The study was conducted in 2024-2025 at the experimental site of the Samarkand Institute of Agri-Innovations and Research, in a temperate climatic zone with hot, dry summers and relatively mild winters (mean annual temperature +14.5˚C; summer maxima of +35˚C - 37˚C).

Two species were studied: V. major L. and V. minor L. Cuttings were taken in spring, during active vegetative growth, from healthy and uniformly aged mother plants. Each cutting was 15 - 20 cm long and had at least 2 - 3 nodes; the lower leaves were removed and the upper leaves were retained, and the base was cut at 45˚ to improve the uptake of water and stimulator solution. Vegetative propagation followed the method of Mityakov and Shakina.

Three commercial stimulators were tested (Figure 1). According to the product descriptions, Gumi-Mix is a humic preparation containing humic acids, amino acids and microelements (Fe, Zn, Mn, Cu); Rootex Gold contains indole-3-acetic acid (IAA) and naphthylacetic acid (NAA); and Kornevin is based on indole-3-butyric acid (IBA). Control cuttings were soaked in distilled water. The bases of the cuttings were soaked for 3, 6 or 12 h in each solution, giving 4 solutions × 3 soaking durations for each species.

Stimulators are generally considered to act on auxin- and cytokinin-related processes and on cell differentiation in the basal tissues of cuttings [9]. Substrate, temperature, humidity and light also influence rhizogenesis [10].

After soaking, the cuttings were planted in pots filled with sand. Fifty cuttings were used for each combination of species, solution and soaking duration (Table 1), i.e. 24 groups and 1200 cuttings in total. Temperature was maintained at 22˚C - 25˚C and relative humidity at about 70% - 80%. Cuttings were kept in natural light without direct sunlight, watered once a week and cultivated under uniform agrotechnical conditions. The experiment lasted 60 days. The labelled pots with cuttings are shown in Figure 2 and Figure 3.

Observations were made every 10 days over the 60-day period. The following variables were recorded: the number of rooted cuttings (expressed as a percentage of the 50 cuttings planted in each group, which is the denominator), the average number of roots per cutting, root length (cm) and the day on which roots were first observed.

Rooting is reported as the number and percentage of rooted cuttings per group (n = 50), and all percentages were recalculated from the counts. For each species and solution, the counts from the three soaking durations were pooled (150 cuttings) and 95% Wilson confidence intervals were calculated. These intervals treat every cutting as an independent observation and ignore any clustering of cuttings within pots, so they may understate the true uncertainty. No hypothesis tests were performed, because the experimental unit and the replication have not yet been established (Section 2.3); differences between treatments are therefore described as numerical differences. Root number and length are reported as means or ranges without dispersion estimates.

Table 1 gives the number of rooted cuttings in each group. Rooting ranged from 80% to 98% in V. major and from 80% to 96% in V. minor. In V. major, Gumi-Mix gave the highest rooting at every soaking duration (3 h: 44/50, 88%; 6 h: 49/50, 98%; 12 h: 48/50, 96%), followed by Kornevin (84%, 94% and 90%), Rootex Gold (82%, 88% and 84%) and the control (80%, 84% and 82%) [6]. In V. minor, Kornevin gave the highest rooting at every soaking duration (3 h: 46/50, 92%; 6 h: 48/50, 96%; 12 h: 45/50, 90%), followed by Gumi-Mix (88%, 94% and 86%); Rootex Gold (82%, 84% and 80%) did not exceed the control (84%, 88% and 80%) [7]. In both species and for all four solutions, 6 h gave the highest rooting.

Table 1. Number and percentage of rooted Vinca major and Vinca minor cuttings (n = 50 cuttings per group) after soaking for 3, 6 or 12 h. Percentages were recalculated from the counts.

Pooled over the three soaking durations (Table 2), rooting in V. major was 94.0% with Gumi-Mix, 89.3% with Kornevin, 84.7% with Rootex Gold and 82.0% in the control. The confidence interval for Gumi-Mix (89.0% - 96.8%) did not overlap that of the control (75.1% - 87.3%). In V. minor, the pooled values were 92.7% for Kornevin, 89.3% for Gumi-Mix, 84.0% for the control and 82.0% for Rootex Gold, and the intervals for Kornevin and Gumi-Mix overlapped broadly.

Table 2. Pooled rooting (3, 6 and 12 h combined; 150 cuttings per species and solution) with 95% Wilson confidence intervals.

Confidence intervals treat each cutting as independent and are descriptive only (Section 2.5).

In V. major, roots first appeared on day 7 with Gumi-Mix, on day 8 with Kornevin and Rootex Gold, and on day 9 in the control (Table 3). The mean number of roots per cutting was 7 with Gumi-Mix at 6 h and 6 at 12 h, 3 - 5 with Kornevin (6 h) and Rootex Gold, and 2 in the control. Root length was 4.9 cm (Gumi-Mix, 6 h), 4.5 cm (Gumi-Mix, 12 h), 3.8 cm (Kornevin, 6 h), 3.5 cm (Rootex Gold) and about 1.5 cm in the control [6]. Gumi-Mix at 6 h thus had 3.5 times as many roots (7 vs 2) and 3.3 times the root length (4.9 vs 1.5 cm) of the control, and roots appeared 2 days earlier (day 7 vs day 9).

Table 3. Rooting traits of Vinca major cuttings.

^aValues read from the original bar chart; the soaking duration was not stated.

In V. minor, roots first appeared on days 7 - 9 with Gumi-Mix, days 8 - 10 with Kornevin, days 9 - 11 with Rootex Gold and days 9 - 12 in the control (Table 4). The number of roots per cutting was 6 - 8 with Gumi-Mix, 5 - 7 with Kornevin, 4 - 6 with Rootex Gold and 3 - 5 in the control, and root length was 5.2 - 6.3, 4.5 - 5.5, 3.8 - 4.6 and 3.0 - 4.3 cm, respectively [7]. Comparing range midpoints, Gumi-Mix cuttings had about 1.8 times as many roots (7 vs 4) and 1.6 times the root length (5.75 vs 3.65 cm) of control cuttings, and roots appeared 2 - 3 days earlier (range limits of 7 and 9 days vs 9 and 12 days). Because these values are ranges without sample sizes or dispersion estimates, the comparison is descriptive.

Table 4. Rooting traits of Vinca minor cuttings (ranges as reported).

Differences between the two species were small and inconsistent. Pooled rooting was higher in V. major with Gumi-Mix (94.0% vs 89.3%) and Rootex Gold (84.7% vs 82.0%) but higher in V. minor with Kornevin (92.7% vs 89.3%) and in the control (84.0% vs 82.0%), and all of these differences were small compared with the confidence intervals in Table 2. The data therefore do not show that either species roots better overall.