This experiment was conducted to examine the influence of drying methods on the essential oil of chamomile (Matricaria chamomilla L.) and its chemical composition. Chamomile flower heads were dried using five different methods: sunlight for 72 h; shade for 1 week; oven at 40 °C for 72 h; solar dryer for 72 h; and microwave for 5 min. Drying methods had slight and nonsignificant impacts on dry biomass of flower heads. The highest percentages of oil in flowers (0.35–0.50%) were observed after solar-drying methods, and the lowest percentage of oil was found after microwave drying (0.24–0.33%). Drying methods significantly influenced the number of identified compounds. The maximum was identified after solar drying (21 compounds), while the lowest was identified after microwave drying (13 compounds), which revealed the solar ability to preserve compounds in contrast to microwave, which crushed the compounds. Major compounds were α-bisabolol oxide A (33.0–50.5%), (Z)-tonghaosu (10.0–18.7%), α-bisabolol oxide B (8.2–15.4%), α-bisabolone oxide A (5.4–14.6%), and chamazulene (1.9–5.2%) of essential oil. Drying methods clearly affected major compounds’ content as the lowest α-bisabolol oxide A was after sun drying, and the lowest α-bisabolol oxide B was after solar drying. (Z)-tonghaosu increased during drying compared to fresh flowers. Solar drying maintained higher chamazulene content (3.0%) compared to other drying methods. The results of this study suggest that drying under the shady conditions preserved chemical composition of essential oil with higher α-bisabolol content compared to other drying methods.

The growth and quality of medicinal plants are greatly affected by environmental stress, with over half of the world’s agricultural land facing water shortages. This research was conducted over two seasons in 2018 and 2019 and aimed to investigate the influence of varying irrigation intervals and partial replacement of mineral fertilizers with biofertilizer (yeast) on the growth, yield, and essential oil content of lemongrass. The study also looked at the effect of the partial substitution of NPK fertilizer with yeast on lemongrass’s ability to withstand water deficit stress. The results showed that water deficit and reducing NPK levels led to a decline in growth characteristics and relative leaf greenness, which was accompanied by an increase in proline content and essential oil percentage. These findings suggest that lemongrass is sensitive to drought and requires adequate nitrogen fertilization. However, extending the irrigation intervals led to an improvement in essential oil content. To achieve high essential oil yield and maintain productivity while considering environmental factors, it is recommended to reduce mineral fertilizer to 50–75% NPK combined with biofertilizer, and space irrigation intervals every 10–15 days. Further research is needed to improve the growth of lemongrass in water-deficient conditions, particularly on newly reclaimed soils.

Owing to its hand-picked flower heads and its applications in organic farming systems, Egyptian chamomile has a good reputation in export markets. This study was carried out to evaluate the growth, productivity and oil quality of chamomile during two successive seasons in El-Sharkia, Egypt, at four different locations, which differed greatly in the salinity of soil and irrigation water. Salinity did not negatively impact yield or essential oil contents. The greatest yield and essential oil content were obtained under high-salinity conditions. Total of 28 compounds were identified. Oxygenated sesquiterpenes were more abundant under high-salinity conditions, while sesquiterpene hydrocarbons were more abundant under low-salinity. The main components were differentiated across locations and harvest times. The main components were bisabolol oxide A, cis-β-farnesene, bisabolol oxide, and bisabolol oxide B. Bisabolol oxide A contents were much greater under high-salinity, while cis-β-farnesene contents were much greater under low-salinity. These results confirmed the impact of soil properties on the quality and productivity of chamomile. By avoiding salt accumulation, the chamomile plants were highly resistant to salinity stress. Increased flower yields and essential oil contents were observed under high-salinity stress, and farmers are encouraged to grow chamomile where saline soil and/or saline irrigation water are present.

Environmental stress has a major influence on the growth and quality of medicinal plants. More than half of the agricultural land worldwide suffers from a lack of water. In this study, we estimated the effect of different irrigation intervals on growth, yield, and essential oil content as well as their effect on the main compounds of the essential oil of lemongrass, Cymbopogon citratus. The major objective was to test how much irrigation consumption can be lowered without a significant impact on yield and quality properties. Water deficit led to significant decreases in growth characteristics including the number of tillers as well as fresh and dry herb yield. In addition, the relative leaf greenness decreased under water deficit, especially in plants irrigated every 20 days. In contrast, proline content increased with increasing water deficit, especially in plants irrigated every 15 and 20 days. Essential oil percentage also increased under a water deficit condition, and the highest essential oil percentage was observed in plants irrigated every 15 and 20 days. However, the yield of essential oil per plant significantly decreased due to decreasing the herb yield. GC-MS analysis identified 31 compounds, mainly geranial and neral. Geranial and neral percentage decreased under a water deficit of 10-day irrigation intervals but increased with increasing the water deficit severity at irrigation intervals of 15 and 20 days. These results suggest that the lemongrass plant was sensitive to drought. Nevertheless, the quality represented by essential oil percentage and the main active substances improved with prolonging the irrigation intervals. This study recommends increasing irrigation intervals to 10 days to maintain small decreases in the yield with higher quality. In addition, it is recommended to conduct more studies to improve the growth of lemongrass under water shortage conditions.

Salinity stress is a significant abiotic factor that limits plant growth and productivity by causing ionic imbalances and oxidative damage. Chelated zinc (Zn) has gained attention as an effective micronutrient to mitigate salinity-induced stress by enhancing antioxidant defense mechanisms, osmotic regulation, and physiological processes. This study aimed to investigate the impact of foliar-sprayed chelated Zn on the alleviation of salinity stress in Calendula officinalis. A pot experiment was conducted with varying salinity levels (0, 1000, 2000, and 3000 ppm NaCl) and Zn concentrations (0, 200, 400, and 600 ppm). The results demonstrated that chelated Zn significantly enhanced the growth parameters, flower yield, and biochemical traits, particularly under high-salinity conditions. Salinity stress was associated with a marked increase in the Na⁺ and K⁺ concentrations and a reduction in the Zn levels in the leaves. However, the foliar application of chelated Zn reduced the Na⁺ and increased the K⁺ concentrations in the leaves, resulting in an elevated K⁺/Na⁺ ratio with higher salinity and Zn application rates. Furthermore, the salinity and chelated Zn treatments stimulated the production of proline, phenols, flavonoids, and antioxidant activity, indicating the plant’s adaptive mechanism to enhance its secondary metabolite production under stress. These findings highlight the potential of chelated Zn to improve the salinity tolerance, supporting sustainable agricultural practices in saline-affected areas. Although salinity reduced the overall growth of C. officinalis, farmers are encouraged to cultivate this plant for its valuable inflorescences under saline irrigation conditions (up to 2000 ppm), combined with chelated Zn foliar applications at 400–600 ppm. We also recommend further research on other micronutrients.