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Diaz-Abril D.M.,National University of Colombia | Velez-Sanchez J.E.,National University of Colombia | Rodriguez P.,Instituto Nacional Of Ciencias Agricolas Inca
Agronomia Colombiana | Year: 2016

Plants adopt physiological defense mechanisms to counteract droughts. In Colombia, there is no information for these mechanisms in pears (Pyrus communis L.), cv. Triunfo de Viena. Therefore, the present study aimed to analyze the hydric conditions of this plant in order to determine if it has developed a mechanism to avoid, reduce, or tolerate water stresses as a defense. This experiment used a pear crop located in the municipality of Sesquile (Colombia), with 16-year-old trees that were subjected to three irrigation treatments: a control that received 100% of this crop’s evapotranspiration (100%ETc), and 73%ETc and 53%ETc treatments were irrigated at 73% and 53% of crop’s evapotranspiration, respectively, for the entire rapid fruit growth period of 2012 to 2013.The results indicated that the irrigation reduction in 53%ETc treatment present an adaptive mechanism in the trees, with a structural change in the cellular wall that allowed for 47% water savings in this fruit growth stage. © 2016, Universidad Nacional de Colombia1. All Rights Reserved.

Camejo D.,CSIC - Center of Edafology and Applied Biology of the Segura | Nicolas E.,CSIC - Center of Edafology and Applied Biology of the Segura | Torres W.,Instituto Nacional Of Ciencias Agricolas Inca | Alarcon J.J.,CSIC - Center of Edafology and Applied Biology of the Segura
Journal of Horticultural Science and Biotechnology | Year: 2010

Measurements of leaf stomatal conductance, leaf CO2 assimilation rate, leaf chlorophyll fluorescence, and a previously published biochemical model have been used to evaluate the thermo-tolerance of the photosynthetic apparatus in two tomato genotypes ('Amalia' and 'Nagcarlang'). The study was carried as two experiments. In Experiment 1, a brief (20 min) increase in leaf temperature to 35°C reduced the photosynthetic rate of 'Amalia' leaves grown at 25°C, but stimulated photosynthesis in 'Nagcarlang', due to an increase in the maximum rate of carboxylation of ribulose-1,5-bisphosphate-carboxylase/ oxygenase (VCmax). The heat-sensitive step in 'Amalia' seemed to be the maximum rate of electron transport (Jmax). However, in Experiment 2, there was no significant difference between Jmax at 25°C and 35°C when plants had been acclimatised to these temperatures.

Falcon-Rodriguez A.B.,Instituto Nacional Of Ciencias Agricolas Inca | Costales D.,Instituto Nacional Of Ciencias Agricolas Inca | Cabrera J.C.,Materia Nova | Martinez-Tellez M.T.,Research Center en Alimentacion y Desarrollo
Pesticide Biochemistry and Physiology | Year: 2011

Enzymatic defense responses and protection against Phytophthora nicotianae were studied in tobacco plants treated with chitosan of different molecular weights (MW) and degrees of acetylation (DA). The concentration and mode of chitosan application affected enzymatic induction in tobacco leaves β-1,3-Glucanase (EC activity required 10 times the polymer concentration relative to the oligochitosan mixture to induce the highest activity above control when treated by foliar spray, indicating the influence of molecular weight in this response. PAL (EC and POD (EC activities increased above control as a result of the influence of polymer degree of acetylation when treatments were applied by foliar spray. A higher DA favored PAL activity, whereas a lower DA induced higher POD activity. Using an in vitro bioassay, it was found that the three chitosan compounds caused a reduction of the infection index of P. nicotianae in tobacco plants that was dependent on elicitor concentrations. There was a significant relationship between the reduction of the infection index and an increase in PAL activity when chitosan was applied by foliar spray and by substrate drench to the plant rhizosphere. These results demonstrate the influence of chitosan physico-chemical properties in plant-induced resistance and the relevance of particular responses in plant protection against pathogens. © 2011.

Rodriguez P.,Instituto Nacional Of Ciencias Agricolas Inca | Mellisho C.D.,CSIC - Center of Edafology and Applied Biology of the Segura | Conejero W.,CSIC - Center of Edafology and Applied Biology of the Segura | Cruz Z.N.,Instituto Nacional Of Ciencias Agricolas Inca | And 3 more authors.
Environmental and Experimental Botany | Year: 2012

Adult pomegranate trees (Punica granatum (L.) cv. Mollar de Elche) were submitted to three irrigation treatments. Control (T0) plants were drip irrigated in order to guarantee non-limiting soil water conditions, T1 plants (deficit irrigation) were drip irrigated according to the criteria commonly used by the growers in the area and T2 plants were subjected to water withholding and recovery periods of 34 and 6 days, respectively, during the summer of 2009. The results indicated that pomegranate plants confront water stress by developing stress avoidance and stress tolerance mechanisms. From the time of deficit irrigation (T1) and water withholding (T2) began to be applied, leaf conductance decreased in order to control water loss via transpiration and to avoid leaf turgor loss (stress avoidance mechanism). Close to the end of the stress period, when maximum stress levels had developed, active osmotic adjustment was triggered, contributing to the maintenance of leaf turgor (stress tolerance mechanism). Other drought tolerance characteristics commonly seen in xeromorphic plants were also observed, such as high relative apoplastic water content (42-58%), which would contribute to the retention of water at low leaf water potentials. © 2011 Elsevier B.V.

Galindo A.,CSIC - Center of Edafology and Applied Biology of the Segura | Rodriguez P.,Instituto Nacional Of Ciencias Agricolas Inca | Mellisho C.D.,CSIC - Center of Edafology and Applied Biology of the Segura | Torrecillas E.,CSIC - Center of Edafology and Applied Biology of the Segura | And 5 more authors.
Agricultural and Forest Meteorology | Year: 2013

Measurements obtained by the continuous monitoring of trunk diameter fluctuations were compared with discrete measurements of midday stem water potential (Ψstem) and midday leaf conductance (gl) in adult pomegranate trees (Punica granatum L. cv. Mollar de Elche). Control plants (T0) were irrigated daily above their crop water requirements in order to attain non-limiting soil water conditions in 2009 and 2010, while T1 plants were subjected to water stress by depriving them of irrigation water for 34 days in 2010, after which time irrigation was restored and plant recovery was studied for 7 days. T1 plants showed a substantial degree of water stress, which developed slowly. Maximum daily trunk shrinkage (MDS) was identified to be the most suitable plant-based indicator for irrigation scheduling in adult pomegranate trees, because its signal:noise ((T1/T0):coefficient of variation) ratio was higher than that for Ψstem ((T1/T0):coefficient of variation) and gl ((T0/T1):coefficient of variation). MDS increased in response to water stress, but when the Ψstem fell below -1.67MPa, the MDS values decreased. For non-limiting water conditions, MDS could be predicted from mean daily air temperature (Tm) through exponential equations fitted to pooled data across several seasons. First-order equations were also obtained by pooling data across several seasons to predict MDS from crop reference evapotranspiration (ETo), mean daily air vapour pressure deficit (VPDm), Tm and solar radiation (Rs), but these should be used only within a certain range of values (ETo, 2.1-7.4mm; VPDm, 0.64-2.96kPa; Tm, 12.1-28.3°C; Rs, 119.4-331.3Wm-2). Hence, automated MDS measurements have the potential to be used in irrigation scheduling of pomegranate, and these values can be normalized to non-limiting water conditions by locally derived empirical relationships with meteorological variables. © 2013 Elsevier B.V.

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