Issue 4 (192)/2022

ALSE and ACS Style
Mohammed, A.L.; Addai, F.; Cobbinah, J.; Bawa, E. Germination and early growth performance of prekese, Tetrapleura tetraptera to seed pretreatment methods and phosphorus fertilizer in the nursery phase. Journal of Applied Life Sciences and Environment 2022, 55 (4), 505-516.
https://doi.org/10.46909/alse-554079

AMA Style
Mohammed AL, Addai F, Cobbinah J, Bawa E. Germination and early growth performance of prekese, Tetrapleura tetraptera to seed pretreatment methods and phosphorus fertilizer in the nursery phase. Journal of Applied Life Sciences and Environment. 2022; 55 (4): 505-516.
https://doi.org/10.46909/alse-554079

Chicago/Turabian Style
Mohammed, Adams Latif, Frank Addai, Joseph Cobbinah, and Elvis Bawa. 2022. “Germination and early growth performance of prekese, Tetrapleura tetraptera to seed pretreatment methods and phosphorus fertilizer in the nursery phase” Journal of Applied Life Sciences and Environment 55, no. 4: 505-516.
https://doi.org/10.46909/alse-554079

Germination and Early Growth Performance of Prekese, Tetrapleura Tetraptera to Seed Pretreatment Methods and Phosphorus Fertilizer in the Nursery Phase

Adams Latif MOHAMMED^1*, Frank ADDAI¹, Joseph COBBINAH¹ and Elvis BAWA²

¹Department of Agroforestry, Kwame Nkrumah University of Science and Technology, Kumasi-Ghana 
²Department of Wildlife and Range Management, Kwame Nkrumah University of Science and Technology, Kumasi-Ghana

*Correspondence: adamsinho224@gmail.com

Received: Apr. 01, 2023. Revised: May 24, 2023. Accepted: May 29, 2023. Published online: Jun. 08, 2023

ABSTRACT. Seeds of Tetrapleura tetraptera trees have poor germination due to their hard and impervious seed coat. This research was conducted to determine the possibilities of reducing seed dormancy using seed pretreatment via the application of sulphuric acid and hot water and then phosphorus for better seedling growth. Seeds pretreated with sulphuric acid had a significantly (P˂0.05) increased germination rate (by 60%) compared to seeds pretreated with hot water (40%). The application of phosphorus fertilizer stimulated the early growth of the species. This research provides information for practical use.

Keywords: germination; hot water; phosphorus fertilizer; sulphuric acid; Tetrapleura tetraptera.

INTRODUCTION

Tetrapleura tetraptera (Schumach and Thonn) from the Fabaceae family is a leguminous tree species found in the lowland tropical rainforest regions of Africa (Okyere-Agyapong et al., 2019). In Ghana, the plant serves as a remedy for diseases, including malaria, diabetes and hypertension (Abii and Amarachi, 2007; Lekana-Douki et al., 2011; Larbie et al., 2020). The plant contains vital phytochemical elements, such as alkaloids, that are important for the normal functioning of the body (Larbie et al., 2020). Tetrapleura tetraptera is usually propagated using the seed; however, only a small percentage of seeds germinate, as many remain dormant due to their hard seed coat, which makes seed germination very difficult (Ibiang et al., 2012). Seed dormancy can be broken by various seed pretreatment methods, such as chemical scarification and hot water treatment, to ensure absorption and uptake of water by the seeds and rapid initiation of the seeds (Usman et al., 2019). Additionally, the seedling phase of T. tetraptera is the most vulnerable phase of its life cycle, and plant growth and survival depend on optimum resources of light, water and nutrients, including phosphorus (Amissah et al., 2015; Okyere-Agyapong et al., 2019). Al-Kahtani et al. (2017) reported that the application of essential nutrient elements, such as phosphorus, will ensure optimum growth, survival of rhizobia in the soil, nodulation and nitrogen fixation of legumes, including Tetrapleura tetraptera.

Despite the nutritional and economic benefits of Tetrapleura tetraptera, the plant’s potential has remained untapped, with several species on the verge of extinction due to overexploitation, a lack of long-term conservation measures, and the ecological consequences of deforestation (Nya et al., 2000; Jimoh, 2005; Omokhua, 2015; Usman et al., 2019). Al-Kahtani et al. (2017) pointed out that phosphorus deficiency and a lack of nodulation could inhibit the initial growth of most legumes, including Tetrapleura tetraptera. However, information on the effect of seed pretreatment methods (sulphuric acid and hot water) on the germination and application of phosphorus fertilizer for the early growth performance of T. tetraptera (prekese) remains scarce (Ibiang et al., 2012; Maku et al., 2014; Usman et al., 2019). This study provided information on the effect of seed pretreatment methods (sulphuric acid and hot water) on the germination and application of phosphorus fertilizer on the early growth performance of prekese for further recommendation in agroforestry and to ensure large-scale propagation of the species for plantation establishment in Ghana.

MATERIALS AND METHODS

Study Area 

Location

The field experiment was situated at the Agroforestry Department demonstration farm at the Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana. It is located at latitude 6.40°N and longitude 1.37°W in the humid Semi-Deciduous Forest zone of Ghana (Figure 1).

Rainfall

It is distinguished by a bimodal pattern of yearly rainfall, with mean values between 1250 and 1500 mm. A minor rainy season that starts in September and lasts until November follows the big wet season, which runs from May through July. In addition, the area endures a long dry season from December through March and a brief one in August.

Temperature and humidity

The site’s mean daily temperature is 25.6°C, with the coldest months from December to February seeing average lows of 20°C and the hottest month, March, seeing average highs of 33°C.

Figure 1 – Map of the Agroforestry Department demonstration farm at the Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana

The site’s average yearly temperature is 26.61°C with 67.6% relative humidity (Adu and Asiamah 1992).

Soil type

According to Neina and Agyarko-Mintah (2022), the soil at the experimental site is well drained and strongly acidic Ferric Acrisol, and the textural class is sandy-loam.

Experimental approach and procedure

Land preparation

The study site was manually cleared of all vegetation and foreign materials with a hoe, cutlass and rake. At the research location, topsoil between 0 and 30 cm deep was removed from the earth’s surface and gathered in bags. When filling the polybags, stones and other extraneous elements were manually removed. Two kilograms of earth were placed inside black polybags with holes in them. To avoid root infiltration, a plastic carpet was laid down on the ground where the polybags were positioned.

Sources of material and viability testing

Sulphuric acid was prepared at different concentrations, and tap water was heated to 100°C. Phosphorus fertilizer was weighed into different quantities using an electronic balance and applied at the rates of 50, 37.5, 25 and 0 kg/ha P on the polybags, whereas Tetrapleura tetraptera seeds were purchased from the Fumesua location of the Forest Research Institute of Ghana (FORIG). The seeds were put through a viability test using the floating technique; those that floated on water after a short period of soaking were deemed non-viable and thrown away, while those that sank to the bottom of the beaker were collected and deemed viable for use in the study.

Seed pretreatment and sowing

A total of 480 seeds were soaked in a 50% solution of sulphuric acid (H₂SO₄) for 2 minutes and subsequently rinsed in distilled water, while another 480 seeds were soaked in hot (boiling) water for 7 minutes. At planting, two 1-cm deep holes were dug in the soil, and two seeds were placed in each. The seeds were then lightly pressed after being coated with a thin layer of soil to guarantee root anchoring during germination.

Post-sowing activities

One week following germination, Tetrapleura tetraptera seedlings were thinned out to one (1) seedling per polybag to maintain consistent development and lessen competition for water and nutrients. Watering was done as needed, along with other cultural traditions, such as weeding.

Phosphorus fertilizer application

Two weeks after germination, phosphorus fertilizers were applied to the Tetrapleura tetraptera seedlings contained in each polybag as per the treatments (50, 37.5, 25 and 0 kg/ha P), and observations were carried out accordingly.

Experimental design and treatment allocation

Eight treatment combinations were allocated randomly and replicated three times in a completely randomized design (CRD). Seeds were randomly collected from the seed lot of each treatment and sown with two seeds per polybag. A total of 1920 seeds were used for the experiment.

The treatment combinations were as follows:

T1: Hot water + 0 kg/ha P;

T2: Hot water + 25 kg/ha P;

T3: Hot water + 37.5 kg/ha P;

T4: Hot water + 50 kg/ha P;

T5: Sulphuric acid + 0 kg/ha P;

T6: Sulphuric acid + 25 kg/ha P;

T7: Sulphuric acid + 37.5 kg/ha P;

and

T8: Sulphuric acid + 50 kg/ha P;

The recommended P rate for legumes is 50 kg/ha (Karanja et al., 2004), where P= phosphorus.

Data collection

Five of the twenty seedlings per treatment were randomly selected, tagged with ribbons, and used for data collection. Data were collected on germination (and thus the germination percentage) for 4 weeks, while height and leaf number were determined within a 2-week interval for 3 months using a metre-rule veneer and a visual count, respectively. Destructive sampling was done at the end of the experiment to visually identify and count the number of nodules, and the above- and belowground biomass (root and shoot dry weight) of Tetrapleura tetraptera seedlings were determined using an electronic balance.

Data analysis

Data collected on germination and growth parameters were analysed for differences using analysis of variance (ANOVA) based on STATISTIX 8 software at a 5% level of significance. The Tukey HSD test was employed to compare the means, which were significantly different. The results were presented in tables using Excel.

RESULTS

Germination of Tetrapleura tetraptera seeds

The germination (%) of the various seed pretreatment methods (sulphuric acid and hot water) on the seeds of Tetrapleura tetraptera is shown in Table 1. The germination of T. tetraptera seeds was significantly higher in the sulphuric acid pre-treatment compared to the hot water (p˂0.05).

Height (cm) of Tetrapleura tetraptera from 4 to 14 weeks after planting (WAP)

The response of the height (cm) of Tetrapleura tetraptera to phosphorus fertilizer over the 14-week growth period is shown in Table 2. On a weekly basis, there was a significant difference in height from 4 to 14 WAP, with P-values ranging from 0.0000 to 0.0004.

Number of leaves of Tetrapleura tetraptera from 4 to 14 WAP

The effect of seed pretreatment methods and phosphorus fertilizer on the number of leaves of Tetrapleura tetraptera from 4 to 14 WAP is illustrated in Table 3. There was a significant (P˂0.05) difference among the treatments on a weekly basis, starting from 4 to 14 WAP. T8 recorded the highest leaf count from 4 to 14 WAP, while T1 had the lowest leaf count from 4 to 14 WAP.

Nodulation, Shoot Dry Weight and Root Dry Weight of Tetrapleuta tetraptera

There was a significant (P˂0.05) difference between the various treatment methods with respect to the number of nodules.

T6 recorded the greatest nodulation (15.9), followed by T4 (15.6), T3 (14.6), T8 (13.5), T2 (12.6), T7 (12.6), T6 (15.9), and T5 (10.6), with the least nodules recorded in T1 and T5 (10.6 each). The root dry weight of the Tetrapleura tetraptera plants followed a sequence similar to the number of nodules (Table 4).

Table 1
Effect of sulphuric acid and hot water on the germination of Tetrapleura tetraptera

CV= Coefficient of variation, DF= Degree of freedom, HSD= Honestly significant difference and T= Treatment. Means with the same superscripts are not significantly different at (P≤0.05%) using the Tukey HSD test

Table 2
Effect of phosphorus fertilizer on the height (cm) of Tetrapleura tetraptera from 4 to 14 WAP

Means with the same superscripts are not significantly different at (P≤0.05%) using the Tukey HSD test

Table 3
Effect of phosphorus fertilizer on the number of leaves of Tetrapleura tetraptera from 4 to 14 WAP

Means with the same superscripts are not significantly different at (P≤0.05%) using the Tukey HSD test

Table 4
Effect of phosphorus fertilizer on the nodulation, dry weight of shoots and dry weight of roots of Tetrapleura tetraptera at 14 WAP

Means with the same superscripts are not significantly different at (P≤ 0.05%) using the Tukey HSD test

Treatment methods did not show a significant difference with regard to shoot dry weight (P˂0.05).

The maximum dry shoot weight was recorded in T6 (6.3 g), followed by T8 (6.17 g), T7 (5.53 g), T4 (5.2 g), T3 (4.7 g), T2 (3.27 g), and T1 (1.27 g), with the lowest shoot dry weight recorded in T5 (1.13 g). There was a significant (P˂0.05) difference between the treatments in relation to dry root weight. The highest dry weight of the root was recorded at T6 (1.40 g), followed by T8 (1.30 g), T7 (1.27 g), T4 (1.20 g), T5 (1.17 g), and T3 (1.07 g). The lowest root dry weight was recorded at T1 and T2 (0.77 g each) (Table 4).

DISCUSSION

Tetrapluera tetraptera can be propagated through both seed and stem cuttings. In terms of sexual propagation, the seeds exhibited epigeal germination. However, the seeds are dormant because of the presence of a hard seed coat that prevents the entry of air and water (FAO, 1976; Deogratias, 2015). The hard seed coat of Tetrapleura tetraptera serves as a protective mechanism, ensuring the survival of the embryo in adverse environmental conditions, such as drought or excessive heat (Lawal, 2016).

However, it also poses a challenge for germination when favourable conditions for growth are present. The impermeable seed coat acts as a physical barrier and hinders the imbibition of water and gas exchange, which is a critical trigger for the initiation of germination processes (Adedire et al., 2015). To overcome hard seed coat dormancy in Tetrapleura tetraptera seeds, various treatments can be applied to break or weaken the hard seed coat. Scarification techniques, such as mechanical scarification, acid scarification and hot water treatment, are commonly employed to enhance water absorption and promote germination (Ejimbe et al., 2007; Adeyemi et al., 2019). These treatments create small openings or weaken the seed coat, allowing water to penetrate and facilitating the rehydration of the dormant embryo.

This study demonstrated that the seeds of Tetrapleura tetraptera pretreated with sulphuric acid had a higher germination percentage compared to seeds pretreated with hot water. This implies that the application of sulphuric acid is an effective way of rendering the seeds of Tetrapleura tetraptera permeable, leading to germination of up to 58.3, 60, 57.5, and 58.3%. This might be attributed to the corrosive ability of sulphuric acid on the hard seed coat of Tetrapleura tetraptera, thereby making the seeds permeable to water and air and promoting higher germination.

The finding is in agreement with previous studies by Asiyire et al. (2008), Lacerna et al. (2004), Onyekwelu (1990) and Sam (2019), who reported sulphuric acid as an effective way of breaking the hard seed coats of plants.

However, this study disagrees with Missanjo et al. (2014), who found that Acacia polyacantha seeds pretreated with hot water were more effective in breaking the hard seed coat, resulting in a greater germination percentage compared to seeds treated with concentrated sulphuric acid.

Furthermore, Sera et al. (2023) demonstrated that using non-thermal plasma as a seed priming method significantly improved seed germination potential compared to untreated seeds.

In addition to nitrogen, phosphorus (P) is one of the most crucial microelements for plant growth and to produce their best yields, adequate P fertilization is necessary (Taliman et al., 2019). Prathap et al. (2022) emphasized that when seeds develop, the phosphorus that plants have received is transferred from the roots and leaves to the seeds, where phytic acid is synthesized.

The significant increase in growth parameters demonstrated by Tetrapleura tetraptera with phosphorus application throughout the experiment demonstrated that there is better growth performance in Tetrapleura tetraptera when phosphorus is added to improve soil nutrient content. The phosphorus applied was absorbed by Tetrapleura tetraptera plants in the initial phase and used for root development, while the residual nutrient was not sufficient for subsequent crop growth support (Yu et al., 2022).

In addition, the substantial influence of P on Tetrapleura tetraptera diameter was possible because the applied P caused cell expansion during the latter stages of the plant’s growth, hence the evidence of a significant improvement in diameter (Ebeid et al., 2015). The effect of P levels on the number of leaves showed that the P applied may have aided cell expansion and the production of photosynthates for vegetative leaf growth. This is in line with the findings of Nakayama et al. (2022), who claimed that all leaf cells divide at the beginning of leaf development just after the leaf primordium emerges from the shoot apical meristem. The cells near the tip of the leaf eventually stop dividing and begin to expand, while the cells at the base continue to divide to support future leaf growth.

Additionally, the application of P influenced nodulation, the weight of the dry shoot, and the weight of the dry root of the Tetrapleura tetraptera plant. P fertilizer dosages enhanced the nodulation, dry shoot weight, and dry root weight; the P level in T6 (H₂SO₄ + 25 kg P) had the highest nodule formation and root dry weight. This could have happened if the cotyledons or endosperm had been present, and the embryo would have grown at the expense of the nutrients it received (Ali et al., 2019).

According to Míguez-Montero et al. (2020), these results demonstrated that phosphorus may induce an increase in nodulation and the weights of the dry shoots and roots of the tested tree and contribute to making it possible for the plant to be established in the field.

CONCLUSIONS

In conclusion, the results showed that the seeds of Tetrapleura tetraptera pretreated with sulphuric acid significantly increased the germination rate (60%) compared to seeds pretreated with hot water (40%). The application of P at T4 (hot water + 50 kg/ha P) had the highest height. T8 (H₂SO₄ + 50 kg/ha P) had the highest leaf number, and T6 (H₂SO₄ + 25 kg P) had the greatest number of nodules (nodulation) and dry shoot and dry root weights of T. tetraptera seedlings.

This study recommends that the seeds of Tetrapleura tetraptera to be pretreated with sulphuric acid to break their hard seed coats to decrease dormancy and improve germination during planting. Phosphorus fertilizer can be applied during the early stages of growth to improve its growth performance because the tested species exhibited a prudent demand for P during the early growth stages.

Furthermore, since the current study only focused on the number of nodules without looking at active and inactive nodules, further research could be conducted to increase the number of minutes the seeds spent in the respective seed pretreatments and to identify the number of active and inactive nodules.

Author Contributions: conceptualisation (A.L.M. and E.B.), methodology (A.L.M., F.A. and J.C.), analysis (F.A. and J.C. and E.B.), data curation (A.L.M. and E.B.), writing (A.L.M., F.A. and J.C.), review (A.L.M. and E.B.), and supervision (A.L.M. and E.B.). All authors declare that they have read and approved the publication of the manuscript in this present form.

Conflicts of Interest: All authors declared no conflict of interest.

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