Damask rose (Rosa damascena Mill.) is an aromatic industrial plant with different applications. Selection of cultivars with high-value metabolites such as flavonoids—with acceptable yields—can lead to elite cultivars for mass propagation in various industries. A field experiment was carried out in a randomized complete block design (RCBD) to evaluate metabolites and some yield-related morphological data. In the present investigation, for the first time 13 flavonoid components of nine Iranian damask rose cultivars were compared using LC-MS/MS. As a result, 13 flavonoids were identified, most of which were reported for the first time in rose petals. Phloridzin (72.59–375.92 mg/100 g dw), diosmetin (82.48–153.16 mg/100 g dw) and biochanin A (0–1066.89 mg/100 g dw) were the most abundant, followed by trans-chalcone (0–106.29 mg/100 g dw) and diosmin (41.55–84.57 mg/100 g dw). Levels of naringenin also ranged from 3.77 in B111 to 54.70 mg/100 g dw in C294, while luteolin varied from 4.37 in B111 to 28.87 mg/100 g dw in C294. The SPME Arrow technique also was applied to determine the real aroma of the studied cultivars. Phenethyl alcohol was the most abundant compound, in the range of 69.28 to 77.58%. The highest citronellol/geraniol (C/G) was observed in D234 (4.52%) and D237 (4.30%), while the lowest amount belonged to A104 (1.28%). Rose oxide, as the most crucial factor for odor, ranged from 0.06% in D237 to 0.15% in D211. Based on cluster and principal component analysis (PCA), D234 cultivar can be suggested as a promising cultivar with high yield, high C/G content and high rose oxide, while D234 and C294 were the most valuable cultivars in terms of flavonoids with high yield. Finally, these cultivars can be introduced for further breeding programs and industrial cultivation.

Much is unknown about the positive effect of plant growth regulators, such as brassinosteroids, on high-temperature stress tolerance in pepper plants. This study aimed to reveal the effect of exogenous brassinosteroids (BRs) on high-temperature-stressed bell peppers by foliar application. BR treatments (1 µM), in both bulk (Br) and nano-encapsulated (N-Br) forms, were applied to pepper plants subjected to high-temperature stress (35 °C). The results indicated an increase in plant biomass, number of fruits, and relative water content and a significantly lower flower abscission in response to Br and N-Br under high temperatures. Br and N-Br applications at high temperatures resulted in the lowest leaf water potential. Br and N-Br, especially N-Br, were more effective than Br in the upregulation of the antioxidant enzyme activity, such as catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and the overall antioxidant capacity of heat-stressed plants. MDA and electrolyte leakage significantly declined as a result of BR application and the proline content of the leaves was significantly higher in Br and N-Br treatments at high temperatures. Further analysis of the data pointed to SOD, DPPH, proline, RWC, and leaf water potential in pepper leaves as the most affected traits in response to brassinosteroid application under high temperature. Glucose and fructose levels also increased under high temperature, and only N-Br administration showed a significant effect on reducing the sugar levels. At high temperatures, the ratio of saturated to unsaturated fatty acids was greatest when neither Br nor N-Br was present. N-Br could reduce this ratio effectively. Conclusively, the overall performance of bell pepper improved in response to both types of BR application with no significant discrimination being found to prioritize the encapsulated form of BR application.

Brassica vegetables are in high demand because they are an essential nutrient source for humans. Glucosinolates (GSLs), a major bioactive compound found in Brassicaceae, are amino acid derivatives that contribute to the health benefits of these crops. Light quality plays a significant role in plant growth and metabolite synthesis, and light-emitting diodes (LEDs) as artificial light sources offer many benefits. This study examined three cultivars of leafy cabbage B. oleracea. var. acephala (Kale), B. oleracea var. viridis (collard), and B. oleracea var. capitata (cabbage) grown under different LED conditions (red, blue, and blue–red) in the growing chamber. The primary objective of this study was to identify the most effective LED light spectrum for promoting GSLs accumulation and enhancing the overall plant quality. The findings of this study demonstrate that LED lights can have varying impacts on the cultivars of leafy cabbage. The different light spectra had varying impacts on the parameters examined in this study. GSLs compounds, particularly glucobrassicin, showed the most significant increase under the blue light treatment, with a 61% increase compared to the control. The R&B (red and blue) light treatment was the most effective in improving the growth traits of the shoot and root in the Kale cultivar. For the collard cultivar, the R&B light increased the leaf length and width, whereas for the cabbage cultivar, it led to an increase in the number of leaves and chlorophyll index. These findings demonstrate that the specific light quality can have different effects on the phytochemical composition and morphological characteristics of the different leafy cabbage cultivars. The blue light spectrum was particularly effective in enhancing GSLs accumulation, while the combination of red and blue light provided the most beneficial effects on overall plant growth and development across the three cultivars studied. These results suggest that the metabolism and phytochemical properties of leafy cabbage cultivars depend on exposure to multiple factors, such as cultivar type and light quality. Therefore, R&B light was the most effective light for most traits and can be suggested for performance.

Drought stress can substantially affect growth and secondary metabolite production in medicinal plants. This study evaluated the growth, physiological responses, and phenolic compound contents of ten Thymus populations under greenhouse and field conditions with three irrigation levels: control, moderate stress, and severe stress (corresponding to 100%, 70% and 40%, respectively, of field capacity). Drought significantly reduced plant height, biomass, and relative water content, with T. serpyllum and T. daenensis-1 showing greater reductions in several growth and physiological traits. In contrast, T. kotschyanus-2 and T. vulgaris generally maintained relatively better growth and water status. Under stress, proline accumulation and electrolyte leakage increased, while photosynthetic pigments declined and carotenoid levels increased in several populations. Total phenolic and flavonoid contents generally increased under drought, particularly in T. vulgaris and T. kotschyanus-2. Rosmarinic acid, the predominant phenolic compound detected, increased significantly under drought stress. Essential oil content ranged from 0.33% to 2.50% across populations and environments and showed population-dependent responses to drought, with increases observed in several populations. Multivariate analyses and drought tolerance indices identified T. kotschyanus-2 as showing relatively better drought performance among the evaluated populations, based on its relatively smaller reductions in biomass, higher relative water content, and favorable biochemical responses. In contrast, T. serpyllum showed comparatively greater sensitivity to drought across several measured traits. Drought reduced growth while enhancing the accumulation of several phenolic and other specialized metabolites, suggesting a potential shift in resource allocation between growth and secondary metabolism. T. kotschyanus-2 showed relatively better drought performance, suggesting its potential for further evaluation under water-limited cultivation conditions. Comparison of the greenhouse and field experiments revealed common drought-response patterns as well as environment-dependent differences in their magnitude.