Pilar Soriano

As a consequence of climate change, temperature and rainfall regimes are being modified, threatening the survival of the current gardening concept in many areas of the world. This situation highlights the need to investigate the potential of other species, especially in more sensitive areas such as the Mediterranean Basin. The aim of this research is to study the resilience of adapted species to promote sustainable gardening. To achieve this, seven species belonging to three families (Amaranthaceae, Lamiaceae and Asteraceae) used or potentially used as ornamentals were selected to compare their tolerance at the germinative stage to different levels of temperature (10 °C to 35 °C) and water stress created by PEG 6000 (−0.10 MPa to −2.5 MPa). Germination percentage, mean germination time, base temperature, thermal time, base water potential and hydrotime were calculated. The results showed a good response to high temperature and low osmotic potential in most of the species, and germination even increased under certain stress levels. Salsola oppositifolia presented by far the best results in terms of germination under high-water-stress conditions and the second best at high temperatures. The extraordinary response of Celosia argentea, an alien species, highlighted the risk of it becoming an invasive species.

Ornamental plant species introduced into new environments can exhibit an invasive potential and adaptability to abiotic stress factors. In this study, the drought stress responses of four potentially invasive ornamental grass species (Cymbopogon citratus, Cortaderia selloana, Pennisetum alopecuroides and P. setaceum) were analysed. Several seed germination parameters were determined under increasing polyethylene glycol (PEG 6000) concentrations. Additionally, plants in the vegetative stage were subjected to intermediate and severe water stress treatments for four weeks. All species registered high germination rates in control conditions (no stress treatment), even at high PEG concentrations, except C. citratus, which did not germinate at −1 MPa osmotic potential. Upon applying the water stress treatments, P. alopecuroides plants showed the highest tolerance, and C. citratus appeared the most susceptible to drought. Stress-induced changes in several biochemical markers (photosynthetic pigments, osmolytes, antioxidant compounds, root and shoot Na⁺ and K⁺ contents), highlighted different responses depending on the species and the stress treatments. Basically, drought tolerance seems to depend to a large extent on the active transport of Na⁺ and K⁺ cations to the aerial part of the plants, contributing to osmotic adjustment in all four species and, in the case of the most tolerant P. alopecuroides, on the increasing root K⁺ concentration under water deficit conditions. The study shows the invasive potential of all species, except C. citratus, in dry areas such as the Mediterranean region, especially in the current climate change scenario. Particular attention should be given to P. alopecuroides, which is widely commercialised in Europe as ornamental.

Plant abundance and distribution are regulated by subtle changes in ecological factors, which are becoming more frequent under global climate change. Species with a higher tolerance to such changes, especially during early lifecycle stages, are highly likely to endure climate change. This study compared the germination adaptability of Halopeplis amplexicaulis and H. perfoliata, which differ in life-form and grow in different environments. Optimal conditions, tolerances and the biochemical responses of seeds to osmotic stresses were examined. Seeds of H. perfoliata germinated in a wider range of temperature regimes and were more tolerant to osmotic stresses than H. amplexicaulis seeds. Neither NaCl nor PEG treatment invoked the H₂O₂ content in germinating seeds of the tested species. Consequently, unaltered, or even decreased activities of H₂O₂ detoxification enzymes and non-enzymatic antioxidants were observed in germinating seeds in response to the aforementioned stresses. High and comparable levels of recovery from isotonic treatments, alongside a lack of substantial oxidative damage indicated that the osmotic stress, rather than the ionic toxicity, may be responsible for the germination inhibition. Hence, rainy periods, linked to water availability, may act as a key determinant for germination and H. perfoliata could be less affected by global warming owing to better germinability under high temperatures compared with H. amplexicaulis. Such studies involving biochemical analysis coupled with the germination ecology of congeneric species, which differ in life-form and occurrence are scarce, therefore are important in understanding the impacts of global changes on species abundance/distribution.

Reproductive strategies for specific populations are closely related to environmental factors. Consequently, they are fundamental for conservation plans and the management of threatened habitats like salt marshes. From this viewpoint, germination strategy under different temperatures and salt conditions, voltammetric parameters and molecular analysis were performed and compared in six Halocnemum populations (four of H. cruciatum and two of H. strobilaceum) growing on Mediterranean (Balearic, Tyrrenic and Adriatic) and Red Sea coasts to establish the relation to environmental variables. Significant interpopulation differences were found in all the evaluated parameters. The Mediterranean populations showed a variable opportunistic germination strategy that was directly related to the drought period length at the studied sites. Consequently, potential environmental predictors of seed response were identified. The most noteworthy were bioclimate, soil texture, continentality index, winter temperatures and summer precipitations. Additionally, voltammetric parameters were evidenced as indicators of maternal plant stress levels and, thus, as potential determinants of future seed responses. The phylogenetic analyses showed a split into two species that did not correspond to germination response. The phylogeographic analyses showed interpopulation differences in haplotype composition for H. cruciatum, but not for H. strobilaceum. In conclusion, the tight connection between seed responses and the ecological parameters of natural populations as an adaptation for successful seedling emergence was proved regardless of its phylogenetic relations.

Agrobiodiversity and adaptability to environmental changes derived from global warming are challenges for the future of agriculture. In this sense, landraces often have high levels of genetic variation, tightly connected with the changing environmental conditions of a territory. The genus Phaseolus, with five domesticated species, is one of the most important sources of proteins, carbohydrates and micronutrients in various countries. This study aimed to compare the adaptation capacity to drought, in the vegetative growth phase, of a commercial cultivar and two landraces traditionally cultivated in the Mediterranean basin of Phaseolus lunatus (Lima bean). Growth and biochemical responses of the analysed genotypes to different water-deficit treatments were evaluated and compared. In addition, the effectiveness of the voltammetric method for evaluating stress levels in cultivated plants was tested. The studied parameters revealed that P. lunatus is a drought-tolerant species, showing similar results for the three cultivars. However, contrary to what was expected from the germination phase results, the commercial variety Peru showed some better responses under water stress conditions. Finally, the voltammetric method proved to be a good and fast tool for assessing oxidative stress in cultivated plants, showing results in agreement with total phenolic compounds and total flavonoid fluctuations.

Coastal habitats with Juniperus sp. pl. represent the mature stage in the ecological succession of dune ecosystems. Maritime junipers (Juniperus macrocarpa), prickly junipers (J. navicularis) and caudate junipers (J. turbinata subsp. turbinata) are dominant in the Iberian Peninsula and Balearic Islands communities. This study analyses the biogeographical distribution of 12 habitats, the biotopes they occupy (stabilised sands, coastal cliffs), their biological value, natural and anthropogenic threats and the risk category, according to the IUCN scale, which varies from vulnerable habitats to those in danger of extinction. Half the studied habitats are classified as vulnerable and others endangered. The latter correspond to small populations located in southeast and east Spain and on the Balearic Islands. Isolation, together with poor seed viability and several anthropic factors, contribute to these communities’ vulnerability.

Agriculture is highly exposed to climate warming, and promoting traditional cultivars constitutes an adaptive farming mechanism from climate change impacts. This study compared seed traits and adaptability in the germinative process, through temperature and drought response, between a commercial cultivar and Mediterranean Phaseolus lunatus L. landraces. Genetic and phylogenetic analyses were conducted to characterize local cultivars. Optimal germination temperature, and water stress tolerance, with increasing polyethylene glycol (PEG) concentrations, were initially evaluated. Base temperature, thermal time, base potential and hydrotime were calculated to compare the thermal and hydric responses and competitiveness among cultivars. Eight molecular markers were analyzed to calculate polymorphism and divergence parameters, of which three, together with South American species accessions, were used to construct a Bayesian phylogeny. No major differences were found in seed traits, rather different bicolored patterns. A preference for high temperatures and fast germination were observed. The ‘Pintat’ landrace showed marked competitiveness compared to the commercial cultivar when faced with temperature and drought tolerance. No genetic differences were found among the Valencian landraces and the phylogeny confirmed their Andean origin. Promoting landraces for their greater resilience is a tool to help overcome the worldwide challenge deriving from climate change and loss of agrobiodiversity.