Evaluation of Quality Factors in Argentine Maize Races

Samples of Argentine maize from 12 landraces were analyzed for starch and amylose content and were evaluated for hardness parameters. Amylose contents of these Argentine landraces were generally higher than for typical dent hybrids grown in the United States. Hardness, as estimated by near‐infrared reflectance; from wavelength shift of the near‐infrared transmittance spectrum absorbance maximum (λ_max) in the 610–680 nm region; and by percentage of γ‐zein in zein‐2 (determined by reversed‐phase HPLC), correlated well with classical definitions of endosperm type and with amylose content. Starch content correlated negatively with hardness. Flint landraces varied substantially in amylose and starch content. The strong correlation between amylose content and maize endosperm hardness confirms and strengthens previous observations, and may provide a compositional basis for endosperm quality.     

Developing new herbicide models from allelochemicals

Plants contain allelochemicals which are their own defence systems and can act as herbicides. Selected examples of guaianolides and heliannuols, which are sesquiterpenes, are discussed in the context of their potential use as natural herbicide templates.     

Water stress effects on growth, development and yield of opium poppy (Papaver somniferum L.)

The effects of pre-anthesis water deficit and cycle length were examined in Papaver somniferum L., cultivated for alkaloid production, in two locations in southern Spain. The vegetative period was shortened by extending the photoperiod through supplemental lighting in the field, while water deficit in pre-anthesis was induced by avoiding irrigations and installing rain shelters. The treatments were: IN (irrigated-normal photoperiod), IL (irrigated-hastened flowering), DN (water deficit in pre-anthesis-normal photoperiod) and DL (water deficit in pre-anthesis and hastened flowering). The artificial photoperiod hastened the flowering by 15 and 21 days, for irrigated and deficit treatments respectively. Seasonal evapotranspiration (ET) ranged from 398 (DN) to 505 mm (IN). There was evidence of root water uptake deeper than 1.5 m. Stomatal conductance was reduced (16%) during water stress, and did not recover in post-anthesis after resuming irrigation. Head yields (capsule + seeds + 7 cm stem) ranged between 3.8 and 4.3 t ha⁻¹; water deficit and short vegetative period both reduced the biomass accumulated, although the effect on yields in these treatments was counterbalanced by a higher harvest index. Early flowering had a detrimental effect on alkaloid concentration in the capsule. Alkaloids yield ranged between 27 and 37 kg ha⁻¹. Water use efficiency (WUE) ranged between 0.78 and 0.96 kg m⁻³ ET for yield and between 63.4 and 73.7 g m⁻³ ET for alkaloids. Water stress increased slightly the Water Use Efficiency. A shorter vegetative phase had no effect on WUE for biomass or yield, but decreased the WUE for alkaloids production.     

Chemical constituents of Tolpis species

Phytochemical research of two Tolpis species, T. webbii and T. sp., led to the isolation of three new compounds: 2,4′-dihydroxy-4-methoxybenzophenone (1) and the triterpenes 21α, 22α-epoxy-20α-hydroxy-20(30)-dihydrotaraxasterol (2) and 3β-hydroxytaraxaster-20-en-30-oic acid (3) together with 16 known compounds. The structures of the new compounds were elucidated by means of extensive IR, NMR, MS and X-ray analysis and by comparison of data reported in the literature.     

The influences of forest stand management on biotic and abiotic risks of damage

? This article synthesizes and reviews the available information on the effects of forestry practices on the occurrence of biotic and abiotic hazards, as well as on stand susceptibility to these damaging agents, concentrating on mammal herbivores, pest insects, pathogenic fungi, wind and fire.

? The management operations examined are site selection, site preparation, stand composition, regeneration method, cleaning and weed control, thinning and pruning, and harvesting. For each of these operations we have examined how they influence the occurrence of biotic and abiotic damaging agents, the susceptibility of European forests, and describe the ecological processes that may explain these influences.

? Overall, we find that the silvicultural operations that have the largest influence on both biotic and abiotic risks to European forest stands are closely related to species composition and the structure of the overstorey. Four main processes that drive the causal relationships between stand management and susceptibility have been identified: effect on local microclimate, provision of fuel and resources to biotic and abiotic hazards, enhancement of biological control by natural enemies and changes in individual tree physiology and development.

? The review demonstrates an opportunity to develop silvicultural methods that achieve forest management objectives at the same time as minimising biotic and abiotic risks.

     

Soybean inoculation: Dose, N fertilizer supplementation and rhizobia persistence in soil

The effect of rate of application of Sinorhizobium (Ensifer) fredii SMH12 or Bradyrhizobium japonicum USDA110 inoculants on grain yields of soybean [Glycine max (L.) Merrill] cv. Osumi was studied in a field experiment laid out in Southern Spain. All inoculant doses tested (10⁴, 10⁵, 10⁶ and 10⁷ rhizobia/seed) produced higher seed yields than those obtained in un-inoculated plots. Increments in nodule dry weight, seed yield and seed N content were observed when the number of rhizobia applied to seed increased from 10⁴ up to 10⁷. The addition of N fertilizer to inoculated soybean plants (50 kg N/ha applied at R1 or R4 stage) did not increase seed yields in comparison with treatments that were only inoculated. Survival of strains SMH12 and USDA110 was monitorized for three years in two different soils of Southern Spain after soybean inoculation. Rhizobia survival was varied dependent on the soil and the rhizobia strain used.     

Partial characterization of alkaline proteases from viscera of vermiculated sailfin catfish Pterygoplichthys disjunctivus Weber, 1991

Vermiculated sailfin catfish (Pterygoplichthys disjunctivus, Weber, 1991), a member of the Loricariidae family and an invasive species of several inland waters around the world, possess an enormous digestive tract representing about 10% of fish weight. Thus, the aim of this study was to partially characterize proteases from their digestive tracts. Azocasein digestion of the crude extract of intestine at different pH values and temperatures revealed the presence of alkaline proteases with optimum activities at pH 9.0 and 50°C. Incubation assays of the crude extract with inhibitors such as phenyl methyl sulfonyl fluoride, N-α-p-tosyl-l-lysine chloromethyl ketone, N-tosyl-phenyalanine chloromethyl ketone, benzamidine, pepstatin A and ethylenediamine tetra-acetic acid showed that trypsin and chymotrypsin are the main alkaline proteinases present. Zymography showed that the crude extract of Pterygoplichthys disjunctivus viscera contained proteases with molecular masses ranging from 21.5 to 116 kDa. Trypsin and chymotrypsin were inhibited by the following ions in decreasing order: Hg²⁺, Fe²⁺, Cu²⁺, Li⁺, Mg²⁺, K⁺, while Mn²⁺, and Ca²⁺ had no effect. Activities decreased continuously as the NaCl concentration increased from 0 to 30%. These results constitute important background information for future studies and for the potential biotechnological use of the crude digestive extract from this invasive species.     

Fish-farming water quality and environmental concerns in Argentina: a regional approach

In spite of the steady increase in fish farming in Argentina, studies on water quality are scarce. Eight fish farms from two different regions in the northeast and east of Argentina were studied to explore source and effluent water quality. Ammonium (NH₄ ⁺), nitrate (NO₃ ⁻), and nitrite (NO₂ ⁻) levels were measured. High nitrate concentrations in water source were observed in the eastern region farms. An increase in NH₄ ⁺, NO₃ ⁻, and NO₂ ⁻ in effluent water was determined in most of the sampled farms. Heavy metals (i.e., cadmium, chromium, copper, iron, manganese, nickel, and zinc) and arsenic concentrations were analyzed. Heavy metal concentrations were below the detection limit in the northern region. However, As was detected in the water source of five farms and was over the recommended limit (100 μgl⁻¹) for aquaculture in one. An increase in Mn and Zn concentrations in effluent water was observed in two farms. The lack of treatment of the effluent water in these farms leads to an increase of nutrients and heavy metal concentrations in the surrounding areas. Environmental effects of fish-farming practices in Argentina are discussed.     

Rootstock influences the response of pistachio (Pistacia vera L. cv. Kerman) to water stress and rehydration

Pistachio cultivation requires the use of rootstock because grafting is the only form of vegetative propagation. The main commercial rootstocks are Pistacia integerrima L., Pistacia atlantica Desf., Pistacia terebinthus L. and Pistacia vera L. Pistachio is considered to be a drought and saline-resistant crop; however, there is little information describing varietal responses of rootstocks to water stress. Some studies have suggested that P. terebinthus L. is the most drought and cold resistant rootstock. The effect of the rootstock on the water relations of the grafted plant is crucial for improving crop performance under water stress conditions and for developing the best irrigation strategy. This work studied the physiological response to water stress of pistachio plants (P. vera L. cv. Kerman) grafted onto three different rootstocks P. terebinthus L., P. atlantica Desf. and a hybrid from crossbreeding P. atlantica Desf. × P. vera L. Plant physiological responses were evaluated during a cycle of drought and subsequent recovery in potted plants. Parameters measured were soil moisture, trunk diameter, leaf area, leaf number, leaf and stem dry weight, stem water potential, leaf stomatal conductance. The results showed different responses of cv. Kerman depending on the rootstock onto which it had been grafted. The hybrid rootstock was associated with a higher degree of stomatal control and reduced leaf senescence compared to P. atlantica and P. terebinthus, despite being associated with the most vigorous shoot growth. P. terebinthus enabled very effective stomatal control but was also associated with the most rapid leaf senescence. P. atlantica was associated with less vigorous shoot growth and similar levels of water stress as occurred with the others rootstocks under conditions of high evaporative demand, which was associated with lower stomatal control. The selection of the most effective rootstock choice for different environmental conditions is discussed.