Physiological mechanisms involved in the recovery of euonymus and laurustinus subjected to saline waters

The scarcity of water has frequently led to saline water being reused for the irrigation of ornamental shrubs. However, before the use of such waters can be expanded, the salt tolerance and other characteristics of the ornamentals involved, need to be considered along with their capacity to recover after salinity exposure. For this reason, Euonymus japonica (euonymus) and Viburnum tinus (laurustinus) plants were submitted for twenty weeks to three irrigation treatments applied at 100% water holding capacity: Control (EC<0.9dSm-1); NaCl solution, NaCl (EC: 4dSm-1); and wastewater, WW (EC: 4dSm-1). This was followed by a recovery period of eight weeks, when all the plants were watered in the control irrigation conditions. The results showed that biomass, leaf number and total leaf area of plants subjected to the saline treatments were lower than in the control at the end of both periods in both species. However, after recovery, only euonymus showed lower growth parameters than those observed in the saline period. The highest Na+ and Cl- concentrations were observed in saline plants at the end of saline period for both species, and were higher in shoots than in roots. The opposite was observed for the K+/Na+ and the Ca2+/Na+ ratios. In Laurustinus, the Ψstem did not diminish in the wastewater-irrigated plants with respect to the control, maintaining osmotic adjustment and a high Ψt, even after recovery, whereas in euonymus this did not occur at the end of recovery period. In both species the Pn and gs were similarly reduced during the saline exposure period. However, the recovery of gas exchange in laurustinus irrigated with wastewater might be closely related to the better water status of these plants. Although the aesthetic value and growth decreased in the plants of both species, the chemical properties of the waters applied had different effects in each case, especially as regards the capacity to recover from salinity. These results underline the importance to studying the physiological mechanisms involved in the recovery of plants. © 2013 Elsevier B.V.This work was supported by the projects: CICYT (AGL 2008-05258-CO2-1-2-AGR and AGL 2011-30022-CO2-01-02) and Fundación Séneca (15356/PI/10).Peer Reviewe

Seasonal changes of maximum daily shrinkage reference equations for irrigation scheduling in olive trees: influence of fruit load

Maximum daily shrinkage (MDS) is the parameter of daily cycle of trunk diameter most widely suggested in irrigation scheduling for several fruit trees. However, as in other plant-measured approaches, the irrigation decision may be difficult due to the influence of the environment on the values obtained. Reference equations of MDS have been established in order to avoid the effects of environmental conditions. Such equations are usually related to simple meteorological data, in order to easily estimate MDS values in full-irrigated conditions. This paper studies the influence of fruit load and the inter-annual variations on the reference equation of MDS in olive trees. These reference equations were calculated during 4 seasons in a full-irrigated orchard and the equations were validated with the data from a different season. The MDS values were related to vapour pressure deficit (VPD) and temperature taken near the experimental orchard. In addition, meteorological data were considered as mean daily or as midday values: only for temperature was the maximum daily value also used. The validation of the equations was made using the fits with all the meteorological data considered (midday and mean daily of VPD and temperature). In addition, two different fits were used in each meteorological data one according to fruit load and other with the complete pool of data. The equations fit were significantly different each season in all the meteorological data considered. However, seasons with similar fruit load were more similar to each other. In both meteorological data considered (VPD and temperature) the midday values improved the fit in respect to mean daily values. The equations obtained with maximum daily temperature were similar in accuracy to the one of midday. The reference equations in which temperature was used obtained a better fit that the ones calculated with VPD. No significant differences were found in the validation when equations according to fruit load or the complete pool data were compared. The limitations and usefulness of these reference equations are also discussed.Ministerio de Ciencia e Innovación, Unión Europea AGL2004-0794-C03-02 and AGL2007-66279-C03-02/AG

Estado actual de la programación del riego en limero mediante medidas del estado hídrico

: En el presente trabajo se realiza una revisi´on sobre aspectos relativos a la utilizaci´on de medidas continuas del estado h´ıdrico del limonero en la programaci´on del riego. Para ello, se analiz´o, la sensibilidad de distintos indicadores del estado h´ıdrico medidos de forma continua o discontinua en las plantas, su significado fisiol´ogico, la obtenci´on de niveles de referencia de los indicadores y los primeros resultados sobre programaci´on del riego

Effect of different quality irrigation water on the growth, mineral concentration and physiological parameters of Viburnum tinus plants

Treated wastewater may be considered an alternative source of water and fertilizer nutrients for landscape plants. However, NaCl, the principal compound in this water, can be detrimental to plants. Viburnum tinus plants were submitted for 4 months to 4 irrigation treatments with water from different sources: control (Control) (EC < 0.9 dS m-1); NaCl solution (NaCl) (EC = 4 dS m-1); irrigation water normally used in the area (IW) (EC = 1.2-1.8 dS m-1) and reclaimed water (RW) (EC = 4 dS m-1). During a recovery period of two months, all the plants were irrigated with the control water. The results showed that biomass was affected in NaCl, IW and RW treatments, both leaf area and height decreased at the end of saline period. These changes were more pronounced in the NaCl treatment, which also caused a decrease in stem diameter and root/shoot ratio. The similar growth alterations founded after the recovery period showed that salts continued to be present in the substrate. Compared with the control, NaCl and RW plants showed a greater rate of Na+ and Cl- absorption by roots. Stem water potential was mainly affected by the NaCl treatment in the last weeks of the saline period. Through the experiment, the stomatal conductance and photosynthesis values were the lowest in plants that received the highest amount of salts, especially NaCl treatment which was the only treatment that did not recover at the end of experiment. Plants of the IW treatment showed slight changes in stomatal conductance and photosynthetic rate with respect to the control, although the reduction in the growth and size of these plants suggests that slight increases in EC could be very toxic for this species. Hence, using different sources of water with similar EC, (NaCl and RW) it is important to know the exact composition, since the toxic effects produced by high concentrations of Na+ and Cl- might be offset by the effect of other ions like magnesium, potassium and phosphorus. In the physicochemical analysis of water, the highest concentrations of these ions were observed in RW and as consequence, their concentrations in plants were not reduced by the Na+ and Cl- effect, phosphorus even increased, improving the plant nutritional balance.This work was supported by the projects: CICYT (AGL 2008- 05258-CO2-1-2- AGR and AGL 2011-30022-CO2-01-02), Fundación Séneca (15356/PI/10) and Vías y Construcción, S. A. (CDTI IDI-20101191).Peer Reviewe

Assessment of the Combined Effect of Temperature and Salinity on the Outputs of Soil Dielectric Sensors in Coconut Fiber

Dielectric sensors are useful instruments for measuring soil moisture and salinity. The soil moisture is determined by measuring the dielectric permittivity, while bulk electrical conductivity (EC) is measured directly. However, permittivity and bulk EC can be altered by many variables such as measurement frequency, soil texture, salinity, or temperature. Soil temperature variation is a crucial factor as there is much evidence showing that global warming is taking place. This work aims to assess how variations in the temperature and salinity of coconut fiber affect the output of EC5 (voltage) and GS3 (permittivity and bulk EC) Decagon sensors. The results showed that the effect of temperature and salinity on the output of the sensors can lead to substantial errors in moisture estimations. At low salinity values, permittivity readings decreased as temperature increased, while voltage readings were not affected, regardless of substrate moisture. The GS3 sensor underestimated the bulk EC when it is measured below 25 °C. The temperature dependence of the voltage of EC5 was not significant up to 10 dS m−1, and the permittivity of the GS3 was more affected by the interaction between temperature and salinity. The effect that salinity has on the permittivity of the GS3 sensor can be reduced if a permittivity–moisture calibration is performed with saline solutions, while the effect resulting from the interaction between temperature and salinity can be minimized using a regression model that considers such an interaction.This research was funded by the Ministry of Science, Innovation, and Universities of Spain, and the European Regional Development Fund, grant number RTI2018-093997-B-I00, and by the Spanish AEI (grant number PCI 2019-103608) under the PRIMA programme in the frame of the PRECIMED project. PRIMA is an Art.185 initiative supported and co-funded under Horizon 2020, the European Union’s Programme for Research and InnovationPeer reviewe

Estrategias de riego en plantas ornamentales. Efectos beneficiosos de la aplicación de riego deficitario

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Aspectos fisiológicos y ornamentales de plantas de geranio en condiciones de consumo hídrico limitado durante la fase de floración

Trabajo presentado en el I Simposio Iberoamericano - IV Jornadas Ibéricas de Horticultura Ornamental, celebrado en Pontevedra (España), en octubre de 2008Plantas de geranio, crecidas durante la época de verano en invernadero, fueron sometidas, coincidiendo con la fase de floración, a un tratamiento control que recibió la cantidad de agua necesaria para compensar las pérdidas de peso del sustrato en base a su máxima capacidad de retención hídrica, y se comparó con otro grupo de plantas regadas al 50% de las plantas control. Los resultados de los controles periódicos, llevados a cabo durante el ensayo y al finalizar el mismo, aportaron que los parámetros del estado hídrico, intercambio gaseoso, y biomasa de las plantas con menos riego se vieron afectados. Valores de potencial hídrico de -0.8 MPa, a mediodía, causaron un importante descenso en la conductancia estomática, afectando a la tasa de fotosíntesis. El déficit hídrico indujo un limitado ajuste osmótico que fue insuficiente para evitar pérdidas de turgencia foliar a mediodía. Los parámetros más relacionados con la calidad ornamental revelaron que aunque a los 42 días desde la aplicación del estrés, la biomasa floral y el número de flores en las plantas sometidas a este tratamiento tuvieron valores menores a la plantas del control, los estudios colorimétricos no mostraron afectaciones durante todo el período evaluado. Este comportamiento indica, que geranio en condiciones de estrés presenta ciertas alteraciones fisiológicas (mecanismos de evitación) que pueden contribuir a minimizar los daños producidos por el estrés hídrico, lo que permite una significativa reducción en el consumo hídrico y posibilita su cultivo en condiciones de baja disponibilidad de agua.Peer Reviewe

Comparison of continuously recorded plant-based water stress indicators for young lemon trees

Continuously recorded plant-based water stress indicators (sap flow and parameters derived from trunk diameter fluctuations) were compared in potted young lemon trees (Citrus limon (L.) Burm. fil, cv. Verna) grafted on sour orange (C. aurantium L.) rootstock submitted to deficit irrigation. Daily maximum (MXTD) and minimum (MNTD) trunk diameters and daily trunk diameter shrinkage (MDS) were directly influenced by the water supply to the trees from the soil. The continuously recorded plant-based water stress indicators presented different degrees of sensitivity when used to estimate the water status of the plants. Sap flow (SF) and MDS were more immediate and sensitive than MXTD and MNTD. However, the higher signal intensity: noise for SF and the fact that its signal intensities remained clearly above unity during the stress period, indicating that the soil water was depleted, point to the greater reliability of this indicator. Also, the possibility of developing further baseline relationships between SF and air vapour pressure deficit in fully irrigated trees in field conditions increases the feasibility of using this parameter in automatic irrigation systems.This research was supported by CICYT (AGL2000- 9387-C05-02 and AGL2003-9387-C05-02) and PETRI (PTR1995-0693-OP-02-01)grants to the authors. M.F. Ortuño was a recipient of a Program I3P research fellowship from CSIC.«dPeer reviewe

Sap flow and trunk diameter fluctuations of young lemon trees under water stress and rewatering

Potted 2-year-old lemon trees (Citrus limon (L.) Burm. fil, cv. Verna) grafted on sour orange (C. aurantium L.) rootstock and growing under field conditions were subjected to water stress by withholding irrigation for 6 days. After that time, irrigation was restored and plant recovery was studied for 8 days. The results indicate that sap flow (SF) measurement by the heat-pulse technique is a suitable plant-based method for estimating the daily transpiration for young lemon plants. The most sensitive continuously recorded plant-based indicators of water stress and recovery were daily minimum trunk diameter (MNTD) and daily maximum trunk shrinkage (MDS) followed by SF. It was concluded that the water supplied to the trees from soil has a direct influence on daily MDS. Besides reflecting tree water status, SF and MNDT were clearly influenced by weather conditions, meaning that it is possible to develop reference or baseline relationships to interpret plant-based indicator measurements for irrigation scheduling.This research was supported by CICYT (AGL2000-9387-C05-02 and AGL2003-9387-C05-02) and PETRI (PTR1995-0693-OP-02-01) grants to the authors. M.F. Ortuño was a recipient of a Program I3P research fellowship from CSIC.Peer reviewe