30,000 years of hydrothermal activity at the lost city vent field

Strontium, carbon, and oxygen isotope data and radiocarbon ages document at least 30,000 years of hydrothermal activity driven by serpentinization reactions at Lost City. Serpentinization beneath this off-axis field is estimated to occur at a minimum rate of 1.2 x 10(-4) cubic kilometers per year. The access of seawater to relatively cool, fresh peridotite, coupled with faulting, volumetric expansion, and mass wasting processes, are crucial to sustain such systems. The amount of heat produced by serpentinization of peridotite massifs, typical of slow and ultraslow spreading environments, has the potential to drive Lost City-type systems for hundreds of thousands, possibly millions, of years.     

Genetic relationships and hybrid vigour in olive (Olea europaea L.) by microsatellites

The olive (Olea europaea) is one of the most important oleaginous crops of the Mediterranean basin. Increased demand for olive oil creates a need for new olive varieties to help meet the requirements of the global market. However, olive breeding has been handicapped by such varied challenges as a prolonged juvenile period, agrotechnical problems and insufficient genetic knowledge. The use of DNA markers has the potential to overcome these problems and increase the effectiveness of classical breeding programmes. In this study, co‐dominant polymorphic simple sequence repeats (SSRs) were used as markers to analyse the genetic relationships between several local and other ‘non‐native’ olive cultivars. Cluster analysis revealed four major groups among the 15 cultivars examined in this study. Table and oil cultivars were clustered in different groups. However, the clusters did not differentiate between cultivars of different geographical origins. In addition, we used the data gathered to analyse genetic relationships to evaluate the effects of heterosis in agricultural traits. Genetic distances between cultivars were determined based on the SSR genotype data and were used for evaluating the possible effects of heterosis in various F₁ populations. Interestingly, phenotypic data of F₁ progenies from crosses between different cultivars indicated the potential effects of heterosis as expressed in several traits. Genetic distance between parents was significantly correlated to F₁ performance for three traits: percentage of dry fruit weight, oil content and commercial oil production. Thus, crosses between olive cultivars exhibiting relatively extensive genetic distances one from the other are expected to result in better progeny performance in future Olea breeding programmes. Our study linked assessment of biodiversity of commercial olive cultivars with the application of this information in olive breeding programmes for selection of specific parents to generate superior new cultivars.     

Addition of a monovalent cationic pesticide to improve efficacy of bipyridyl herbicides in Hulah Valley soils

Bipyridyl herbicides are widely used in agriculture and gardening for non-selective weed control. Since they are toxic and relatively expensive, it is ecologically and economically desirable to reduce the amounts applied. A decrease in efficacy of these herbicides is caused by dust accumulated on leaves of weeds. This inactivation arises from the adsorption of the herbicides on dust particles, mainly made of clay minerals, lime and soil organic matter. In order to improve the efficacy and so lower the amounts applied, formulations were developed which include cationic pesticides approved for agricultural use, such as mepiquat or difenzoquat. Such addition restored the efficacy of the bipyridyl herbicides by reducing their binding to dust particles. The proposed formulations, which were tested on a number of different dust-covered plants, allowed the amounts of herbicide applied to be reduced to 50% of the minimum recommended rate. Neither mepiquat or difenzoquat had any herbicidal activity when sprayed alone at the added rates. The results suggest a procedure that may lower the required rates of contact herbicides, reducing costs and toxicity. This procedure, which can be applied immediately, may have broad implications in farming and gardening.     

Subatmospheric pressure storage of mango fruits

Ripening of mango fruit is markedly delayed when the pressure in the storage chamber is reduced below 100 mm Hg, and fruit storage life is thus prolonged. The prolongation of storage life is inversely related to the pressure; control fruit stored at 760 mm Hg started to ripen after 16 days in storage at 13°C, while fruit stored at 100 and 75 mm Hg after 25 and 35 days, respectively. Fruit stored at 50 mm Hg remained unripe for 35 days. No effect on ripening was recorded at pressures above 250 mm Hg, while at pressures below 50 mm Hg the fruit desiccated. All fruits stored at subatmospheric pressure ripened 3–4 days after transfer to shelf life at 25°C. However, green mango fruits of the colored cultivars like ‘Haden’ and ‘Maya’, stored at subatmospheric pressure for a prolonged period, did not develop the proper red or orange color during shelf-life, but turned pale yellow instead. Treatment with ethylene upon removal from storage slightly improved color development in these fruits.     

Changes in amylase activity,starch and sugars contents in mango fruit pulp

Amylase activity in developing mango fruits increased parallel to the increase in fruit weight. During ripening there was a decrease in starch content and an increase in the reducing and non-reducing sugars. The enzyme preparation which was extracted from acetone powders of mango fruit was inhibited by inhibitors of both α- and β-amylases, and mercapto-ethanol reversed the inhibition by p-hydroxymercuribenzoate. Polyacrylamide gel electrophoresis of the solubilized enzyme has shown only one main band of amylase activity and has indicated the presence of a proteinaceous amylase inhibitor in the fruit pulp. Changes taking place during development and ripening, as well as the nature of the amylolytic activity in mango fruits, are discussed.     

Survival of plant pathogens under structural solarization

Structural solarization of greenhouses is a nonchemical sanitation procedure. The method involves dry heating, since maximal temperatures may exceed 60°C and consequent relative humidity (r.h.) is low (ca 15%), under fluctuating temperature and r.h. regimes. Thirty-five structural solarization experiments were performed over 7 years, testing one bacterial and five fungal plant pathogens. Various aspects of pathogen thermal inactivation under this method were studied. Thermal inactivation of the various pathogens differed according to the organism and inoculum form. Sensitivity to heat was highest withClavibacter michiganensis subsp.michiganensis and lowest withFusarium oxysporum f.sp.radicislycopersici inoculum in dry infected tomato stems, with ED₈₀ values of 7 and 47 days, respectively; intermediate values were obtained forPythium sp.,F. oxysporum f.sp.melonis, F. oxysporum f.sp.basilici andSclerotium rolfsii. The maximal ambient temperatures were in the range of 28.2° to 33.1°C. Structural solarization for sanitation can be a useful component of integrated pest management in greenhouses. http://www.phytoparasitica.org posting Sept. 28, 2004.     

Partial purification and some properties of polyphenol oxidase extracted from litchi fruit pericarp

Litchi (Litchi chinensis Sonn.) fruit peel polyphenol oxidase (PPO) was partially purified 21 fold by ammonium sulfate fractionation and gel filtration. Pyrogallol, catechol, and 4-methylcatechol were good substrates for the enzyme; with no activity observed with chlorogenic acid, p-cresol, resorcinol, or tyrosine. The optimal pH for PPO activity was 7.0 with 4-methylcatechol, with the enzyme being most stable at pH 7.4. The enzyme was relatively temperature stable with maximum activity at 70 °C and requiring a little less than 10 min at 90 °C for 50% loss of activity. The K_m and V_max for the enzyme, with 4-methylcatechol, were 10 mM and 1.47 × 10⁴ units/min per mg protein, respectively. The enzyme was not activated by SDS. Reduced glutathione, -cysteine, tropolone, thiourea, FeSO₄, and SnCl₂ markedly inhibited PPO activity, whereas MnSO₄ and CaCl₂ enhanced PPO activity. Data obtained in this study might help to better understand and control commercially, litchi fruit peel browning.     

A serpentinite-hosted ecosystem: the Lost City hydrothermal field

The serpentinite-hosted Lost City hydrothermal field is a remarkable submarine ecosystem in which geological, chemical, and biological processes are intimately interlinked. Reactions between seawater and upper mantle peridotite produce methane- and hydrogen-rich fluids, with temperatures ranging from <40 degrees to 90 degrees C at pH 9 to 11, and carbonate chimneys 30 to 60 meters tall. A low diversity of microorganisms related to methane-cycling Archaea thrive in the warm porous interiors of the edifices. Macrofaunal communities show a degree of species diversity at least as high as that of black smoker vent sites along the Mid-Atlantic Ridge, but they lack the high biomasses of chemosynthetic organisms that are typical of volcanically driven systems.