Improvement and breeding
Sanaz Rajabi Khamseh; Mahmoud Bahador; Hossein Safikhani Mahmoudzadeh; Habib Yousefian
Abstract
Background and Objectives: Marigold (Calendula officinalis L.) is a medicinal and ornamental herbaceous plant belonging to the Asteraceae family. Since ancient times, it has been valued for its leaves, roots, flowers, and seeds, owing to the presence of bioactive compounds such as ...
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Background and Objectives: Marigold (Calendula officinalis L.) is a medicinal and ornamental herbaceous plant belonging to the Asteraceae family. Since ancient times, it has been valued for its leaves, roots, flowers, and seeds, owing to the presence of bioactive compounds such as flavonoids, carotenoids, steroids, terpenoids, phenolic acids, mucilages, and vitamin E. Salinity stress is among the most critical factors limiting plant production, particularly in arid and semi-arid regions. The present study aimed to evaluate the effect of foliar application of salicylic acid on the growth characteristics and photosynthetic pigment content of marigold under saline conditions.
Methodology: This experiment was conducted as a factorial arrangement within a completely randomized design, with three replications, in pots at the research greenhouse of the University of Agricultural Sciences and Natural Resources, Sari. The treatments included salinity (sodium chloride) at five levels (0, 50, 100, 150, and 200 millimolar) as the first factor, and foliar application of salicylic acid at three levels (0, 1, and 2 millimolar) as the second factor. Planting was carried out on December 1, 2013, in pots measuring 25 cm × 25 cm, each containing four plants and irrigated with 200 milliliters every two days. Distilled water was used for the zero-millimolar treatment. Salinity stress was initiated at the four-leaf stage. Foliar application of salicylic acid was performed twice during the four-leaf stage. To facilitate acclimatization, the pots were placed outdoors before the experiment. Harvesting was conducted on February 28 at the full flowering stage. After harvest, measurements included plant height, the number of flowers, the dry weight of flowers, the dry weight of aerial parts, photosynthetic pigments, the relative water content of leaves, and electrolyte leakage. Data analysis was performed using SAS software.
Results: The results indicated that foliar application of salicylic acid significantly improved plant height, dry weight of shoots, number of flowers, dry weight of flowers, chlorophyll a and b content, carotenoid levels, relative leaf water content, and electrolyte leakage. The highest values for these traits (excluding electrolyte leakage) were obtained with one mM salicylic acid treatment under control (0 mM) salinity. The lowest values were recorded in 0 mM salicylic acid and 200 mM salinity treatment, showing reductions of 193.3% in plant height, 70.8% in shoot dry weight, 332% in number of flowers, 430% in flower dry weight, 186.7% in chlorophyll a, 216.7% in chlorophyll b, 185.7% in carotenoids, and 215.9% in relative leaf water content compared to 1 mM salicylic acid treatment at zero salinity. The lowest electrolyte leakage occurred in treatments with 1 and 2 mM salicylic acid and irrigation with distilled water, representing a 481.5% reduction compared with the non-sprayed treatment at 200 mM salinity.
Conclusion: In general, foliar application of salicylic acid partially alleviated the adverse effects of salinity and had a significant positive influence on the evaluated traits up to a salinity level of 100 mM. Among the salicylic acid treatments, the one mM concentration exerted the highest effect in reducing stress impact, producing the highest values for the measured traits.
