Bulk Elastic Moduli and Solute Potentials in Leaves of Freshwater, Coastal, and Marine Hydrophytes. Are Marine Plants More Rigid?

Bulk modulus of elasticity (ɛ), depicting the flexibility of plant tissues, is recognized as an important component in maintaining internal water balance. Elevated ɛ and comparatively low osmotic potential (Ψπ) may work in concert to effectively maintain vital cellular water content. This concept, termed the ‘cell water conservation hypothesis’, may foster tolerance for lower soil-water potentials in plants while minimizing cell dehydration and shrinkage. Therefore, the accumulation of solutes in marine plants, causing decreases in Ψπ, play an important role in plant–water relations and likely works with higher ɛ to achieve favourable cell volumes. While it is generally held that plants residing in marine systems have higher leaf tissue ɛ, to our knowledge no study has specifically addressed this notion in aquatic and wetland plants residing in marine and freshwater systems. Therefore, we compared ɛ and Ψπ in leaf tissues of 38 freshwater, coastal and marine plant species using data collected in our laboratory, with additional values from the literature. Overall, 8 of the 10 highest ɛ values were observed in marine plants, and 20 of the lowest 25 ɛ values were recorded in freshwater plants. As expected, marine plants often had lower Ψπ, wherein the majority of marine plants were below −1.0 MPa and the majority of freshwater plants were above −1.0 MPa. While there were no differences among habitat type and symplastic water content (θsym), we did observe higher θsym in shrubs when compared with graminoids, and believe that the comparatively low θsym observed in aquatic grasses may be attributed to their tendency to develop aerenchyma that hold apoplastic water. These results, with few exceptions, support the premise that leaf tissues of plants acclimated to marine environments tend to have higher ɛ and lower Ψπ, and agree with the general tenets of the cell water conservation hypothesis

Effects of a Pre-Molt Calcium and Low-Energy Molt Program on Laying Hen Behavior During and Post-Molt

The objectives of this study were to compare the behavior of the laying hen kept in a cage system when offered a pre-molt calcium treatment and low-energy molt diets versus a traditional feed-withdrawal during induced molt. A total of 144 Hy-Line W-36 laying hens (85 wk of age), weighing 1.7 ± 0.2 kg, were used. Laying hens were housed 3 per cage (30.5 cm wide × 40.6 cm deep × 44.5 cm high), providing 413 cm 2 per hen. Six treatments were compared in a 2 × 3 factorial design with 2 Ca (coarse and fine) pre-molt treatments and 3 molt diets: feed withdrawal (FW), soybean hulls (SH), and wheat middlings (WM). The Ca pre-molt treatment was defined as the period when the hens received either a combination of fine (0.14 mm in diameter) and coarse (2.27 mm in diameter) CaCO3 or an all-fine CaCO3 mixed into a commercial diet for 1 wk. Both diets were formulated to contain 4.6% Ca, such that only the particle size of the CaCO3 differed between the 2 treatments. Hens had free access to feed and water and had a 24-h photoperiod. The 3 molt diets were applied (FW, SH, or WM) for a total of 28 d. The hens assigned to the FW diet were deprived of feed for 7 d with free access to water followed by 21 d of skip-a-day feeding restricted to 60 g of feed/hen per feeding day. The hens fed the WM and SH molt diets were given free access to feed and water during the entire 28 d molt period. Lighting was reduced to 8 h for the first 3 wk and was then increased to 12 h at the start of the last week of molt. Behavior was recorded by camera once before molt, twice during molt, and twice post-molt for 2 h in the morning and 2 h at night. The acquisition of 2 postures and 5 behaviors were obtained by 2 experienced observers who viewed the recordings using 24 h mode onto the Observer software using a 1 min scan sampling technique. Postures and behaviors were not different among treatments during the baseline period. The Ca pre-molt treatment had no carryover effect during or post-molt. The hens assigned to the FW molt diet spent more time in active postures and feeding and drinking behaviors during molt compared to hens fed the other 2 molt diets. Post-molt, all hens, regardless of molt diet, spent the same amount of time in each of these behaviors. The hens assigned to the FW molt diet spent more time preening during molt compared to post-molt, whereas the hens fed the WM and SH molt diets did not differ between the 2 periods (Table 1). In conclusion, these low-energy molt diets did not adversely affect the postures and behaviors of the laying hen and are therefore acceptable dietary alternatives to FW for inducing molt

Effects of a Pre-Molt Calcium and Low-Energy Molt Program on Laying Hen Production Before, During and Post-Molt

The objectives of this study were to compare the production of laying hens when offered a Ca pre-molt treatment and low-energy molt diets versus a traditional feed-withdrawal (FW) before, during, and after an induced molt. A total of 792 Hy-Line W-36 laying hens (85 wk of age, 1.7 ± 0.2 kg), housed 3 per cage, (413 cm 2 /hen) were used. Six treatments were compared in a 2 × 3 factorial design with 2 Ca (coarse and fine) pre-molt treatments and 3 molt diets: FW, soybean hulls (SH), and wheat middlings (WM). The Ca pre-molt treatment was defined as the period when the hens received either a combination of fine (0.14 mm in diameter) and coarse (2.27 mm in diameter) CaCO3 or an all-fine CaCO3 mixed into a commercial diet for 1 wk. Both diets were formulated to contain 4.6% Ca, such that only the particle size of the CaCO3 differed between the 2 treatments. Hens had free access to feed and water and had a 24-h photoperiod. The 3 molt diets were applied for a total of 28 d. The hens assigned to the FW molt diet were deprived of feed for 7 d with free access to water followed by 21 d of skip-a-day feeding restricted to 60 g of feed/hen per feeding day. The hens fed the WM and SH molt diets were provided free access to feed and water during the entire 28 d molt period. Lighting was reduced to 8 h for the first 3 wk and was then increased to 12 h at the start of the last week of molt. During the 22 wk post-molt, hens were fed a laying hen diet and lighting was increased by 1 h each week to 16 h. The fine-Ca pre-molt treatment was more effective than the coarse-Ca pre-molt treatment at decreasing egg production during molt and increasing egg production after molt regardless of which molt diet was fed (P \u3c 0.05). The FW molt diet resulted in the most complete molt with a greater decrease in egg production during molt (P \u3c 0.05). The SH molt diet compared to the WM molt diet was more effective at inducing molt with lower egg production and ovary and oviduct weights during molt (P \u3c 0.05), however, the WM molt diet resulted in the highest egg production and body weight post-molt compared to the other 2 molt diets (P \u3c 0.05). In conclusion, a fine-Ca pre-molt treatment and a low-energy molt diet containing WM or SH can be useful alternatives to a FW molt

Coastal plant growth and CO2 enrichment: Can the productivity of black needle rush keep pace with sea level rise?

The rate of sea level change has varied considerably over geological time, with rapid increases (0.25 cm yr-1) at the end of the last ice age to more modest increases over the last 4,000 years (0.04 cm yr-1; Hendry 1993). Due to anthropogenic contributions to climate change, however, the rate of sea level rise is expected to increase between 0.10 and 0.25 cm year-1 for many coastal areas (Warrick et al. 1996). Notwithstanding, it has been predicted that over the next 100 years, sea levels along the northeastern coast of North Carolina may increase by an astonishing 0.8 m (0.8 cm yr-1); through a combination of sea-level rise and coastal subsidence (Titus and Richman 2001; Parham et al. 2006). As North Carolina ranks third in the United States with land at or just above sea level, any additional sea rise may promote further deterioration of vital coastal wetland systems. (PDF contains 4 pages

Plasma cholesterol levels and brain development in preterm newborns.

BackgroundTo assess whether postnatal plasma cholesterol levels are associated with microstructural and macrostructural regional brain development in preterm newborns.MethodsSixty preterm newborns (born 24-32 weeks gestational age) were assessed using MRI studies soon after birth and again at term-equivalent age. Blood samples were obtained within 7 days of each MRI scan to analyze for plasma cholesterol and lathosterol (a marker of endogenous cholesterol synthesis) levels. Outcomes were assessed at 3 years using the Bayley Scales of Infant Development, Third Edition.ResultsEarly plasma lathosterol levels were associated with increased axial and radial diffusivities and increased volume of the subcortical white matter. Early plasma cholesterol levels were associated with increased volume of the cerebellum. Early plasma lathosterol levels were associated with a 2-point decrease in motor scores at 3 years.ConclusionsHigher early endogenous cholesterol synthesis is associated with worse microstructural measures and larger volumes in the subcortical white matter that may signify regional edema and worse motor outcomes. Higher early cholesterol is associated with improved cerebellar volumes. Further work is needed to better understand how the balance of cholesterol supply and endogenous synthesis impacts preterm brain development, especially if these may be modifiable factors to improve outcomes