Physiological response and secondary metabolites of three lavender genotypes under water deficit.

Lavandula genus is a considerable medicinal plant in pharmaceutical and cosmetics industries. Considering increasing threat of drought in the world, it is important to identify genotypes which can tolerate drought. It is also important to characterize quantity and quality of essential oils, and tolerance indicators of these genotypes against drought stress. Therefore, an experiment was conducted in Gorgan University of Agricultural Sciences and Natural Resources, Iran, during 2017 and 2018, to investigate these factors. It was a factorial experiment based on randomized complete block design with two treatments, three genotypes (Lavandula angustifolia cv. Hidcote, Lavandula angustifolia cv. Munstead, and Lavandula stricta), and four levels of drought stress (irrigation regimes) (I1: 100-90% (control), I2: 80-70%, I3: 60-50% and I4: 30-40% of field capacity) which was done with three repetitions. Drought increased amount of proline in leaves, antioxidant activity, activity of catalase, peroxidase, ascorbate peroxidase, and superoxide enzymes, malondialdehyde content, total flavonoids, total phenol, total sugar and essential oil percentage. The PCA analysis of different irrigation regimes showed that in the first component, the best traits are antioxidant enzymes CAT, SOD, APX, while in the second component, only the trait Catalase is the best trait. The results of PCA analysis in lavender genotypes showed that L. stricta exhibits the most affected physiological changes while trying to adjust to changes in the water status of the environment, under the imposed conditions and shows the highest resistance. But it reduced dry weight of aerial parts, relative water content of leaves, and efficacy of essential oil. Lavandula stricta genotype had the highest amount of essential oil, but the highest dry weight of the aerial parts and essential oil yield were related to L. angustifolia cv. Hidcote and L. angustifolia cv. Munstead genotypes. In all evaluated genotypes, with increasing drought stress, monoterpene compounds were decreased and sesquiterpene compounds were increased. Totally it was shown that drought effect on evaluated traits depends on genotype and nature of traits; this indicates that by choosing drought-tolerant genotypes in breeding programs, high quantity and quality of essential oil, as well as tolerance to drought stress can be achieved.

Light and temperature requirements for germination in the Mediterranean shrub Lavandula stoechas (Lamiaceae).

Available studies are far from giving a complete figure for the germination requirements of many Mediterranean Basin species. In this study, we investigated the germination properties of Lavandula stoechas L. (Lamiaceae) in response to different light and temperature regimes. We performed comprehensive experiments to test the effect of fixed and alternating temperatures, dark versus light conditions, and thermodormancy or thermoinhibition on several germination properties in three populations of L. stoechas from southwestern Turkey. Germination patterns showed a substantial variation among populations. Germination percentage was higher in the light conditions than in the dark at most temperatures, and alternating temperatures substituted light for the germination. The requirement of L. stoechas seeds to light for germination gradually increased through lower and higher temperatures than 15 °C. High temperature (30 °C) reduced the germination percentage to zero. However, in the presence of light, seeds were able to germinate after transferring to the optimum temperature (thermoinhibition), but this was not the case in darkness (thermodormancy). Seed germination in L. stoechas was stimulated by light, suggesting that germination has a phytochrome-mediated response. Our study makes an inference to the fire-environment interactions in the germination of Mediterranean seeder species by showing that both light and alternating temperatures stimulate germination in L. stoechas, a species well-known with its fire-related germination. Comprehensive germination studies are required for a better understanding of the early life-stage adaptations of plants to Mediterranean conditions, and for developing more robust strategies for conservation and ecosystem restoration.

Drought-Induced Mortality: Branch Diameter Variation Reveals a Point of No Recovery in Lavender Species.

In the context of climate change, determining the physiological mechanisms of drought-induced mortality in woody plants and identifying thresholds of drought survivorship will improve forecasts of forest and agroecosystem die-off. Here, we tested whether continuous measurements of branch diameter variation can be used to identify thresholds of hydraulic failure and physiological recoverability in lavender (Lavandula angustifolia and Lavandula × intermedia) plants exposed to severe drought. Two parameters of branch diameter variation were tested: the percentage loss of diameter and the percentage loss of rehydration capacity. In two greenhouse experiments with different growth conditions, we monitored variation in branch diameter in the two lavender species exposed to a series of drought/rewatering cycles that varied in drought-stress intensity. Water potential, stomatal conductance, loss of xylem hydraulic conductance, and electrolyte leakage were also measured. We observed that plants were not able to recover when percentage loss of diameter reached maximum values of 21.3% ± 0.6% during drought, regardless of species and growth conditions. A percentage loss of rehydration capacity of 100% was defined as the point of no recovery, and was observed with high levels of cellular damage as estimated by electrolyte leakage measured at 75.4% ± 9.3% and occurred beyond 88% loss of xylem hydraulic conductance. Our study demonstrates that lavender plants are not able to recover from severe drought when they have used up their elastic water storage. Additionally, drought-induced mortality in these species was not linked to xylem hydraulic failure but rather to high levels of cell damage.

Within-plant variation in seed size and inflorescence fecundity is associated with epigenetic mosaicism in the shrub Lavandula latifolia (Lamiaceae).

Background and Aims: Sub-individual variation in traits of homologous structures has multiple ecological consequences for individuals and populations. Assessing the evolutionary significance of such effects requires an improved knowledge of the mechanisms underlying within-plant phenotypic heterogeneity. The hypothesis that continuous within-plant variation in some phenotypic traits can be associated with epigenetic mosaicism was examined. Methods: Fifteen individuals of the long-lived, evergreen Mediterranean shrub Lavandula latifolia were studied. Five widely spaced 'modules', each consisting of a single inflorescence plus all its subtending basal leaves, were collected from each shrub. Genomic DNA was extracted from leaf samples and genome-wide cytosine methylation determined by reversed phase high-performance liquid chromatography (HPLC) with spectrofluorimetric detection. The number and mean mass of seeds produced were determined for each inflorescence. An assessment was made of whether (1) leaves from different modules in the same plant differed significantly in global DNA cytosine methylation, and (2) mosaicism in cytosine methylation contributed to explain variation across modules in number and size of seeds. Key Results: Leaves from different modules in the same plant differed in global DNA cytosine methylation. The magnitude of epigenetic mosaicism was substantial, as the variance in DNA methylation among modules of the same shrub was greater than the variance between individuals. Number and mean mass of seeds produced by individual inflorescences varied within plants and were quadratically related to cytosine methylation of subtending leaves, with an optimum at an intermediate methylation level (approx. 25 %). Conclusions: The results support a causal link between global cytosine methylation of leaves in a module and the size and numbers of seeds produced by the associated inflorescence. It is proposed that variation in global DNA methylation within L. latifolia shrubs may result from the concerted action of plant sectoriality and differential exposure of different plant parts to some environmental factor(s) with a capacity to induce durable epigenetic changes.

Mutielemental concentration and physiological responses of Lavandula pedunculata growing in soils developed on different mine wastes.

This study aimed to: i) evaluate the accumulation and translocation patterns of potentially hazardous elements into the Lavandula pedunculata and their influence in the concentrations of nutrients; and ii) compare some physiological responses associated with oxidative stress (concentration of chlorophylls (Chla, Chlb and total), carotenoids, and total protein) and several components involved in tolerance mechanisms (concentrations of proline and acid-soluble thiols and total/specific activity of catalase (CAT) and superoxide dismutase (SOD)), in plants growing in soils with a multielemental contamination and non-contaminated. Composite samples of soils, developed on mine wastes and/or host rocks, and L. pedunculata (roots and shoots) were collected in São Domingos mine (SE of Portugal) and in a reference area with non-contaminated soils, Corte do Pinto, with the same climatic conditions. São Domingos soils had high total concentrations of several hazardous elements (e.g. As and Pb) but their available fractions were small (mainly <5.8 % of the total). Translocation behaviour of elements was not clear according to the physiological importance of the elements. In general, plant shoots from São Domingos had the highest elements concentrations, but only As, Mn and Zn reached phytotoxic concentrations. Concentration of Chlb in shoots from São Domingos was higher than those from Corte do Pinto. No significant differences were obtained between concentrations of Chla, total protein, proline and acid-soluble thiols in shoots collected in both areas, as well as SOD activity (total and specific) and specific CAT activity. Total CAT activity varied with population being lower in the shoots of the plants from São Domingos, but no correlation was obtained between this enzymatic activity and the concentrations of the studied elements in shoots. Lavandula pedunculata plants are able to survive in soils developed on different mine wastes with multielemental contamination and low fertility showing no symptoms (visible and physiological) of phytotoxicity or deficiency.

Differential activity of autochthonous bacteria in controlling drought stress in native Lavandula and Salvia plants species under drought conditions in natural arid soil.

The effectiveness of autochthonous plant growth-promoting rhizobacteria was studied in Lavandula dentata and Salvia officinalis growing in a natural arid Mediterranean soil under drought conditions. These bacteria identified as Bacillus megaterium (Bm), Enterobacter sp. (E), Bacillus thuringiensis (Bt), and Bacillus sp. (Bsp). Each bacteria has different potential to meliorate water limitation and alleviating drought stress in these two plant species. B. thuringiensis promoted growth and drought avoidance in Lavandula by increasing K content, by depressing stomatal conductance, and it controlled shoot proline accumulation. This bacterial effect on increasing drought tolerance was related to the decrease of glutathione reductase (GR) and ascorbate peroxidase (APX) that resulted sensitive indexes of lower cellular oxidative damage involved in the adaptative drought response in B. thuringiensis-inoculated Lavandula plants. In contrast, in Salvia, having intrinsic lower shoot/root ratio, higher stomatal conductance and lower APX and GR activities than Lavandula, the bacterial effects on nutritional, physiological and antioxidant enzymatic systems were lower. The benefit of bacteria depended on intrinsic stress tolerance of plant involved. Lavadula demonstrated a greater benefit than Salvia to control drought stress when inoculated with B. thuringiensis. The bacterial drought tolerance assessed as survival, proline, and indolacetic acid production showed the potential of this bacteria to help plants to grow under drought conditions. B. thuringiensis may be used for Lavandula plant establishment in arid environments. Particular characteristic of the plant species as low shoot/root ratio and high stomatal conductance are important factors controlling the bacterial effectiveness improving nutritional, physiological, and metabolic plant activities.

Micropropagation of Lavandula spp.

Lavandula species are some of the most popular ornamental and medicinal plants with great economic values. These species are vegetative propagated by stem cuttings. However, the poor rooting ability and vulnerability of plantlets to contamination are major limiting factors for propagation. In vitro culture methods are suitable to overcome these limitations. This chapter describes protocols for in vitro propagation of Lavandula viridis L'Hér and Lavandula vera DC. Nodal shoot proliferation of L. viridis and plant regeneration from leaf-derived callus of L. vera by an "open culture system" are highlighted.

Local versus regional intraspecific variability in regeneration traits.

Intraspecific trait variability has a fundamental contribution to the overall trait variability. However, little is known concerning the relative role of local (e.g. disturbances and species interaction) and regional (biogeographical) processes in generating this intraspecific trait variability. While biogeographical processes enhance plant trait variability between distant populations, in fire-prone ecosystems, recurrent fires may have a preponderant role in generating variability at a local scale. We hypothesize that plants respond to the local spatio-temporal heterogeneity generated by fire by having a relatively large local variability in regeneration traits in such a way that overrides the variability at a broader biogeographical scale. We test this hypothesis by assessing the intraspecific variability in fire-related regeneration traits of two species (Cistus salviifolius and Lavandula stoechas) growing in fire-prone ecosystems of the Mediterranean Basin. For each species, we selected six populations in two distant regions, three in the east (Anatolian Peninsula) and three in the west (Iberian Peninsula). For each species and population, we analysed the following regeneration traits: seed size, seed dormancy and stimulated germination by fire-related cues (heat and smoke). To evaluate the distribution of the variability in these traits, we decomposed the variability of trait values at each level, between regions (regional) and between population within region (local), using linear mixed-effect models. Despite the biogeographical and climatic differences between regions, for the two species, intraspecific variability in regeneration traits was higher at a local (within regions) than at a regional scale (between regions). Our results suggest that, in Mediterranean ecosystems, fire is an important source of intraspecific variability in regeneration traits. This supports the prominent role of fire as an ecological and evolutionary process, producing trait variability and shaping biodiversity in fire-prone ecosystems.

Lognormal distribution of individual lifetime fecundity: insights from a 23-year study.

Individual variance in lifetime fecundity within populations is a life-history parameter of crucial evolutionary and ecological significance. However, knowledge of its magnitude and underlying mechanisms in natural populations is biased toward short-lived taxa. This paper summarizes results of a 23-year study on a population of the Mediterranean shrub Lavandula latifolia. We document the within-population pattern of individual variation in instantaneous and lifetime fecundity (as estimated by inflorescence production) and explore the mechanisms producing the lognormal distribution of individual fecundities by means of an individual-based simulation model. Throughout the study period, a few individuals consistently produced most inflorescences while the majority of plants exhibited moderate-to-low fecundities. The shape of yearly distributions of annual fecundities varied little across years, and most annual fecundity distributions did not depart significantly from a lognormal. The distribution of individual lifetime fecundity did not depart from lognormality. Despite the simplicity of the premises of our simulation model, it was remarkably successful at predicting the shapes of fecundity distributions and the early establishment of a persistent fecundity hierarchy. The agreement between model results and empirical data supports the view that multiplicative interactions of randomly varying environmental effects can play a central role in determining individual variation in lifetime fecundity in L. latifolia, and suggests that environmental stochasticity can be decisive in the genesis of strong fecundity hierarchies in long-lived plants.

Expression of spearmint limonene synthase in transgenic spike lavender results in an altered monoterpene composition in developing leaves.

We generated transgenic spike lavender (Lavandula latifolia) plants constitutively expressing the limonene synthase (LS) gene from spearmint (Mentha spicata), encoding the LS enzyme that catalyzes the synthesis of limonene from geranyl diphosphate. Overexpression of the LS transgene did not consistently affect monoterpene profile in pooled leaves or flowers from transgenic T(0) plants. Analyses from cohorts of leaves sampled at different developmental stages showed that essential oil accumulation in transgenic and control plants was higher in developing than in mature leaves. Furthermore, developing leaves of transgenic plants contained increased limonene contents (more than 450% increase compared to controls) that correlated with the highest transcript accumulation of the LS gene. The levels of other monoterpene pathway components were also significantly altered. T(0) transgenic plants were grown for 2 years, self-pollinated, and the T(1) seeds obtained. The increased limonene phenotype was maintained in the progenies that inherited the LS transgene.

Effectiveness of aroma on work efficiency: lavender aroma during recesses prevents deterioration of work performance.

The present study investigated whether exposure to aromas during recess periods affects work performance. Subjects comprised 36 healthy male students (mean age, 24.2 +/- 2.2 years) who were randomly divided into three groups: (1) control group, not exposed to aroma during recesses; (2) jasmine group, exposed to jasmine aroma during recesses; and (3) lavender group, exposed to lavender aroma during recesses. All participants completed five work sessions performing a task requiring concentration on a computer monitor, with each session lasting 60 min. Recess periods of 30 min were provided between each session. To clarify the time at which work concentration was lowest, work performance for the control group was analyzed. Concentration was lowest in the afternoon period, where afternoon drowsiness is strongest. Comparison of the three groups for this time period indicated significantly higher concentration levels for the lavender group than for the control group. No such effect was noted for the jasmine group. Although lavender is a sedative-type aroma, use during recess periods after accumulation of fatigue seems to prevent deterioration of performance in subsequent work sessions.