Elizabeth Bastías

Zea mays L. amylacea from the Lluta Valley (Arica-Chile) tolerates salinity stress when high levels of boron are available

Elevated levels of boron occurring naturally in soil or irrigation waters are detrimental to many crops grown in agricultural regions of the world. If such levels of boron are accompanied by conditions of excessive salinity, as occurs in the Lluta valley in Northern Chile, the consequences can be drastic for crops. A variety of sweet corn from this valley (Zea mays L. amylacea) has arisen as a consequence of practiced seed selection, suggesting that it is extremely tolerant to high salt and boron levels. In the present study, seeds ofZea mays L. amylacea were collected in order to study their physiological mechanisms of tolerance to high levels of NaCl and boron. Concentrations of 100 and 430 mM NaCl and 20 and 40 mg kg−1 boron were imposed as treatments. The plants did not exhibit symptoms of toxicity to either NaCl and boron during the 20 days of treatment. Na+ accumulation was substantial in roots, while boron was translocated to leaves. Boron alleviated the negative effect of salinity on tissue K+ and maintained membrane integrity. The higher values of water potential seem to be related to the capacity of this ecotype to maintain a better relative water content in leaves. Despite the fact that boron enhanced slightly the effect of salinity on CO2 assimilation, no effect on photochemical parameters was observed in this ecotype. Osmotic adjustment allows this ecotype to survive in high saline soils; however the presence of boron makes this strategy unnecessary since boron contributed to the maintenance of cell wall elasticity.

Boric acid and salinity effects on maize roots. Response of aquaporins ZmPIP1 and ZmPIP2, and plasma membrane H+‐ATPase, in relation to water and nutrient uptake

Under saline conditions, an optimal cell water balance, possibly mediated by aquaporins, is important to maintain the whole-plant water status. Furthermore, excessive accumulation of boric acid in the soil solution can be observed in saline soils. In this work, the interaction between salinity and excess boron with respect to the root hydraulic conductance (L(0)), abundance of aquaporins (ZmPIP1 and ZmPIP2), ATPase activity and root sap nutrient content, in the highly boron- and salt-tolerant Zea mays L. cv. amylacea, was evaluated. A downregulation of root ZmPIP1 and ZmPIP2 aquaporin contents were observed in NaCl-treated plants in agreement with the L(0) measurements. However, in the H3BO3-treated plants differences in the ZmPIP1 and ZmPIP2 abundance were observed. The ATPase activity was related directly to the amount of ATPase protein and Na+ concentration in the roots, for which an increase in NaCl- and H3BO3+ NaCl-treated plants was observed with respect to untreated and H3BO3-treated plants. Although nutrient imbalance may result from the effect of salinity or H3BO3 alone, an ameliorative effect was observed when both treatments were applied together. In conclusion, our results suggest that under salt stress, the activity of specific membrane components can be influenced directly by boric acid, regulating the functions of certain aquaporin isoforms and ATPase as possible components of the salinity tolerance mechanism.

Interactions between salinity and boron toxicity in tomato plants involve apoplastic calcium

The lack of consensus about the mutual relations between salinity and boron (B) toxicity with respect to the physiological response of plants necessitates investigation of the interactions of soluble B with salinity. In this investigation, the effect of B was compared with Ca in order to elucidate whether the two nutrients have similar effects and/or to elucidate a relationship under salinity. Following addition of B or Ca, salinity was applied to tomato plants and the cell wall and plasma membrane permeability, measured as water permeability and electrolyte leakage, in relation to amino acid and ion cell wall composition, were determined. As the relationship between B and salinity was complex, several hypotheses are established. The increase of aquaporin functionality due to the presence of B and Ca compared with NaCl-treated plants could be the most feasible, whereas there is currently no satisfactory explanation for the results for the cell wall amino acid composition. In addition, the elemental composition results revealed that, in addition the known interactions between B and Ca with respect to cell wall stability, Mg and Mn were also increased in NaCl+B and NaCl+Ca treatments, suggesting their possible involvement in the cell wall function necessary for plant growth.

Combined effect of boron and salinity on water transport: The role of aquaporins

Boron toxicity is an important disorder that can limit plant growth on soils of arid and semi arid environments throughout the world. Although there are several reports about the combined effect of salinity and boron toxicity on plant growth and yield, there is no consensus about the experimental results. A general antagonistic relationship between boron excess and salinity has been observed, however the mechanisms for this interaction is not clear and several options can be discussed. In addition, there is no information, concerning the interaction between boron toxicity and salinity with respect to water transport and aquaporins function in the plants. We recently documented in the highly boron- and salt-tolerant the ecotype of Zea mays L. amylacea from Lluta valley in Northern Chile that under salt stress, the activity of specific membrane components can be influenced directly by boron, regulating the water uptake and water transport through the functions of certain aquaporin isoforms. Addendum to: Martinez-Ballesta Mdel C, Bastías E, Zhu C, Schäffner AR, González-Moro B, González-Murua C, Carvajal M. Boric acid and salinity effects on maize roots. Response of aquaporins ZmPIP1 and ZmPIP2, and plasma membrane H+-ATPase, in relation to water and nutrient uptake. Physiol Plant 2008; 132:479-90.

Mitigating effect of salicylic acid in the anatomy of the leaf of Zea mays L. lluteño ecotype from the Lluta Valley (Arica-Chile) under NaCl

Se sabe que la aplicacion del acido exogeno salicilico (SA) desempena un papel en la respuesta de las plantas a la salinidad y al estres osmotico. En anos recientes se ha demostrado que el SA aumenta las concentraciones de solutos organicos para la osmorregulacion en las plantas sometidas a estres salino. Por lo tanto, se realizo un experimento para investigar el impacto de factores exogenos como el SA en la morfologia de los tejidos de maiz lluteno. El tratamiento consistio en NaCl y SA (0,1 mM). El estres salino afecta negativamente la anatomia de la hoja, pero mostro un efecto positivo de SA en la composicion de estructuras tales como los vasos del xilema, la anatomia Kranz, celulas mesofilicas, tejidos epidermicos, laminas foliares y el desarrollo del cloroplasto. Tambien aumento el numero de estomas por unidad de area. Finalmente, la presencia de acido salicilico en condiciones salinas tiene efectos favorables sobre la morfologia de maiz lluteno, probablemente contribuyendo a la tolerancia a la salinidad.

CHARACTERIZATION OF THE PHYSIOLOGICAL RESPONSE OF THE HIGHLY-TOLERANT TOMATO CV. ‘PONCHO NEGRO’ TO SALINITY AND EXCESS BORON

The variety of tomato (Solanum lycopersicum) called ‘Poncho Negro’ by farmers represents an important source of genetic resources of agricultural interest, because it has managed to thrive at levels of salinity and excess B that other varieties of the same species find impossible. This work was conducted under controlled growth conditions in a greenhouse, evaluating and obtaining plant material that served for physiological, chemical, and biochemical determinations. Stress conditions were supplied by irrigation, using different concentrations of sodium chloride (NaCl; 75 and 150 mM) and excess boron (B; 5 and 20 mg L−1). The rate of net carbon dioxide (CO2) assimilation, the quantum efficiency of photosynthesis and the relative water content (RWC) were measured. In addition, B, sodium (Na+), potassium (K+), and calcium (Ca2+), soluble sugars, and proline were quantified. The results suggest that ‘Poncho Negro’ accumulated Na+ mainly in the roots, partly limiting its entry into the aerial parts. In addition, it should be noted that the interaction of B and salinity reduced the movement of Na+ to the leaves. The ability of cv. ‘Poncho Negro’ to minimize leaf Na+ accumulation, accumulate more leaf B than control plants, and maintain its K+ level, when grown with an excess of B, possibly allowed the observed increase in the rate of photosynthesis. In addition, these tomato plants used proline and soluble sugars as osmo-regulators under high-B and saline conditions. Under all stress conditions studied, this variety of tomato was able to regulate its water content, with RWC values of approximately 86%.

Long Non-Coding RNAs Responsive to Salt and Boron Stress in the Hyper-Arid Lluteño Maize from Atacama Desert

Long non-coding RNAs (lncRNAs) have been defined as transcripts longer than 200 nucleotides, which lack significant protein coding potential and possess critical roles in diverse cellular processes. Long non-coding RNAs have recently been functionally characterized in plant stress–response mechanisms. In the present study, we perform a comprehensive identification of lncRNAs in response to combined stress induced by salinity and excess of boron in the Lluteño maize, a tolerant maize landrace from Atacama Desert, Chile. We use deep RNA sequencing to identify a set of 48,345 different lncRNAs, of which 28,012 (58.1%) are conserved with other maize (B73, Mo17 or Palomero), with the remaining 41.9% belonging to potentially Lluteño exclusive lncRNA transcripts. According to B73 maize reference genome sequence, most Lluteño lncRNAs correspond to intergenic transcripts. Interestingly, Lluteño lncRNAs presents an unusual overall higher expression compared to protein coding genes under exposure to stressed conditions. In total, we identified 1710 putatively responsive to the combined stressed conditions of salt and boron exposure. We also identified a set of 848 stress responsive potential trans natural antisense transcripts (trans-NAT) lncRNAs, which seems to be regulating genes associated with regulation of transcription, response to stress, response to abiotic stimulus and participating of the nicotianamine metabolic process. Reverse transcription-quantitative PCR (RT-qPCR) experiments were performed in a subset of lncRNAs, validating their existence and expression patterns. Our results suggest that a diverse set of maize lncRNAs from leaves and roots is responsive to combined salt and boron stress, being the first effort to identify lncRNAs from a maize landrace adapted to extreme conditions such as the Atacama Desert. The information generated is a starting point to understand the genomic adaptabilities suffered by this maize to surpass this extremely stressed environment.

Vegetable Waste Compost Used as Substrate in Soilless Culture

One of the main environmental impacts of forced systems in horticulture – such as plastic covers and soilless culture is the generation of organic plant residues and substrate waste. For example, the surface area of greenhouse cultivated crops in the province of Almeria, in southeastern Spain, exceeds 30,000 ha. These generate approximately 1,000,000 tons of solid plant waste per year. Greenhouse industry residues cause serious environmental and visual pollution, making it necessary to look for new ways to eliminate these plant residues. This mass not only acts as a host for pests, microorganisms, rats and insects; it also has other harmful environmental effects such as pollution of the soil by toxic elements, effluent runoff, and the emission of bad smells. Conway (1996) indicated that an important factor for sustainable agriculture in areas using protected systems is the need to eliminate the harvest residues of these crops. Controlled composting appears to be an effective method of eliminating residues by recycling them. For example, Ozores-Hampton et al. (1999) reported that in Florida 1.5 million tons of compost could be produced per year. The wastes generateed by intensive agriculture systems are very varied and frequently cannot be reused directly. Cara and Ribera (1998) indicated that greenhouses generate 29.1 tons of vegetable waste per ha and 6-10 tons of substrate remains per year in the province of Almeria (Spain). A less indiscriminate form of management of these residues, however, could turn them into usable products. This would also reduce their environmental impact. Callejon et al., 2010 indicated that the assessment of the environmental impact of a potential waste treatment plants showed that it would be better to recycle and compost waste than to try to obtain energy from it through combustion. This compost can be used as a soil conditioner or to improve the structure in degraded soils or those with low organic matter content. Another alternative is to reuse these residues, incorporating them as ecologically friendly substrates in soilless cultivation in the form of compost. Using waste materials, most of them locally produced, as soilless growing media has been the subject of an important number of studies, especially as an alternative to peat for ornamental potted plants (e.g., Ingelmo et al., 1997; Offord et al., 1998; Lao and Jimenez, 2004a,b), and less frequently for vegetable production (Shinohara et al., 1999; Ball et al., 2000) and even for tomato transplant production (Ozores-Hampton et al., 1999). However, it

DETERMINACIÓN TAXONÓMICA DE FRAGMENTOS DE MADERA DE CONTEXTO FUNERARIO DE LA CULTURA CHINCHORRO

Los aborigenes costeros del sur peruano y norte de Chile desarrollaron la cultura Chinchorro y alcanzaron su apogeo hacia el 3.000 A.C; se reconocen actualmente como el grupo humano mas antiguo que practico la momificacion artificial. Esta practica consistia en la evisceracion y tratamiento intensivo del cuerpo, reemplazando o reforzando los huesos por armazones de madera a objeto de afirmar el esqueleto. El objetivo del presente trabajo fue otorgar filiacion taxonomica a maderos utilizados en la practica de momificacion y en la confeccion de algunos implementos de pesca y labranza seleccionados del ajuar funerario, sobre la base de la comparacion de caracteres anatomicos de la madera. El material arqueologico utilizado provino de troncos de cuerpos adultos y de un neonato, asi como de implementos de pesca y de labranza como arpones, asa de un chinguillo y mango de herramienta, respectivamente, de los sitios Morro-1 (Mo-1), Maderas Enco (ME), Maestranza Chinchorro (MCh) y Playa Miller 3 (PLM-3), Arica. Para efectos comparativos se construyo una coleccion de referencia con especimenes de doble origen: i). plantas lenosas actuales de valles costeros del extremo norte de Chile, proximos a los sitios arqueologicos estudiados e ii). implementos del ajuar funerario confeccionados en madera y pertenecientes a sitios precolombinos. Los resultados muestran accion antropica en los maderos utilizados como refuerzo de esqueleto; el trabajo previo consistio en eliminar toda la corteza y dejar solo xilema, a diferencia de la madera utilizada en la confeccion de algunos implementos de pesca y labranza, que no presento evidencias de trabajo previo. Schinus molle (pimiento), Anacardiaceae, fue identificada como fuente de madera en la confeccion del asa de un chinguillo (Mo-1) y de un arpon (PLM-3); posiblemente tambien se uso como refuerzo del tronco de un neonato (MCh/C4)

Interactive effects of excess boron and salinity on response curves of gas exchange to increase in the intensity of light of Zea mays amylacea from the Lluta Valley (Arica-Chile)

espanolLos altos niveles de B (boro) acompanados por condiciones de excesiva salinidad, como ocurre en el valle de Lluta en el norte de Chile; cuyas consecuencias pueden ser drasticas para los cultivos. En el presente estudio, semillas de Zea mays L. amylacea fueron sembradas con el fin de estudiar las curvas de respuesta de intercambio gaseoso con el aumento la intensidad de la luz en condiciones de altos niveles de NaCl y B. Las concentraciones fueron de 100 mM NaCl (baja salinidad) o 430 mM NaCl (alta salinidad), o un exceso de B suministrado como acido borico para obtener concentraciones 20 y 40 mg kg-1 B que se aplico en la solucion nutritiva durante 20 dias. Nuestros resultados complementan los estudios anteriores del ecotipo amylacea y confirman el alto grado de tolerancia a la salinidad y al exceso de B. Una alta intensidad luminica intensifica los parametros de intercambio gaseoso como tasa fotosintetica, tasa de transpiracion y la conductancia estomatica que aumenta en forma gradual. La concentracion de CO2 intercelular y la eficiencia del uso del agua (EUA) no mostraron diferencias entre los tratamientos, excepto a alta salinidad. Las plantas que crecen en condiciones de alta salinidad, independiente de la presencia de B, mostraron un alto requerimiento cuantico a altas intensidad de luz. EnglishHigh levels of B (boron) are accompanied by conditions of excessive salinity, as occurs in the Lluta Valley in northern Chile; the consequences can be drastic for crops. In the present study, seeds of Zea mays L. amylacea were grown in order to study the response curves of gas exchange to increase in the intensity of light at high levels of NaCl and B. Concentrations of 100 mM NaCl (low salinity) or 430 mM NaCl (high salinity), or an excess of B supplied as boric acid to obtain 20 and 40 mg kg-1 B were applied in the nutrient solution for 20 days. Our results complement other studies with the amylacea ecotype and confirm the high degree of tolerance to salinity and excess boron. Higher light intensified the gas exchange parameters photosynthetic rate, transpiration rate and CO2 stomatal conductance, which gradually increased. Intercellular CO2 concentration and water-use efficiency (WUE) showed no differences between treatments, except for high leaf CO2 at high salinity. The plants grown under high salt, independent of the presence of B, showed a high quantum requirement at higher light intensities.