Poplar GTL1 Is a Ca2+/Calmodulin-Binding Transcription Factor that Functions in Plant Water Use Efficiency and Drought Tolerance

Diminishing global fresh water availability has focused research to elucidate mechanisms of water use in poplar, an economically important species. A GT-2 family trihelix transcription factor that is a determinant of water use efficiency (WUE), PtaGTL1 (GT-2 like 1), was identified in Populus tremula × P. alba (clone 717-IB4). Like other GT-2 family members, PtaGTL1 contains both N- and C-terminal trihelix DNA binding domains. PtaGTL1 expression, driven by the Arabidopsis thaliana AtGTL1 promoter, suppressed the higher WUE and drought tolerance phenotypes of an Arabidopsis GTL1 loss-of-function mutation (gtl1-4). Genetic suppression of gtl1-4 was associated with increased stomatal density due to repression of Arabidopsis STOMATAL DENSITY AND DISTRIBUTION1 (AtSDD1), a negative regulator of stomatal development. Electrophoretic mobility shift assays (EMSA) indicated that a PtaGTL1 C-terminal DNA trihelix binding fragment (PtaGTL1-C) interacted with an AtSDD1 promoter fragment containing the GT3 box (GGTAAA), and this GT3 box was necessary for binding. PtaGTL1-C also interacted with a PtaSDD1 promoter fragment via the GT2 box (GGTAAT). PtaSDD1 encodes a protein with 60% primary sequence identity with AtSDD1. In vitro molecular interaction assays were used to determine that Ca2+-loaded calmodulin (CaM) binds to PtaGTL1-C, which was predicted to have a CaM-interaction domain in the first helix of the C-terminal trihelix DNA binding domain. These results indicate that, in Arabidopsis and poplar, GTL1 and SDD1 are fundamental components of stomatal lineage. In addition, PtaGTL1 is a Ca2+-CaM binding protein, which infers a mechanism by which environmental stimuli can induce Ca2+ signatures that would modulate stomatal development and regulate plant water use

Surface Characteristics of Chemically Modified Newsprint Fibers Determined by Inverse Gas Chromatography

The surface characteristics of treated waste newsprint fibers were investigated using inverse gas chromatography (IGC). The surfaces of waste newsprint fibers were modified with γ-aminopropyltrie-thoxysilane, dichlorodiethylsilane (DCS), phthalic anhydride (PA), and maleated polypropylene. The effectiveness of these surface treatments was monitored by the IGC adsorption curves using n-alkanes and acid-base probes. The empirical acid (KA) and base (KD) characteristics (i.e., electron donor/ acceptor abilities) of untreated and treated newsprint fibers were determined using Schultz's method and were correlated with the surface chemical compositions determined from X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The results indicated that the surface of untreated newsprint fibers had an acidic characteristic due to the electron acceptor character of the hydroxyl protons. The newsprint fibers reacted with phthalic anhydride or malcated polypropylene also exhibited an acidic surface behavior attributed to pendent carboxylic groups. Dichlorodiethylsilane produced a strong acidic surface attributed to the highly electronegative nature of the chlorine atoms of dichlorodiethylsilane. However, when the fibers were reacted with γ-aminopropyltriethoxysilane, the basic characteristic (electron donor ability) of the fiber surface was increased, presumably by the presence of attached amino groups

Aging mechanisms in cellulose fiber reinforced cement composites

This paper examines the effects of laboratory scale accelerated aging exposures on the changes in physical and mechanical properties of commercially produced cellulose fiber reinforced cement composites. Two different accelerated aging methods were used to simulate the possible aging mechanisms for which the material may experience under service conditions, both methods being compared to material naturally weathered for 5 yr in roofing. The first aging method consisted of different cycles of water immersion, carbonation, and heating exposures whereas in the second method, cycles of water immersion, heating and freeze-thaw exposures were used. The porosity, water absorption, permeability of nitrogen and compressive shear strength of the composites were examined before and after aging exposures. The surface morphologies of the composites fractured in compression shear tests were examined using scanning electron microscope. Experimental results showed that the compressive shear strength of the accelerated aged composites were related to the microstructures within the composites. Both natural weathering and accelerated aging in CO2 environment reduced the porosity, water absorption, and nitrogen permeability in the cement matrix, and enhanced the durability of the cellulose fiber-cement composites. The aging test based on artificial carbonation was more effective in simulating natural aging performance of the composites, while the freeze-thaw cycling method failed to induce significant aging effects on the composites even after 21 cycles

Surface characterization of esterified cellulosic fibers by XPS and FTIR spectroscopy

X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy techniques were used to study the surface chemical compositions of cellulosic fibers before and after treatments. The fibers were treated with phthalic anhydride and maleated polypropylene for surface modifications. Both XPS and FTIR spectroscopy analysis indicated that chemical bonds between hydroxyl groups of cellulosic fibers and anhydride moieties of phthalic anhydride and maleated polypropylene have occurred through esterification reaction. These chemical reagents have been added to the surface of cellulosic fibers in the form of monoester, i.e., the formation of esterified cellulosic fibers bearing a pendent carboxylic group

X-ray Photoelectron Spectroscopy study of silane-treated newsprint-fibers

The nature of adhesion in multicomponent materials such as cellulosic fibers/thermoplastic composites is strongly dependent on the surface properties of the components. X-ray Photoelectron Spectroscopy (XPS) was used to characterize the surfaces of untreated and treated newsprint-fibers. Gamma-aminopropyltriethoxysilane and dichlorodiethylsilane were used for the surface modification of the fibers. The XPS analysis indicated that coupling between the silanes and the newsprint-fibers has occurred, and that silanols were adsorbed to the surface of newsprint-fibers by two different mechanisms: (1) an ether linkage between the silanols and the hydroxyl groups of the fibers and (2) a hydrogen bonding between the amine and the hydroxyl groups of the fibers. The formation of the hydrogen bonding was evidenced by the two observed amino states, i.e., a covalent non-protonated form and an ionic protonated form

Contrasting Growth Response of Jack Pine and Trembling Aspen to Climate Warming in Quebec Mixedwoods Forests of Eastern Canada Since the Early Twentieth Century

Forest monitoring studies show contrasting trends in tree growth rates since the mid-twentieth century. However, due to their focus on annual and decadal dynamics, they provide limited insight into the effects of long-term climatic variability on tree growth. Here, we relied on a large tree-ring dataset (∼2,700 trees) of two common North American shade-intolerant tree species, trembling aspen (Populus tremuloides Michx.) and jack pine (Pinus banksiana Lambert), to assess their lifespan-long growth dynamics in the mixedwood forests of Québec. We also determined how the environmental conditions of the stands influenced tree growth. We observed a significant increase in the radial growth rate of trembling aspen during the study period, while the jack pine decline was not significant. Over the whole study region, the trees growing in sites with lower competition, and those at the lower sections of the terrain slope experienced more of the positive effects of temperature on growth rates. Our study suggests that the tree growth response to climate warming may be species-specific and will vary across the boreal mixedwoods