Effects of drought hardening on the carbohydrate dynamics of Quercus acutissima seedlings under successional drought.

Introduction: As precipitation patterns are predicted to become increasingly erratic, the functional maintenance of warm-temperate forests constitutes a key challenge for forest managers. In this study, 2-year-old Quercus acutissima seedlings were selected to elucidate the mechanisms whereby they respond to soil water fluctuations and the drought hardening effects on plant carbohydrate dynamics. Methods: Seedlings were trained under different soil water conditions for 2 months: drought (D), well-watered (W), 1-month drought and then 1-month well-watered (D-W), and 1-month well-watered and then 1-month drought (W-D). The functional traits involved in water- and carbon-use strategies were explored at the end of the hardening period. Compared with seedlings in group W, seedlings in groups D, D-W, and W-D had increased potential for carbon uptake (i.e., light saturated point, maximum ribulose-1,5-bisphosphate (RuBP) saturated rate, and electron transport rate) and water uptake (i.e., fine root-to-coarse root ratio) and downregulated growth and mitochondrial respiration to decrease carbon consumption. After water fluctuation hardening, we performed a successional dry-down experiment for 1 month to detect carbohydrate dynamics and explore the acclimation caused by prior hardening. Results and discussion: Our results revealed that there were more soluble sugars allocated in the leaves and more starch allocated in the stems and roots of seedlings hardened in the D, W-D, and D-W treatments than that of seedlings hardened in the W treatment. No significant changes in total non-structural carbohydrates were found. In addition, we found near-zero (seedlings trained by D and D-W treatments) or negative (seedlings trained by W-D treatment) growth of structural biomass at the end of the dry-down experiment, which was significantly lower than that of W-hardened seedlings. This suggests that there was a shift in allocation patterns between carbon storage and growth under recurrent soil drought, which can be strengthened by drought memory. We conclude that Q. acutissima seedlings adjusted water- and carbon-use strategies in response to water fluctuations, whereas stress memory can enhance their overall performance in reoccurring drought. Therefore, taking advantage of stress memory is a promising management strategy in forest nurseries, and drought-trained seedlings might be more suitable for afforestation practices in sites characterized by fluctuating soil water content, considering the ongoing global climatic changes.

Extraction and deproteinization process of polysaccharide from purple sweet potato.

Extraction and deproteinization process of polysaccharide from purple sweet potato (PPSP) were optimized via the response surface methodology (RSM). The results indicated that the optimal conditions of extraction in hot water of PPSP were as follows: The extraction temperature was 120℃, the extraction time was 2.5 hr, and the solid-liquid ratio was 1∶10 (g/ml). The optimal conditions of Sevage deproteinization were as under the oscillation time was 20 min, the deproteinization times was twice, and polysaccharide solution-Sevage reagent ratio was 1:1 (ml/ml). The extraction yield of PPSP was 3.32%, and the protein removal rate was 93.14% in such a condition.

Plant Size Plays an Important Role in Plant Responses to Low Water Availability and Defoliation in Two Woody Leguminosae Species.

Plant size influences plant responses to combined environmental factors under climate change. However, their roles in plant ecophysiological responses are not fully understood. Two rapidly growing Leguminosae species (Robinia pseudoacacia and Amorpha fruticosa) were used to examine plant responses to combined drought and defoliation treatments (two levels of both treatments). Both 1.5 month-old seedlings and 3 month-old seedlings were grown in a greenhouse, and seedling growth, leaf gas exchanges, stem hydraulics, and concentrations of non-structural carbohydrates were determined after 60 days of treatment. Our results indicated defoliation had no significant effect on plant height, basal diameter, and total biomass whatever plant sizes and species. Under the low water availability treatment, the defoliated seedlings significantly increased by 24% in stem water potential compared with non-defoliated seedlings in large R. pseudoacacia. Compared with the high water availability in large non-defoliated R. pseudoacacia seedlings, the low water availability significantly reduced by 26% in stem starch concentration to maintain the stem soluble sugar concentration stable, but not in small R. pseudoacacia seedlings. We also found a negative correlation between leaf and root soluble sugar concentration under low water availability in A. fruticosa. The results demonstrate defoliation could relieve the effect of low water availability in large seedlings. Large seedlings had more compensatory mechanisms in response to defoliation and drought treatments than small seedlings, thus species with large carbon reserves are more recommended for vegetation restoration under combined drought and defoliation conditions. Future studies with more species are crucial for obtaining more rigorous conclusions.

Biodiversity, environmental context and structural attributes as drivers of aboveground biomass in shrublands at the middle and lower reaches of the Yellow River basin.

Biodiversity-biomass relationships have been debated for decades and remain subject to controversy. Understanding the relationship between biodiversity and biomass will be crucial for soil and water conservation of the whole basin of the Yellow River. The positive effects of biodiversity on aboveground biomass are altered via two fundamental mechanisms-niche complementarity and selection effects-and are modulated by environmental context and community structure in natural communities. Most studies of biodiversity-biomass relationships have focused on grasslands and forests, rather than on shrublands. We combine multiple biotic variables (biodiversity, functional identity and community structural attributes) and environmental context with aboveground biomass across shrubland habitat types (temperate hilly, temperate montane and subtropical montane) at neighbourhood and community spatial scales, to evaluate the effects of these factors on shrubland aboveground biomass, in the Yellow River basin. We found aboveground biomass was influenced primarily by the community-weighted mean plant maximum height, followed by species richness and community-weighted mean specific leaf area. Furthermore, individual plant size inequality, mean annual precipitation and water availability either directly or indirectly influenced aboveground biomass. The biodiversity-aboveground biomass relationship was stronger at the broader spatial scale. Thus, our findings indicate that both niche complementarity and selection effects shape the effects of biodiversity on shrubland aboveground biomass, although selection effects are more important. Moreover, they indicate that water is the most important environmental factor for determining aboveground biomass, and suggest that community structure and spatial scale could influence shrubland aboveground biomass and its response to biodiversity.

Preparation of Redox-Sensitive Shell Cross-Linked Nanoparticles for Controlled Release of Bioactive Agents.

Redox-sensitive shell cross-linked (SCL) poly(2-(dimethylamino)ethyl methacrylate)-block-polystyrene (PDMAEMA-b-PS) nanoparticles have been facilely fabricated by surfactant-free emulsion reversible addition-fragmentation chain transfer polymerization (SFE-RAFT), in which amphiphilic C12H25-PDMAEMA copolymers acted as stabilizers. 1H NMR, dynamic light scattering (DLS), and transmission electron microscopy (TEM) were applied to investigate the compositions and the morphologies of the resultant nanoparticles. Then, the as-prepared nanoparticles were used as a carrier to encapsulate of hydrophobic drugs, and the release could be triggered by a redox reagent, dithiothreitol (DTT). The SCL nanoparticles had a good biocompatibility. These properties indicated that these nanoparticles would be used as promising drug delivery vehicles.

Photocatalytic activity of heterostructures based on TiO2 and halloysite nanotubes.

A one-step solvothermal method was used to prepare TiO(2)/halloysite composites. TiO(2) nanoparticles were deposited on the platform of the halloysite nanotubes (HNTs). XRD, FT-IR, FE-SEM, and TEM were applied to investigate the structures and morphologies of the resultant samples. The as-prepared TiO(2)/HNTs photocatalyst exhibits pH sensibility on the degradation of methanol and a higher photocatalytic activity on the degradation of acetic acid. The combination of the photocatalytic property of TiO(2) and the unique structure of halloysite endowed this material with a bright perspective in degradation of organic pollutant.