Abstract
Effects of drought and aerosol stresses were studied in a factorial experiment based on a Randomized Complete Design with triplicates on two ornamental shrubs. Treatments consisted of four levels of water container (40%, 30%, 20%, and 10% of water volumetric content of the substrate) and, after 30 days from experiment onset, three aerosol treatments (distilled water and 50% and 100% salt sea water concentrations). The trial was contextually replicated on two species: Callistemon citrinus (Curtis) Skeels and Viburnum tinus L. ‘Lucidum’. In both species, increasing drought stress negatively affected dry biomass, leaf area, net photosynthesis, chlorophyll a fluorescence, and relative water content. The added saline aerosol stress induced a further physiological water deficit in plants of both species, with more emphasis on Callistemon. The interaction between the two stress conditions was found to be additive for almost all the physiological parameters, resulting in enhanced damage on plants under stress combination. Total biomass, for effect of combined stresses, ranged from 120.1 to 86.4 g plant−1 in Callistemon and from 122.3 to 94.6 g plant−1 in Viburnum. The net photosynthesis in Callistemon declined by the 70% after 30 days in WC 10% and by the 45% and 53% in WC 20% and WC 10% respectively after 60 days. In Viburnum plants, since the first measurement (7 days), a decrease of net photosynthesis was observed for the more stressed treatments (WC 20% and WC 10%), by 57%. The overall data suggested that Viburnum was more tolerant compared the Callistemon under the experimental conditions studied.
Highlights
IntroductionThe Mediterranean environment is characterized by high summer temperatures often associated with shortage and poor quality of irrigation water
Significant differences were detected in the root/shoot ratio for the three factors, while the interactions were only significant for DxS and AxS
Significant interactions were observed between the water regime and saline aerosol treatment: plants, under the water content (WC) 10% treatment, were the most stressed due to the lack of water and were the most affected by the adoption of the saline solution
Summary
The Mediterranean environment is characterized by high summer temperatures often associated with shortage and poor quality of irrigation water. These conditions represent a limit for optimal plant growth and somehow even survival [1]. Álvarez et al [4] have investigated on drought and saline aerosol stress separately, but only a few studies report the effect of interaction between these stresses. These two abiotic stresses share common physiological, biochemical, and molecular responses in plants. Plants can undergo synergistic negative effects subjected to both stresses [5]
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