Stresses

Among global biodiversity hotspots, the Mediterranean Basin is expected to become the one containing the largest extent of urban land, leaving natural forest fragments embedded within urban areas. Consequently, urban forests represent key reservoirs of biodiversity in rapidly urbanizing regions. However, how tree species adjust to the fragmentation and altered conditions of these forests remains poorly understood. We evaluated the seasonal variation in leaf functional traits of Quercus frainetto in an urban and a natural forest stand belonging to the same phytosociological association, Roso arvensis-Quercetum cerridis, in the municipality of Campobasso (Italy), and compared these patterns with those of the co-dominant Q. cerris sampled in the same stands and campaigns. Specific leaf area (SLA), leaf dry matter content (LDMC), leaf thickness, chlorophyll, flavonols and anthocyanins were measured in June, July and September 2023 and analysed using linear mixed-effects models, together with satellite-derived environmental variables. Q. frainetto showed a seasonal shift toward a more conservative leaf economy, with declining SLA and increasing LDMC and flavonols. In the urban forest, Q. cerris combined relatively high SLA with consistently higher LDMC and higher flavonol content than Q. frainetto in July and September, whereas in the natural forest these differences were restricted to single sampling dates. Overall, in the stands studied, the urban functional profile of Q. cerris was more consistent with tolerance to warmer and seasonally drier conditions than that of Q. frainetto, a pattern that requires validation across multiple sites and years.

Plant establishment, encompassing seed germination and early seedling development, represents one of the most critical and vulnerable phases in the plant life cycle. During these transitions, plants encounter a wide range of abiotic stresses, which impair survival and establishment, ultimately affecting crop productivity. This review synthesizes current knowledge on the physiological, biochemical, and molecular mechanisms during the seed-to-seedling transition and responses to major abiotic stresses, such as drought, salinity, extreme temperatures, waterlogging, nutrient imbalances, and variable light. During germination, drought and salinity disrupt water uptake and imbibition kinetics and trigger hormonal signaling, osmotic adjustment, and antioxidant defense responses. Extreme temperatures further alter metabolic activation, enzyme stability, and membrane integrity, thereby affecting germination success. In contrast, waterlogging induces hypoxic conditions, which impair aerobic respiration and trigger adaptive responses such as anaerobic metabolism, fermentation, and aerenchyma formation. In parallel, the transition from skotomorphogenesis to photomorphogenesis requires precise coordination of phytochrome- and cryptochrome-mediated signaling networks, ensuring successful seedling emergence under variable light environments. Nutrient stress, including both deficiency and toxicity, affects reserve mobilization, root system architecture, and early seedling vigor. Emerging strategies, including seed priming, biopriming, nanotechnology-based interventions, and molecular breeding, are also discussed as approaches to enhance stress resilience during establishment. A deeper understanding of stage-specific regulation and mechanisms during seed-to-seedling development can provide critical insight for developing climate-resilient crops that maintain robust establishment under increasingly variable environmental conditions.

Benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), a salicylic acid (SA) analogue, induces resistance to several tomato pests and pathogens, including the whitefly Bemisia tabaci. However, the transcriptional mechanisms underlying BTH-induced responses to the biotic stress due to infestation by this insect remain incompletely understood. Here, we first investigated whether BTH treatment alters the tomato transcriptome consistently with activation of SA-associated defence. Gene expression in BTH-treated and untreated plants of susceptible tomato cv. Moneymaker was analysed using the Affymetrix GeneChip Tomato Genome Array. BTH treatment resulted in 1280 differentially expressed transcripts, including 502 upregulated and 778 downregulated transcripts. This was associated with increased expression of defence-related genes, including WRKY transcription factors and pathogenesis-related proteins, together with repression of genes involved in jasmonic acid signalling and photosynthetic processes. Subsequent B. tabaci infestation only slightly modified these transcriptional changes, with most differential transcripts shared between infested and uninfested plants. Comparison of BTH-treated Moneymaker with resistant Motelle (carrying the Mi-1 gene) identified 1241 differentially expressed transcripts. Overall, the results support a model in which BTH establishes a distinct SA-associated transcriptional state that is relatively stable following B. tabaci attack, while differing substantially from the constitutive transcriptomic profile associated with Mi-1-mediated genetic resistance.