Improvement and breeding
Bohloul Abaszadeh; Sahar Fanaee; Davood Bakhshi
Abstract
Background and objectives: Plants are exposed to various environmental stresses during their growth period in nature and under field conditions. Due to its medicinal and therapeutic properties, Silybum marianum L. Gaertn. has been used since ancient times for the treatment of liver and gallbladder diseases. ...
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Background and objectives: Plants are exposed to various environmental stresses during their growth period in nature and under field conditions. Due to its medicinal and therapeutic properties, Silybum marianum L. Gaertn. has been used since ancient times for the treatment of liver and gallbladder diseases. This study aimed to investigate the response of Silybum marianum to plant growth regulators under different soil moisture conditions.Methodology: The present study was conducted in the agricultural year 1401-1400 at the Forests and Rangelands Research Institute research farm located in Karaj, Iran. The research farm is 5 kilometers southeast of Karaj city at a geographical latitude of 35 degrees and 48 minutes north and a longitude of 51 minutes east, with an elevation of 1320 meters above sea level. The study was carried out in a randomized complete block design with three replications. The experimental treatments included different levels of field capacity (90%, 75%, 50%, 25% FC) and foliar application with plant growth regulators such as salicylic acid (75-150 mg.l-1), spermine (70-140 mg.l-1), brassinosteroid (C28) (1-1.2 µM), and water (control). Soil moisture levels were determined daily using the weighing method and TDR (Time Domain Reflectometry) in the range between field capacity and 25% soil moisture content. Irrigation was conducted according to the desired treatments throughout the growth period based on the plotted graph and with the help of TDR. Foliar spraying was performed seven days apart in three stages, five months after seed sowing in April. At the end of the study, traits including average leaf number, leaf area, canopy diameter, number of lateral branches, root length, root collar diameter, days to leaf emergence, fruit antioxidant capacity, fruit color index, seed ash percentage, leaf sugar content, thousand seed weight, fruit yield, and oil content were measured.Results: The study showed that the reduction of field capacity (FC) reduced growth and yield traits in the plant compared to the control treatment. However, the foliar application of plant growth regulators improved growth traits effectively. For instance, the leaf number in the 25% field capacity treatment was almost halved compared to the control treatment (90% field capacity). Foliar spraying with brassinosteroids prevented a significant decrease in leaf number in the plant under different field capacity levels. The highest leaf area was observed in the treatment with 140 mg.l-1spermine + 75% field capacity. Foliar spraying with spermine and brassinosteroids had a significant effect on improving growth traits under stress conditions. Foliar spraying with spermine or brassinosteroids resulted in the highest oil content in the fruit under 50% field capacity conditions. Under 75% field capacity, foliar spraying with brassinosteroids (1 µM) increased fruit yield in the plant by 71% compared to the control treatment at the same stress level and by 5.5% compared to the control treatment under 90% field capacity conditions. The correlation analysis between color indices and fruit antioxidant capacity showed a positive and significant correlation between the percentage of fruit antioxidant capacity and brightness index (L), indicating that fruits with darker colors had higher antioxidant capacity. However, the redness index (a) and yellowness index (b) had a negative and significant correlation with fruit antioxidant capacity.Conclusion: The research findings have shown that reducing field capacity reduces plants' vegetative and reproductive growth parameters. However, foliar spraying plants with plant growth regulators improves plant growth conditions under water-limited conditions. In general, based on the research results, foliar spraying of plants with spermine at a concentration of 140 mg.l-1 helps improve the growth and performance characteristics, increasing the plant's resistance to moisture stress conditions in the soil.
