Water and nutrient uptakes efficiencies in rosemary plants under different fertigation treatments

The aim of this work was to evaluate the effects of different fertigation treatments: T₀ (control treatment), T₁ (raw leachates from C. melo) and T₂ (raw leachates from C. melo blended with tap water (50/50% v/v)) on plant growth, nutrient concentration in leachate and water and nutrient use efficiencies of rosemary. At the end of experiment, rosemary plants fertigated with leachates decreased the total dry weight and the water use efficiency compared to the control treatment. The fertigation with leachates from C. melo affected the values of the nutrient concentrations in leachates from rosemary plants during the experimental period and improved the nitrogen (NUE) and phosphorus (PUE) use efficiencies compared to the control treatment. Our results indicate that reuse of horticultural leachates for the fertigation of rosemary plant in containers assumes a water and nutrient savings, but from an environmental point of view, there is a risk of pollution.     

Silicon,biological seed treatment and cutting reduce the intensity of leaf spot diseases affecting Lolium multiflorum

Italian ryegrass is a major pasture crop cultivated mainly for feeding cattle in southern Brazil. The choice of crop is based on nutritional quality and the shortage of pastures that occur during the winter in the southernmost part of Brazil. In this region, the production of biomass and seeds are threatened by diseases, in particular fungal diseases that affect the foliage. In this study we identified and monitored the natural occurrence of a complex of leaf spotting diseases and evaluated the effects of combined management practices to reduce the intensity of foliar diseases: seed treatment with Trichoderma atroviride, soil amendment with silicon and cutting frequency (none, one or two cuts). Three diseases were present in a two-season experiment: grey leaf spot (Pyricularia oryzae), brown leaf spot (Bipolaris sorokiniana) and parrot's eye leaf spot (Cercospora sp.). Grey leaf spot had the highest severity, regardless of treatment, during the first season, and was the only disease present in the following season. Grey leaf spot dominated, and plants receiving only one cut were more prone to P. oryzae infection. The treatments with silicon or T. atroviride reduced the relative disease by 40% to 80%, in relation to untreated and uncut regimes. This study showed the main leaf spot diseases associated with L. multiflorum. Moreover, it demonstrates for the first time in the region the effectiveness of reducing leaf spot via the application of silicon in the soil, inoculation of seeds with T. atroviride and managing the cutting regime.     

Postharvest treatment of isothiocyanates to control Alternaria rot in netted melon

The fungicidal activity of allyl-isothiocyanate (allyl-ITC), benzyl-isothiocyanate (benzyl-ITC) and a mixture of isothiocyanates (allyl-ITC, benzyl-ITC, phenyl-isothiocyanate and 2-phenylethyl-isothiocyanate; MCIT), was tested in netted melon infected with Alternaria alternata as, was the effect of these compounds on the postharvest quality. Fruits were inoculated with A. alternata and exposed to allyl-ITC, benzyl-ITC, or MCIT, at 0.25 and 0.5 mg ml⁻¹ concentrations. A commercial fungicide, Captan (CF), was used as a positive control. The fruit was stored at 20°C and 92% relative humidity for up to 8 days. Allyl-ITC and MCIT at both tested concentrations, significantly reduced Alternaria rot, by 82.73% to 88.67%. None of the ITC treatments had a significant effect on weight loss, total soluble solids, titratable acidity or pH. Fruits treated with 0.5 mg ml⁻¹ of AITC were more firm than others. Treatment with allyl-ITC, benzyl-ITC, or MCIT appears to be a promising alternative to synthetic fungicides for controlling postharvest diseases in netted melon.     

The effect of Tuber melanosporum Vitt. mycorrhization on growth, nutrition, and water relations of Quercus petraea Liebl., Quercus faginea Lamk., and Pinus halepensis Mill. seedlings

Mycorrhizal and nonmycorrhizal Quercus faginea Lamk., Quercus petraea Liebl., and Pinus halepensis Mill. one-year-old seedlings inoculated with Tuber melanosporum Vitt. have been analyzed with the purpose of studying the influence of mycorrhization on their growth, water relations, and mineral nutrition. The mycorrhization improved Q. petraea and P. halepensis seedling growth. In addition, the mycorrhization created an elastic adjustment in P. halepensis, although it did not cause any osmotic adjustment. Additionally, the mycorrhization increased phosphorus uptake in Q. faginea and P. halepensis, content of all nutrients in P. halepensis, and N content in Q. petraea.     

Ontogenetic changes in stomatal and biochemical limitations to photosynthesis of two co-occurring Mediterranean oaks differing in leaf life span

A quantitative analysis was applied to the stomatal and biochemical limitations to light-saturated net photosynthesis under optimal field conditions in mature trees and seedlings of the co-occurring evergreen oak, Quercus ilex L., and the deciduous oak, Q. faginea Lam. Stomatal limitation to photosynthesis, maximal Rubisco activity and electron transport rate were determined from assimilation versus intercellular leaf carbon dioxide concentration response curves of leaves that were subsequently analyzed for nitrogen (N) concentration, mass per unit area, thickness and percent internal air space. In both species, seedlings had a lower leaf mass per unit area, thickness and leaf N concentration than mature trees. The root system of seedlings during their third year after planting was dominated by a taproot. A lower leaf N concentration of seedlings was associated with lower maximal Rubisco activity and electron transport rate and with assimilation rates similar to or lower than those of mature trees, despite the higher stomatal conductances and potential photosynthetic nitrogen-use efficiencies of seedlings. Consequently, stomatal limitation to photosynthesis increased with tree age in both species. In both seedlings and mature trees, a lower assimilation rate in Q. ilex than in Q. faginea was associated with lower stomatal conductance, N allocation to photosynthetic functions, maximal Rubisco activity and electron transport rate, and potential photosynthetic nitrogen-use efficiency but greater leaf thickness and leaf mass per unit area. Tree-age-related changes differed quantitatively between species, and the characteristics of the two species were more similar in seedlings than in mature trees. Despite higher stomatal conductances, seedlings are more N limited than adult trees, which contributes to lower biochemical efficiency.