Annals of botany最新文献

Background and aims: Climate change poses a growing threat to population maintenance in harsh desert habitats with high precipitation variability. Desert seeds may germinate at different times as a bet-hedging strategy to cope with increased rainfall fluctuation. As a result, a population may consist of seedlings of various sizes. However, it remains unknown how the variation in seedling sizes affects their capacity to cope with different rainfall scenarios, thus impairing our capacity to manage population under climate change.

Methods: To fill this gap in knowledge, we examined how seedling size (large seedlings with an average height of 14.30 cm vs. small seedlings with an average height of 5.85 cm) affects the strategy seedlings use to cope with a gradient of rainfall treatments (-75%, -50%, -25%, 0%, +25%, +50%, +75%) for Artemisia ordosica Krasch., a dominant shrub widely used for ecological restoration in the Mu Us Sandland.

Key results: We found that seedling performance was affected both by rainfall intensity and seedling size. Seedling survival and growth declined with reduction in rainfall. Moreover, large seedlings allocated more biomass to roots, thus increasing their capacity for water absorption, resulting in relatively less reduction in their total biomass under water stress. In contrast, small seedlings invested more in aboveground growth, likely to compete for light.

Conclusions: Our study demonstrates that seedling size may strongly affect the responses of seedlings to rainfall variation. As a result, populations having recruitment of seedlings with different sizes may better spread mortality risk under variable rainfall conditions. Therefore, our results suggest that species with flexible germination time may be highly suitable for desert vegetation restoration under climate change.

Background and aims: Seed persistence in soil depends on environmental factors that affect seed dormancy and germination, such as temperature and water availability. In high-elevation ecosystems, rapid changes in these environmental factors because of climate change can impact future plant recruitment. To date, our knowledge on how soil seed banks from high-elevation environments will respond to climate change and extreme climate-related events is limited. Here, using the seedling emergence method, we investigated the effects of reduced snow cover, fire and drought on the density and diversity of germinants from soil seed banks of two high-elevation plant communities: a tall alpine herbfield and a treeline ecotone.

Methods: In Autumn 2020, we collected soil samples and characterized the standing vegetation of both communities at Kosciuszko National Park, Australia. Subsequently, we carried out a factorial experiment and subjected the soil samples to a series of manipulative treatments using greenhouse studies.

Key results: The treeline had a larger and more diverse soil seed bank than the herbfield. A reduction in snow had a negative effect on the number of germinants in the herbfield and increased the dissimilarity with the standing vegetation, whereas the treeline responses were mainly neutral. Fire did not significantly affect the number of germinants but decreased the evenness values in both communities. The drought treatment reduced the number and richness of germinants and increased the dissimilarity with the standing vegetation in both communities. Plant functional forms explained some of the detected effects, but seed functional traits did not.

Conclusions: Our study suggests that simulated climate change will affect plant recruitment from soil seed banks in a variety of ways. Changes in snow cover and incidences of fire and drought might be key drivers of germination from the soil seed bank and therefore the future composition of alpine plant communities.

Background and aims: Pollinators provide critical ecosystem services, maintaining biodiversity and benefitting global food production. However, plants, pollinators and their mutualistic interactions can be affected by drought, which has increased in severity and frequency under climate change. Using two annual, insect-pollinated wildflowers (Phacelia campanularia and Nemophila menziesii), we asked how drought impacts floral traits and foraging preferences of a solitary bee (Osmia lignaria) and explored potential implications for plant reproduction.

Methods: In greenhouses, we subjected plants experimentally to drought to induce water stress, as verified by leaf water potential. To assess the impact of drought on floral traits, we measured flower size, floral display size, nectar volume and nectar sugar concentration. To explore how drought-induced effects on floral traits affected bee foraging preferences, we performed choice trials. Individual female bees were placed into foraging arenas with two conspecific plants, one droughted and one non-droughted, and were allowed to forage freely.

Key results: We determined that P. campanularia is more drought tolerant than N. menziesii, based on measures of turgor loss point, and confirmed that droughted plants were more drought stressed than non-droughted plants. For droughted plants of both species, the floral display size was reduced and the flowers were smaller and produced less, more-concentrated nectar. We found that bees preferred non-droughted flowers of N. menziesii. However, bee preference for non-droughted P. campanularia flowers depended on the time of day and was detected only in the afternoon.

Conclusions: Our findings indicate that bees prefer to visit non-droughted flowers, probably reducing pollination success for drought-stressed plants. Lack of preference for non-droughted P. campanularia flowers in the morning might reflect the higher drought tolerance of this species. This work highlights the potentially intersecting, short-term physiological and pollinator behavioural responses to drought and suggests that such responses might reshape plant-pollinator interactions, ultimately reducing reproductive output for less drought-tolerant wildflowers.

Background and aims: Floral volatiles, visual traits and rewards mediate attraction and defence in plant-pollinator and plant-herbivore interactions, but these floral traits might be altered by global warming through direct effects of temperature or longer-term impacts on plant resources. We examined the effect of warming on floral and leaf volatile emissions, floral morphology, plant height, nectar production, and oviposition by seed predators.

Methods: We used open-top chambers that warmed plants in the field by +2-3 °C on average (+6-11 °C increase in daily maxima) for 2-4 weeks across 1-3 years at three sites in Colorado, USA. Volatiles were sampled from two closely related species of subalpine Ipomopsis with different pollinators: Ipomopsis aggregata ssp. aggregata, visited mainly by hummingbirds, and Ipomopsis tenuituba ssp. tenuituba, often visited by hawkmoths.

Key results: Although warming had no detected effects on leaf volatiles, the daytime floral volatiles of both I. aggregata and I. tenuituba responded in subtle ways to warming, with impacts that depended on the species, site and year. In addition to the long-term effect of warming, temperature at the time of sampling independently affected the floral volatile emissions of I. aggregata during the day and I. tenuituba at night. Warming had little effect on floral morphology for either species and it had no effect on nectar concentration, maximum inflorescence height or flower redness in I. aggregata. However, warming increased nectar production in I. aggregata by 41 %, a response that would attract more hummingbird visits, and it reduced oviposition by fly seed predators by ≥72 %.

Conclusions: Our results suggest that floral traits can show different levels of plasticity to temperature changes in subalpine environments, with potential effects on animal behaviours that help or hinder plant reproduction. They also illustrate the need for more long-term field warming studies, as shown by responses of floral volatiles in different ways to weeks of warming vs. temperature at the time of sampling.

Background and aims: Changing precipitation regimes can influence terrestrial plants and ecosystems. However, plant phenological responses to changing temporal patterns of precipitation and the underlying mechanisms are largely unclear. This study was conducted to explore the effects of seasonal precipitation redistribution on plant reproductive phenology in a temperate steppe.

Methods: A field experiment was undertaken with control (C), advanced (AP) and delayed (DP) growing-season precipitation peaks and the combination of AP and DP (ADP). Seven dominant plant species were selected and divided into two functional groups (early- vs. middle-flowering species, shallow- vs. deep-rooted species) to monitor reproductive phenology, including budding, flowering and fruiting dates and the reproductive duration for four growing seasons, 2015-2017 and 2022.

Key results: The AP, but not DP treatment advanced the phenological (i.e. budding, flowering and fruiting) dates and lengthened the reproductive duration across the four growing seasons and seven monitored species. In addition, the phenological responses showed divergent patterns among different plant functional groups, which could be attributed to shifts in soil moisture and its variability in different months and soil depths. Moreover, species with lengthened reproductive duration increased phenological overlap with other species, which could have a negative impact on their dominance under the AP treatment.

Conclusions: Our findings reveal that changing precipitation seasonality could have considerable impacts on plant phenology by affecting soil water availability and variability. Incorporating these two factors simultaneously in the phenology models will help us to understand the response of plant phenology under intensified changing precipitation scenarios. In addition, the observations of decreased dominance for the species with lengthened reproductive duration suggest that changing reproductive phenology can have a potential to affect community composition in grasslands under global change.

Background and aims: Climate change is a global phenomenon affecting species, which in arid regions will translate into more frequent and intense periods of drought. The Sonoran Desert is becoming hotter and drier, and many organisms are rapidly changing in abundance and distribution. These population attributes depend directly on the dynamics of the population, which in turn depends on the vital rates of its individuals; yet few studies have documented the effects of climate change on the population dynamics of keystone species such as the saguaro cactus (Carnegiea gigantea). Although saguaros have traits that enable them to withstand present environmental conditions, climate change could make them vulnerable if forced beyond their tolerance limits.

Methods: We evaluated the effect of climate change on 13 saguaro populations spanning most of the species' distribution range. Using field data from 2014 to 2016, we built an integral projection model (IPM) describing the environmentally explicit dynamics of the populations. We used this IPM, along with projections of two climate change scenarios and one no-change scenario, to predict population sizes (N) and growth rates (λ) from 2017 to 2099 and compared these scenarios to demonstrate the effect of climate change on the future of saguaro cactuses.

Key results: We found that all populations will decline, mainly due to future increases in drought, mostly hindering recruitment. However, the decline will be different across populations, since those located near the coast will be affected by harsher drought events than those located further inland.

Conclusions: Our study demonstrates that climate change and its associated increase in drought pose a significant threat to the saguaro cactus populations in the Sonoran Desert. Our findings indicate that the recruitment of saguaros, vital for establishing new individuals, is particularly vulnerable to intensifying drought conditions. Importantly, regional climate trends will have different impacts on saguaro populations across their distribution range.

Plant reproduction is highly susceptible to temperature stress. The development of the male gametophyte in particular represents a critical element in the reproductive cycle with high sensitivity to elevated temperatures. Various methods have been used to test the effect of temperature stress on pollen performance or to determine the degree of susceptibility of given species and genotypes. The information gained informs the development of new crop varieties suited to grow under warmer conditions arising through climate change and facilitates predicting the behaviour of natural populations under these conditions. The characterization of pollen performance typically employs the terms 'pollen viability' and 'pollen vigour', which, however, are not necessarily used consistently across studies. Pollen viability is a nominal parameter and is often assayed relying on cellular features as proxy to infer the capability of pollen grains to germinate and complete double fertilization. Alternatively, pollen germination can be determined through in vitro growth assays, or by monitoring the ability of pollen tubes to complete different progamic steps in vivo (ability to reach an ovule, release sperm cells, lead to seed set). Pollen vigour is an ordinal parameter that describes pollen tube growth rate or the efficiency of pollen tube growth as inferred by its morphology or growth pattern. To ensure consistent and relevant terminology, this review defines these terms and summarizes the methodologies used to assess them.

Background and aims: Host identity can strongly affect the performance of root hemiparasitic plants. Legumes have frequently been observed to be particularly beneficial hosts and it has been suggested that they are in general good hosts due to their association with rhizobia, but exceptions have been observed.

Methods: We studied the interactions of the root hemiparasite Rhinanthus alectorolophus with 30 legume species. We related parasite performance and morphology to traits of uninfected hosts and the number and size of haustoria. We also analysed sections of haustoria quantitatively using morphometrics.

Key results: There was enormous variation in the biomass and other traits of R. alectorolophus with the different legume species. The suitability of a legume species as a host had a significant phylogenetic component (Pagel's λ= 0.51). Parasite performance increased with the biomass of uninfected hosts. In contrast, host root traits explained little of the variation in parasite performance and there was no anatomical evidence of defence against infection. Parasite biomass was very strongly and positively related to the number of haustoria formed, but part of the variation due to host identity could not be explained by the host traits studied and the number of haustoria, suggesting a role for variation in the quality of compounds provided by the hosts. Damage to the hosts increased with mean parasite mass, but some legumes were tolerant of parasite attack. Sensitivity of the hosts to parasitism showed only a very weak phylogenetic signal (λ < 0.01).

Conclusions: Legumes are not universally good hosts for root hemiparasites. Instead their quality as hosts ranges from very beneficial to very poor. Moreover, clades within the legumes differ in their suitability as hosts for hemiparasites. Parasites grow best with fast growing legumes that quickly produce large root systems with which many and large haustoria are formed.

Background and aims: Mount Kinabalu is an isolated, geologically young mountain (the Pliocene and early Pleistocene) in northern Borneo harboring a highly diverse flora with a high level of endemism. It is one of the global centers of fern diversity, but how this diversity has evolved has not been studied to date. We assess patterns of evolutionary legacies in the fern flora of Mount Kinabalu, with an emphasis of testing the tropical niche conservatism hypothesis.

Methods: We used several metrics of phylogenetic structure, including phylogenetic diversity (PD), mean nearest taxon distance (MNTD), mean pairwise distance (MPD), and their respective standardized effect sizes (PDses, MNTDses and MPDses), which represent different depths of evolutionary history, to investigate patterns of evolutionary legacies in the fern flora of Mount Kinabalu.

Key results: We found that there was a decrease of PDses with elevation, reflecting a tropical origin of ferns and a gradual evolutionary adaptation to colder environments by fewer successive lineages. However, when separating the evolutionary old non-polypod lineages from the modern polypod radiation, we found a decrease of MNTD with elevation for the former, reflecting an ongoing upslope evolutionary trend, whereas for the modern polypod radiation, the inverse was true. Within the polypods, terrestrial and epiphytic species also showed different patterns, with the former showing a hump-shaped pattern for all phylogenetic diversity metrics, whereas the latter showed a more or less linear decline. Again, this suggests different evolutionary histories for ferns inhabiting the forest floor and canopy, due to the influence of the different habitat conditions. Finally, we found that mean annual temperature had a much stronger effect on phylogenetic diversity metrics than annual precipitation.

Conclusions: We found that the current fern assemblages on Mount Kinabalu show a strong evolutionary legacy that mirrors that of other mountains, suggesting a global consistency in phylogenetic diversity patterns of ferns along elevational transects, presumably due to a combination of dispersal between mountains and evolutionary convergence.

Background: Plant senescence is a genetically controlled process that results in the programmed death of plant cells, organs, or the entire plant. This process is essential for nutrient recycling and supports the production of plant offspring. Environmental stresses such as drought and heat can hasten senescence, reducing photosynthetic efficiency and significantly affecting crop quality and yield.

Scope: This mini-review seeks to clarify the complex metabolic and biochemical transformations involved in plant senescence by explaining the mechanisms in a straightforward and connected manner. It focuses on key cellular processes such as genetically programmed or stress-induced senescence, chlorophyll metabolism and nutrient recycling, while also exploring the roles of signaling molecules and pathways.

Conclusions: Understanding the complexities of plant senescence may help manage crop aging, address climate change, and cut post-harvest losses. Enhancing crop resilience to stress and decelerating aging can reduce the need for overproduction, thereby decreasing pollution and conserving resources. Tackling food waste, which constitutes about one-third of global supplies, is crucial for ensuring food security and fostering environmental sustainability.