The effect of mechanical stress on transplants of three ornamental Asteraceae species

Transplants of Tagetes patula L., T. erecta L. and Calendula officinalis L. were subjected to brushing treatment until appearance of visible inflorescence buds. At the end of treatment, plant height was statistically significantly decreased only in C. officinalis, whereas, at the beginning of flowering, the height of plants was statistically equal to untreated groups in all examined species. In T. patula, the treatment also did not influence other measured morphological parameters. However, in T. erecta, treated plants had higher numbers of lateral branches and leaves, and, in C. officinalis, the treatment resulted in more upright stems. Besides, treated plants in both T. erecta and C. officinalis had a higher number of inflorescence buds. The results indicate that brushing is not effective method for reducing plant height in the examined cultivars of T. patula and T. erecta, yet may be a valuable tool to improve some commercially important characteristics in T. erecta and C. officinalis transplants. However, some plants were damaged by brushing treatment, especially in C. officinalis. Further research is therefore needed to find the effectiveness of methods of applying mechanical stress in which physical contact with plants is reduced or avoided