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Land use changes by humans have eliminated more than half of the wetlands in Florida over the last 200 years, and additional losses are anticipated as a consequence of climate change and ongoing development activities that will accommodate a rapidly growing human population. Both spell danger for the biodiversity and ecosystem services in Florida, and data are needed to inform conservation priorities and actions concerning threatened or endangered wetland species. We modeled the projected distribution of an endangered epiphyte native to the forested wetlands in South Florida, Guzmania monostachia (Bromeliaceae), in response to changing climate and sea level conditions. We constructed ecological niche models (ENMs) under the present framework by using georeferenced occurrence points and projected them into the past and future under different scenarios. Our future climate-based ENMs predicted small losses in suitable habitat for G. monostachia in South Florida, with expansions into higher latitudes due to the warmer climate. In contrast, the models predicted a considerable, although non-detrimental, loss of suitable habitat due to rising sea levels. The combined results suggest that human activity is and will remain the largest threat to G. monostachia in Florida, and conservation efforts should focus on preserving existing habitats that will remain above sea level and explore possibilities for assisted migration. [ABSTRACT FROM AUTHOR]

Land use changes by humans have eliminated more than half of the wetlands in Florida over the last 200 years, and additional losses are anticipated as a consequence of climate change and ongoing development activities that will accommodate a rapidly growing human population. Both spell danger for the biodiversity and ecosystem services in Florida, and data are needed to inform conservation priorities and actions concerning threatened or endangered wetland species. We modeled the projected distribution of an endangered epiphyte native to the forested wetlands in South Florida, Guzmania monostachia (Bromeliaceae), in response to changing climate and sea level conditions. We constructed ecological niche models (ENMs) under the present framework by using georeferenced occurrence points and projected them into the past and future under different scenarios. Our future climate-based ENMs predicted small losses in suitable habitat for G. monostachia in South Florida, with expansions into higher latitudes due to the warmer climate. In contrast, the models predicted a considerable, although non-detrimental, loss of suitable habitat due to rising sea levels. The combined results suggest that human activity is and will remain the largest threat to G. monostachia in Florida, and conservation efforts should focus on preserving existing habitats that will remain above sea level and explore possibilities for assisted migration.

Premise: Because of its broad range in the neotropical rainforest and within tree canopies, the tank bromeliad Guzmania monostachia was investigated as a model of how varying leaf hydraulic conductance (Kleaf) could help plants resist and recover from episodic drought. The two pathways of Kleaf, inside and outside the xylem, were also examined to determine the sites and causes of major hydraulic resistances within the leaf. Methods: We measured leaf hydraulic conductance for plants in the field and laboratory under wet, dry, and rewetted conditions and applied physiological, anatomical, and gene expression analysis with modeling to investigate changes in Kleaf. Results: After 7 d with no rain in the field or 14 days with no water in the glasshouse, Kleaf decreased by 50% yet increased to hydrated values within 4 d of tank refilling. Staining to detect embolism combined with modeling indicated that changes outside the xylem were of greater importance to Kleaf than were changes inside the xylem and were associated with changes in intercellular air spaces (aerenchyma), aquaporin expression and inhibition, and cuticular conductance. Conclusions: Low values for all conductances during drying, particularly in pathways outside the xylem, lead to hydraulic resilience for this species and may also contribute to its broad environmental tolerances. [ABSTRACT FROM AUTHOR]

The Crassulacean acid metabolism (CAM) can be a transitory strategy for saving water during unfavourable conditions, like a dry season. In some cases, CAM can also contribute to the maintenance of photosynthetic integrity, even if carbon gain and growth are impaired. CAM occurs in different intensities, being stronger or weaker depending on the degree of nocturnal malic acid accumulation. For example, Guzmania monostachia is an epiphytic tank bromeliad that shows an increase in its nocturnal organic acid accumulation and a variable CAM behaviour when exposed to water deficit. In this context, this study aimed at investigating whether the weak CAM displayed by this species may mitigate the harmful effects of water limitation on its photosynthetic activity. To this, bromeliads were submitted to well-watered and water deficit conditions. Guzmania monostachia plants under water deficiency conditions showed a reduction on atmospheric carbon assimilation without exhibiting changes in PSII integrity and carbohydrate production while showed an increase in nocturnal malic acid accumulation. Additionally, spots with high PSII efficiency in the leaf portion with a greater nocturnal malic acid accumulation were observed in plants exposed to water shortage conditions. These high-efficiency spots might be associated with a greater malate decarboxylation capacity. Also, the malic acid contributed to approximately 50% of the total carbon assimilated under water deficit. These results suggest that weak CAM may participate in photo-protection and it appears to meaningfully contribute to the overall carbon balance, being an important metabolic strategy to maintain plant fitness during water deficit periods. [ABSTRACT FROM AUTHOR]

Background and Aims The functional relevance of heteroblasty, an abrupt morphological change in the ontogeny of a considerable number of angiosperm species, is still largely unresolved. During the ontogeny of many epiphytic Tillandsioids (Bromeliaceae), such a change occurs when small individuals transform into larger, tank-forming individuals that are capable of external water storage. Apart from its fundamental effect on plant water relations, the associated transition from narrow to broader leaves also affects plant architecture. The morphological changes and their effect on light interception may be especially relevant for heteroblastic species in the moist understorey, which are expected to be limited primarily by light. Methods A functional structural plant model (Yplant) was used to construct digital replicas of atmospheric and tank-forming individuals of four species, two of them naturally growing in exposed conditions and two occurring in understorey sites. This allowed the determination of leaf display efficiencies as well as a systematic analysis of leaf architectural traits and their effect on light interception. Key Results Modifying existing plant morphologies showed that broader leaves cause more self-shading within the plant. This supports the hypothesis that species from the light-limited understorey benefit from the early atmospheric life form through increased light capture. Modelling plant morphology that continuously followed the ontogenetic trajectories of the leaf architectural traits revealed that the rising total leaf number in atmospheric individuals constantly increased self-shading. Therefore, at a certain ontogenetic stage, a tipping point was reached when the tank form was even favourable in terms of light capture as it was associated with fewer leaves. Conclusions The effects of changes in leaf morphology and leaf architecture on plant light capture may explain the common occurrence of heteroblastic species in the understorey of Neotropical forests, which does not negate a simultaneous positive effect of heteroblasty on plant water relations. [ABSTRACT FROM AUTHOR]

Guzmania monostachia is an epiphytic heteroblastic bromeliad that exhibits rosette leaves forming water-holding tanks at maturity. Different portions along its leaf blades can display variable degrees of crassulacean acid metabolism (CAM) up-regulation under drought. Since abscisic acid (ABA) can act as an important long-distance signal, we conducted a joint investigation of ontogenetic and drought impacts on CAM intensity and ABA levels in different leaf groups within the G. monostachia rosette. For this, three groups of leaves were analysed according to their position within the mature-tank rosette ( i.e., younger, intermediate, and older leaves) to characterize the general growth patterns and magnitude of drought-modulated CAM expression. CAM activity was evaluated by analysing key molecules in the biochemical machinery of this photosynthetic pathway, while endogenous ABA content was comparatively measured in different portions of each leaf group after seven days under well-watered (control) or drought treatment. The results revealed that G. monostachia shows more uniform morphological characteristics along the leaves when in the atmospheric stage. The drought treatment of mature-tank rosettes generally induced in older leaves a more severe water loss, followed by the lowest CAM activity and a higher increase in ABA levels, while younger leaves showed an opposite response. Therefore, leaf groups at distinct ontogenetic stages within the tank rosette of G. monostachia responded to drought with variable degrees of water loss and CAM expression. ABA seems to participate in this tissue-compartmented response as a long-distance signalling molecule, transmitting the drought-induced signals originated in older leaves towards the younger ones. [ABSTRACT FROM AUTHOR]

We compared the effects of different light environments on leaf hydraulic conductance ( Kleaf) for two congeneric epiphytes, the tank bromeliads Guzmania lingulata (L.) Mez and Guzmania monostachia (L.) Rusby ex Mez. They occur sympatrically at the study site, although G. monostachia is both wider ranging and typically found in higher light. We collected plants from two levels of irradiance and measured Kleaf as well as related morphological and anatomical traits. Leaf xylem conductance ( Kxy) was estimated from tracheid dimensions, and leaf conductance outside the xylem ( Kox) was derived from a leaky cable model. For G. monostachia, but not for G. lingulata, Kleaf and Kxy were significantly higher in high light conditions. Under both light conditions, Kxy and Kox were co-limiting for the two species, and all conductances were in the low range for angiosperms. With respect to hydraulic conductances and a number of related anatomical traits, G. monostachia exhibited greater plasticity than did G. lingulata, which responded to high light chiefly by reducing leaf size. The positive plasticity of leaf hydraulic traits in varying light environments in G. monostachia contrasted with negative plasticity in leaf size for G. lingulata, suggesting that G. monostachia may be better able to respond to forest conditions that are likely to be warmer and more disturbed in the future. [ABSTRACT FROM AUTHOR]

Abstract: Guzmania monostachia is an epiphyte tank bromeliad capable of up-regulating crassulacean acid metabolism (CAM) in response to several environmental stimuli, including drought and light stress. In other plant species, abscisic acid (ABA) and nitric oxide (NO) seem to be involved in CAM induction. Because the leaves of tank bromeliads perform different functions along their length, this study attempted to investigate whether ABA and NO are involved in regulation of CAM expression in this species by quantifying these compounds in apical and basal portions of the leaf, and whether there would be differences in this event for each leaf portion. Detached leaves exposed to a 30% polyethylene glycol solution showed a significant upregulation of CAM on the seventh day of treatment only in the apical portion, as indicated by nocturnal acid accumulation and phosphoenolpyruvate carboxylase (PEPC) activity. On the three days prior to CAM induction, ABA, NO and H2O2 were quantified. The amounts of ABA were higher in PEG-exposed leaves, along their entire length. NO, however, was higher only in the apical portion, precisely where CAM was up-regulated. H2O2 was higher only in the basal portion of PEG-exposed leaves. Our results suggest that ABA might be a systemic signal to drought, occurring in the entire leaf. NO and H2O2, however, may be signals restricted only to the apical or basal portions, respectively. [Copyright &y& Elsevier]

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Predispersal characteristics that affect the reproductive success in plants may influence their colonizing ability. We evaluated this hypothesis in two sympatric epiphytic bromeliads in Costa Rica, Guzmania monostachia and Tillandsia fasciculata, that show contrasting levels of local seedling recruitment. Genets of G. monostachia, the species with higher recruitment, may reach the reproductive stage faster because of a higher growth rate (6 vs. 13 yr). In addition, in established genets, new asexual ramets develop and reproduce annually, whereas in T. fasciculata, the slower offshoot development implies at least 3 yr to disperse a new batch of seeds. A higher and more continuous seed production in G. monostachia is possible because of a shorter time from flowering to seed dispersal (8-9 vs. 16-20 mo), along with the production of more flowers (29 vs. 22) and naturally pollinated fruits per inflorescence (89% vs. 79% fruit set) and more seeds per fruit (321 vs. 240). Both species showed a high occurrence of spontaneous autogamy that matched the highly selfing condition estimated using microsatellite markers. In all, G. monostachia displayed the reproductive traits of a pioneer species. Here, we emphasize the importance of seed availability in determining the population and community structure of epiphytic bromeliads in secondary and mature forests, along with factors affecting dispersal and plant survival. [ABSTRACT FROM AUTHOR]

• CAM is induced in Guzmania monostachia plants after 20 days of water deficit and rewatering reverse this condition. • PEPCK is transcriptionally and post-translationally regulated in G. monostachia under drought. • CAM-upregulated plants presented their highest ϕPSII and decarboxylation activity at noon. • CAM-induced plants seemed to have lower photorespiration than non-induced plants. Crassulacean acid metabolism (CAM) is a photosynthetic pathway characterized by nocturnal CO 2 fixation into organic acids followed by their diurnal decarboxylation. Decarboxylation activity is time regulated, usually presenting higher activity in the middle of the day. This process can be performed by phosphoenolpyruvate carboxykinase (PEPCK) and/or by malic enzyme, resulting in an increase in internal CO 2 concentration which may act to suppress photorespiration. It is suggested that the CO 2 provided by the decarboxylation can improve the photochemical use of energy in CAM plants. This photosynthetic pathway also contributes to improve water use efficiency, and, in an interesting way, some species can engage this photosynthesis when subjected to water deficit. Guzmania monostachia is a bromeliad that occupies habitats with intermittent water availability and CAM can be induced by water deficit. To test the light-time modulation of decarboxylation activity and light-energy use in G. monostachia , we analyzed the activity of PEPCK, the main decarboxylating enzyme for this bromeliad, as well as the photochemical and non-photochemical quenching and organic acids contents at three times of the day. Results showed a diurnal modulation where the highest PEPCK decarboxylation activity coincided with an increase in the photochemical quenching and a decrease in the non-photochemical quenching. In addition, a reduction in acid content was observed, strongly indicating the interface between CO 2 generation through acid decarboxylation and its effect on PSII photochemical activity and photorespiration in CAM-induced plants. The same was not observed for well-watered plants. Also, PEPCK activity modulation may be related to transcriptional and post-translational regulation, since an increase in transcript abundance and a modulation in the dephosphorylated enzyme activity was noted. Moreover, we suggest that the time modulation of PEPCK plays an important role in regulating PSII energy use in CAM plants. [ABSTRACT FROM AUTHOR]