Expression of the ethylene biosynthetic machinery in maize roots is regulated in response to hypoxia

Ethylene regulates plant growth in response to many adverse environmental conditions, including the induction of aerenchyma, i.e. the formation of air spaces, in flooded roots in an effort to maintain oxygen levels. In this work, quantitative RT-PCR and in situ RNA hybridization were used to determine how the expression of the ethylene biosynthetic machinery in maize roots is spatially and temporally regulated following exposure to 4% oxygen (i.e. hypoxia) for up to 24 h, conditions that induced aerenchyma formation in the fully-expanded region of the root and reduced cytoplasmic density throughout the root. Expression of ACC oxidase, the ethylene forming enzyme, was observed in the root cap, protophloem sieve elements, and companion cells associated with metaphloem sieve elements. Exposure to 4% oxygen induced ACC oxidase expression in these cell types as well as in the root cortex. ACC synthase, which generates the ethylene precursor, was expressed in the root cap and the cortex and its expression was induced in cortical cells following low oxygen treatment. The induction of expression of the ethylene biosynthetic machinery was accompanied by an induction of ethylene evolution and a reduced rate of root growth. These results suggest that maize roots respond to conditions of hypoxia by inducing the spatially restricted expression of the ethylene biosynthetic machinery, resulting in increased ethylene production

Comparative response of Lemnaceae clones to copper(II), chromium(VI), and cadmium(II) toxicity

Vascular plants such as aquatic macrophytes have been used as reference organisms in ecotoxicological assessments of environmental toxicants in aquatic systems for more than two decades (Lewis 1995; Wang and Freemark 1995; Lytle and Lytle 2001). Lemnaceae are the most extensively studied family (Wang 1990; Wang 1992; Mohan and Hosetti 1999) and were incorporated to standardized protocols by environmental protection agencies or organizations (USEPA 1996; Environment Canada 1999; OECD 2000). Lemna gibba and Lemna minor were the selected species among the Lemnaceae family for most of the standarized protocols. A limitation in the selection of these reference species is distribution; L. gibba is widely distributed in South America while L. minor is not found in the Neotropical region (Landolt 1986; Landolt 1996). The search for reference organisms to be used in ecotoxicological testing with bioassays in the Pampean Region of Buenos Aires Province (Argentina) comprises the use of fish, amphibians, crustaceans and algae from surface water bodies (Ronco et al. 2000a). Previous local reports using vascular plants aimed at assessing toxicity with seeds (Sobrero et al. 1996; Ronco et al. 2000b). The present study reports data on the comparative response of a local clone of L. gibba with two collection clones of L. gibba and L. minor to three environmentally relevant toxic metals using laboratory toxicity tests.Instituto de Fisiología Vegeta

Dal fronte della lotta antigradine: ‹cartoline› trentine, 1949-1981

La difesa attiva o “lotta” contro la grandine ha antiche origini e ancora oggi si confonde spesso con credenze popolari. In questo articolo si racconta l’epopea dei razzi esplodenti quale mezzo di “lotta alla grandine” in Trentino e in Italia, una tecnica che iniziò a diffondersi appena dopo la fine della Seconda Guerra mondiale, sotto la spinta delle aspettative, degli entusiasmi contagiosi e di metodi di validazione dal significato (oggi) dubbio, che si avvalevano di conoscenze ancora parziali e non ben consolidate. Nei decenni centrali del secolo scorso i razzi esplodenti furono al centro di uno sforzo “bellico” distribuito in tutta Italia, documentato da relazioni periodiche e da uno speciale registro di ciascun evento meteorologico: le “cartoline dei temporali”. Tali cartoline venivano compilate per ogni evento temporalesco dalla fine del 1800 fino agli anni 1970; in alcuni formati veniva annotato anche l’effetto “osservato” delle misure antigrandine. Agli occhi di chi oggi rilegge le vicende, si evidenzia un disallineamento non chiaro ai protagonisti di allora: le cartoline dovevano servire come banca dati per validare l’efficacia dei razzi esplodenti, ma le basi scientifiche del loro presunto effetto erano già state messe in discussione 50 anni prima.Attraverso la lettura di 1650 cartoline dei temporali, provenienti da 117 località della provincia di Trento, raccolte presso l’archivio meteorologico storico del CREA1, recentemente organizzato nel corso del progetto ASTRO2, si racconta, nella sua cronologia, la diffusione e il successivo abbandono dei razzi esplodenti come mezzo di difesa attiva. L’infondatezza del funzionamento dei razzirisulta evidente anche da alcuni elementi scientifici riportati, che prendono in coinsiderazione anche altre “armi” di lotta alla grandine. In fondo, l’epopea dei razzi esplodenti è la storia di un errore sistematico di valutazione, tutt’oggi diffuso in molti ambiti, noto in psicologia come “bias di conferma”, in cui le persone tendono a selezionare (a vedere solo) gli elementi a favore di una data spiegazione e a screditare i fatti contrari. Ancora oggi, ritornano proposte commerciali di “moderni” mezzi esplodenti contro la grandine di “sicura” efficacia

Influence of aqueous extracts of Johnson grass rhizomes on mycorrhizal colonization and plant growth of Mentha x piperita L.

El objetivo del presente trabajo fue evaluar el efecto de extractos acuosos de rizomas de Sorghum halepense (sorgo de Alepo) sobre la colonización micorrícica, la viabilidad de las estructuras fúngicas, la biomasa total, la conductividad relativa de las membranas celulares y la fotosíntesis de plantas de Mentha x piperita L. Estacas de menta enraizadas inoculadas y no inoculadas con Glomus intraradices B1 o Glomus mosseae crecieron durante 60 días en una mezcla de perlita:vermiculita:arena tindalizada, regadas con solución de Hoagland y con cuatro concentraciones de extracto acuoso de rizomas de sorgo de Alepo S: 0 %, 5 %, 10 %, 15 %. El experimento fue realizado en invernáculo siguiendo un diseño experimental completamente al azar en un factorial 3 x 4. El mayor nivel de colonización micorrícica se presentó en los tratamientos libres de sorgo de Alepo, 87 % y 92 % para G. mosseae y G. intraradices respectivamente, disminuyendo significativamente con la mayor dosis de extracto. La viabilidad de las estructuras fúngicas también disminuyó significativamente. La dependencia micorrícica aumentó un 35 % con la mayor dosis de extracto. Las mayores concentraciones redujeron significativamente la biomasa total y la fotosíntesis neta, aumentando la conductividad relativa de las membranas de hojas y raíces. Las plantas inoculadas mostraron un mejor comportamiento comparadas con las no inoculadas. Los extractos acuosos de sorgo de Alepo disminuyeron el crecimiento de las plantas mientras que la inoculación con hongos micorrícicos morigeró sus efectos adversos.The aim of this work was to evaluate the effects of aqueous extracts of rhizomes of Sorghum halepense on mycorrhizal colonization, succinate dehydrogenase activity, total dry weight, relative conductivity cell membrane and net photosynthesis in Mentha x piperita plants. Rooted cuttings non inoculated or inoculated with Glomus intraradices or Glomus mosseae grown during 60 days into an inert tyndallized substrate, irrigated with Hoagland solution and four concentrations of aqueous extracts of Johnson grass rhizomes: 0 %, 5 %, 10 % and 15 %. The experiment was carried out in a greenhouse, in 3 x 4 factorial arrangement, in completely randomized design. The higher mycorrhizal colonization occur in treatments without Johnson grass, 87 % and 92 % by G. mosseae y G. intraradices respectively, and decreasing significantly with the higher doses of extract. The fungus structures viability decreasing significantly with the higher doses of extract, and the mycorrhizal dependency increased by 35 % with the highest dose of extract. The higher concentrations of extract reduced the total biomass and photosynthesis, and increase the relative conductivity the membranes of leaves and roots. The inoculated plants showed a better performance than non-inoculated. Aqueous extracts of Johnson grass decreased plant growth while inoculation with mycorrhizal fungi reduces adverse effects.Instituto de Fisiología Vegeta

Impact of Cool Materials on Ambient Temperatures in an Urban Area

The urban heat island is a problem that affects our cities and results in a warmer climate in the urban and residential areas compared to the surrounding rural areas. One solution to this problem involves the use of materials with high solar reflectance and high thermal emissivity, the so-called “Cool Materials”. Their surface temperatures are much lower than those of typical building materials. Usually Cool Materials are used to decrease heat flow entering in a building, but if used on an urban scale, their lower surface temperature lead to a lower heat exchange between air and surfaces, helping to decrease the air temperature of the urban environment. The paper reports the results of a study carried out on a densely populated area in Rome of about 500.000 m2. The study was divided into three parts. The first part involves the comparison and the analysis of data collected by weather stations of airports and public agencies located both in urban areas and in peripheral areas in order to monitor the magnitude of the heat island effect. The second part includes measurements of the thermal properties of some Cool asphalts. The third part is focused on numerical analysis of the phenomenon through the creation of a model included in a S.V.A.T. software that allows to compare the outdoor air temperature of an area before and after a hypothetical use of Cool Materials on external surfaces of buildings and street pavements. The results of this study demonstrated the significant influence of cool materials on the reduction of the heat island phenomenon