Effect of biological factors on some growth characteristics of the Crocus sativus L. plant

Abstract

Crocus sativus L. is an autumn-flowering species belonging to the Iridaceae family. This study was conducted under greenhouse conditions at the Plant Production Technology Department, Agricultural Technical College, Northern Technical University, to evaluate the effects of the environmentally friendly biological agents Trichoderma harzianum T-22 and Bacillus subtilis on vegetative growth, flowering, stigma production, enzymatic activity, and corm yield of saffron using two application methods. Significant differences were observed between biological treatments and the untreated control. Corm immersion with T. harzianum T-22 promoted the earliest vegetative bud emergence (17.56 days). The same fungal treatment also produced the tallest plants, reaching 8.75 and 7.40 cm depending on the application method, whereas untreated plants reached only 3.42 cm. Both fungal and bacterial treatments significantly reduced the time required for flower bud emergence, with T-22 showing the shortest periods (89.77 and 89.81 days). Corm immersion with fungal and bacterial agents also shortened the time to first flower opening to 125.6 and 126.1 days, respectively. Fresh and dry stigma weights were significantly higher in biologically treated plants than in the control, which recorded only 0.021 and 0.002 g, respectively. Peroxidase activity in saffron leaves was highest in plants treated with T-22, reaching 0.096 unit min-¹ g-¹ fresh weight. Biological treatments also significantly increased corm number, corm fresh weight, cormlet number, and cormlet fresh weight compared with the control. Overall, T. harzianum T-22 and B. subtilis improved saffron growth, flowering, physiological activity, and yield under greenhouse conditions.

The results of the statistical analysis of vegetative growth characteristics, represented by the number of days for vegetative bud emergence, showed significant differences between the biological treatments and the control treatment. The best result was obtained with the fungal biological treatment (T-22) by immersing the corms for 17.56 days. As for the height of saffron plants, the tallest plants were those treated with the fungal biological agent (T-22) at rates of 8.75 cm and 7.40 cm, respectively, using both methods of application, while the shortest were the plants not treated with biological agents, at 3.42 cm. The results of the floral growth characteristics showed the significant superiority of the fungal and bacterial biological agents in both methods of use in terms of the number of days required for the emergence of the flower bud, with the best results achieved by the fungal biological agent (T-22), which required the lowest number of days for emergence, at 89.77 and 89.81 days, respectively. A significant superiority was also observed in the number of days required for the first flower to open when treated with fungal and bacterial biological agents by immersing saffron corms at rates of 125.6 and 126.1 days, respectively. They differed significantly from the other treatments studied in the experiment. In terms of fresh and dry stigma weight, fungal and bacterial biological  agents showed a significant advantage over the Comparison treatment, which resulted in lower weights (0.021 and 0.002 g, respectively).At the same time, the results of the peroxidase enzyme assessment in saffron leaves, which plays an important role in the oxidation of phenolic substances to protect plants from infection, showed significant differences between the biological agents, the highest being with the fungal biological agent (T-22) at 0.096 unit/minute/gram fresh weight. This was significantly different from the other treatments. The results of the statistical analysis of the corms and creams yield of saffron plants showed a significant superiority of biological fertilizers in terms of corms number, wet weight, creams number, and wet weight compared to the control treatment.