Towards a more flexible representation of water stress effects in the nonlinear Jarvis model

To better interpret summer maize stomatal conductance （gs） variation under conditions of changing water status at different growth stages, three water stress indicators, soil water content （SWC）, leaf-air temperature difference （AT） and leaf level water stress index （CWSIL） were employed in Jarvis model, which were Js, JT and Jc models respectively. Measurements of gs were conducted in a summer maize field experiment during the year 2012-2013. In the insufficient irrigation exper- iment, three levels of irrigation amount were applied at four different growth stages of summer maize. We constructed three scenarios to evaluate the performance of the three water stress indicators for estimating maize gs in a modified Jarvis model. Results showed that JT and Jc models had better simulation accuracy than the Js model, especially at the late growth stage （Scenario 1） or considering the plant recovery compensation effects （Scenario 2）. Scenario 3 indicated that the more environmental factors were adopted, the better prediction performance would be for Js model. While for JT model, two environmental factors （photosynthesis active radiation （PAR）, and vapor pressure deficit （VPD）） seemed good enough to obtain a reliable simulation. When there were insufficient environmental data, CWSI, would be the best option. This study can be useful to understand the response of plant stomatal to changing water conditions and will further facilitate the application of the Jarvis model in various environments.

Screening of Rice Accessions for Tolerance to Drought and Salt Stress Using Morphological and Physiological Parameters

Drought and salinity are the most widespread soil problems, posing a big threat to food security in rice growing regions. The present study evaluated the performance of eleven rice genotypes using morphological and physiological parameters, under induced drought and salinity conditions. The seedlings were raised in 5 kg of homogenous soil in plastic bags in the greenhouse. For the drought experiment, each bag was watered with 200 ml of water twice daily until plants reached the five-leaf stage when watering was suspended for 2 weeks for the drought stressed plants but not suspended for the control plants. The experiment was a 2 × 11 factorial and the set up was arranged using the completely randomized design with three replications. Data were taken on Plant height, Number of tillers, leaf length, Number of green leaves, Number of dead leaves, Leaf rolling score (LRS) and Rate of water loss. The salinity experiment was set up in a similar manner except that the plants were irrigated twice a day for 2 weeks with 200 ml of treatment solution containing either 0 mM NaCl or 75 mM and data were collected on plant height, number of tillers, shoot fresh weight, shoot dry weight, Na+ and K+ concentrations, relative water content and chlorophyll content. Data from both experiments were subjected to Analysis of variance test using the GenStat software 10th edition and the means separated using least significant difference test. Individual stress response index (ISRI) was calculated for each parameter and the means used in grouping the varieties. Of the genotypes evaluated, four (FARO 44, NERICA 2, NERICA 8 and NERICA 5) were identified as tolerant, two (NERICA 4 and FARO 57) as moderately tolerant, while the rest were found to be sensitive to drought. Equally, two varieties (FARO 44 and RAM 137) stood out in the salinity screening as tolerant varieties, five were moderately tolerant while four (FARO 64, FARO 52, NERICA 2 and FARO 55) were clearly susceptible. FARO 44 is the only genotype that showed tolerance to both drought and salinity. The identified drought and salinity tolerant rice genotypes from this study can be recommended as genetic sources for future breeding programs for drought and salinity tolerance in rice.

Application of Hydrogen Peroxide as an Environmental Stress Indicator for Vegetation Management

Adaptive vegetation management is time-consuming and requires long-term colony monitoring to obtain reliable results. Although vegetation management has been widely adopted, the only method existing at present for evaluating the habitat conditions under management involves observations over a long period of time. The presence of reactive oxygen species （ROS） has long been used as an indicator of environmen- tal stress in plants, and has recently been intensely studied. Among such ROS, hydrogen peroxide （H202） is relatively stable, and can be conveniently and accurately quantified. Thus, the quantification of plant H202 could be applied as a stress indicator for riparian and aquatic vegetation management approaches while evaluating the conditions of a plant species within a habitat. This study presents an approach for elucidating the applicability of H202 as a quantitative indicator of environmental stresses on plants, particularly for vegetation management. Submerged macrophytes and riparian species were studied under laboratory and field conditions （Lake Shinji, Saba River, Eno River, and Hii River in Japan） for H202 formation under various stress conditions. The results suggest that H202 can be conveniently applied as a stress indicator in environmental management.

Analysis of Stress Strain State of X-60 Pipe Weld Joints Employing Magnetic-Anisotropy Indicator of Mechanical Stress

This research presents an experimental study of analysis of stress strain state SSS of X-60 pipe weld joints employing magnetic anisotropy indicator of mechanical stresses Stress Vision (IMS) using of “before and after” comparison approach taking readings on pipe base metal, weld area and heat affected zone (HAZ) before and after hydrotest. Test results were compared with X-ray testing results for welded joints and with metallographic testing. Test results demonstrate the relevance of applied test conditions and redistribution of residual stresses. A new equation was established for estimating the residual (technological) and operating stresses in other pipelines with a tolerance of 15% in the field of elastic deformation (up to the yield point), according to Hooke law.

Role of dietary gamma-aminobutyric acid in broiler chickens raised under high stocking density

The present study was conducted to evaluate the effects of dietary gamma-aminobutyric acid(GABA)in broiler chickens raised in high stocking density(HSD)on performance and physiological responses.A total of 900 male broiler chicks(Ross 308)at 1 d old were assigned in a 2×2 factorial arrangement to 4 treatments(10 replicates per treatment)with stocking density,7.5 birds/m^2(low stocking density;LSD)or 15 birds/m^2(HSD),and dietary GABA,0 or 100 mg/kg.Chickens raised in HSD exhibited a decrease in body weight gain in all phases(P<0.05)and feed intake in starter and whole phases(P<0.01),and an increase in feed conversion ratio in the finisher phase(P<0.01)compared with LSD-raised chickens.However,dietary GABA did not affect growth performance nor interacted with stocking density on production variables.The HSD vs.LSD increased relative liver weight on d 35 whereas dietary GABA increased relative liver weight and decreased relative bursa weight on d 21.Both stocking density and dietary GABA affected yield and quality of breast and leg muscles.Dietary GABA increased(P<0.05)width of tibia on d 35 and interacted(P=0.054)with stocking density on breaking stocking density on d 35.The HSD vs.LSD group lowered(P<0.05)feather coverage scores.Significant interaction between stocking density and GABA on surface temperature of shank on d 21 was noted(P=0.024).Dietary GABA exhibited an opposite effect on the concentrations of cecal short-chain fatty acids depending on stocking density leading to a moderate to significant interaction.Stocking density decreased alpha-1-acid glycoprotein whereas dietary GABA decreased heterophil-to-lymphocyte ratio and corticosterone in blood or serum samples.Serum biochemical parameters were altered by stocking density or dietary GABA.It is concluded that dietary GABA alleviated stress indices including corticosterone and heterophilto-lymphocyte ratio,but failed to reverse stocking density-induced growth depression.