Plant water uptake from soil through a vapor pathway.

Water uptake from the soil via a vapor pathway was tested. Viburnum suspensum L. plants were divided into: (1) irrigated, (2) drought with vapor and (3) drought without vapor treatments.

Testing plant use of mobile vs immobile soil water sources using stable isotope experiments.

We tested for isotope exchange between bound (immobile) and mobile soil water, and whether there is isotope fractionation during plant water uptake. These are critical assumptions to the formulation of the 'two water worlds' hypothesis based on isotope profiles of soil water. In two different soil types, soil-bound water in two sets of 19-l pots, each with a 2-yr-old avocado plant (Persea americana), were identically labeled with tap water.

Water uptake of Alaskan tundra evergreens during the winter-spring transition.

Premise Of The Study: The cold season in the Arctic extends over 8 to 9 mo, yet little is known about vascular plant physiology during this period. Evergreen species photosynthesize under the snow, implying that they are exchanging water with the atmosphere. However, liquid water available for plant uptake may be limited at this time.

Stomatal pore size and density in mangrove leaves and artificial leaves: effects on leaf water isotopic enrichment during transpiration.

We tested the hypothesis that the previously observed low isotopic enrichment of mangrove leaf water is caused by larger stomatal pores and lower densities compared with freshwater plants. First, we measured and compared pore size and density in mangroves, transitional and freshwater species in South Florida. We pooled this data with other reports encompassing 14 mangrove species and 134 freshwater species and tested for differences in pore size and density between mangroves and freshwater plants.

Are leaf physiological traits related to leaf water isotopic enrichment in restinga woody species?

During plant-transpiration, water molecules having the lighter stable isotopes of oxygen and hydrogen evaporate and diffuse at a faster rate through the stomata than molecules having the heavier isotopes, which cause isotopic enrichment of leaf water. Although previous models have assumed that leaf water is well-mixed and isotopically uniform, non-uniform stomatal closure, promoting different enrichments between cells, and different pools of water within leaves, due to morpho-physiological traits, might lead to inaccuracies in isotopic models predicting leaf water enrichment. We evaluate the role of leaf morpho-physiological traits on leaf water isotopic enrichment in woody species occurring in a coastal vegetation of Brazil known as restinga.

Aphids alter host-plant nitrogen isotope fractionation.

Plant sap-feeding insects and blood-feeding parasites are frequently depleted in (15)N relative to their diet. Unfortunately, most fluid-feeder/host nitrogen stable-isotope studies simply report stable-isotope signatures, but few attempt to elucidate the mechanism of isotopic trophic depletion. Here we address this deficit by investigating the nitrogen stable-isotope dynamics of a fluid-feeding herbivore-host plant system: the green peach aphid, Myzus persicae, feeding on multiple brassicaceous host plants.

Lake and watershed characteristics rather than climate influence nutrient limitation in shallow lakes.

Both nitrogen (N) and phosphorus (P) can limit primary production in shallow lakes, but it is still debated how the importance of N and P varies in time and space. We sampled 83 shallow lakes along a latitudinal gradient (5 degrees 55 degrees S) in South America and assessed the potential nutrient limitation using different methods including nutrient ratios in sediment, water, and seston, dissolved nutrient concentrations, and occurrence of N-fixing cyanobacteria. We found that local characteristics such as soil type and associated land use in the catchment, hydrology, and also the presence of abundant submerged macrophyte growth influenced N and P limitation.

Ephemeral clonal integration in Calathea marantifolia (Marantaceae): Evidence of diminished integration over time.

A major advantage of clonal growth forms is the intergenerational transfer of resources through vascular connections (clonal integration). Connections linking ramets can be persistent or ephemeral. For species with ephemeral connections, whether the extent of clonal integration changes over time is unclear.

Seasonal plant water uptake patterns in the saline southeast Everglades ecotone.

The purpose of this study was to determine the seasonal water use patterns of dominant macrophytes coexisting in the coastal Everglades ecotone. We measured the stable isotope signatures in plant xylem water of Rhizophora mangle, Cladium jamaicense, and Sesuvium portulacastrum during the dry (DS) and wet (WS) seasons in the estuarine ecotone along Taylor River in Everglades National Park, FL, USA. Shallow soilwater and deeper groundwater salinity was also measured to extrapolate the salinity encountered by plants at their rooting zone.

Plants use macronutrients accumulated in leaf-cutting ant nests.

Leaf-cutting ants (Atta spp.) are known for their extensive defoliation in neo-tropical forests and savannahs. Debate about the costs and benefits of their activities has been largely dominated by their detrimental effects on agriculture and agroforestry.

A faster plant stem-water extraction method.

Oxygen and hydrogen isotope ratios of stem water have been used by several studies which relate the ecophysiology of plants to their water source. Undoubtedly, there are several other applications and research areas which could use this type of analysis. However, the most often used methods of extracting stem water are slow, limiting the rate of sampling and consequently preventing a deeper understanding of spatial and temporal plant water source use.

Rainfall exclusion in an eastern Amazonian forest alters soil water movement and depth of water uptake.

Deuterium-labeled water was used to study the effect of the Tapajós Throughfall Exclusion Experiment (TTEE) on soil moisture movement and on depth of water uptake by trees of Coussarea racemosa, Sclerolobium chrysophyllum, and Eschweilera pedicellata. The TTEE simulates an extended dry season in an eastern Amazonian rainforest, a plausible scenario if the El Niño phenomenon changes with climate change. The TTEE excludes 60% of the wet season throughfall from a 1-ha plot (treatment), while the control 1-ha plot receives precipitation year-round.

Metabolic fate of exogenous 15NH4Cl in the gulf toadfish (Opsanus beta).

This study was undertaken to determine whether gulf toadfish (Opsanus beta) could metabolize ammonia from their environment into other, less toxic products. To this end, gulf toadfish were exposed to 3.8 mM 15NH(4)Cl in seawater for 24 and 48 h.

Seasonal changes in the diets of migrant and non-migrant nectarivorous bats as revealed by carbon stable isotope analysis.

Three species of nectar-feeding bats migrate from tropical and subtropical Mexico into the Sonoran and Chihuahuan deserts during the spring and summer months. We examined geographic and seasonal changes in the diet of one migrant species, Leptonycteris curasoae, using carbon stable isotope techniques to determine the relative importance of C3 and CAM (Cactaceae, Agavaceae) plants in its diet. We also examined the diet of a non-migratory nectar-feeding bat, Glossophaga soricina, from southern Mexico using the same techniques.

Water utilization of tropical hardwood hammocks of the Lower Florida Keys.

Predawn water potential of representative plant species, together with stable isotope composition of stem water and potential water sources were investigated in four low-elevation tropical hardwood hammocks in the Lower Florida Keys, during a one year period. Hammock species had the lowest water potentials when soil water content was low and/or soil salinity was high, but differences in groundwater salinity had no effect on the water potential. Comparison of D/H ratio of plant stem water with soil and ground water corroborates the conclusion that they are primarily utilizing soil water and not groundwater.

Comparative study of water uptake and photosynthetic gas exchange between scrub and fringe red mangroves, Rhizophora mangle L.

The red mangrove (Rhizophora mangle L.) occurs frequently in both scrub and fringe mangrove forests. Our previous study demonstrated that individuals of this mangrove species growing in scrub and fringe forests differ significantly in both morphological and physiological characteristics.

Water relations of coastal plant communities near the ocean/freshwater boundary.

Salinity and isotope ratios were determined in water from several wells in the Florida Keys, and tidal inlets. Both D/H and O/O ratios of water from wells and tidal inlets were highly correlated to their salinity. Water from standing pools was enriched in deuterium and oxygen-18 relative to their salinity because of evaporation processes.

Utilization of Freshwater and Ocean Water by Coastal Plants of Southern Florida.

The coastal vegetation of southern Florida is undergoing dramatic changes due to the instability of the ocean water-freshwater boundary. These vegetation changes will be determined by the response of each particular species to saline ocean water, particularly whether it can use ocean water or not. In this study, isotopic data were used to determine the relative usage of freshwater or ocean water by plants in the Florida keys.

Carbon, oxygen and hydrogen isotope abundances inStylites reflect its unique physiology.

Natural abundances of oxygen-18, carbon-14, carbon-13 and deuterium were measured inStylites andicola, a terrestrial vascular plant lacking stomates, and two terrestrial plant species having stomates that grew nearby. No substantial differences in oxygen-18 and carbon-13 abundances were observed among the three species. The deuterium concentration inStylites was much higher than in the other species, confirming a previous report of CAM inStylites.