Use of babassu decomposed stem substrate on the vegetative propagation of Euphorbia splendens

The present study aimed to evaluate the use of the babassu decomposed stem under different proportions in substrate composition for the vegetative propagation of Euphorbia splendens. The experiment was conducted in a greenhouse and we used a completely randomized design with six treatments and four repetitions. Six types of substrates were formulated using a mixture of babassu decomposed stem (BDS) and soil (SL) in the proportions of 100% SL, 20:80 % BDS:SL, 40:60 %, BDS:SL, 60:40 % BDS:SL, 80:20 % BDS:SL and 100 % BDS. The seedlings were evaluated at 45 days after cutting by measuring the diameter of the longest shoot, number of leaves, number of shoots, root length, root volume, largest shoot length, fresh weight of the aerial part, root fresh weight, dry weight of the aerial part, and root dry weight. The treatments that presented normality and homoscedasticity were submitted to simple linear regression analysis. The proportion of the substrate of 20: 80% BDS: SL has a greater length of the largest shoot about the substrate 80:20% BDS: SL. The diameter of the largest sprout, the number of leaves, and the root length decreased due to the increase in the proportion of babassu decomposed stem in the substrates. The production of seedlings using cuttings of Euphorbia splendens is facilitated by the fact that it is a species with easy rooting, therefore, it is not necessary to use substrates with proportions of babassu decomposed stem and soil for its vegetative propagation.


Introduction
The substrate selection is especially important to produce healthy and vigorous seedlings. However, obtaining this organic compost depends on the cost and availability in the locality (Santos et al., 2015) combined with the physical and chemical characteristics that promote moisture retention, so water and nutrients are available to meet plant needs . Therefore, the use of alternative substrates from industrial or agroindustrial waste can be a solution to make both activities more sustainable (Costa et al., 2013).  (Gomes et al., 2008). Among these native species, the Euphorbiaceae family stands out in economic activity due to its use in food and medicine from popular knowledge (Trindade and Lameira, 2015).
The christ thorn (Euphorbia splendens), also popularly known in Brazil as the crown of thorns, Christ plant, Well Married, and Two Brothers (Vasconcellos & Amorim, 2003), is a shrub of the Euphorbia family, constituted by a climbing stem and prickly, tortuous and prostrate branches so this plant has reduced architecture (bush) with leaves of matte green color, small usually arranged at the stem apex, however, the christ thorn does not have leaves in winter, unlike its flowers which are present in all seasons. The flowers are in pairs and supported by two bracts (Biachini et al., 1994).
There is great economic viability to produce Euphorbia splendens seedlings using low-cost and easily accessible substrates. Therefore, the present study aimed to evaluate the use of the babassu decomposed stem under different proportions in substrate composition for the vegetative propagation of Euphorbia splendens. Research, Society and Development, v. 9, n. 9, e861997916, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i9.7916 5

Methodology
The experiment was carried out in a greenhouse with 70% luminosity control, from We performed the physical (Table 1) and chemical (Table 2) analyzes of the substrates before installing the experiment when the substrates had soil in their composition, we performed the granulometric analysis: 384 g coarse sand kg -1 , 336 g fine sand kg -1 , 112 g silt kg -1 , 168 g of total clay kg -1 , 38 g of natural clay kg -1 , sandy loam texture class, and soil flocculation degree of 77 g / 100 g. Table 1. Density (D), particle density (PD), and porosity (P) of the substrates based on babassu decomposed stem (BDS).

Substrates
Density (  For the production of Euphorbia splendens seedlings, we collected cuttings from the stock plant around five centimeters in length, casually allocated in polyethylene bags with dimensions of 12 x 20 cm. The seedlings were watered daily. At 45 days after cutting, The variables evaluated were: a) number of shoots (NB) and number of leaves (NF) -was evaluated by counting live cuttings that had sprouting, b) largest Research, Society and Development, v. 9, n. 9, e861997916, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i9.7916 7 shoot length (CMB) -measured using a ruler graduated in cm, c) diameter of the longest shoot (DB) -obtained by the digital caliper in mm, d) root length (CR) -measured using a ruler graduated in cm, e) root volume (VR) -performed by measuring the displacement of the water column in a graduated cylinder, in cm 3 , f) fresh weight of the aerial part (MFPA) and root fresh weight (MFSR) -weighed on an electronic scale (accuracy= ± 0.01 g) in g, dry weight of the aerial part (MSPA) and root dry weight (MSSR) -the material was dried in a forced-air circulation oven (65°C) until constant weight during 72 hours.
Data were submitted to the Shapiro-Wilk test (p> 0.05) and f test (p <0.05) to verify the normality and homoscedasticity of variances, respectively. Then, the means that demonstrated significance were compared by the Tukey test at 5% probability. The treatments that presented normality and homoscedasticity were submitted to simple linear regression analysis.

Results and discussion
There was a significant effect by the F test (p <0.05) for the fresh weight of the aerial part, root volume, the diameter of the longest shoot, number of leaves, largest shoot length and root length of Euphorbia splendens seedlings (Table 3).   Garreto et al. (2020) also observed that the volume and dry mass of the root of Polyscias spp. the seedlings did not differ in substrates with decomposed babassu stem.
DMB, NF, CMB, NB and CR were the variables that showed normality and homoscedasticity (Table 3). For these variables, we adjusted the linear models under the proportions of the decomposed babassu stem in the substrates. There was a significant effect on the linear regressions of DMB, NF and RC (Table 4).  Development, v. 9, n. 9, e861997916, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i9 The diameter of the largest shoot of Euphorbia splendens seedlings decreased by 0.03 mm with an increase of 1% in the proportion of BDS (Figure 1). According to the model adjusted with high precision (R² = 0.86), we observed that DMB of Euphorbia splendens seedlings had 3.95 mm without using the studied substrates.
These results differ from those found by Oliveira Neto et al. (2018), the authors observed the better root and shoot developments of pomegranate (Punica granatum L.) cuttings, using substrates with a mixture of babassu decomposed stem and soil The number of leaves decreased as the proportion of BDS increased ( Figure 2). We observed that increasing 1% of the proportion of BDS in the substrate decreased 0.15 the number of leaves of Euphorbia splendens seedlings. Euphorbia splendens seedlings without using the studied substrates showed around 22 leaves.
Research, Society and Development, v. 9, n. 9, e861997916, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i9.7916 Root length in seedling production is an important variable for the establishment of seedlings on the substrate. However, the root length of Euphorbia splendens seedlings showed a decrease due to the increase in the proportions of the babassu decomposed stem. For each addition of 1% BDS to the substrate, the root length decreased by 0.14 cm. Euphorbia splendens seedlings not submitted to the proportions of the studied substrates may have a root length of 15.29 cm. These results occurred because this ornamental species presents rusticity in propagation; in other words, rapid sprouting after rooting (Rossa et al., 2019).

Final Considerations
The proportion of the substrate of 20: 80% BDS: SL has a greater length of the largest shoot about the substrate 80:20% BDS: SL.
The diameter of the largest sprout, the number of leaves, and the root length decreased due to the increase in the proportion of babassu decomposed stem in the substrates.
The production of seedlings using cuttings of Euphorbia splendens is facilitated by the fact that it is a species with easy rooting, therefore, it is not necessary to use substrates with proportions of babassu decomposed stem and soil for its vegetative propagation.
New studies on the propagation of Euphorbia splendens seedlings by cuttings should be carried out.