Associations between leaf developmental stability, variability, canalization, and phenotypic plasticity in Abutilon theophrasti.

Developmental stability, canalization, and phenotypic plasticity are the most common sources of phenotypic variation, yet comparative studies investigating the relationships between these sources, specifically in plants, are lacking. To investigate the relationships among developmental stability or instability, developmental variability, canalization, and plasticity in plants, we conducted a field experiment with Abutilon theophrasti, by subjecting plants to three densities under infertile vs. fertile soil conditions. We measured the leaf width (leaf size) and calculated fluctuating asymmetry (FA), coefficient of variation within and among individuals (CVintra and CVinter), and plasticity (PIrel) in leaf size at days 30, 50, and 70 of plant growth, to analyze the correlations among these variables in response to density and soil conditions, at each of or across all growth stages. Results showed increased density led to lower leaf FA, CVintra, and PIrel and higher CVinter in fertile soil. A positive correlation between FA and PIrel occurred in infertile soil, while correlations between CVinter and PIrel and between CVinter and CVintra were negative at high density and/or in fertile soil, with nonsignificant correlations among them in other cases. Results suggested the complexity of responses of developmental instability, variability, and canalization in leaf size, as well as their relationships, which depend on the strength of stresses. Intense aboveground competition that accelerates the decrease in leaf size (leading to lower plasticity) will be more likely to reduce developmental instability, variability, and canalization in leaf size. Increased developmental instability and intra- and interindividual variability should be advantageous and facilitate adaptive plasticity in less stressful conditions; thus, they are more likely to positively correlate with plasticity, whereas developmental stability and canalization with lower developmental variability should be beneficial for stabilizing plant performance in more stressful conditions, where they tend to have more negative correlations with plasticity.

Dynamic morphological plasticity in response to emergence timing in Abutilon theophrasti (Malvaceae).

Selections on emergence time might be conflicting, suggesting the existence of the optimal emergence time for plants. However, we know little about this and how morphological plasticity contributes to the strategies of plants in response to emergence timing. To better understand this issue from a dynamic perspective, we conducted a field experiment by subjecting plants of Abutilon theophrasti to four emergence treatments (ET1 ~ ET4) and measuring a number of mass and morphological traits on them at different growth stages (I ~ IV). On day 50, 70, and/or final harvest, among all ET treatments, plants germinated in late spring (ET2) performed the best in total mass, spring germinants (ET1) and ET2 performed better in stem allocation, stem, and root diameters than later germinants (ET3 and ET4); summer germinants (ET3) had the highest reproductive mass and allocation, while late-summer germinants (ET4) had the greatest leaf mass allocation, with greater or canalized leaf number, and root length traits than others. Plants that emerged in late spring can maximize their growth potential, while those with either advanced or delayed emergence are still capable of adaptation via allocation and morphological plasticity. Early germinants (ET1 and ET2) preferred stem growth to leaf and reproductive growth, due to sufficient time for reproduction in the growth season. With limited time for growth, plants that emerged late may prefer to quicken leaf growth (indicated by increased leaf mass allocation and leaf number) at the cost of stem or root growth for the complete life cycle, reflecting both positive and negative effects of delayed emergence.

Morphological canalization, integration, and plasticity in response to population density in Abutilon theophrasti: Influences of soil conditions and growth stages.

Phenotypic integration and developmental canalization have been hypothesized to constrain the degree of phenotypic plasticity, but little evidence exists, probably due to the lack of studies on the relationships among the three processes, especially for plants under different environments. We conducted a field experiment by subjecting plants of Abutilon theophrasti to three densities, under infertile and fertile soil conditions, and analyzing correlations among canalization, integration, and plasticity in a variety of measured morphological traits after 50 and 70 days, to investigate the relationships among the three variables in response to density and how these responses vary with soil conditions and growth stages. Results showed trait canalization decreased and phenotypic integration and the degree of plasticity (absolute plasticity) in traits increased with density. Phenotypic integration often positively correlated with absolute plasticity, whereas correlations between trait canalization and plasticity were insignificant in most cases, with a few positive ones between canalization and absolute plasticity at low and medium densities. As plants grew, these correlations intensified in infertile soil and attenuated in fertile soil. Our findings suggested the complexity of the relationship between canalization and plasticity: Decreased canalization is more likely to facilitate active plastic responses under more favorable conditions, whereas increased level of integration should mainly be an outcome of plastic responses. Soil conditions and growth stage may affect responses of these correlations to density via modifying plant size, competition strength, and plastic responses in traits. We also predicted that decreased canalization can be advantageous or disadvantageous, and the lack of response to stress may demonstrate a stronger ability of adaptation than passive response, thus should be adaptive plasticity as active response.

Root morphological responses to population density vary with soil conditions and growth stages: The complexity of density effects.

AIM: How plants cope with increases in population density via root plasticity is not well documented, although abiotic environments and plant ontogeny may have important roles in determining root response to density. To investigate how plant root plasticity in response to density varies with soil conditions and growth stages, we conducted a field experiment with an annual herbaceous species (Abutilon theophrasti). METHODS: Plants were grown at low, medium, and high densities (13.4, 36.0, and 121.0 plants m-2, respectively), under fertile and infertile soil conditions, and a series of root traits were measured after 30, 50, and 70 days. RESULTS: Root allocation increased, decreased, or canalized in response to density, depending on soil conditions and stages of plant growth, indicating the complex effects of population density, including both competitive and facilitative effects. MAIN CONCLUSIONS: Root allocation was promoted by neighbor roots at early stages and in abundant resource availability, due to low-to-moderate belowground interactions among smaller plants, leading to facilitation. As plants grew, competition intensified and infertile soil aggravated belowground competition, leading to decreased root allocation in response to density. Root growth may be more likely restricted horizontally rather than vertically by the presence of neighbor, suggesting a spatial orientation effect in their responses to density. We emphasized the importance of considering effects of abiotic conditions and plant growth stages in elucidating the complexity of density effects on root traits.

Trade-off relationship and internal mechanism of plant leaf size and number in Hulunbuir grassland, China.

The trade-off between leaf size and number is the basis for plant growth strategies. It is of great significance to study the underlying mechanism of leaf size and number trade-offs for well understanding plant growth strategies. In this study, leaf size was expressed by the dry mass of single leaf, while leafing intensity was expressed by the number of leaves per unit stem volume. We used standardized major axis regression analysis method to examine the trade-off relationship between leaf size and number in Hulunbuir grassland. There was a significant negative isometric-growth trade-off between leaf size and number in Chenqicuogang (typical steppe) and Chenqibayi (meadow steppe). There was a significant negative allometric-growth trade-off between leaf size and number in Xeltala (meadow steppe). The underlying mechanism of the relationship between leaf size and number depended on the leaf and stem biomass allocation mechanism and the changes of the stem tissue density.

Tea Catechins Protect Goat Skeletal Muscle against H2O2-Induced Oxidative Stress by Modulating Expression of Phase 2 Antioxidant Enzymes.

To study the mechanisms of tea catechins (TCs) in goat muscles against oxidative stress, skeletal muscle cells (SMCs) induced by H2O2 or not were incubated with TCs or 3H-1,2-dithiole-3-thione (D3T) and were defined as H2O2, H2O2D3T, H2O2TC, D3T, and TC treatments, respectively. Results showed that, similar to effects of D3T, TCs regulated mRNA and protein expression of antioxidant enzymes by suppressing Keap1 protein expression in SMCs from 1.58 ± 0.12 to 0.71 ± 0.21 and 1.03 ± 0.11 in H2O2TC and TC groups, respectively; however, effects differed in oxidative condition of cells and among enzymes. In stressed cells, TCs increased catalase and glutathione S-transferases (GST) activities (P < 0.001), whereas both enzymes' activities decreased (P < 0.001) to 2.97 ± 0.37 U/mg protein or 42.1 ± 1.85 mU/mg protein, respectively, in unstressed SMCs. Subsequently, an in vivo experiment in goats fed grain supplemented with TCs or D3T following infusion with H2O2 was conducted to further verify mechanisms of TC action. As seen in vitro, TCs reduced Keap1 protein expression (P < 0.001) from 2.11 ± 0.37 to 1.34 ± 0.13 and 1.43 ± 0.23 in H2O2TC and TC groups, respectively, in muscle. However, dietary TCs increased plasma CuZn superoxide dismutase and GST activities (P < 0.001) regardless of oxidative stress. Moreover, feeding TCs to goats under both conditions increased meat color and tenderness (P ≤ 0.001). In conclusion, TCs protected goat muscles against oxidative stress and subsequently improved meat quality by modulating phase 2 antioxidant enzymes and Keap1 expression.

Effects of supplementation with dietary green tea polyphenols on parasite resistance and acute phase protein response to Haemonchus contortus infection in lambs.

The objective of this study was to determine the effects of supplementation with dietary green tea polyphenols (GTPs) on parasite resistance and acute phase protein (APP) response to Haemonchus contortus infection in lambs. Thirty male Ujumqin lambs were randomly assigned to five treatment groups for an 8-week feeding period. Treatments included: (1) uninfected as control, (2) infected but not given GTP (INFGTP0) and (3)-(5) infected and fed 2, 4, or 6g GTP/kg feed (dry matter basis; INFGTP2, INFGTP4, and INFGTP6, respectively). Fecal and blood samples were collected to determine fecal egg count (FEC), packed cell volume (PCV), and APP concentrations. Live weight was measured once every 2 weeks. At the end of the feeding period, lambs were slaughtered to determine the adult H. contortus burden. The results demonstrated interaction effects between treatment and sampling time on the average daily gain (ADG; P=0.0005), FEC (P<0.0001), PCV (P=0.0005), and concentrations of serum amyloid A (SAA), haptoglobin (Hp), lipopolysaccharide binding protein (LBP), and α1-acid glycoprotein (α1AGP) (P<0.0001). From days 0 to 56, the ADG values for all infected lambs were lower than that of uninfected lambs, but the ADG values for all GTP-fed lambs were higher than that of INFGTP0 lambs, especially from days 28 to 42. The FECs of all GTP-fed lambs were higher than those of uninfected lambs but lower than that of INFGTP0 lambs. The PCVs of all infected lambs were lower than those of uninfected lambs, but PCV increased with increasing amounts of GTP supplementation. Furthermore, supplementation with different concentrations of GTP significantly reduced the numbers of adult H. contortus, including both males and females (P<0.0001), and the H. contortus burden in INFGTP6 lambs was reduced to uninfected levels. Overall, the SAA, Hp, LBP, and α1AGP concentrations of all infected lambs were higher than those of uninfected lambs from days 0 to 56. Two peaks in expression were observed from days 0 to 3 and at day 28, and APP concentrations of all GTP-fed lambs were lower than those of INFGTP0 lambs, except for SAA in INFGTP6 lambs. In conclusion, quantitative measurements of APP responses to H. contortus infection provide valuable diagnostic information for monitoring infection progression and treatment responses in lambs. An appropriate dose of dietary GTP supplementation can increase host resistance by reducing H. contortus burden and weight loss and suppressing blood APP expression.

[Sowing date of corn in semiarid region of Jilin Province, Northeast China in adapting to climate change].

Under the background of global climate change, the climate in semiarid region of west Jilin Province changed greatly, producing a profound impact on the corn production in this region. In this study, the corn seeds were under three treatments (accelerating germination at 10 and 25 degrees C, and dry seeds), and a field experiment with early sowing and traditional sowing was conducted in 2008 to investigate the effects of early sowing these seeds on the seedling emergence, growth, and yield, and compare the effects of early sowing and traditional sowing dates on the corn production and yield. In 1961-2010, the first day of the growth season of corn in semiarid region of west Jilin Province was advanced, the air temperature increased significantly, and the precipitation displayed a decreasing trend. At present, the corn sowing date in this region could be advanced to 11th, April. Accelerating germination at 10 degrees C, directly sowing dry seeds, and bed-irrigation sowing all benefited the seedling emergence and cold resistance of early-sown seeds, and the corn plant height and leaf area under early sowing were significantly higher, with the yield increased by 35% - 48%, compared with those under traditional sowing.

Effect of tea catechins on regulation of antioxidant enzyme expression in H2O2-induced skeletal muscle cells of goat in vitro.

Skeletal muscle cells (SMCs) of goats were stress induced with 1 mM H(2)O(2) in the absence or presence of 0.5, 5, and 50 µg/mL tea catechins (TCs) incubation. Cells were harvested at 48 h postincubation with TCs to investigate the effects of TCs on cell proliferation, cell membrane integrity, antioxidant enzyme activities, and antioxidant enzyme genes and protein expression levels. Results showed that H(2)O(2) induction inhibited cell proliferation with or without TC incubation; moreover, the inhibition effect was enhanced in the presence of TCs (P < 0.001). H(2)O(2)-induced stress increased the lactate dehydrogenase (LDH) activity in the absence or presence of TC incubation, but concentrations of TCs, less than 5 µg/mL, showed protective functions against LDH leakage than in other H(2)O(2)-induced treatments. The catalase (CAT) activity increased when SMCs were stress induced with H(2)O(2) in the absence or presence of TC incubation (P < 0.001). H(2)O(2)-induced stress decreased CuZn superoxide dismutase (CuZn-SOD) and glutathione peroxidase (GPx) activities, whereas this effect was prevented by incubation with TCs in a concentration-dependent manner. H(2)O(2)-induced stress with or without TC incubation had significant effects on mRNA and protein expression levels of CAT, CuZn-SOD, and GPx (P < 0.001). CAT and CuZn-SOD mRNA expression levels were increased by different concentrations of TC incubation, and this tendency was basically consistent with corresponding protein expression levels. The GPx mRNA expression level increased with a low concentration of TCs but decreased with concentrations greater than 5 µg/mL of TCs, whereas GPx protein expression in all TC-incubated groups was lower than in the control treatment. The current findings imply that TCs had an inhibitory effect on cell proliferation and enhanced damage to the cell membrane integrity, but TCs affected antioxidant status in SMCs by modulating antioxidant enzyme activities at mRNA and protein expression levels.

[Salinization-alkalization of Leymus chinensis grassland in Songnen Plain of Northeast China].

Field survey and site study were conducted to approach the process and causes of salinization-alkalization of Leymus chinensis grassland in Songnen Plain, and to examine the hypothesis of soil disturbance-bareness. In the grassland, surface soil (0-30 cm) had a lower salt content, while deeper soil (> 30 cm) was in adverse. Thereby, the grassland was defined as soil-salted grassland. There was an increasing salt content in surface soil. This process was called as soil salinization-alkalization, and the grassland under the salinization:alkalization was named as alkali-salinized grassland. The leading reason for the surface soil salinization-alkalization was that the surface soil originally with low salt content was disturbed and lost away, subsurface soil rich in salt emerged as new surface soil, and the salt in deeper soil layers accumulated in the new surface soil and other soil layers. Secondary halophyte communities formed on the surface-soil-disturbed new bare land, but the communities had no succession sequence. The degradation process of the grassland was soil degradation first, followed by vegetation degradation, halophyte invasion, and successive evolution from nearly primitive condition.

[Risk assessment of ecological disasters in Jilin Province based on GIS].

Based on the principles of natural disasters risk formation, and considering the natural and social features of Jilin Province, relevant indices were selected from the aspects of hazard, exposure, vulnerability and emergency responses, and recovery capability, and Natural Disaster Risk Index method, Weighted Comprehensive Analysis, and Analytic Hierarchy Process were used to build the risk assessment model of ecological disasters in this Province. The contribution of each index was assessed, and the regionalization map of the ecological disasters risk in Jilin Province was built based on GIS, which would provide scientific references in accurately understanding the risk level of ecological disasters and in decision-making of eco-environment restoration and management in Jilin Province.

[Soil moisture and interspecific relationships between grass and legume on mixed grassland: a research review].

From the viewpoints of plant morphology and physiology, this paper discussed the survival strategy of grass and legume on mixed grassland under water stress, their competition for water and the hydraulic facilitation effects of legumes on water resource utilization, and the impact of drought on biological nitrogen fixation and nitrogen transfer of legume. It was indicated that to promote the productivity of grassland in arid area, the mechanisms of competition and coexistence between grass and legume should be further studied, and one of the main aspects should be the effects of water stress on their aboveground and belowground competitions and their feedback on the competitions.