suggest that temperature should be more strongly considered as a contributing factor promoting the evolution of belowground bud placement, specifically in rhizomatous and non‐geophytic taxa. Bulbous, cormous, and tuberous taxa need closer examination of other mechanisms, such as anatomical constraints or genetic controls, in order to begin to understand the causes behind the evolution of their underground morphology.

Plants, although sessile organisms, are nonetheless able to move their body parts; for example, during root contraction of geophytes or in the gravitropic reaction by woody stems. One of the major mechanisms enabling these movements is the development of specialized structures that possess contractile properties. Quite unlike animal muscles, for which the action is driven by protein–protein interactions in the protoplasma, the action of plant ‘muscles’ is polysaccharide-based and located in the uniquely designed, highly cellulosic cell wall that is deposited specifically in fibers. This review describes the development of such cell walls as a widespread phenomenon in the plant kingdom, gives reasons why it should be considered as a tertiary cell wall, and discusses the mechanism of action of the ‘muscles’. The origin of the contractile properties lies in the tension of the axially oriented cellulose microfibrils due to entrapment of rhamnogalact-uronan-I aggregates that limits the lateral interaction of microfibrils. Long side chains of the nascent rhamnogalacturonan-I are trimmed off during cell wall maturation leading to tension development. Similarities in the tertiary cell wall design in fibers of different plant origin indicate that the basic principles of tension creation may be universal in various ecophysiological situations.

• Geophytes, plants with buds on underground structures, are found throughout the plant tree of life. These below ground structures allow plants to inhabit highly seasonal and disturbance-prone environments across ecosystems. Past researchers have hypothesised that the bulbous, cormous and tuberous habits promote diversification, but this had yet to be tested. • Using a comprehensive monocot data set of almost 13 000 taxa, we investigated the effects of the geophytic habit on diversification using both state-dependent and state-independent models. • We found that geophytes exhibit increased rates of diversification relative to nongeophytes. State-dependent analyses recovered higher yet similar rates of diversification for bulbous, cormous and tuberous taxa compared with rhizomatous and nongeophytic taxa. However, the state-independent model returned no difference in rates among the different traits. • Geophytism shows higher rates of diversification relative to nongeophytes but we found little support for the hypothesis that the evolution of the bulb, corm or tuber appears to provide a diversification increase relative to rhizomatous and nongeophytic taxa. Our broad-scale analysis highlights the overall evolutionary importance of the geophytic habit (i.e. below-ground bud placement). However, our results also suggest that belowground morphological diversity alone cannot explain this rate increase. In order to further test the evolutionary significance of these underground structures, future studies should consider these in combination with other biotic and abiotic factors.

The extraordinary diversity of orchids has captivated scientists for more than a century, yet their complex spatial patterns at large scales remain poorly resolved. On islands, orchid diversity patterns are especially puzzling. While some islands are centres of orchid diversity, orchids are underrepresented on most islands. To disentangle such complex patterns, key functional differences among orchids must be considered – a distinction seldom made in biogeographical analyses. Using a global dataset of 454 islands, we tested prominent hypotheses in island biogeography, while simultaneously making the distinction between epiphytes and two terrestrial life forms (geophytes and non‐geophytes). Orchid diversity was unevenly distributed across islands and life forms. Epiphytic orchid diversity strongly increased with temperature, illustrating the near confinement of epiphytes to the tropics. Geophytes became proportionally more important with increasing seasonality, highlighting their ability to withstand harsh climatic conditions. Epiphytes and non‐geophytes both displayed responses (e.g. negative relationship with seasonality) related to their dependence on consistently favourable conditions, possibly because of the absence of subterranean storage organs. This highlights that the factors explaining orchid diversity differ strongly with, and are related to, life form. We suggest that key functional differences within and across plant families be considered in future studies to better understand drivers of complex diversity patterns.

Background and AimsThe genome size of an organism is determined by its capacity to tolerate genome expansion, given the species' life strategy and the limits of a particular environment, and the ability for retrotransposon suppression and/or removal. In some giant-genomed bulb geophytes, this tolerance is explained by their ability to pre-divide cells in the dormant stages or by the selective advantage of larger cells in the rapid growth of their fleshy body. In this study, a test shows that the tendency for genome size expansion is a more universal feature of geophytes, and is a subject in need of more general consideration.MethodsDifferences in monoploid genome sizes were compared using standardized phylogenetically independent contrasts in 47 sister pairs of geophytic and non-geophytic taxa sampled across all the angiosperms. The genome sizes of 96 species were adopted from the literature and 53 species were newly measured using flow cytometry with propidium iodide staining.Key ResultsThe geophytes showed increased genome sizes compared with their non-geophytic relatives, regardless of the storage organ type and regardless of whether or not vernal geophytes, polyploids or annuals were included in the analyses.ConclusionsThe universal tendency of geophytes to possess a higher genome size suggests the presence of a universal mechanism allowing for genome expansion. It is assumed that this is primarily due to the nutrient and energetic independence of geophytes perhaps allowing continuous synthesis of DNA, which is known to proceed in the extreme cases of vernal geophytes even in dormant stages. This independence may also be assumed as a reason for allowing large genomes in some parasitic plants, as well as the nutrient limitation of small genomes of carnivorous plants.

Palestine has rich floristic diversity due to its location, diverse biogeographical zones, and various topographical features. The Royal Irises ( Iris section Oncocyclus ), are a monophyletic group of herbaceous geophytes, consisting of 33 species, endemic to the Middle East. Within the West Bank of Palestine, three Royal Irises are documented. However, their distribution, population size, and status are not studied comprehensively. This study focused on evaluating the occurrence, distribution range, population size, status, number of flowers, inflorescence coloration variety, and habitats of the vulnerable and endemic Iris haynei , the endangered and sub-endemic Iris lortetii , and the vulnerable and sub-endemic Iris atrofusca . I. lortetii was found in 10 sites within Nablus district, with more than 12625 clones and 25088 flowers flowers recorded. I. haynei were documented in 4 sites within Jenin district, three are new to science, where 10729 clones and 9562 flowers were recorded. I. atrofusca was reported in 13 localities in Tubas and Ramallah districts, where 1853 clones and 8460 flowers were recorded, whereas six locatities are new to science. 12, 12, and 7 unique variations in coloration of inflorescences were observed for I. lortetii , I. atrofusca , and I. haynei , respectively. The results indicate that the population size and the distribution range of the three Royal Irises are larger than previously reported, whereas the documented inflorescences’ coloration variations are unique and considerable. This study sheds light on hotspot occurrence sites of endangered and vulnerable species in Palestine, which can assist in laying adequate conservation actions and management plans in the future.

This article is a Commentary on Jánosi et al. (2020), 228: 1535–1547.

Gladiolus is a well-known bulbous plant producing impressive cut spikes. Hydrogen sulfide (H 2 S) and nitric oxide (NO) are vital signaling molecules required for the proper functioning of plant metabolism. Preharvest applications of these molecules to crops have gained attention in recent years due to their positive role in tackling abiotic stresses, although, their role in geophytes is comparatively less studied. We assessed the effects of preharvest H 2 S and NO treatments on development, flowering, harvest and postharvest performance of gladiolus inflorescences. NO and H 2 S + NO treatments increased preharvest performance of plants associated with corm production, inflorescences length and harvest time. Individual and combined treatments improved postharvest vase life (VL) up to 3.4 days. Total soluble proteins (TSP) were increased in response to H 2 S, NO and H 2 S + NO treatments by 39%, 43%, and 55%, respectively compared to the controls. Soluble sugars (SS) were increased after NO and H 2 S + NO treatments by up to 25% and 42%, respectively. Postharvest catalase (CAT) activity was higher by 65%, 68%, and 76% after H 2 S, NO and H 2 S + NO treatments, respectively. Malondialdehyde (MDA) was decreased by all preharvest treatments by up to 88%, although, only the combined H 2 S + NO treatment reduced H 2 O 2 and superoxide dismutase (SOD) activity. The results confirm that preharvest treatments with H 2 S, NO and H 2 S + NO may positively affect growth, floral traits and postharvest performance of cut gladiolus inflorescences.

The establishment and success of polyploids are thought to often be facilitated by ecological niche differentiation from diploids. Unfortunately, most studies compared diploids and polyploids, ignoring variation in ploidy level in polyploids. To fill this gap, we performed a large-scale study of 11,163 samples from 1,283 populations of the polyploid perennial geophyte Allium oleraceum with reported mixed-ploidy populations, revealed distribution ranges of cytotypes, assessed their niches and explored the pattern of niche change with increasing ploidy level. Altogether, six ploidy levels (3 x −8 x ) were identified. The most common were pentaploids (53.6%) followed by hexaploids (22.7%) and tetraploids (21.6%). Higher cytotype diversity was found at lower latitudes than at higher latitudes (>52° N), where only tetraploids and pentaploids occurred. We detected 17.4% of mixed-ploidy populations, usually as a combination of two, rarely of three, cytotypes. The majority of mixed-ploidy populations were found in zones of sympatry of the participating cytotypes, suggesting they have arisen through migration (secondary contact zone). Using coarse-grained variables (climate, soil), we found evidence of both niche expansion and innovation in tetraploids related to triploids, whereas higher ploidy levels showed almost zero niche expansion, but a trend of increased niche unfilling of tetraploids. Niche unfilling in higher ploidy levels was caused by a contraction of niche envelopes toward lower continentality of the climate and resulted in a gradual decrease of niche breadth and a gradual shift in niche optima. Field-recorded data indicated wide habitat breadth of tetraploids and pentaploids, but also a pattern of increasing synanthropy in higher ploidy levels. Wide niche breadth of tetra- and pentaploids might be related to their multiple origins from different environmental conditions, higher “age”, and retained sexuality, which likely preserve their adaptive potential. In contrast, other cytotypes with narrower niches are mostly asexual, probably originating from a limited range of contrasting environments. Persistence of local ploidy mixtures could be enabled by the perenniality of A. oleraceum and its prevalence of vegetative reproduction, facilitating the establishment and decreasing exclusion of minority cytotype due to its reproductive costs. Vegetative reproduction might also significantly accelerate colonization of new areas, including recolonization of previously glaciated areas.

Mediterranean coastal dunes are among the most threatened ecosystems in Europe. Analysing temporal trends in a site with exceptionally well-preserved zonation and minimal anthropogenic disturbance offers a unique opportunity to deepen our understanding of vegetation dynamics under low-impact conditions in these vulnerable ecosystems. This study examines the temporal dynamics of coastal dune ecosystems within the Castelporziano Presidential Estate, which hosts intact Mediterranean dune systems with complete vegetation zonation. Revisiting 80 historical plots initially surveyed 30 years ago, we analysed changes in plant species occurrence and abundance over time using ordination and similarity percentage analysis. Additionally, we assessed shifts in typical, ruderal, and alien species, ecological indicator values, and an index based on rhizomatous geophyte grasses to evaluate the system’s erosion control capacity. Our results revealed no significant decline in species richness in foredunes and dune grasslands, contrasting with trends observed in other coastal dunes in Central Italy. Instead, we recorded an increase in typical species abundance in foredunes, likely resulting from limited human disturbance over the past 30 years. These changes are probably related to ongoing successional dynamics. Coastal shrublands underwent more pronounced changes, transitioning toward woodlands and experiencing an increase in typical species. These transformations suggest positive successional shifts. Our findings indicate that the coastal dune ecosystem is well-preserved, largely due to restricted human disturbance and effective management. This study underscores the value of resurveying methodologies for monitoring vegetation dynamics, offering critical insights to support conservation efforts for these unique Mediterranean habitats.