Effect of root temperature on carob growth: Nitrate versus ammonium nutrition

The response of carob (Ceratonia siliqua L.) seedlings grown at different root zone temperatures affected by nitrate and ammonium nutrition was studied. When root temperatures ranged from 10 to 35°C, ammonium‐fed plants were significantly larger than nitrate‐fed plants. Ammonium‐fed plants displayed toxicity symptoms and were much smaller at 40°C root temperature in comparison with the nitrate‐fed plants grown at the same root temperature. Root/shoot ratio slightly increase with root temperature in ammonium‐ and nitrate‐fed plants in a similar way, and shoot demand per root unit decreased with root temperature between 15 and 25°C. There was a general increase in net photosynthesis with root temperature, though nitrate‐fed plants were more sensitive to low and ammonium‐fed plants to high temperatures. Increasing the root temperature of ammonium fed plants from 10 to 40°C leads to a 30% increase in the amount of photosynthates sent to the roots. The presence of ammonium resulted in the distribution of newly fixed carbon away from carbohydrates and into nitrogen compounds. Potassium, calcium, and nitrogen content of the plants also increased with increasing root temperature.     

Salinity of nutrient solution influences the shelf-life of fresh-cut lettuce grown in floating system

Quality, microbiological and enzymatic characteristics of fresh-cut lettuce (Lactuca sativa var. longifolia, ‘Duende’), grown in floating system with three electrical conductivities of nutrient solutions (2.8, 3.8 and 4.8 mS cm^?1), were investigated in order to evaluate the effect of salinity on product shelf-life during cold storage (9 d at 4 °C). Pre-harvest salinity of 3.8 and 4.8 mS cm^?1 improved the properties of fresh-cut lettuce, since CO₂ production was reduced with a subsequent control of the decay process. Fresh-cut processing caused an activation of polyphenol oxidase and peroxidase; in all cases the product obtained by salinity treatments was less subject to oxidase activity and browning phenomena during storage. Increased salinity reduced the number of mesophilic bacteria and of moulds and yeasts, assessed by plate counts on different culture media; in contrast, Enterobacteriaceae levels were unaffected by pre-harvest treatments. The research demonstrated that an increase in nutrient solution electrical conductivity, through the use of floating system, affects fresh-cut lettuce characteristics, improving shelf-life of the product.     

Species distribution models applied to plant species selection in forest restoration: are model predictions comparable to expert opinion?

An expert on local flora usually is the best option for plant species selection in most ecological restoration projects; although species selection often needs to be dealt with swiftly as well as on a limited budget, and obtaining the opinion of a local expert may not always be an economically viable alternative. In such cases, species distribution models (SDM) may offer a faster and more cost effective alternative. We asked six experts to rank native tree species according to their suitability at 24 forest sites. The predictive performance of the suitability rankings was evaluated by assessing their ability to discriminate present from absent species in the observed tree assemblages at each evaluation site. We used the area under the receiver operating characteristic curve to calculate the probability that the estimated suitability for a species present at a particular evaluation site is greater than the estimate for an absent species (both picked at random). Suitability rankings were also obtained from the predictions of SDM and the same procedure was used to estimate the predictive performance of the set of models at each site. The experts offered concordant suitability rankings at almost every evaluation site. There were no significant differences in the predictive performance of the SDM and four of the experts, although the SDM performed slightly better than the other two experts. Our results point to the suitability of the proposed species distribution modeling approach to obtain fast and cost effective recommendations for species selection in forest restoration projects.     

Cone beam computed tomography and intraoral radiography for diagnosis of dental abnormalities in dogs and cats

The development of veterinary dentistry has substantially improved the ability to diagnose canine and feline dental abnormalities. Consequently, examinations previously performed only on humans are now available for small animals, thus improving the diagnostic quality. This has increased the need for technical qualification of veterinary professionals and increased technological investments. This study evaluated the use of cone beam computed tomography and intraoral radiography as complementary exams for diagnosing dental abnormalities in dogs and cats. Cone beam computed tomography was provided faster image acquisition with high image quality, was associated with low ionizing radiation levels, enabled image editing, and reduced the exam duration. Our results showed that radiography was an effective method for dental radiographic examination with low cost and fast execution times, and can be performed during surgical procedures.     

Changes in soil properties and humic substances after long‐term amendments with manure and crop residues in dryland farming systems

After 16 years of periodical applications of either farmyard manure or crop wastes at two levels of mineral N fertilization to a Calcic Haploxeralf in the semiarid central Spain, we found significant changes in chemical fertility levels and in the concentration, chemical composition, and carbon mineralization rates of soil organic matter (SOM). The changes in SOM quality were related to significant improvements of soil physical properties, mainly aggregate stability and water retention. Such changes were related to the increased concentration of humic colloids in soil, the mineral N dose, and the type of organic matter applied. When compared with the control plots, the organic matter accumulated in the amended plots tended to be less transformed, and its total concentration and humification degree decreased with increasing external N‐inputs. Humic acids from the amended plots showed a more marked aliphatic character (mainly after N addition) than those from control plots. Farmyard manure led to a significant improvement of soil physical properties, but had a comparatively small effect in promoting biodegradation and humification of crop wastes. This could be due to the high biological stability of the manure used which, in semiarid Mediterranean fields, usually leads to an accumulation of little transformed SOM.     

Establishment techniques affect productivity,nutritive value and atmospheric N2 fixation of two sunn hemp cultivars

Nitrogen fertilization is a common practice for sustaining forage production in forage systems in southeastern United States. Warm-season annual legumes may be an alternative forage to warm-season perennial grasses that do not require N fertilization. Sunn hemp (Crotalaria juncea L.) is a fast-growing, warm-season annual legume native to India and Pakistan. The objective of this 2-year study was to assess the herbage accumulation (HA), atmospheric N₂ fixation (ANF) and nutritive value of sunn hemp. Treatments were the factorial arrangement of two sunn hemp cultivars (“Crescent Sun” and “Blue Leaf”), three seeding rates (17, 28 and 39 kg seed/ha) and seed inoculation (inoculated or non-inoculated seeds), distributed in a randomized complete block design with four replicates. Crescent sun had greater HA (3,218 vs. 1764 kg DM/ha) and ANF (41 vs. 25 kg N/ha). Blue leaf had greater crude protein (CP) (188 vs. 176 g/kg) and in vitro digestible organic matter (IVDOM) concentrations (564 vs. 531 g/kg) than crescent sun. Non-inoculated seed had greater CP than inoculated seed, 188 and 177 g/kg, respectively, and inoculation did not affect HA. Intermediate seeding rate (28 kg/ha) decreased HA (2002 kg DM/ha), while HA from high and low seeding rates (17 and 39 kg/ha, respectively) did not differ (2,863 and 2,615 kg DM/ha respectively). Planting non-inoculated crescent sun at 17 kg/ha seeding rate is a feasible management practice to produce sunn hemp in subtropical regions; however, inoculation should always be recommended for proper establishment.     

Development of cotton pests exhibiting different feeding strategy on water-stressed and kaolin-treated cotton plants

Consistent data demonstrate the positive response of sap-sucking insects to water-stressed plants, but there is a lack of information about the performance of chewing species, including whether their responses vary according to their feeding specializations. We tested the hypothesis that herbivores with distinct feeding strategies and host specialization will respond differently to two plant conditions, i.e. water deficit and kaolin treatment, where the latter is used to reduce abiotic and biotic plant stressors. We determined the development and reproduction of four major cotton pest species with different feeding strategies (chewing and sap sucking) and with specializations ranging from monophagous to polyphagous using well-watered or water-stressed cotton plants, which were treated or not treated with kaolin. Three chewing (lepidopteran) species, Alabama argillacea (Hüb.), Heliothis virescens (Fabr.) and Chrysodeixis includens (Walk), as well as one sap-sucking species, Bemisia tabaci (Gen.), were used as models. The neonate larvae of all three chewing species exhibited lower survival when fed the leaves of water-stressed plants. In addition, the neonate larvae fed leaves from water-stressed and kaolin-treated plants did not complete their development or they exhibited low survival. Older larvae also exhibited significantly lower survival on kaolin-treated plants. The effects on life history traits were more obvious in monophagous chewing species compared with polyphagous species when fed leaves from water-stressed plants. The performance of B. tabaci was superior on water-stressed and untreated kaolin plants. Thus, water-stressed and kaolin-treated plants negatively affected all chewing species, whereas water-stressed plants only positively affected the sap-sucking species.     

Modeling bleaching of tomato derivatives at subzero temperatures

This work was addressed to obtain a predictive model of the rate of bleaching in tomato derivatives at subzero temperatures. To this aim, a tomato puree was freeze-dried and equilibrated at increasing solid fractions. The bleaching rate was assessed by measuring tomato color during storage for up to 18 months at temperatures from -30 to 0 degrees C. The temperature dependence of the tomato-bleaching rate was neither predictable using the Arrhenius equation nor simply related to tomato physical state. The lack of a clear Arrhenius relation was attributed to the occurrence of temperature-dependent phenomena, such as ice crystallization and oxygen solubility modifications, which strongly changed the local concentration of reactants. A modified Arrhenius equation predicting the tomato-bleaching rate in the entire temperature range was proposed. Tomato concentration, and hence its physical state, affected the temperature dependence of bleaching, modifying apparent activation energy and frequency factor of the modified Arrhenius equation. In light of these considerations, a mathematical model was set up and validated to accurately predict the tomato-bleaching rate on the basis of only its concentration and storage temperature.     

Mineral nutrition and adventitious rooting in microcuttings of Eucalyptus globulus

We characterized the adventitious rooting response of Eucalyptus globulus Labill. to various concentrations of calcium, nitrogen, phosphorus, iron, manganese, zinc, boron and copper. The parameters analyzed were percent rooting, root number, root length and mean rooting time. Root number and root length were significantly affected by mineral nutrition, whereas mean rooting time and rooting percentage seemed to be closely related to auxin availability. Root number was affected by calcium, nitrogen source and zinc, whereas root length was influenced by concentrations of phosphorus, iron and manganese, and by nitrogen source. Based on these results, we evaluated various combinations of several concentrations of these minerals in each rooting phase. Cuttings that were rooted in an optimized mineral nutrient medium and acclimatized to ex-vitro conditions for two months showed significantly higher survival after transplanting and drought stress than cuttings rooted in basal medium and treated in the same way.