María Fernanda Ortuño

Plant growth regulators (PGRs) are commonly used in horticulture to improve crop quality, save water, and enhance plant resilience to stress. In this study, we examined the effects of two PGRs, paclobutrazol (PBZ) and mepiquat chloride (MC), on the growth and health of Salvia officinalis ‘Icterina’, a popular ornamental and aromatic plant. Parameters such as growth and development, water status, chlorophyll levels, nutrient content, photosynthetic performance, and gas exchange were evaluated. The study took place in a greenhouse with automatic watering and three plant groups: one treated with PBZ, another with MC, and a control group (untreated). Only one application of growth retardants was made, with 0.1 L per pot of a 100 mg/L solution of PBZ, and 0.1 L per pot of a 2.5 g/L solution of MC. The results showed that both PBZ and MC treatments reduced the plant’s water consumption, with PBZ being more effective in limiting leaf growth and promoting the accumulation of substances in the leaves. Both PGRs resulted in smaller plants, reducing the need for soil and potting materials. The MC treatment improved nutrient absorption, reducing the requirement for fertilizers. When subjected to environmental stress from March to June in the greenhouse, Salvia plants benefited from the application of both PGRs, as they helped maintain photosynthetic activity. These findings contribute to improving the sustainability of nursery practices by utilizing PGRs to conserve resources and mitigate the impact of stressful environmental conditions on sage plants.

Water deficit is one of the most important abiotic factors that reduce the agricultural productivity. The impact of irrigation levels on bioactive compounds of one commercial pomegranate cultivar (‘Mollar de Elche’) was studied through LC–MS-based untargeted metabolomics approach. Two treatments were applied to explore crop responses to the timing and the regime of the irrigation applications. The main goal of the present study was to validate the untargeted metabolomics approach as analytical tool to find new markers related with the water deficit. Robust classification and prediction model was built with the use of supervised technique, partial least squares discriminant analysis (PLS-DA). The results revealed that pomegranate juices obtained from plants grown under DI_r conditions experimented physiological stress, which significantly increased their bioactive compounds (polyphenols, phenylpropanoids, peptides, benzoic acid, tannins, and phospholipids) in comparison with the Control treatments. The results indicate that controlled irrigation stress would increase the production of bioactive compounds by increasing the phenylpropanoids metabolism. New metabolites were tentatively identified in pomegranate juice by the untargeted metabolomics techniques. This study showed, for the first time, the satisfactory application of the untargeted metabolomics approach using an UHPLC-QTOF system to identify bioactive secondary metabolites from pomegranate juices to discriminate among different irrigation conditions.

The objective of this study was to identify the physiological mechanisms used by Cistus heterophyllus Desf. Subsp. carthaginensis (Pau) M. B. Crespo & Mateo, a species in critical danger of extinction, to cope with two typical abiotic conditions. During the summer of 2021, plants were cultivated under a shade mesh that intercepted 50% of the incident solar radiation (SHADE) and in natural conditions (SUN). Three irrigation treatments were also applied: control, T1, moderate water deficit; T2, 60% of the control, severe deficit; and T3, 30% of the control. Therefore, there were six treatments (SUN-T1, SUN-T2, SUN-T3, SHADE-T1, SHADE-T2, SHADE-T3). Plants were more affected by solar radiation than by deficit irrigation. Although leaf water potential, stomatal conductance and root biomass decreased by up to 45%, 63% and 65%, respectively, as deficit irrigation increased, plants were able to develop a leaf osmotic adjustment and an improved intrinsic water-use efficiency to maintain their growth and survival rate. Shade conditions improved gas exchange, reduced leaf temperature and induced the synthesis of chlorophylls, regardless of the irrigation level imposed. This indicated that radiation was the most limiting factor in our experiment. Applying 50% of the radiation and a moderate water deficit would help to obtain a good plant development and high survival rate in future recovery and conservation programs for the species.

The use of reclaimed water is considered an efficient tool for agricultural irrigation; however, the high salinity associated to this water could compromise plant quality and yields. Balm and spearmint plants were submitted for 15 days to three irrigation treatments in a controlled chamber: control with EC: 1.2 dS m⁻¹ (control), reclaimed water from secondary effluent (EC: 1.6 dS m⁻¹) (S) and water from secondary effluent with brine (EC: 4.4 dS m⁻¹) (SB). The plant water status, stomatal and hormonal regulation, nutritional response, concentration of amino acids and plant oxidative stress-based markers, as well as growth were evaluated. Both species irrigated with saline reclaimed water reduced leaf water potential and gas exchange in comparison with control plants, following 2 days of exposure to irrigation treatments. Nevertheless, spearmint plants recovered photosynthetic activity from the seventh day onwards, maintaining growth. This was attributed to hormonal changes and a greater accumulation of some amino acids and some plant oxylipins (phytoprostanes) in comparison to balm plants, which contributed to the improvement in the organoleptic and health-promoting properties of spearmint. A longer irrigation period with saline reclaimed water would be necessary to assess whether the quality of both species, especially spearmint, could further improve without compromising their growth.

Although the use of marginal-quality water can be an effective measure to alleviate water scarcity, it often contains a high concentration of salts that can compromise crop growth. As a result, farmers apply more water than necessary to leach salts away from the root zone, resulting in wasted water and the release of fertilizers into the groundwater. In this study, we assessed the effects of three salinity levels of irrigation water (1.8 dS m⁻¹, 3.3 dS m⁻¹, and 4.9 dS m⁻¹) on the physiology and ornamental traits of Hebe andersonii cv. Variegata. The experiment was carried out with potted plants in a greenhouse for seven months. We also studied the feasibility of growing this cultivar without leaching salts. The results showed that Hebe plants can be grown without leaching using water up to 3 dS m⁻¹. This setup produces plants with high water use efficiency and without reducing their ornamental value. Meanwhile, irrigation with 5 dS m⁻¹ water reduced the quality of Hebe but did not compromise its physiological processes. The photosynthesis of Hebe under salinity conditions was mainly controlled by stomata, which was related to the level of salt stress and water status of the plant. Salinity had no significant effects on photosystem II, which can be explained by the fact that Hebe was able to dissipate the excess excitation energy as heat effectively. Hebe was able to avoid ion toxicity and maintain a suitable nutrient balance under the salinity levels tested in this experiment.

This work attempts to identify which of two species with different levels of salinity tolerance, Salvia officinalis L. or Asteriscus maritimus L., is more suitable for irrigation with reclaimed wastewater, as well as the effect of the arbuscular mycorrhiza Glomus iranicum on the plant. The experiment was carried out in a growth chamber with a first phase, where both species were irrigated with good quality water, a second phase in which the plants were irrigated with reclaimed wastewater, and a third phase in which the plants were irrigated with good quality water again (recovery). Salinity caused a reduction in leaf water potential, stomatal conductance and net photosynthesis in both species. The percentage of mycorrhization was higher in Asteriscus than in Salvia, mitigating the decrease in leaf water potential. There was osmotic adjustment in Salvia, although the proline content increased in both species. The damages produced were clearer in Salvia, in which lipid peroxidation values were higher. Likewise, the visual appearance of the leaves showed symptoms of toxicity in this species, although the mycorrhizae diminished these effects. Irrigation with good quality water induced the recovery of lipid peroxidation in both species, as well as the appearance of new leaves in Salvia.

Many plant producers tend to overwater crops to prevent water stress and salt-induced damage. These practices waste irrigation water and cause leaching that harms the environment and increases production costs. In order to optimize water consumption and minimize the environmental impact of plant production, this study aimed to determine the physiological and morphological responses of Hebe andersonii to three substrate volumetric water contents (49%, 39%, and 32%). The experiment was conducted in a greenhouse with an irrigation protocol that consisted of adding small volumes of water to avoid leaching while monitoring substrate moisture with dielectric soil sensors. The results showed that moderately low substrate moisture improved the water-use efficiency, while growth was significantly reduced under more severe water deficit conditions (but without leaf chlorosis or abscission). The photosynthetic activity of Hebe was primarily controlled by the stomatal aperture, which was co-determined by the substrate moisture and seasonal temperature. Hebe leaves promoted non-photochemical quenching when carbon assimilation was limited by a water deficit, and accumulated solutes through an osmotic adjustment process (especially Cl⁻, Na⁺, and K⁺) to maintain their water status. Overall, Hebe andersoni cv. Variegata could successfully grow and improve its water-use efficiency in low substrate moisture and under a non-draining irrigation regime.

Cistus species can form ectomycorrhizae and arbuscular mycorrhizal fungus that can bring benefits when plants are under water stress conditions. However, the application of some ectomycorrhizae on the water uptake under drought through physiological traits and hormonal regulation is less known. The experiment was performed during three months in a growth chamber with Cistus albidus plants in which the combined effect of the ectomycorrhiza Pisolithus tinctorious inoculation and two irrigation treatments (control and water-stressed plants) were applied. Irrigation absence caused significant decrease in aerial growth and tended to decrease soil water potential at the root surface, leading to a decrease in leaf water potential. Under these conditions, the abscisic acid and salicylic acid content increased while the precursor of ethylene decreased. Although the mycorrhization percentages were not high, the inoculation of P. tinctorious improved the water status and slightly cushioned the rise in leaf temperature of water-stressed plants. The ectomycorrhiza decreased the scopoletin values in leaves of plants subjected to deficit irrigation, indicating that inoculated plants had been able to synthesize defense mechanisms. Therefore, Pisolithus tinctorious alleviated some of the harmful effects of water scarcity in Cistus plants, being its use a sustainable option in gardening or restoration projects.