Efecto del uso de aguas de distinta calidad en el desarrollo, aspectos fisiológicos, nutricionales y ornamentales de plantas de Euonymus japonica Thunb. y Viburnum tinus L.

Abstract

This thesis evaluates the effect of using water of different quality in the development, physiological and agronomical behaviour of two ornamental species of different origin, euonymus (Euonymus japonica Thunb.) and laurustinus (Viburnum tinus L.), growing in both soil and pots. It also evaluates the beneficial effects of arbuscular mycorrhizal fungi on plants under these conditions. The experiments performed were designed to: 1) determine the response of euonymus and laurustinus irrigated with water of different qualities and different saline levels, growing in pots under greenhouse conditions and during both saline and recovery periods. 2) study the application and effectiveness of the mycorrhizal fungus Glomus iranicum var. tenuihypharum on euonymus plants growing in pots in greenhouse conditions and irrigated with two types of water of different sources. 3) evaluate the daily behaviour pattern of euonymus and the use of two techniques to measure of canopy temperature (manual measurement with thermographic camera and continuous measurement with infrared thermometers) to estimate the water status of plants irrigated with two types of water from different source and quality, under pot and greenhouse conditions, and 4) analyze the effectiveness of Glomus iranicum var. tenuihypharum in laurustinus plants growing in soil under field conditions irrigated with water from different source and quality. The results showed the following: 1) The use of water from different sources (saline water and reclaimed wastewater) but with similar electrical conductivity (4 dS m-1) seriously affected the development and growth of euonymus and laurustinus. However, after a recovery period, laurustinus plants were more resistant than euonymus plants, maintaining gas exchange and stem water potential values close to those of the control plants, while realizing osmotic adjustment during the recovery period. 2) The application of reclaimed wastewater with the same electrical conductivity (4 dS m-1) but with a composition differing from that of previous experiment did not have a negative effect on both growth and the ornamental value of euonymus because the toxic effects produced by the high saline content were offset by other beneficial ions. Therefore, the reclaimed wastewater components maintained the good nutritional status of plants. However, the application of Glomus iranicum var. tenuihypharum in the same plants had no additive effect. The positive effect of mycorrhizae was more evident in plants irrigated with Control water (1 dS m-1), which improved the uptake of phosphorus into the plant and the water status. 3) The daily physiological behavior of euonymus plants irrigated with reclaimed wastewater reflected osmotic stress felt as a result of salts accumulation in the plant. However, parameters such as stomatal conductance and fluorescence tended to recover after midday, even reaching values above the control plants, confirming the resistance of the photosynthetic apparatus to salinity in these conditions. The canopy temperature of the plant (Tc) throughout the day was influenced by the high concentration of salts from the reclaimed wastewater treatment. In addition, the Tc measured by thermal imager was closely correlated with the measured by infrared thermometer, validating both techniques in the diagnosis of water status. 4) The AMF Glomus iranicum var. tenuihypharum successfully colonized the roots of laurustinus growing in soil and showed a high percentage of enzymatic activity. As a result, the soil structure improved, beneficial nutrients were accumulated in the leaves, toxic ion levels decreased and the water status increased in plants irrigated with reclaimed wastewater. In conclusion, obtaining plants irrigated with reclaimed wastewater with an acceptable ornamental value depends to a great extent on the species selected and the source, type of treatment and composition of the treated water. The use of water of a moderate salinity in resistant species, together with a suitable leaching level, could minimize the negative effects of this kind of water. Furthermore, the physiological mechanisms developed by these plants during both saline and recovery period vary between species. From the results obtained, mycorrhizal inoculation of the plant is most effective when the irrigation water applied contains a higher concentration of toxic ions and is poor in nutrients. However, its effectiveness depends not only on the intensity and duration of the salt stress, but also on other factors such as the plant species used, the type of AMF selected and the association between them, the characteristics of the soil or substrate and the water regime applied.