Search Results (54)

CRABS CLAW (CRC) is a member of the plant-specific YABBY transcription factor family, defined by the presence of a C2C2 zinc-finger domain and a C-terminal YABBY domain. CRC is essential for proper floral development, functioning in the termination of the floral meristem, maintenance of adaxial–abaxial polarity within the gynoecium, and regulation of nectary and leaf morphogenesis. CRC orchestrates its diverse regulatory functions through interaction networks comprising other transcription factors and plant developmental regulators, including chromatin-modifying enzymes and proteins involved in auxin biosynthesis, transport, and signaling. The roles of genes and proteins interacting with CRC or CRC have been characterized in several model plant species, and the number of identified CRC/CRC-associated interactions continues to expand, revealing both species-specific and conserved functional roles across angiosperms. Many functions of CRC and its interacting partners have been elucidated through the analysis of anatomical and physiological phenotypes associated with specific gene mutations. The functional roles of CRC in plant development appear to have been acquired progressively through evolutionary diversification. These evolutionary changes have been associated with the relative conservation of CRC gene copy number and a predominant role of mutations occurring in non-coding regulatory regions. These properties are attributed to the relatively limited number of genes comprising the CRC regulatory network and the capacity to induce dosage-dependent effects via the emergence of novel proteins with overlapping or analogous functions. The identification and functional characterization of CRC transcription factors across diverse plant species has advanced rapidly in recent years, yet a comprehensive synthesis of these findings has not been presented in a dedicated article. Therefore, this study reviews the current knowledge on CRC transcription factors, with a focus on their identification, expression patterns, and functional roles in plant development. Full article

Plant-insect mutualisms often drive the evolution of adaptive morphological and physiological traits, enabling ecological specialization and diversification. Fig trees (Ficus spp., Moraceae) and their pollinating wasps (Agaonidae) are engaged in a brood-site pollination mutualism that exemplifies such adaptive specializations. This study investigates the morphological and ecological roles of maculae, characterized as distinct-pigmented regions on the fig surface, in the mutualistic interaction between Ficus citrifolia and fig wasps. Through morphological analyses using light and electron microscopy, we demonstrated that maculae concentrate numerous stomata and exhibit secretory activity. This activity is evidenced by the exudation of a sugary-like solution and by the presence of epidermal and subepidermal cells with features consistent with sugar- and terpene-secreting cells, such as abundant starch reserves, numerous mitochondria, plastids containing osmiophilic droplets, a Golgi complex with dilated cisternae, oil bodies, and extensive endoplasmic reticulum. Histochemical tests confirmed a terpenic-sugary secretion in the macula cells. We demonstrated that non-pollinating fig wasps avoid ovipositing through macular regions. This behavior may reflect a selective pressure to prevent structural damage to maculae caused by ovipositor insertion, thus preserving their functional integrity. Temperature measurements revealed that figs are up to 10% cooler on average than the ambient air. Therefore, our findings suggest that fig maculae are multifunctional structures, simultaneously performing the roles of extrafloral nectaries, gas exchange, and thermal regulation, which are crucial for maintaining suitable internal conditions for wasp larval development. These results provide novel insights into previously underexplored plant adaptations supporting specialized brood-site pollination mutualisms. Full article

Nepenthes L. species (tropical pitcher plants) are a classic example of carnivorous plants. The Nepenthes traps are highly specialized pitchers with a zoned structure. On the outer surface of the pitcher, there are nectaries and various types of trichomes, including glandular trichomes. The main aim of our study was to examine these glandular trichome structures and check the distribution of the homogalacturonans (HGs) and hemicelluloses in the cell wall of trichome cells. The structure of Nepenthes bicalcarata Hook. f. and Nepenthes albomarginata T.Lobb ex Lindl. trichomes was analyzed using light and electron microscopy. The antibodies were used against the wall components [anti-pectic homogalacturonans (HGs): JIM5 (low methylesterified HGs), LM19 (low methylesterified HGs), CCRC-M38 (a fully de-esterified HGs), JIM7 (highly esterified HGs), LM20 (esterified HGs), LM5 (galactan) and anti-hemicelluloses: LM25 (xyloglucan), LM15 (galactoxyloglucan), CCRC-M138 (xylan), and LM10 antibody (xylan)]. The localization of the examined compounds was determined using immunohistochemistry techniques. The presence of endodermal and transfer cells supports the idea that peltate trichomes actively transport solutes. Also, the presence of pectic homogalacturonans and hydrophilic hemicelluloses indicates that water or aqueous solutions are transported through the trichomes’ cell walls. Our study supports the idea that these trichomes may act as hydathodes or hydropotes. Full article

Spring ephemerals have different pollination strategies to avoid the rareness and/or low activity of insect pollinators caused by low temperature in early spring. However, limited research has been conducted on the effects of elaborate petals and the pseudonectaries on petals on pollinator attraction. We examined the role of the elaborate petals and the pseudonectaries in pollinator attractions of the spring ephemeral Eranthis stellata (Ranunculaceae) using a combination of observational and experimental approaches. The results indicated that the color contrast created by the yellow pseudonectaries that did not secrete nectar on the white petals, was more attractive to both bees and flies as nectar guides, but only bees with relatively longer tongues could access nectar at the base of the petal tubes. Also, the pseudonectaries were food deception for fly visitors. Food deception as a mechanism to increase the efficiency of pollination has not been reported for Ranunculaceae or other basal eudicots. Full article

Studies on the gain or loss of nectar during the course of evolution in Dendrobium Sw. (Orchidaceae) are able to provide important information concerning the reproductive biology of this enormous orchid genus and highlight reproductive barriers—in particular, changes to compatibility. By employing a literature search on the compatibility system of Dendrobium, supplemented by new experimental data of 13 taxa investigated by means of microscopy, histochemistry, and phylogenetic analysis, we aimed to ascertain whether there is, in this genus, a relationship between self-compatibility (SC) and the presence of nectar. Nectariferous plant species are thought to be visited more frequently by pollinators, resulting in geitonogamy or selfing; therefore, the presence of nectar in some Dendrobium species may promote self-incompatibility (SI), whereas a lack of nectar may increase cross-pollination. Our investigations confirmed that the capacity for nectar secretion was gained and lost several times in this genus, and that similarly organized nectar spurs were present in all species investigated, regardless of their ability to produce nectar. SI, SC, and the presence or absence of nectar have all evolved independently, but, of the 42 taxa investigated whose status both relating to nectar presence and compatibility was known, nectar was more frequent in self-incompatible taxa. Full article

Herbivores can negatively impact plant reproduction by altering floral traits, pollination, and fruit production. To counteract this, plants developed defense mechanisms, such as the biotic defense resulting from associations with ants. The aim of this study was to investigate whether leaf herbivory at different intensities influences reproductive success and extrafloral nectar secretion patterns in a savanna plant, Banisteriopsis malifolia (Malpighiaceae). Plants were subjected to simulated leaf herbivory and divided into three groups: Control (damage < 5%), T15 (15% leaf area removed), and T50 (50% leaf area removed). Assessments continued until fruiting. The findings indicate an increase in extrafloral nectar sugar concentration after simulated herbivory. Increasing foliar damage significantly delayed the time to bloom, decreased the number of inflorescences per plant, and reduced the size of buds and flowers. Foliar damage significantly decreased fruit size. Furthermore, ant foraging was influenced by herbivory, with a predominance of aggressive ants on plants with high levels of damage. Our study shows that varying levels of leaf damage affect extrafloral nectar secretion, ant foraging behavior, and plant reproductive structures. These findings highlight how insect herbivores and the level of damage they cause influence plant fitness and consequently community structure. Full article

Plants express many types of defenses in response to herbivory damage. These defenses can be displayed as a sequence or they can overlap, increasing efficiency in protection. However, leaf defense shifts during leaf development, including extrafloral nectaries (EFNs), are neglected in natural tropical systems. To address this gap, our study evaluates the shifts in defense strategies of Eriotheca gracilipes, focusing on extrafloral nectaries and leaf toughness across leaf development stages. We also simulate herbivory by cutting the leaves to address the role of visiting ants against herbivores. We observed that E. gracilipes exhibits a defense turnover, shifting from indirect defenses (e.g., EFNs) in young leaves to physical defenses in adult leaves. Simulated herbivory led to heightened ant visitation, which correlated with decreased herbivory rates, indicating that ant recruitment acts as an effective deterrent. We observed a peak of EFN activity in young leaves, increased foliar toughness in adult leaves, and reduced herbivory on ant-patrolled young leaves. Additionally, E. gracilipes demonstrated tolerance to up to 10% foliar loss with no significant impact on leaf asymmetry, although 50% foliar loss increased asymmetry in newly flushed leaves. These results highlight E. gracilipes’ adaptive flexibility by attracting protective ants when vulnerable and enhancing structural defenses as leaves develops, E. gracilipes minimizes herbivory impact. This study provides valuable insight into the adaptive roles of EFNs and tolerance in E. gracilipes, contributing to a broader understanding of plant defense strategies. Full article

The natural pollinator of the major species of commercially-grown vanilla, Vanilla planifolia, is unknown, and the crop requires hand pollination to achieve significant levels of fruit set; however, the traditional technique (using a toothpick) is costly, as it requires skilled personnel. To overcome this problem, two native Australian bees, Tetragonula carbonaria and Austroplebeia australis, and the blowfly, Lucilia cuprina, were trialled as pollinators. Three alternatives to the toothpick method were also trialled. The appearance of vanilla flowers under ultraviolet radiation was examined to determine the presence of cryptic pollination guides, and the chemical composition of nectar from extrafloral nectaries and aroma volatiles from the flowers were characterised. None of the three insects effected pollination due to their small size and behaviour; other insect pollinators need to be identified. The alternative mechanical methods of pollination trialled resulted in fruit set; however, the percentages of fruit set were lower than the traditional toothpick method, and the fruit were of inferior quality. The nectar produced predominantly consisted of sucrose and melezitose. Melezitose is a strong attractant of various ant species, which may explain the concentration of ants around the nectaries and the apparent lack of nectar production in part of this study. The aroma volatiles included monoterpenoids, terpenes, sesquiterpenoids, aromatics, nitrogen-containing compounds and fatty acids, the most abundant being a-pinene and eucalyptol. Illumination of the flowers with UV-A radiation revealed fluorescence from the stamens, the column and the callus, which is located on the labellum. These observations may aid the identification and use of potential pollinators. Full article

Rocklands are present in South Florida, both on the peninsula and in the Keys. Previous work has shown that extrafloral nectaries on pine rockland plants in the Florida Everglades and surrounding areas play a role in attracting ant protectors. Species with nectaries are more abundant and ant activity greater in more recently burned pine rockland habitats compared with longer undisturbed rockland hammock forest. The floristic composition and prevailing climate of Keys rocklands differs substantially from those on the mainland, so we sought to investigate ant activity and the abundance of plants with extrafloral nectaries in Big Pine Key rockland habitats. Standard baiting methods were used to assess ant abundance and potential predation activity in hardwood hammock, shrubby pine rockland, and open pine rockland sites. Ant activity was the lowest in open pine rockland, greatest in hardwood hammock, and intermediate in shrubby pine rockland, the opposite of what has been observed in previous studies in southern peninsular Florida and on Andros, Bahamas. Sampling vegetation at these same sites revealed a larger proportion of plant species with extrafloral nectaries in the pine rocklands than the hammock, as observed previously in Everglades habitats. Possible reasons for differences in ant activity in Keys rockland habitats are discussed. Full article

Discussing homology relationships among secretory structures remains a relatively underexplored area in botanical research. These structures are widely dispersed within Malpighiales, one of the largest orders of eudicots. Within Malpighiales, both extranuptial and nuptial nectaries are present, and they do not seem homoplastic or share evolutionary connections. Particularly in Malpighiaceae, extensive research has focused on the ecological interactions mediated by glands. Botanists largely agree that elaiophores in sepals of Neotropical Malpighiaceae have evolved from extrafloral nectaries on leaves. However, the evolutionary origin of elaiophores has yet to be thoroughly examined, particularly in comparison to outgroups. This study provides empirical evidence on the ontogeny of elaiophores and investigates their evolutionary origins and homology relationships across different lineages of Malpighiales using comparative anatomy. Our findings suggest that elaiophores are likely homologous to extranuptial nectaries found in sepals of other Malpighiales lineages, originating from nectaries on leaves. This discussion is a starting point for future studies exploring the evolution of nectaries found in flowers, whether extranuptial or nuptial, and their potential origins from nectaries in vegetative organs such as leaves. Understanding these relationships could shed light on the selective pressures influencing floral morphologies. Full article

The net outcomes of mutualisms are mediated by the trade-offs between the costs and benefits provided by both partners. Our review proposes the existence of a trade-off in ant protection mutualisms between the benefits generated by the ants’ protection against the attack of herbivores and the losses caused by the disruption of pollination processes, which are commonly not quantified. This trade-off has important implications for understanding the evolution of extrafloral nectaries (EFNs), an adaptation that has repeatedly evolved throughout the flowering plant clade. We propose that the outcome of this trade-off is contingent on the specific traits of the organisms involved. We provide evidence that the protective mutualisms between ants and plants mediated by EFNs have optimal protective ant partners, represented by the optimum point of the balance between positive effects on plant protection and negative effects on pollination process. Our review also provides important details about a potential synergism of EFN functionality; that is, these structures can attract ants to protect against herbivores and/or distract them from flowers so as not to disrupt pollination processes. Finally, we argue that generalizations regarding how ants impact plants should be made with caution since ants’ effects on plants vary with the identity of the ant species in their overall net outcome. Full article

Are parasitoids less likely to find their Lepidoptera hosts on non-native hostplants than native hostplants? We predicted that with longer periods of coevolution between herbivores and the plants they consume, the parasitoids that provide top-down control would be more attuned to finding their hosts on native plants. To test this hypothesis, we collected immature stages of sulfur butterflies (the cloudless sulfur (Phoebis sennae) and the orange-barred sulfur (Phoebis agarithe) over a three-year period (2008–2011) from native and ornamental hostplants in the genus Senna in three different parts of the urban landscape of Miami, Florida, USA. We reared the immature specimens to pupation and either eclosion of adults or emergence of parasitoids and compared the levels of parasitization among the three areas, and among native vs. exotic hostplants. We found, contrary to our prediction, that caterpillars feeding on non-native leguminous hostplant species were more likely to be parasitized than those feeding on native hostplants. We discuss this surprising finding in the light of recent findings in other plant/herbivore/parasitoid systems. Full article

Spiders, abundant and diverse arthropods which occur in vegetation, have received little attention in studies investigating spider–plant interactions, especially in plants which have extrafloral nectaries (EFNs). This study examines whether spiders attracted to EFNs on the plant Heteropterys pteropetala (Malpighiaceae) function as biological protectors, mitigating leaf herbivory and positively impacting plant fitness, through manipulative experiments. Spiders are attracted to EFNs because, in addition to consuming the resource offered by these structures, they also consume the herbivores that are attracted by the nectar. At the same time, we documented the reproductive phenology of the plant studied and the abundance of spiders over time. Our results revealed that the plant’s reproductive period begins in December with the emergence of flower buds and ends in April with the production of samarids, fruits which are morphologically adapted for wind dispersal, aligning with the peak abundance of spiders. Furthermore, our results demonstrated that spiders are attracted to plants that exude EFNs, resulting in a positive impact on reducing leaf area loss but with a neutral effect on protecting reproductive structures. By revealing the protective function of spiders’ vegetative structures on plants, this research highlights the ecological importance of elucidating the dynamics between spiders and plants, contributing to a deeper understanding of ecosystems. Full article

Although flower pollinator interactions are known to be mediated by floral traits, not enough attention has been paid to the research of secretory tissues and volatile components of sunflower disc florets as potentially important parameters in breeding programs. (1) To our knowledge, this is the first integrated study aimed at better understanding the attractiveness of sunflower capitula to insects. In the study, we have made a very detailed comparative analysis of secretory tissues and the characterization of the volatile components (VOCs) of disc florets in 10 wild perennial Helianthus species. (2) For anatomical analyses, cross-sections were obtained from the nectary zone of disc florets using a cryotechnique procedure. Micromorphological observation and morphological and anatomical analysis of disc florets were performed using light and scanning electron microscopy. For VOCs, we applied headspace, GC-FID, and GC/MS analyses. (3) The obtained results indicate that there is a difference between the analyzed traits among studied species. H. eggertii, H. hirsutus, H. mollis, H. resinosus, and H. tuberosus had high disc diameter values, a high cross-section area and disc floret corolla length, as well as the largest cross-section area and thickness of the disc florets nectary. In the analyzed VOCs, 30 different compounds were detected. The highest yield and quantity of α-Pinene was observed in H. mollis. (4) Inflorescence features, such as receptacle diameter, corolla and secretory tissue properties, and floret VOCs production and characterization, provided valuable information that can be used as guidelines in sunflower breeding programs to maximize pollinator attractiveness and increase seed yield. Full article

Floral nectar contains sugars and numerous other compounds, including amino acids, but little is known about their function and origin in nectar. Therefore, the amino acid, sugar, and inorganic ion concentrations, as well as the activity of alanine aminotransferase (AlaAT) and glutamine synthetase (GS) in nectar, nectaries, and leaves were analyzed in 30 Pitcairnia species. These data were compared with various floral traits, the pollinator type, and the phylogenetic relationships of the species to find possible causes for the high amino acid concentrations in the nectar of some species. The highest concentrations of amino acids (especially alanine) in nectar were found in species with reddish flowers. Furthermore, the concentration of amino acids in nectar and nectaries is determined through analyzing flower color/pollination type rather than phylogenetic relations. This study provides new insights into the origin of amino acids in nectar. The presence of almost all amino acids in nectar is mainly due to their transport in the phloem to the nectaries, with the exception of alanine, which is partially produced in nectaries. In addition, active regulatory mechanisms are required in nectaries that retain most of the amino acids and allow the selective secretion of specific amino acids, such as alanine. Full article