Influence of phytohormones on vegetative propagation of different forms of pannonian thyme (Thymus pannonicus All.)

Abstract

The paper examined the impact of the application of three different phytohormones (INCIT 2, INCIT 5 and INCIT 8, all based on a-Naphthalene Acetic Acid (NAA)), with the cuttings of two forms of Pannonian thyme (the L-16 form, with hairy leaves, and the L-9 form, with hairless leaves), established during two periods (March and May), on the percentage of the rooted cuttings and the morphological properties of the seedlings. As the control, the variant without the application of the phytohormones was taken. The research was conducted in the period from 2019 to 2020, in a plastic greenhouse, using the plant collection of the Institute for Medicinal Plants Research "Dr Josif Pančić", which is located in Pančevo city, Serbia (44°52'20"N; 20°42'06"E; 74 m.a.s.l.). For this research was used the Pannonian thyme species (Thymus pannonicus All.) from the Lamiaceae family, which is grown and produced at the Institute. Plant establishment was carried out in four repetitions with 33 cuttings per each variant. Standard measures of care were used during the period of production of Pannonian thyme. The measurement was performed after 60 days from the date of conducted the experiment. The following parameters were measured: the percentage of rooted cuttings (%), the mass of the rooted plantlings (g), the mass of roots (g), the length of rooting (cm) and the number of root hairs of the formed rootings. The measuring was done using a ruler, millimetre paper and an analytical balance. Given the results achieved, INCIT 2 proved to be the most suitable phytohormone for the rooting of Pannonic thyme cuttings, with the average percentage of rooted cuttings of 61.3%. The lowest rooting percentage was recorded in the control variant, only 29.4%. Satisfactory rooting was found in the cuttings treated with INCIT 8 (57.6%). The L-16 form cuttings showed a higher rooting rate, an average of 53.8%, whereas the L-9 form cuttings had a lower average percentage of rooted cuttings (45.0%) for both plant establishment periods. Greater success and quality in the rooting of cuttings was recorded in the second (May) period of plant establishment, averaging 58.1%, which was higher by 17.4% than the percentage of rooted cuttings in the first establishment period (40.7%). It is important to note that the rooting of the L-9 form was significantly higher in the second establishment period (58.1%) than that in the first establishment period (31.9%).