Organic matter stabilization in two Andisols of contrasting age under temperate rain forest

Recent studies with Andisols show that the carbon (C) stabilization capacity evolves with soil age relative to the evolution of the mineral phase. However, it is not clear how soil mineralogical changes during pedogenesis are related to the composition of soil organic matter (SOM) and ¹⁴C activity as an indicator for the mean residence time of soil organic matter (SOM). In the present study, we analyzed the contribution of allophane and metal–SOM complexes to soil C stabilization. Soil organic matter was analyzed with solid-state ¹³C nuclear magnetic resonance spectroscopy. Additionally, the soil was extracted with Na-pyrophosphate (Al_p, Fe_p) and oxalate (Al_o, Si_o, and Fe_o). Results supported the hypothesis that allophane plays a key role for SOM stabilization in deep and oldest soil, while SOM stabilization by metal (Al and Fe) complexation is more important in the surface horizons and in younger soils. The metal/C_p ratio (C_p extracted in Na-pyrophosphate), soil pH, and radiocarbon age seemed to be important indicators for formation of SOM–metal complexes or allophane in top- and subsoils of Andisols. Changes in main mineral stabilization agents with soil age do not influence SOM composition. We suggest that the combination of several chemical parameters (Al_p, Fe_p and C_p, metal/C_p ratio, and pH) which change through soil age controls SOM stabilization.     

NUTRITIONAL RESPONSES OF CITRUS ROOTSTOCKS TO SALINITY: PERFORMANCE OF THE NEW HYBRIDS FORNER-ALCAIDE 5 AND FORNER-ALCAIDE 13

This study assesses the nutritional behavior of the new citrus rootstocks Forner-Alcaide no.5 (FA-5) and Forner-Alcaide no.13 (FA-13) under saline conditions compared to that of their parents, Cleopatra mandarin (CM) and Poncirus trifoliata (PT). Eighteen month-old plants grafted with Valencia orange scions were used in the experiment. The plants were grown in a greenhouse and irrigated over an eight-week period with nutrient solutions to which different amounts of sodium chloride (NaCl) had been added, namely 0, 20, 40 and 60 mM. Relative growth and the uptake of major mineral elements [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] were then determined. It was noted that the reduction in relative growth caused by salt treatment was greater in plants grafted on PT than those on FA-13, FA-5 and CM. Increasing the salt level in the growth medium reduced the absorption of the above mineral elements in all scion-rootstock combinations. However, this decrease was generally more marked in plants grafted on PT than in those on CM and FA-5. Plants on FA-13 showed an intermediate behavior. Positive correlations were found between growth and mineral element uptake by salt treated plants. Nutrient uptake was also plotted against chloride (Cl) and sodium (Na) concentrations in leaves and roots at increasing salt levels. This showed that N absorption was closely correlated (inversely) with Cl content in leaves, whereas K, Ca and Mg uptakes were correlated (inversely) with Na concentration in roots. This suggests that the accumulation of saline ions impacts growth and nutrient uptake by citrus plants.     

Managing plant-environment-symbiont interactions to promote plant performance under low temperature stress

Low-temperature stresses, also referred to as cold temperature stresses, including chilling and freezing temperatures, are among the major abiotic stresses that severely reduce plant yield, quality, and marketability and pose a serious threat to plant production during whole plant life cycles. Plant-environment-symbiont interactions determine the symbiotic and crop performance and tolerance to biotic and abiotic stresses. To achieve the optimum outcome, it is essential to consider not only plant-symbiont relationships, but also symbiont adaptation and symbiont-symbiont interactions under changing environmental conditions and different plant growth stages. Improving multi-symbiotic component systems and symbiont breeding together can be a useful strategy to improve symbiosis and, thus, crop production. In this review article, the role of interactions between multi-symbiotic components and plant-environment-symbiont relationships and the related biotechnology approaches are discussed in order to find the most effective sustainable and environmentally friendly agricultural practices to improve crop performance and mitigate the adverse effects of low temperatures on plants.     

Wild rocket – effect of water deficit on growth,flowering, and attractiveness to pollinators

Wild rocket, Diplotaxis tenuifolia (L.) DC. (Brassicaceae), is one of the three cultivated rocket species, the demand and production of which have recently increased in Mediterranean countries where irrigation water is scarce. Besides its use as a crop, D. tenuifolia has been observed to flower for a long period and to be attractive to pollinators. In this study we assessed the effect of drought stress and moderate- and severe-deficit irrigation on growth, flower development, and attractiveness to pollinators in D. tenuifolia. The results showed that in greenhouse conditions, potted D. tenuifolia could be without irrigation for 4 days without affecting its growth, flowering, and attractiveness to pollinators. However, lack of irrigation for 8 days or longer significantly reduced the vegetative growth, number of open flowers, total floral area, flower diameter, corolla tube diameter, and corolla tube length of D. tenuifolia. This study shows that regulated-deficit irrigation can improve water use efficiency, and depending on the purpose of growing D. tenuifolia, as a crop or as a beneficial plant to attract pollinators, it can reduce water consumption from 40% to 70% without affecting its vegetative and floral development and without reducing its attractiveness to pollinators.     

Characterization of Rhizoctonia Species Associated with Foliar Necrosis and Leaf Scorch of Clonally-propagated Eucalyptus in Brazil

The objective was to identify and characterize the causal agent of foliar necrosis and leaf scorch of Eucalyptus spp. in Brazil. Nineteen putative isolates of Rhizoctonia obtained from Eucalyptus plants during clonal propagation were compared with isolates from other hosts and with tester strains of anastomosis groups of Rhizoctonia solani. Features compared were morphological characteristics of anamorphs and teleomorphs, numbers of nuclei per cell in the vegetative hyphae, anastomosis of hyphae, and ability to produce necrotic lesions on cuttings and damping-off of E. grandis×E. urophylla hybrid seedlings. Rhizoctonia solani AG1 (AG1-IB like) was the most frequent causal agent isolated from Eucalyptus plants and cuttings with symptoms of leaf scorch and foliar necrosis respectively. These isolates were highly virulent on Eucalyptus cuttings and presented naturally epiphytic growth on Eucalyptus shoots. Binucleate isolates and isolates of R. solani AG4 were also virulent on cuttings and were most virulent on Eucalyptus seedlings causing pre- and post-emergence damping-off. Virulence on Eucalyptus cuttings and seedlings was not restricted to a single species or anastomosis group of Rhizoctonia.     

An Aboriginal Australian genome reveals separate human dispersals into Asia

We present an Aboriginal Australian genomic sequence obtained from a 100-year-old lock of hair donated by an Aboriginal man from southern Western Australia in the early 20th century. We detect no evidence of European admixture and estimate contamination levels to be below 0.5%. We show that Aboriginal Australians are descendants of an early human dispersal into eastern Asia, possibly 62,000 to 75,000 years ago. This dispersal is separate from the one that gave rise to modern Asians 25,000 to 38,000 years ago. We also find evidence of gene flow between populations of the two dispersal waves prior to the divergence of Native Americans from modern Asian ancestors. Our findings support the hypothesis that present-day Aboriginal Australians descend from the earliest humans to occupy Australia, likely representing one of the oldest continuous populations outside Africa.     

Evolution of Portuguese community forests and their governance based on new institutional economics

Forest governance is under reorganisation in many European countries, because of the changes in property and forest tenure rights. Portuguese community-based forestry is an interesting research subject from a New Institutional Economics perspective. Community forests (an important part of community lands known as baldios) cover half a million hectares in the north and the centre of the country and are owned by local communities. Their average size of over 400 hectares and diversity of resources underscore their value, and their management contributes to rural development. Recent laws intend for the complete transfer of their tenure rights to communities and local authorities. In this study, we analysed the transformational processes of Portuguese community-based forestry. To structure this analysis and shed light on forest management-related problems, we followed the 'four-level institutional analysis' developed by Williamson. Particular attention was paid to the first three levels. The first concerned social practice and informal rules. We are describing the history of baldios, their use by rural populations, and the subsequent occupation by the State for afforestation. The second level addressed the institutional environment and formal rules. Here, we focused on the recognition of baldio community properties and their legal framework development. The third level addressed management and the interaction of actors in transaction cost savings. Here, we examined the current community-based management models and future trends. In our analysis, we identified the causes underlying baldio management problems at different levels, which highlight the importance of new governance models and economic activities. The analysis showed that overall, the Portuguese community forest governance is a flexible structure capable of adapting to political and demographic changes and offering valuable support for the development of rural areas in the north and centre of the country. Additional empirical research is needed to improve knowledge on the impact of institutions on the management of community forests, both nationally and internationally.

     

Sulfated-polysaccharide fraction from red algae Gracilaria caudata protects mice gut against ethanol-induced damage

The aim of the present study was to investigate the gastroprotective activity of a sulfated-polysaccharide (PLS) fraction extracted from the marine red algae Gracilaria caudata and the mechanism underlying the gastroprotective activity. Male Swiss mice were treated with PLS (3, 10, 30 and 90 mg·kg(-1), p.o.), and after 30 min, they were administered 50% ethanol (0.5 mL/25 g(-1), p.o.). One hour later, gastric damage was measured using a planimeter. Samples of the stomach tissue were also obtained for histopathological assessment and for assays of glutathione (GSH) and malondialdehyde (MDA). Other groups were pretreated with l-NAME (10 mg·kg(-1), i.p.), dl-propargylglycine (PAG, 50 mg·kg(-1), p.o.) or glibenclamide (5 mg·kg(-1), i.p.). After 1 h, PLS (30 mg·kg(-1), p.o.) was administered. After 30 min, ethanol 50% was administered (0.5 mL/25 g(-1), p.o.), followed by sacrifice after 60 min. PLS prevented-ethanol-induced macroscopic and microscopic gastric injury in a dose-dependent manner. However, treatment with l-NAME or glibenclamide reversed this gastroprotective effect. Administration of propargylglycine did not influence the effect of PLS. Our results suggest that PLS has a protective effect against ethanol-induced gastric damage in mice via activation of the NO/K(ATP) pathway.     

Partial purification and immobilization/stabilization on highly activated glyoxyl-agarose supports of different proteases from flavourzyme

The fractioning of some components and their immobilization of Flavourzyme, a commercial protease/aminopeptidase preparation, has been investigated to improve its specificity and stability. Adsorption of Flavourzyme on two ionic exchangers yielded two fractions with endoprotease activity and one fraction containing aminopeptidase activity. The use of an amine agarose gel has made it possible to purify a 43 kDa protein with only endoprotease activity. Immobilization of this endoprotease and the original Flavourzyme preparation onto glyoxyl-agarose provided derivatives that were more thermostable than their soluble counterparts. Tests using immobilized Flavourzyme and immobilized purified endoprotease for the hydrolysis of chickpea proteins showed that both preparations can be used for the production of protein hydrolysates and compare very favorably with the original crude Flavourzyme in terms of reducing the production of free amino acids. This was especially so in the case of immobilized endoprotease, which produced only 0.2% free amino acids. Keeping free amino acids content low is very important in protein hydrolysates for nutritional use to avoid excessive osmotic pressure.