Salinity stress affects growth and physiology of mulberry (Morus sp.)

Mulberry (Morus sp.) plant is used to feed silkworms, and the leaves contain compounds with medicinal properties of secondary metabolites. However, the content of these compounds tends to increase under stress conditions, for instance, salt stress. This study, therefore, aimed to determine the accessions of mulberry with tolerance for salt stress. The stem cuttings of seven accessions from 5 regions, Bogor, Pati, Situbondo, Bali, and Gowa, were planted following a factorial randomized block design with 3 replications. Subsequently, the first factor using the accessions, and the second factor using NaCl solution (0.0%, 0.2%, 0.3%, and 0.4% concentrations) were performed. The variables observed were growth (leaves number, plant height, and shoots number), photosynthesis rate, total chlorophyll, and proline content. The results showed that the M6 accession exhibited tolerance under high salt stress, based on the leaves number, plant height, shoot number, photosynthesis rate, and proline content. Furthermore, an increase in salt concentration was discovered to cause a decrease in growth, photosynthesis rate, and total chlorophyll content. Also, proline accumulation stimulated by high salt stress possibly plays an important role in salinity tolerance.

Influence of biochar and microorganisms co-application on the remediation and maize productivity in cadmium-contaminated soil.

The synergistic effects of biochar and microorganisms on the adsorption of Cd and on cereal plant physiology remained unclear. Therefore, this experiment was performed to evaluate the combined effects of biochar pyrolyzed from (maize-straw (BC1), cow-manure (BC2), and poultry-manure (BC3), and microorganisms including (T. harzianum L. and B. subtilis L.), to evaluate, how incorporation of biochar positively influences microorganisms growth and nutrients uptake in plant, and how it mitigates under various Cd-stress levels (0, 10, and 30ppm). Cd2 (30 ppm) had the highest reduction in the intercellular CO2, SPAD value, transpiration rate, water use efficiency, stomatal conductance, and photosynthesis rate, which were 22.36, 34.50, 40.45, 20.66, 29.07, and 22.41% respectively lower than control Cd0 (0 ppm). Sole application BC, resulted in enhanced intercellular CO2, SPAD value, transpiration rate, water use efficiency, stomatal conductance, and photosynthesis rate were recorded in BC2, which were 7.27, 20.54, 23.80, 5.96, 13.37, and 13.50% respectively greater as compared to control and decreased the Cd-concentration in root and shoot of maize by 34.07 and 32.53%, respectively as compared to control. Similarly, among sole microorganism’s inoculation, minimized the Cd-concentration in shoot, root, and soil by 23.77, 20.15, and 10.35% respectively than control. These results suggested that integrated application of cow manure biochar BC2 and inoculation of microorganisms MI3 as soil amendments had synergistic effects in improving the adsorption of nutrients and decreasing the Cd-uptake in maize, and enhancing the physiology of plant grown in Cd-polluted soils as opposed to using either biochar or inoculating microorganisms alone.

Age-Related Changes in Sensitivity of Tomato (Solanum lycopersicum L.) Leaves to Continuous Light

Tomato (Solanum lycopersicum L.) belongs to the crops that are the most sensitive to continuous lighting (CL). We studied age-dependent changes in the sensitivity of tomato leaves to CL. The leaves exposed to CL from a lag-phase of their growth exhibited pronounced chlorosis with the loss of 30% chlorophyll after 2 weeks. The values of the maximum (Fv/Fm) and actual (φII) quantum yields of the PSII photochemical activity were decreased, the photosynthesis rate was suppressed, and the relative electrolyte leakage was enhanced. In contrast, the leaves were less sensitive to CL if they had passed their early growth (lag-phase) under normal light conditions (16-h photoperiod) and encountered the CL as late as in the log-phase. In this case, the chlorophyll content, the photosynthesis rate, and the electrolyte leakage were close to the levels of the control leaves grown at the 16-h photoperiod except for the antioxidant enzymes—catalase, ascorbate peroxidase, and guaiacol peroxidase—which were more active. The conclusion was drawn that the age-related changes in the CL-sensitivity are due to the difference in activities of the antioxidant enzymes. In general, the elder plants were less sensitive to CL than the younger ones.

Concentrations-dependent effect of exogenous abscisic acid on photosynthesis, growth and phenolic content of Dracocephalum moldavica L. under drought stress

Main Conclusion The drought conditions and the application of ABA reduce the photosynthetic activity, and the processes related to the transpiration of Dracocephalum moldavica L. At the same time, the plant increases the production of phenolic compounds and essential oil as a response to stress conditions. Abstract In the semi-arid regions, drought stress is the most important environmental limitations for crop production. Abscisic acid (ABA) plays a crucial role in the reactions of plants towards environmental stress such as drought. Field experiments for two consecutive years in 2016 and 2017 were conducted to evaluate the effect of three watering regimes (well-watered, moderate and severe drought) and five exogenous ABA concentrations (0, 5, 10, 20 and 40 μM) on growth, photosynthesis, total phenolic and essential oil content of Dracocephalum moldavica L. Without ABA application, the highest photosynthetic rate (6.1 μmol CO2 m−2 s−1) was obtained under well-watered condition and, moderate and severe drought stress decreased photosynthesis rate by 26.39% and 34.43%, respectively. Some growth parameters such as stem height, leaf area, leaf dry weight and biological yield were also reduced by drought stress. ABA application showed a decreasing trend in photosynthesis rate and mentioned plant growth parameters under all moisture regimes. The highest seed yield (1243.56 kg ha−1) was obtained under well-watered condition without ABA application. Increasing ABA concentration decreased seed yield in all moisture regimes. The highest total phenolic content (8.9 mg g−1 FW) and essential oil yield (20.58 kg ha−1) were obtained from 20 and 5 μM ABA concentration, respectively, under moderate drought stress.

Wheat physiological traits response in standard and ecological agricultural systems

This research was conducted on a farm of Payam-e-Noor University in Piranshahr, in West Azerbaijan province of Iran, during 2014-2015 and 2015-2016 crop sessions to investigate the wheat physiological traits response to standard and ecological agricultural systems. The experiment was conducted as a split-plot design with two factors and three replications. The first factor, which was considered the main plot, included high, low-input, and ecological agricultural systems. Subplots were seed pre-treatment, including control (without priming), hydro priming, and food priming with ascorbate. The results showed that the least photosynthesis rate and mesophilic conductance were related to low-input agricultural system; however, in the ecological system, the transpiration, substomatal carbon dioxide, and water use efficiency of photosynthesis were the lowest. Also, seed priming increased the photosynthesis rate, mesophilic conductivity, and water use efficiency of photosynthesis.

Shading Effects on Leaf Gas Exchange, Leaf Pigments and Secondary Metabolites of Polygonum minus Huds., an Aromatic Medicinal Herb

The growing demand for high value aromatic herb Polygonum minus-based products have increased in recent years, for its antioxidant, anticancer, antimicrobial, and anti-inflammatory potentials. Although few reports have indicated the chemical profiles and antioxidative effects of Polygonum minus, no study has been conducted to assess the benefits of micro-environmental manipulation (different shading levels) on the growth, leaf gas exchange and secondary metabolites in Polygonum minus. Therefore, two shading levels (50%:T2 and 70%:T3) and one absolute control (0%:T1) were studied under eight weeks and 16 weeks of exposures on Polygonum minus after two weeks. It was found that P. minus under T2 obtained the highest photosynthesis rate (14.892 µmol CO2 m−2 s−1), followed by T3 = T1. The increase in photosynthesis rate was contributed by the enhancement of the leaf pigments content (chlorophyll a and chlorophyll b). This was shown by the positive significant correlations observed between photosynthesis rate with chlorophyll a (r2 = 0.536; p ≤ 0.05) and chlorophyll b (r2 = 0.540; p ≤ 0.05). As the shading levels and time interval increased, the production of total anthocyanin content (TAC) and antioxidant properties of Ferric Reducing Antioxidant Power (FRAP) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) also increased. The total phenolic content (TPC) and total flavonoid content (TFC) were also significantly enhanced under T2 and T3. The current study suggested that P.minus induce the production of more leaf pigments and secondary metabolites as their special adaptation mechanism under low light condition. Although the biomass was affected under low light, the purpose of conducting the study to boost the bioactive properties in Polygonum minus has been fulfilled by 50% shading under 16 weeks’ exposure.

The CAP Optimisation Hypothesis Provides Improved Formulations for Stomatal Conductance and Photosynthesis in JSBACH

<p>Stomatal conductance formulations are of great importance to how land surface models predict carbon assimilation and transpiration in vegetation. In this study, novel stomatal conductance formulations based on the CAP optimisation hypothesis (Dewar et al. 2018) are implemented in the land surface model JSBACH. Besides new stomatal conductance functions, the CAP framework enables a computational streamlining of the resolution of photosynthesis rate and leaf internal CO<sub>2</sub> concentration.</p><p>The formulations are based on the CAP optimisation hypothesis coupled to different photosynthesis models. Models constructed this way incorporate non-stomatal limitations to photosynthesis through the coupling of carbon assimilation to the soil-to-leaf hydraulic pathway. This entails a direct link from soil water status to stomatal conductance, photosynthesis rate and leaf internal CO<sub>2 </sub>concentration. While this construction does away with the need for some previous fitted or empirical parameters, new parameters are required to represent xylem hydraulic conductance and downregulation of photosynthesis during drought stress.</p><p>These new models are compared to the widely used USO stomatal conductance model (Medlyn et al. 2011). A standalone version of JSBACH is run for single grid cells representing two boreal Scots pine (<em>Pinus sylvestris</em>) dominated sites in Finland (Hyytiälä and Sodankylä). Climate forcing is done with FLUXNET data from 2001 through 2012 and observations are from eddy covariance measurements from the two sites.</p><p>Preliminary results indicate that some of the new formulations give reasonable results. This is very promising, since they are more detailed and theoretically robust than their semi-empirical predecessors, yet streamline the computational process.</p><p>References:<br>Dewar et al. 2018, <em>New Phytol. </em>217: 571–581<br>Medlyn et al. 2011, <em>Glob. Change Biol.</em> 17: 2134–2144</p>

Deep placement of nitrogen fertilizer improves yield, nitrogen use efficiency and economic returns of transplanted fine rice

Rice (Oryza sativa L.) feeds to two-third of the global population by serving as staple food. It is the main export commodity of several countries; thus, contributes towards foreign exchange earnings. Unfortunately, average global rice yield is far below than its genetic potential. Low nitrogen (N) use efficiency (NUE) is among the major reasons for low average yield. Current study evaluated the impact of nitrogen fertilizer application methods (conventional and deep placement) on growth, yield-related traits, chlorophyll contents, photosynthesis rate, agronomic N-use efficiency (ANUE), partial factors productivity of applied N (PFP) and economic returns of two different transplanted rice varieties (Basmati-515 and Super-Basmati). Fertilizer application methods significantly affected allometry, yield-related traits, chlorophyll contents, photosynthesis rate, ANUE, PFP and economic returns. Deep placement of N-fertilizer (DPNF) observed better allometric traits, high chlorophyll contents, photosynthesis rate, ANUE, PFP, yield attributes and economic returns compared to conventional application of N-fertilizer (CANF). Similarly, Basmati-515 had better allometric and yield-related traits, chlorophyll contents, photosynthesis rate, ANUE, PFP and economic returns than Super-Basmati. Regarding interactions among N-fertilizer application methods and rice varieties, Basmati-515 with DPNF resulted in higher chlorophyll contents, photosynthesis rate, ANUE, PFP, allometric and yield related traits and economic returns than CANF. The lowest values of these traits were observed for Super-Basmati with no application of N-fertilizer. Both varieties had better yield and economic returns with DPNF compared to CANF. It is concluded that DPNF improved yield, ANUE and economic returns; therefore, should be opted to improve productivity of transplanted fine rice. Nonetheless, lower nitrogen doses need to be tested for DPNF to infer whether it could lower N use in rice crop.