Improving growth and physiological indices of cabbage seedlings through different concentrations of selenium under alkaline stress conditions

Background and Objectives: Alkaline stress, by creating high pH and the accumulation of sodium ions, can lead to proton deficiency and the destruction or inhibition of the electrochemical gradient/potential in root cells, which consequently disrupts water and ion absorption. Alkaline stress slows down photosynthesis and consequently plant growth. Alkalinity also causes the formation of insoluble forms of iron, zinc and copper that are not absorbable by the plant, resulting in reduced chlorophyll synthesis and yellowing of young leaves. In recent years, many researchers have proposed the biological enrichment technique to reduce selenium deficiency in humans. Selenium is one of the non-essential but beneficial elements for plants that can neutralize or somewhat reduce the effects of alkaline stress.

Materials and Methods: The experiment was conducted as a factorial in a randomized complete block design with three replications in the fall and winter of 2024 in the greenhouse complex of Shahid Chamran University of Ahvaz. The experimental treatments included selenium concentrations (0, 5, 15, and 30 mg/L) and bicarbonate levels (0, 3, and 6 meq/L). After applying the treatment and completing the experiment, morphological traits such as seedling height and hypocotyl length were measured using a ruler, hypocotyl diameter was measured using a digital caliper, fresh and dry weights of shoots and roots were measured using a scale and dried in an oven at 70 °C for 48 h, leaf area was measured using a leaf area meter, and physiological traits of cabbage seedlings such as photosynthetic pigments were measured using a spectrophotometer, relative leaf water content, and electrolyte leakage were calculated using standard equations.



Results: The results showed that adding selenium to the culture medium under alkaline stress generally led to an increase in the fresh and dry weight of different organs. Under stress conditions, the highest shoot fresh weight (2 g)-a key indicator of seedling quality-was observed in the 15 mg/L selenium + 3 meq/L bicarbonate treatment which compared to the treatment of 0 mg/L selenium + 3 meq/L bicarbonate stress, increased the shoot fresh weight of cabbage seedlings by 16.27%, which is one of the interesting findings of this study.

The use of selenium under alkaline stress conditions reduced ion leakage and increased the relative water content of cabbage seedlings. The results of this study showed that selenium at optimal concentrations can act as a factor improving plant growth and tolerance to alkaline stress. However, high concentrations of selenium can have toxic effects and damage plant growth. For instance, in the non-stress treatment increasing the selenium concentration to 30 mg/L reduced seedling fresh weight by 59.44% compared to the 0 mg/L selenium treatment.

Conclusion: Research results show that cabbage has the ability to enrich selenium. Appropriate levels of selenium treatment can improve the growth and quality of cabbage. Considering the unusual water consumption in seedling production greenhouses in the south of the country and the subsequent development of yellow leaves and thin stems, it seems absolutely necessary to provide a practical solution for enriching cabbage and solving the problems of seedling production units. Considering the moderation of the adverse effects of water quality used in the greenhouse by optimal selenium levels, it seems that this is an important step towards developing sustainable agriculture and increasing agricultural production in areas with alkaline water research by modifying conventional agricultural practices. Based on the results, a selenium concentration of 15 mg/L is recommended to moderate the negative effects of alkali stress and improve seedling growth in greenhouses producing of cabbage seedlings, especially in greenhouses with alkaline water.