The density of apical cells of dark-grown protonemata of the mossCeratodon purpureus

Summary Determinations of plant or algal cell density (cell mass divided by volume) have rarely accounted for the extracellular matrix or shrinkage during isolation. Three techniques were used to indirectly estimate the density of intact apical cells from protonemata of the mossCeratodon purpureus. First, the volume fraction of each cell component was determined by stereology, and published values for component density were used to extrapolate to the entire cell. Second, protonemal tips were immersed in bovine serum albumin solutions of different densities, and then the equilibrium density was corrected for the mass of the cell wall. Third, apical cell protoplasts were centrifuged in low-osmolarity gradients, and values were corrected for shrinkage during protoplast isolation. Values from centrifugation (1.004 to 1.015 g/cm³) were considerably lower than from other methods (1.046 to 1.085 g/cm³). This work appears to provide the first corrected estimates of the density of any plant cell. It also documents a method for the isolation of protoplasts specifically from apical cells of protonemal filaments.Abbreviations BSA bovine serum albumin - ER endoplasmic reticulum - V_v volume fraction     

Gravitropic moss cells default to spiral growth on the clinostat and in microgravity during spaceflight

In addition to shoots and roots, the gravity (g)-vector orients the growth of specialized cells such as the apical cell of dark-grown moss protonemata. Each apical cell of the moss Ceratodon purpureus senses the g-vector and adjusts polar growth accordingly producing entire cultures of upright protonemata (negative gravitropism). The effect of withdrawing a constant gravity stimulus on moss growth was studied on two NASA Space Shuttle (STS) missions as well as during clinostat rotation on earth. Cultures grown in microgravity (spaceflight) on the STS-87 mission exhibited two successive phases of non-random growth and patterning, a radial outgrowth followed by the formation of net clockwise spiral growth. Also, cultures pre-aligned by unilateral light developed clockwise hooks during the subsequent dark period. The second spaceflight experiment flew on STS-107 which disintegrated during its descent on 1 February 2003. However, most of the moss experimental hardware was recovered on the ground, and most cultures, which had been chemically fixed during spaceflight, were retrieved. Almost all intact STS-107 cultures displayed strong spiral growth. Non-random culture growth including clockwise spiral growth was also observed after clinostat rotation. Together these data demonstrate the existence of default non-random growth patterns that develop at a population level in microgravity, a response that must normally be overridden and masked by a constant g-vector on earth.     

Tip-growing cells of the moss Ceratodon purpureus Are gravitropic in high-density media

Gravity sensing in plants and algae is hypothesized to rely upon either the mass of the entire cell or that of sedimenting organelles (statoliths). Protonemata of the moss Ceratodon purpureus show upward gravitropism and contain amyloplasts that sediment. If moss sensing were whole-cell based, then media denser than the cell should prevent gravitropism or reverse its direction. Cells that were inverted or reoriented to the horizontal displayed distinct negative gravitropism in solutions of iodixanol with densities of 1.052 to 1.320 as well as in bovine serum albumin solutions with densities of 1.037 to 1.184 g cm(-3). Studies using tagged molecules of different sizes and calculations of diffusion times suggest that both types of media penetrate through the apical cell wall. Estimates of the density of the apical cell range from 1.004 to 1.085. Because protonemata grow upward when the cells have a density that is lower than the surrounding medium, gravitropic sensing probably utilizes an intracellular mass in moss protonemata. These data provide additional support for the idea that sedimenting amyloplasts function as statoliths in gravitropism.     

Individual phenolic response and peroxidase activity in peel of differently sun-exposed apples in the period favorable for sunburn occurrence

Extreme weather events like high solar radiation can cause stress in apple fruits (Malus domestica Borkh.). The aim of the study was to make a screening of individual phenols and peroxidase activity in apple peel as a response to sunburn and different sun-exposures in the period when weather conditions are suitable for sunburn occurrence. Apple fruits of ‘Golden Delicious’ and ‘Braeburn’ were sampled. Fruit temperature and color were measured prior HPLC–MS² and peroxidase activity analyses. Sunburned peel was darker and more yellow-red in comparison to healthy peel, which appeared yellow-green. Fruit temperature, total as well as individual flavonols and dihydrochalcones, total hydroxycinnamics and perixodase activity were highest in sunburned peel in comparison with healthy sun-exposed peel, furthermore both were different than shaded sides of both fruits and peel of apples inside the tree crown; moreover in sunburned peel dihydrochalcones were determined for the first time. Chlorogenic acid was up to 2.5 times higher, 3-hydroxy-phloretin-2′-O-xyloglucoside was up to 10 times higher and quercetin-3-galactoside was up to 33 times higher in sunburned peel, comparing to shaded sided peels. Flavanols did not show a distinct pattern. A deeper insight in phenolic response against environmental stress caused by high solar radiation and high air temperatures has been made.     

Climate change impacts on life cycle greenhouse gas (GHG) emissions savings of biomethanol from corn and soybean

Purpose

The purpose of this study is to assess and calculate the potential impacts of climate change on the greenhouse gas (GHG) emissions reduction potentials of combined production of whole corn bioethanol and stover biomethanol, and whole soybean biodiesel and stalk biomethanol. Both fuels are used as substitutes to conventional fossil-based fuels. The product system includes energy crop (feedstock) production and transportation, biofuels processing, and biofuels distribution to service station.

Methods

The methodology is underpinned by life cycle thinking. Crop system model and life cycle assessment (LCA) model are linked in the analysis. The Decision Support System for Agrotechnology Transfer – crop system model (DSSAT-CSM) is used to simulate biomass and grain yield under different future climate scenarios generated using a combination of temperature, precipitation, and atmospheric CO₂. Historical weather data for Gainesville, Florida, are obtained for the baseline period (1981–1990). Daily minimum and maximum air temperatures are projected to increase by +2.0, +3.0, +4.0, and +5.0 °C, precipitation is projected to change by ±20, 10, and 5 %, and atmospheric CO₂ concentration is projected to increase by +70, +210, and +350 ppm. All projections are made throughout the growing season. GaBi 4.4 is used as primary LCA modelling software using crop yield data inputs from the DSSAT-CSM software. The models representation of the physical processes inventory (background unit processes) is constructed using the ecoinvent life cycle inventory database v2.0.

Results and discussion

Under current baseline climate condition, net greenhouse gas (GHG) emissions savings per hectare from corn-integrated biomethanol synthesis (CIBM) and soybean-integrated biomethanol synthesis (SIBM) were calculated as ?8,573.31 and ?3,441 kg CO₂-eq. ha^?1 yr^?1, respectively. However, models predictions suggest that these potential GHG emissions savings would be impacted by changing climate ranging from negative to positive depending on the crop and biofuel type, and climate scenario. Increased atmospheric level of CO₂ tends to minimise the negative impacts of increased temperature.

Conclusions

While policy measures are being put in place for the use of renewable biofuels driven by the desire to reduce GHG emissions from the use of conventional fossil fuels, climate change would also have impacts on the potential GHG emissions reductions resulting from the use of these renewable biofuels. However, the magnitude of the impact largely depends on the biofuel processing technology and the energy crop (feedstock) type.     

Metal ion requirement of bifunctional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase from rat liver

The metal ion requirement for both enzymatic activitiesof the bifunctional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosaminekinase (E.C. 5.1.3.14/ 2.7.1.60), the key enzyme of N-acetylneuraminic acidbiosynthesis in ratliver, was investigated. UDP-N-acetylglucosamine 2-epimerase was active inimida-zole/HCl buffer in the complete absence of any metal ion. 200 mM Na + , K + , Rb + and Cs +activated enzymeactivity up to five-fold, whereas lower concentrations of thesemonovalent metal ions showed only a small effect on UDP-N-acetylglucosamine 2-epimeraseactivity. In sodium phosphate buffer the enzyme activitywas increased by 0.5 mM Mg , Sr , Ba and Mn , while in the presence of 200 mM NaCl UDP-N-acetyl-glucosamine2-epimerase activity showed astronger activation by these divalent metal ions. In imidazole/HClbuffer, UDP-N-acetylglucosamine2-epimerase activity was partially inhibited by 0.5 mM Be , Mg , Ba ,Mn , Sn and Fe , and completely inhibited by 0.5 mM Zn and Cd . Divalent metal ions were essen-tialforN-acetylmannosamine kinase activity, the most effective being Mg , followed byMn and Co .The optimal concentration of these metal ions was 3 mM. Less effective were Ni and Cd , whereas Ca ,Ba , Cu , Fe and Zn showed no effect on enzyme activity.