Physiological and biochemical effects of Lantana camara L. allelochemicals on the seed germination of Avena sativa L.

ABSTRACT Lantana camara (L.) is considered one of the main weeds of agricultural crops, and allelochemicals produced by this species may be a source for the development of natural herbicides. In this study, phytotoxic effects of L. camara aqueous extracts on seed germination and seedling growth of Avena sativa (L.) were assessed. The experimental design was completely randomized, in a 2 x 5 factorial scheme, with treatments resulting from two assays, testing five concentrations of the extract (0 %, 2.5 %, 5.0 %, 7.5 % and 10 %; vv-1). During the seed germination, physiological (e.g., seed imbibition, germination and vigor) and biochemical (e.g., catalase, ascorbate peroxidase, proline, phenols, malondialdehyde and hydrogen peroxide) proprieties were evaluated. The leaf extracts of L. camara affected the response variables on A. sativa by reducing the germination speed index (phases I and II) and seed viability (phase III of germination), thus causing a solute leakage and increasing the production of reactive oxygen forms and, finally, lipid peroxidation. Extract concentrations above 2.5 % inhibit the growth of epicotyls. Therefore, the studied allelochemicals showed potential to be exploited in the development of natural herbicides.

Development and maturation of mango fruits cv. ‘Ubá’ in Visconde do Rio Branco, Minas Gerais State, Brazil

ABSTRACT Several criteria have been used to determine fruit maturity, which are based on the appearance and chemical composition of the produce at harvest time. The objective of this study was to evaluate the physical, chemical and physiological changes that occur during the development of mango cv. ‘Ubá’, aiming to determine the stages of fruit development until complete maturation. The experiment was carried out in an approximately 30-year-old orchard in Visconde do Rio Branco, MG (21º00'37"S, 42º50'26"W and 352 m altitude). Weekly, 25 fruits of 15 hoses were collected from the anthesis to the complete maturation in the plant. Samplings took place from August 2007 to January 2008. The characteristics evaluated were length, smaller and larger diameter; CO2 production; color parameters L*, a*, and b* of skin and pulp; fresh and dry mass (fruit, skin, pulp, and seed); solute leakage; pulp firmness; soluble solids (SS); titratable acidity (TA); SS/TA ratio; Vitamin C; carotenoids, starch, and soluble sugars. The development of mango fruit cv. ‘Ubá’ took 23 weeks. The developmental pattern fit a simple sigmoidal model. Fruits attached to the plant reached the respiratory climacteric stage between 20 and 21 weeks after anthesis.

Solid Matrix Priming Treatment with O2 Enhanced Quality of Leek Seed Lots

This study aims to determine the effect of solid matrix priming (SMP) treatment with an air composition of O2, N2, air, vacuum on four leek (Allium ampeloprasum L.) seed lots of various ages, in terms of enhancing germination, mean germination time, electrical conductivity of solute leakage and catalase activity. Untreated seeds were used as control. Solid matrix priming at a seed: vermiculite: water ratio of 2.5:1.25:3.75 (w/w/w) was applied at 20 °C for 24 hours in the dark. Solid matrix priming with O2 was found to give the highest germination, lowest mean germination time, lowest electrical conductivity (reduced solute leakage) and the highest catalase activity among all treatments and lots. SMP treatment with air provided positive response, while N2 and vacuum treatments were found to be less effective. The advantages of solid matrix priming were more pronounced in lower quality lot than in the higher quality ones. The results indicated that oxygen enrichment in SMP may enhance leek seed quality.

ASSESSING THE FORWARD OSMOSIS PERFORMANCES USING CTA MEMBRANE: EFFECT OF SOLUTION VOLUME RATIO AND TYPE OF DRAW SOLUTE

Osmotically-driven forward osmosis (FO) has gained significant attention in the last decade due to its potential application in various disciplines. Draw solution serves as the driving force in FO process for inducing water transport across the membrane. FO technology can be used to reject or concentrate high valuable products in the chemical and bioprocess industries which often encounter great challenge in terms of dilute product formation. In this study, commercial cellulose triacetate (CTA) flat sheet FO membrane was investigated using several types of inorganic draw solute. Pure water fluxes ranged from 5.20 to 6.30 L.m-2.h-1 were achieved for selected draw solutes. The reverse solute leakage was shown by the increment of conductivity in the feed solution. Among the draw solutes, NaCl demonstrated highest reverse solute leakage (72.45 µS cm-1) attributed to its relatively smaller molecular size. The water fluxes at feed to draw solution volume ratios of 1:2 and 1:3 were found to be slightly lower than that to the volume ratios of 1:0.6 and 1:1. With respect to sodium succinate feed solution, MgCl2 was capable of generating higher osmotic pressure and thus higher water flux was observed compared to NaCl draw solute. Overall, the selected inorganic draw solutes demonstrated encouraging FO performances and could be used for concentrating sodium succinate solution.

Succinate Functionalization of Hyperbranched Polyglycerol-Coated Magnetic Nanoparticles as a Draw Solute During Forward Osmosis

Hyperbranched polyglycerol-coated magnetic nanoparticles (SHPG-MNPs) were functionalized with succinate groups to form a draw solute for use in a forward osmosis (FO). After the one-step synthesis of hyperbranched polyglycerol-coated magnetic nanoparticles (HPG-MNPs), the polyglycerol groups on the surfaces of the HPG-MNPs were functionalized with succinic anhydride moieties. The resulting SHPG-MNPs showed no change of size and magnetic property compared with HPGMNPs and displayed excellent dispersibility in water up to the concentration of 400 g/L. SHPG-MNPs solution showed higher osmotic pressure than that of HPG-MNPs solution due to the presence of surface carboxyl groups in SHPG-MNPs and could draw water from a feed solution across an FO membrane without any reverse draw solute leakage during FO process. Moreover, the water flux remained nearly constant over several SHPG-MNP darw solute regeneration cycles applied to the ultrafiltration (UF) process. The SHPG-MNPs demonstrate strong potential for use as a draw solute in FO processes.

Recalcitrant and orthodoxSpartinaseeds or isolated embryos exhibit similar leachate patterns immediately following desiccation

Solute leakage is used as an indicator of membrane damage during desiccation of recalcitrant seeds. We re-examined this phenomenon and its utility by comparing recalcitrantSpartina alternifloraand orthodoxSpartina pectinataseeds, as well as drying isolated embryos or embryos isolated after whole-seed drying. During drying, intact seed leakage (electrical conductivity and absorbance at 280 nm) was independent of seed moisture content, dormant/non-dormant state or desiccation tolerance. Embryos from bothSpartinaspecies, isolated after drying within the intact seed, exhibited increased leakage, especially below 40% (dry weight basis, DWB) seed moisture, the critical water content for viability loss inSpartina alterniflora. When isolated embryos were dried, the pattern and extent of increased solute leakage were similar in bothSpartinaspecies, even thoughS. pectinataembryos were >95% viable andS. alternifloraembryos were < 20% viable. We conclude that increased solute leakage is an artefact of embryo excision and not an accurate indicator of desiccation damage to recalcitrantSpartina alternifloraseeds.

EDTA: a synthetic draw solute for forward osmosis

The draw solution is the driving force of the forward osmosis (FO) process; however, the solute loss of the draw solute to the feed side is a general, financial limitation for most applications. The anthropogenic amino acid ethylenediaminetetraacetic acid (EDTA) was investigated as a draw solution for FO. At concentrations of approximately 1.0 osmol/kg, EDTA demonstrated comparable water fluxes (Jv = 5.29 L/m2 h) to the commonly used salt, NaCl (Jv = 4.86 L/m2 h), and both produced better water fluxes than glucose (Jv = 3.46 L/m2 h). EDTA showed the lowest solute loss with Js (reverse solute loss or solute leakage) = 0.54 g/m2 h. The molecular weight, degree of ionisation and charge of EDTA played a major role in this efficiency and EDTA was therefore well rejected by the membrane, showing a low Js/Jv ratio of 0.10 g/L. Owing to the low solute loss of EDTA and its resistance to biodegradation, this compound has the potential to be used as a draw solute for FO during long periods without requiring much replenishment.

Oscillatory phase separation in giant lipid vesicles induced by transmembrane osmotic differentials

Giant lipid vesicles are closed compartments consisting of semi-permeable shells, which isolate femto- to pico-liter quantities of aqueous core from the bulk. Although water permeates readily across vesicular walls, passive permeation of solutes is hindered. In this study, we show that, when subject to a hypotonic bath, giant vesicles consisting of phase separating lipid mixtures undergo osmotic relaxation exhibiting damped oscillations in phase behavior, which is synchronized with swell–burst lytic cycles: in the swelled state, osmotic pressure and elevated membrane tension due to the influx of water promote domain formation. During bursting, solute leakage through transient pores relaxes the pressure and tension, replacing the domain texture by a uniform one. This isothermal phase transition—resulting from a well-coordinated sequence of mechanochemical events—suggests a complex emergent behavior allowing synthetic vesicles produced from simple components, namely, water, osmolytes, and lipids to sense and regulate their micro-environment.

The effect of desiccation on viability and membrane lipid composition of Acer pseudoplatanus seeds

The viability of desiccation-intolerant sycamore (<em>Acer pseudoplatanus</em> L.) seeds during desiccation was investigated by tetrazolium and by a germinability test, together with membrane permeability and membrane phospholipid composition. Loss of viability was associated with an increase of solute leakage, reduced content of all phospholipid groups, decrease of unsaturated fatty acids and the unsaturated/saturated fatty acids ratio. Growth of malondialdehyde content was also observed. Some results were compared with those for tolerant to desiccation Norway maple (<em>Acer platanoides</em> L.) seeds. The results indicate active participation of membranes in the desiccation process in tolerant seeds and their decomposition in intolerant ones. The destruction of membranes was the result of lipid peroxidation, probably due to the free radical effect.

Citronellol Disrupts Membrane Integrity by Inducing Free Radical Generation

Citronellol, an oxygenated monoterpene, is found naturally in the essential oils of several aromatic plants and has been reported to exhibit growth inhibitory and pesticidal activities. However, its mechanism of action is largely unexplored. We investigated the effect of citronellol, which is lipophilic in nature on membrane integrity in terms of lipid peroxidation, conjugated dienes content, membrane permeability, cell death, and activity of the enzyme lipoxygenase in roots of hydroponically grown wheat. Citronellol (50 - 250 μM) caused a significant inhibition of root and shoot growth. Furthermore, exposure to citronellol enhanced the solute leakage, increased the malondialdehyde content and lipoxygenase activity, and decreased the conjugated diene content. This indicates that citronellol induces generation of reactive oxygen species (ROS) resulting in lipid peroxidation and membrane damage. This was confirmed by in situ histochemical studies indicating cell death and disruption of membrane integrity. We conclude from this study that citronellol inhibits the root growth by ROS-mediated membrane disruption.