Use of selenium to increase antioxidant activity and water use efficiency in arugula (Eruca vesicaria ssp. Sativa) exposed to drought stress

Environmental stress can directly or indirectly affect the formation of reactive oxygen species. Oxidative stress damages cell constituents such as carbohydrates, lipids, nucleic acids and proteins, reducing plant growth, respiration and photosynthesis. In recent decades, evidence has shown that small doses of selenium act as an antioxidant and plant biostimulant, promoting growth and improving resistance to abiotic stress such as drought. As such, the aim of this study was to assess the effect of selenium foliar feeding (0, 150 and 300 ppm) on the antioxidant activity, water use efficiency and yield traits of arugula grown with and without drought stress (50% and 100% ETc) in a protected environment. A randomized block design was used, with a 2x3 factorial scheme and four repetitions. Antioxidant activity increased in treatments with 150 ppm of fertilizer and exposure to drought stress. Plants in these treatments obtained higher water use efficiency, yield and leaf area values than those not submitted to drought stress.

Chitosan Hydrochloride Decreases Fusarium graminearum Growth and Virulence and Boosts Growth, Development and Systemic Acquired Resistance in Two Durum Wheat Genotypes

Fusarium head blight (FHB) is a devastating disease for cereals. FHB is managed by fungicides at anthesis, but their efficacy is variable. Conventional fungicides accumulate in the soil and are dangerous for animal and human health. This study assayed the antifungal ability of chitosan hydrochloride against Fusarium graminearum. Chitosan reduced F. graminearum growth and downregulated the transcript of the major genes involved in the cell growth, respiration, virulence, and trichothecenes biosynthesis. Chitosan promoted the germination rate, the root and coleoptile development, and the nitrogen balance index in two durum wheat genotypes, Marco Aurelio (FHB-susceptible) and DBC480 (FHB-resistant). Chitosan reduced FHB severity when applied on spikes or on the flag leaves. FHB severity in DBC480 was of 6% at 21 dpi after chitosan treatments compared to F. graminearum inoculated control (20%). The elicitor-like property of chitosan was confirmed by the up-regulation of TaPAL, TaPR1 and TaPR2 (around 3-fold). Chitosan decreased the fungal spread and mycotoxins accumulation. This study demonstrated that the non-toxic chitosan is a powerful molecule with the potential to replace the conventional fungicides. The combination of a moderately resistant genotype (DBC480) with a sustainable compound (chitosan) will open new frontiers for the reduction of conventional compounds in agriculture.

Water Use Strategies of Dominant Species (Caragana korshinskii and Reaumuria soongorica) in Natural Shrubs Based on Stable Isotopes in the Loess Hill, China

Water is a key and limiting factor for ecosystem processes (carbon dioxide fixation, vegetation growth, respiration, etc.) and functions (NPP, Net Primary Productivity) in arid and semi-arid areas. As the main regulator, knowledge of plant water use patterns is essential in understanding the SPAC (Soil-Plant-Atmosphere-Continuum) cycle. The tree-planting project in the southern and northern mountains of Lanzhou city aims to improve the ecological environment and promote urban construction. In this study, we analyzed the water use strategies of the dominant plants C. korshinskii and R. soongorica in natural shrubs of southern and northern mountains of Lanzhou city using oxygen stable isotope techniques. The result showed that the flexible water uptake pattern of C. korshinskii and its faster response to precipitation pulse, compared with R. soongorica, might help it to make full use of water and nutrients and adapt to the dry environment. However, R. soongorica progressively switched to suck up deeper soil water and increased the water use proportion from 0.5% to 84.4% as the seasons changed, indicating a greater degree of ecological plasticity. The flexible water use strategies of C. korshinskii and R. soongorica in the same habitat reduced competition for water and nutrients and enhanced adaptability to arid environments. The work presented here provides insights into vegetation restoration and ecological management for the southern and northern mountains of Lanzhou city.

Spatio-temporal variation in NPP and correlation analysis with aerosol loading and PAR in China during 2001-2017

<p>The net primary productivity (NPP) reflects the growth or production of terrestrial vegetation and plays an important role in the carbon cycle on the earth. It quantifies the difference between the organic matter produced by photosynthesis and the loss of maintenance and growth respiration. The investigation of the spatio-temporal variation in NPP is significant for monitoring plant photosynthesis and carbon uptake in terrestrial ecosystems. In this study, the variability and trend of NPP in China during 2001-2017 are analysed using level 4 MODIS product (MOD17A2H). Additionally, to explore whether the NPP change in recent decades are related with the photosynthetically active radiation (PAR) variation caused by increasing aerosol loading, the correlation between NPP, PAR and aerosol optical depth (AOD) are analysed at national, regional, and pixel scales. The results show that the annual mean NPP shows higher values in the southeast than in the northwest. The highest NPP level above 2.5 gCm<sup>-2</sup>day<sup>-1</sup> is mainly distributed in tropical humid regions, including Zhejiang, Fujian, Guangdong and western Yunnan. The NPP increases with an amplitude of 0.131 gCm<sup>-2</sup>day<sup>-1</sup> during the study period. The forests have higher mean levels of NPP (1.808 gCm<sup>-2</sup>day<sup>-1</sup>) and larger increasing magnitudes (0.35 gCm<sup>-2</sup>day<sup>-1</sup>) than those of croplands and grasslands. The NPP and AOD show a negative correlation (-0.6<R<-0.2) at a significance level of 0.05 over the middle area of China. The PAR direct and diffuse components generally have positive (0<R<sub>PARdir_NPP</sub><0.6) and negative correlations (-0.6<R<sub>PARdif_NPP</sub><0) with NPP, respectively, in most of China except the northeast and Tibetan Plateau. The NPP have stronger correlations (0.215 and -0.218) with the direct and diffuse PAR in forests than in croplands and grasslands, implying that NPP is more sensitive to the change in PAR in forests than in other vegetation cover types.</p>

Processes and Precipitates

Biology is about things: organisms, but also about the processes in which they and their parts are involved as participants—reproduction, growth, respiration, hibernation, migration, interaction, selection, adaptation, evolution. The deeper one goes, the more these processes seem to matter—processes such as mitosis, meiosis, catabolism, anabolism, and so on. Yet at each stage we are confronted with the same dichotomy between things and the processes in which they are involved, down to molecules and their reactions. Is it possible to conceptualize a metaphysically superior revisionist biology in which everything basic is processual, without losing touch with the things of standard biological discourse? This chapter argues that it is, by understanding continuant things as precipitates of processes and thus by construing the whole organic sphere as au fond processual.