3.2.1. Cutting Tests
The cutting experiments were conducted with cuttings taken from 5 to 8-year-old adult donor plants (ADP) and 1-year-old juvenile donor plants (JDP) (
Table 3). The ADP and JDP cuttings were planted four days after being harvested and on the same day, respectively.
In the first cutting experiment, carried out with ADP cuttings, almost all the cuttings treated with IBA and the control cuttings dried out 53 days after the experiment was set up. The percentage of individuals that sprouted leaves and persisted was 5%: one control cutting and one treated with AIB at 1000 mg/l. The temperature and relative humidity were monitored after the end of the first cutting test and every hour for 30 days.
The age of the mother plant proved to be an important factor for the cuttings’ behavior in cultivation. In the JDP test, the rate of sprouting and root development was considerably higher than in the ADP test. Added to this is the difference in the planting time after collection, with immediate planting and the more favorable temperature and humidity conditions in the JDP test. The effect of maturation and aging of donor plants has been reported to influence the performance of rooted cuttings, such that a general decline in the rooting capacity and quality of nursery-grown plants is observed, as well as a reduction in survival, associated with donor plants that have reached a state of reproductive maturity [
25].
The second cutting experiment was set up with JDP cuttings and, after planting the cuttings, the temperature and relative humidity were monitored every hour for 45 days.
At the end of the second cutting test, at 70 days, four control cuttings and four cuttings treated with AIB at 1000 mg/l had sprouted leaves and developed roots. This represented 38% of the cuttings with persistent sprouting, which did not dry out during the cutting test.
In between tests, of the 762 records, 8.5% had temperatures higher than 32 °C. The highest temperature was 39.9 °C and the lowest 10.1 °C. As for relative humidity, 34% of the records were lower than 70%, and the average relative humidity for the period was 76%.
In the second cutting test of the 1104 records, 3.4% had temperatures higher than 32 °C. The highest temperature was 37.8 °C and the lowest 14.5 °C. As for relative humidity, 32% of the records were lower than 70%, and the average relative humidity for the period was 79%.
C. pulchra showed tolerant behavior to high temperatures, similar to the conditions in the Caatinga and Cerrado environments, where wild populations live, in full sun. Under greenhouse growing conditions, the plants did not stunt despite lower light levels. The optimum temperature range for cultivation was from 20–30 °C, with faster development and greater production. Although the plants come from dry environments, they grew well at 77% relative humidity.
For
C. pulchra cuttings, young, less lignified plants are more suitable for collecting branches, indicating that the age of the plant interferes with this type of approach, already evidenced in other cutting experiments with other species, where cuttings taken from juvenile individuals exhibited significantly higher rooting percentages than those taken from adult individuals [
13,
26]. Other conditions for the greater success of the second cuttings may have been the speed with which the cuttings were planted; unlike in the first test, with cuttings received from Bahia, in the second test, the cuttings were immediately planted. These results guide sustainable exploration efforts for this species, with the cultivation of seedlings from young plants kept in a nursery being a better strategy than field collection. This approach speeds up and makes the seedling production process cheaper, eliminating the need for collection.
3.2.2. Development Monitoring
The plants from seed germination had measurements taken every 40 days with n = 4 different times (t
0 = 40 days, t
1 = 80 days, t
2 = 120 days, and t
3 = 160 days). Three t-tests were applied to compare the average height of the plants grown in the two different substrates. According to the 95% confidence interval, there is 95% confidence that the true average height difference at 40 days is between 2.57 cm and 5.57 cm; at 80 days it is between 5.59 cm and 11.42 cm; and at 120 days between 4 cm and 18.21 cm. The average height of the plants in red latosol was greater compared to the plants in commercial garden soil. Thus, the differences in average plant height in the different substrates were statistically significant (
Table 6).
The average diameter difference was also compared using three t-tests. The tests showed that the differences in the average diameter of the plants grown in the different substrates were statistically significant. The red latosol, on average, provides the largest plant diameter.
The period in which there was the greatest difference in average height and diameter development between the plants grown in the different substrates was 120 days. In red latosol, the average height was 37.44 cm, and the average diameter was 2.99 mm. In commercial garden soil, the average height was 36.91 cm, and the average diameter was 2.92 mm (
Table 7).
When comparing all the parameters analyzed for the two substrates, the commercial garden soil brought greater benefits to the C. pulchra plants compared to the red latosol. Despite the better development, there was a low proportion of surviving plants in red latosol. A difference test of proportion was carried out on surviving plants at 120 days of cultivation.
A high mortality rate was observed for plants from seed germination grown in red latosol, with the number of individuals decreasing over time, with one surviving at 160 days (
Table 8;
Figure 5). This may have occurred because latosol has low fertility, acidity, and high aluminum content, which, when in excess, is toxic to plants [
27].
The difference test for the proportion of surviving plants in the two types of substrates (
Table 9) showed that there was a high proportion of plant mortality in red latosol at 120 days. A priori, the proportion of surviving plants in the commercial garden soil was significantly higher than the proportion of surviving plants in the red latosol. The test was significant, and the Agresti–Caffo 95% CI indicates a 95% confidence that the true difference in survival rate at 120 days is between 47.70% and 75.41%. In other words, a
C. pulchra plant grown in commercial garden soil is expected to have between 47.70% and 75.41% more probability of survival at 120 days of cultivation.