The effect of exogenous spermine (SPM) on Castilleja tenuiflora shoots developing under nitrogen deficiency (ND) stress was evaluated. Shoots cultivated in a temporary immersion system were subjected to four experimental treatments: (1) control; (2) exogenous SPM; (3) ND; and (4) ND+SPM. Shoots were longer in the ND+SPM treatment (6.3 ± 0.5 cm) than in the ND treatment (4.2 ± 0.5 cm). The total chlorophyll content was similar in the control and SPM treatments (0.41 µg mg⁻¹ FM) and the highest values of total phenolic content were detected at 21 days in the ND+SPM treatment (84.1 ± 0.05 GAE g⁻¹ DM). In the ND+SPM treatment, the phenylalanine ammonia lyase activity increased earlier than in ND treatment, and reached its maximum at day 21 (3.9 ± 0.2 µmol E‐CIN h⁻¹ mg⁻¹ protein). Compared with the control, the ND and ND+SPM treatments resulted in increased secondary metabolites contents in both root and aerial parts. The strongest effect was in the roots, where the SPM and ND+SPM treatments both resulted in increased quercetin content (4.3‐fold that in the control). Our results showed that SPM partially counteract the damage caused by ND and results in increased contents of valuable bioactive compounds.

Hamelia patens (Rubiaceae), known as firebush, is a source of bioactive monoterpenoid oxindole alkaloids (MOAs) derived from monoterpenoid indole alkaloids (MIAs). With the aim of understanding the regulation of the biosynthesis of these specialized metabolites, micropropagated plants were elicited with jasmonic acid (JA) and salicylic acid (SA). The MOA production and MIA biosynthetic-related gene expression were evaluated over time. The production of MOAs was increased compared to the control up to 2-fold (41.3 mg g DW⁻¹) at 72 h in JA-elicited plants and 2.5-fold (42.4 mg g DW⁻¹) at 120 h in plants elicited with SA. The increment concurs with the increase in the expression levels of the genes HpaLAMT, HpaTDC, HpaSTR, HpaNPF2.9, HpaTHAS1, and HpaTHAS2. Interestingly, it was found that HpaSGD was downregulated in both treatments after 24 h but in the SA treatment at 120 h only was upregulated to 8-fold compared to the control. In this work, we present the results of MOA production in H. patens and discuss how JA and SA might be regulating the central biosynthetic steps that involve HpaSGD and HpaTHAS genes.

Climate change can reshape the climatic conditions available to mountain plants. Using MaxEnt, we modelled the current and future climatic suitability of Castilleja tenuiflora Benth., a medicinal hemiparasitic plant, across Mexico and quantified its spatial overlap with Mexican Protected Natural Areas (PNAs). The final model (LQ, RM = 0.5), calibrated with 194 spatially filtered presence records and seven bioclimatic predictors, achieved a mean spatial-validation AUC of 0.794 ± 0.093. Annual mean temperature and temperature seasonality were the dominant predictors, jointly accounting for approximately 96% of model contribution. Current climatic suitability above the 10th-percentile training-presence threshold (P10 = 0.162865) covered approximately 548,819 km². Future projections using CMCC-ESM2 under SSP1-2.6 and SSP5-8.5 for three periods spanning 2021–2080 showed net contractions in climatically suitable area under all scenarios. By 2061–2080, the area above P10 decreased by 41.6% under SSP1-2.6 and by 65.3% under SSP5-8.5. Across all projections, losses of climatically suitable area substantially exceeded gains, while the area maintaining suitable conditions decreased towards the end of the century; proportionally greater contractions were observed at more restrictive suitability thresholds. Currently, approximately 48,690 km² of ≥P10 climatic suitability overlaps the PNA network, decreasing to 23,638 km² under SSP5-8.5 by 2061–2080. Nevado de Toluca, Iztaccíhuatl-Popocatépetl, and Pico de Orizaba consistently retained areas above the P90 suitability threshold under current conditions and all six future projections. These results indicate a substantial potential contraction of climatic suitability for C. tenuiflora and highlight protected areas retaining suitable climatic conditions as priorities for field verification, monitoring, and conservation planning.