MMOLUTSI Et Al. V4N1 AFJ. 2020

Agriculture and Forestry Journal Available online at: Vol. 4, Issue 1, pp. 47-54, June, 2020 http://ojs.univ-tlemcen.dz/index.php/AFJ/

E-ISSN 2602-5795

Published by university of Tlemcen - ALGERIA

Application and Use of Presowing Treatment Methods to Improve Germination of Vachellia karroo (Hayne) Banfi & Galasso

Galalea Gillian MMOLUTSI 1, Christinah MATSUANE 1, Witness MOJEREMANE 2* , Thembinkosi MATHOWA 1 and Demel TEKETAY 2 1Department of Crop and Soil Sciences, Faculty of Agriculture,Botswana University of Agriculture and Natural Resources, Private Bag 0027, Gaborone, Botswana. 2Department of Range and Forest Resources, Faculty of Natural Resources, Botswana University of Agriculture and Natural Resources, Private Bag 0027, Gaborone, Botswana. *Corresponding author email: [email protected]; [email protected]

ARTICLE INFO ABSTRACT

Article history: A germination experiment of Vachellia karroo seeds was conducted at the Botswana University of Agriculture and Natural Resources, Department of Crop and Soil Sciences laboratory, from September Received: 31 December 2019 to October 2018. Seeds were collected along the Segoditshane River in Gaborone to investigate the Accepted after corrections effect of different pre-sowing treatment methods on their germination. The experiment was laid out in 09 March 2020 a completely randomized design (CRD) with five treatments (control, mechanical scarification, boiling

water, hot water and concentrated sulphuric acid (98.8%). Boiling water (30, 60, 180 and 300 seconds)

and concentrated sulphuric acid (15, 30, 45 and 60 minutes) had four levels of exposure time. The Keywords: highest significant (p < 0.01) cumulative germination percentages were recorded in seeds subjected to

Seed dormancy, Germination sulphuric acid for 45 and 60 minutes, mechanical scarification (shortest germination mean time of 2.0 - mean time, Germination 2.3) and boiling water at 30 and 60 seconds (moderate germination mean time of 5 -5.9) whereas, the index, Pre-sowing treatment, control treatment had the least cumulative germination percentage of 2%. As expected, the same trend Germination percentage, was revealed for germination index. The seeds possess seed coat imposed dormancy, which requires Germination rate, Tree sowing treatments. The best treatments for releasing dormancy in V. karroo were sulphuric acid and nursery. mechanical scarification and because of the risks associated with the use of sulphuric acid, the researchers recommend mechanical scarification as the suitable treatment method in tree nurseries.

1. Introduction

Vachellia karroo (Hayne) Banfi & Galasso (Family: Fabaceae, sub-family; Mimosoideae), commonly known as “sweet thorn”, is one of the most abundant and widespread Vachellias in southern Africa (Timberlake, 1980 ; Lagerwall, 2016) . Formerly known as Acacia karroo, the species was recently transferred to the genus Vachellia (Kyalangalilwa, 2013) . Vachellia karroo is a multipurpose species native to Zimbabwe, Botswana, Swaziland, Lesotho, Namibia, South Africa, Mozambique, Zambia, Malawi and south of Angola (Timberlake,1980 ; Barnes et al.,1996) . The species grows well in open woodland and wooded grassland (Van Wyk, 1990) .

Vachellia karroo is a deciduous small shrub 3.5 m or tree up to 15 m tall, with a spreading, roundish crown and low branching stem (Timberlake, 1980 ; Van Wyk 1990 ; Palgrave 2002) . The species is characterized by a dark and rough bark; striking, long, paired, white thorns; yellow, sweet smelling, ball-like flowers producing copious amounts of nectar (Setshogo and Venter 2003) . The pods are sickle-shaped and dehisce by splitting lengthwise in the middle (Setshogo and Venter, 2003) . Under favourable conditions, this species grows fast and is well adapted to arid and semi-arid environments constrained by drought, high temperatures, salinity and extreme light (Van Wyk, 1990 ; Palgrave, 2002 ; Ben Zetta et al., 2017).

It is one of the fastest-growing Vachellia species and produces high-density wood (800-890 kg m -3) (Kheloufi et al., 2017) .The species provides different types of goods and services to the community. It produces palatable leaves, flowers and pods that provide excellent fodder for cattle, goats and game (Van Wyk, 1990 ; Setshogo and Venter, 2003) . The species produces edible gum, which is also used for pharmaceutical products (Van Wyk, 1990) . It is an excellent source of pollen and nectar (Setshogo and Venter 2003 ; Kheloufi et al., 2017) , which make the species ideal for bee farmers (Venter and Venter, 2012) . The bark contains 19% tannin (Venter and Venter, 2012) used for tanning leather (Setshogo and Venter, 2003 , Venter and Venter, 2012) . Like many Vachellia species, the ability of V. karroo to develop dual symbiosis with Rhizobia and endomycorrhizal fungi contributes to fix nitrogen, provides shade, and stabilizes sand dunes and disturbed areas. It has a moderately dense crown that provides a suitable environment for sustained production of nutritious perennial grasses, such as Panicum maximum Jacq. and Cenchrus ciliaris L. (Barnes et al., 1996) .

© 2020 Agriculture and Forestry Journal This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial 3.0 International License Mmolutsi et al. Agric. For. J. Vol. 4, No. 1 (2020) 48

The successful regeneration of shrub and tree species under varied environmental conditions depends on their ability to produce sufficient seeds, exhibit high seed viability, seedling survival and growth (Khumbongmayum et al., 2005) . The use of seeds is the cheapest method of propagating many tree species (Tigabu and Oden, 2001) worldwide. However, on numerous occasions viable seeds of some plant species fail to germinate when exposed to favourable conditions (sufficient water, good aeration and a suitable temperature) due to dormancy (Bewley, 1997 ; Finch-Savage and Leubner-Metzger, 2006 ; Ibiang et al., 2012 ; Chahtane et al., 2017) . According to de Moraiset al. (2014) , dormancy is an inherited trait in seeds assigned to the palisade cell layer whose cell walls are thick and covered externally by a waxy cuticle. Dormancy evolved differently across shrub and tree species due to adaptation to their environment (Botsheleng et al., 2014) . Numerous plants use dormancy as a strategy to survive (Donohue et al., 2010 ; Huang et al., 2010 ; Salazar et al., 2011) in the soil seed bank until conditions are suitable for germination (Graeber et al., 2012 ; Mark and Ooi, 2012) .

Seeds of most Vachellia species exhibit poor germination or experience delayed germination due to dormancy that inhibit water imbibition and oxygen uptake by the developing embryo (Mucunguzi and Oryem-Origa,1996 ; Grubb and Coomes, 1997 ; Baskin and Baskin, 2004 ; Walters et al., 2004 ; Aref et al.,2011) . In nature, hard seed coats are cracked or softened by fire (Bradstock and Auld, 1995 ; Mbalo and Witkowski, 1997 ; Walters et al., 2004) , extreme temperatures, digestive acids in the stomachs of animals or by the abrasion of blowing sand (Luna et al., 2009) . In laboratories and tree nurseries, artificial methods are used to speed up germination. Seed dormancy influences the successful execution of afforestation and reforestation programs in arid and semi-arid environments. To break seed dormancy or enhance germination, Vachellia seeds often require pre-sowing treatment (Aref et al., 2011 ; Azad et al., 2011) . Several artificial techniques have been used to break the hard seed coat and increase seed permeability. The techniques include physical (manual scarification, boiling water and cold water, dry heat and fire and chemical pre-sowing treatments (sulphuric acid, alcohols and organic solvents) (Hanna 1984 ; Teketay, 1996 ; 1998;Uniyal et al., 2000 ; Okunomo and Bosah, 2007 ; Aref et al., 2011 ; Mousavi et al., 2011 ; Ghassali et al., 2012 ; Botsheleng et al., 2014 ; Fredrick et al., 2016 ; Mojeremane et al., 2017 , 2018 ; Odirile et al., 2019) . Vachellia karroo is one of the species characterised by physical dormancy (Baskin and Baskin, 2014) . The aim of the present study was, therefore, to evaluate the influence of pre-sowing treatments on the germination of Vachellia karroo seeds.

2. Materials and Methods

2.1. Study site

The study was conducted at Botswana University of Agriculture and Natural Resources, located at Sebele (23°34' S and 25°57' E, altitude of 994 m) 10 km from the center of Gaborone, the Capital City of Botswana, along the A1 North-South highway. Seeds used were collected from 15 randomly selected trees along the Segoditshane River, Phase 2 and Gaborone in July 2018.

2.2. Experimental design

The experiment was set up in September 2018 in a laboratory, and room temperature of 25 ± 3°C was maintained throughout the experiment. The experiment was laid-out in a completely randomized design (CRD) with five main treatments (control, mechanical scarification, boiling water, hot water and concentrated sulphuric acid (98.8%). Boiling water had four different levels of time exposure (30, 60, 180 and 300 seconds) whereas, concentrated sulphuric acid had four different levels of time exposure (15, 30, 45 and 60 minutes). Each treatment had four replications of 25 seeds. Seeds were germinated in 90 mm petri dishes lined with cotton wool and closed with lids to reduce water loss by evapotranspiration (Schroder et al., 2013) . The petri dishes were kept moist by spraying with distilled water.

2.3. Seed characteristics

The number of seeds in a pod was determined from five replications of 10 pods. Seeds were, then, categorized as intact, aborted or dead/eaten. Seed length, width and breadth were determined from five replicates of ten seeds using an electronic digital caliper (0-150 mm). The mass (weight) of single seeds was determined by weighing the using an electronic analytic balance (Model: PW 124) in four replications of 25 seeds. Ten replications of 100 seeds were weighed to determine the 1000 seed weight.

2.4. Experimental procedures

For the 98% concentrated sulphuric acid, four replications of 25 seeds for each exposure time (15, 30, 45 and 60 minutes) were put into heat resistant non-corrosive glass beakers (Botsheleng et al., 2014) . The acid was added slowly to a level covering all seeds and shaken occasionally. After each exposure time, the seeds were sieved-out using an acid resistant sieve and the acid drained off simultaneously into the beaker and, then, washed thoroughly in running tap and distilled water to remove all the acid for safe handling. With regard to boiling water, four replications of 25 seeds for each exposure time (30, 60, 180 and 300 seconds) were enclosed in coffee filter papers, which were clipped tightly to prevent them from falling before immersing in boiling water

(Setlhabetsi et al., 2019) . Seeds were removed from the pot after each exposure time and immersed in cold distilled water to cool down before sowing. For hot water treatment, four replications of 25 seeds were enclosed in coffee filter papers and clipped to prevent them from falling before putting them in a beaker. Boiling water was poured into the beaker with seeds and left to cool gradually for 24 hours at room temperature (Mojeremane et al., 2027 ; Setlhabetsi et al., 2019). With regard to mechanical scarification, seeds were scarified by carefully nicking the seed coat at the distal end using a nail cutter (Mojeremane et al., 2017 ; Odirile et al., 2019). In the control treatment, untreated seeds were included to compare the effect of no pre -sowing treatment on seed germination.

2.5. Germination assessment

Germination counts were recorded daily. Seeds were considered as germinated when the radical had protruded about two millimeters. Counted germinated seeds were removed from petri dishes after recording. The experiment was terminated after 20 days.

2.6. Data analysis

Data collected on germination of seeds was used to calculate the following: i. Germination percentage (GP) for each treatment using the equation: GP (%) = (germinated seeds/total tested seeds) × 100 ii. Germination mean time (GMT) using the equation (Scott et al., 1984) : GMT (days) = GMT (days) = ΣTi Ni/S; where, Ti = number of days from the beginning of the experiment; Ni = number of seeds germinated per day and S = total number of seeds germinated. iii. Germination index (GI) using the formula: GI = (G1/1) + (G2/2) +...+ (Gx/x) according to Esechie (1994) ; where, G = germination day 1, 2…, and x = the corresponding day of germination. Data were subjected to analysis of variance (ANOVA) using Analytical Software (2013). All data percentage values were arcsine transformed prior to statistical analysis to meet the requirement of normality assumption for analysis of variance (Zar, 2010) . Significant differences of means were tested using Tukey’s Honestly Significant Difference (HSD) Test at the significance level of p ≤0.05.

3. Results and discussion

3.1. Seed characteristics

The number of intact Vachellia karroo seeds in each pod ranged between 1 and 8 seeds. The number of seeds eaten or damaged by insects ranged between 0 and 8 seeds per pod, while their aborted counterparts varied between 3 and 12 seeds per pod. The seed length ranged from 6.6 and 7.2 mm, whereas the seed width and breadth ranged from 3.8 and 5.5 mm and 1.75 and 2.5 mm, respectively. The mass of single seeds ranged from 0.04 to 0.07g, while the 1000 seeds weight ranged from 48 -50 g.

3.2. Seed germination

Seed germination percentage, germination mean time and germination index were significantly (p < 0.01) affected by pre-sowing seed treatments (Table 1). Germination in nicking, hot water, boiling water (30 and 60 seconds) and sulphuric acid (45 and 60 minutes) treatments gave a significantly (p < 0.01) higher germination percentages than other treatments, including the control. There was no statistical difference in germination among the nicked, hot water, boiling water (30 and 60 seconds) and sulphuric acid (45 and 60 minutes) treated seeds. Several studies reported that seeds of Vachellia species are characterized by hard seed coats that act primarily as physical barrier to imbibition of water and entrance of oxygen (Holmes et al., 1987 ; Nasr et al., 2013 ; Ben Zetta et al., 2017) as well as the growth of the embryo (Nasr et al., 2013) .

The results revealed that nicking improved the germination of V. karroo seeds compared with the control (Table 1). This result is consistent with those of studies conducted using other plant species (Teketay, 1996 ; Shiferaw et al., 2004 ; Travlos et al., 2007 ; Bamel et al., 2007 ; Botsheleng et al., 2014 ; Mojeremane et al., 2017 ; Odirile et al., 2019) . Travlos et al. (2007) reported that nicking or scratching the seed coat promoted germination of Tylosema esculentum (Burch.) A. Schreiber seeds. Shiferaw et al. (2004) reported that nicking or scratching Prosopis juliflora (Sw.) DC. seeds resulted in 100% germination. Odirile et al. (2019) nicked Vachellia erioloba (E.Mey.) P.J.H.Hurter seeds and reported 98% germination. Mojeremane et al. (2017) observed 69% germination in nicked Vachellia rehmanniana (Schinz) Kyal. & Boatwr. seeds compared with 3% in the control treatment. Nicking cracked the hard seed coat and allowed uptake of water and oxygen, which may have stimulated rapid and uniform germination (Teketay, 2005 ; Botsheleng et al., 2014) , thereby, elongating the embryonic axis (Botsheleng et al., 2014) . Although nicking improved seed germination, it may be a bottleneck when treating small sized seeds or a large number of seeds to produce many seedlings (Mapongmetsem et al., 1999 ; Baskin and Baskin, 2014) . There is also a possibility of damaging the endosperm, cotyledons or embryo during nicking, which may result in low germination.

Table 1. Effect of pre-sowing seed treatments on germination parameters of V. karroo

Treatments Germination parameters Germination (%) GMT GI Control 0.3 d 3.5 bc 0.02 d Nicking 87.2 a 2.0 d 0.97 a Hot water (24 hours) 85.2 a 3.9 abc 0.95 a Boiling water (30 seconds) 85.2 a 5.0 abc 0.95 a Boiling water (60 seconds) 85.2 a 5.9 ab 0.95 a Boiling water (180 seconds) 60.9 b 5.6 abc 0.70 b Boiling water (300 seconds) 34.0 c 7.2 a 0.42 c Sulphuric acid (15 minutes) 11.0 d 6.2 ab 0.17 d Sulphuric acid (30 minutes) 51.1 bc 5.8 abc 0.60 bc Sulphuric acid (45 minutes) 89.1 a 2.3 cd 0.99 a Sulphuric acid (60 minutes) 88.1 a 2.3 cd 0.98 a Significance ** ** ** HSD (0.05) 21.59 3.57 0.23 CV (%) 14.36 32.32 13.29

** Highly significant at p < 0.01. Means separated using Tukey’s Honestly Significant Difference (HSD) Test at p ≤ 0.05. Means within columns followed by the same letters across treatments are not significantly different. GMT = germination mean time, GI = germination index and CV = coefficient of variation in percentage.

Soaking seeds in hot water for 24 hours enhanced germination in the present study. This result is consistent with results of germination experiments conducted on many tropical shrub and tree species (Sajeevukumar et al., 1995 ; Aref, 2000 ; Mwase and Mvula, 2011 ; Daz, 2014 ; Mojeremane et al., 2018 ; Odirile et al., 2019) . Improved germination may be attributed to softening of the hard coats by hot water, which allowed seeds to imbibe water prior to sowing. Prior studies reported that pre-treating seeds in hot water is simple, cheap, reliable and suitable for a large number of seeds (Ortega-Baes et al., 2002, Himanen et al., 2012) .

Soaking V. karroo seeds in boiling water for 30, 60 180 and 300 seconds was effective in improving seed germination compared with the control (Table 1). However, seed germination decreased with increasing soaking time, which is consistent with results of other studies (Idu and Omonhinmin, 1999 ; Mojeremane et al., 2018) . Idu and Omonhinmin (1999) scarified Dichrostachys cinerea L. Wight & Arn. seeds in boiling water for 10, 40, 60, 300 and 900 seconds and recorded the highest germination in seeds immersed in boiling water for 10 and 40 seconds. Mojeremane et al. (2018) soaked Peltophorum africanum Sond. In boiling water for 60, 180 and 300 seconds and recorded germination of 87, 32, and 24%, respectively. These results suggest that soaking seeds in boiling water for 180 and 300 seconds caused damage to the internal parts of some seeds, resulting in low germination. In contrast with our results, other studies conducted on other shrub and tree species observed no germination in seeds soaked in boiling water for 60, 180 and 300 seconds (Kahaka, 2017 ; Mojeremane et al., 2017) . They attributed poor seed germination to the boiling water, which probably damaged the embryo.

Sulphuric acid (30, 45 and 60 minutes) enhanced seed germination in this study compared with the control (Table 1). This result is consistent with results of experiments conducted on seeds of other plant species, which demonstrated that sulphuric acid improved seed germination (Herron and Clemens, 2001 ; McDonald and Omoruyi, 2003 ; Cirak et al., 2004 ; Keshtkar et al., 2008 ; Likoswe et al., 2008 ; Sosnoskie and Cardina, 2009; Aref et al., 2011 ; Mojeremane et al., 2018 ; Odirile et al., 2019) . Sulphuric acid wears out hard seed coats (Ali et al., 2011 ; Nasr et al., 2013) and allows imbibition, which triggers germination (Aliero, 2004 ; Amusa, 2011) . In contrast, soaking seeds in sulphuric acid for 15 minutes did not improve germination compared with control. Mojeremane et al. (2017) reported similar results in Vachellia rehmanniana (Schinz) Kyal. & Boatwr seeds. This may be attributed to the hard coat of V. karroo seeds that requires soaking periods of more than 15 minutes in concentrated sulphuric acid to disrupt the seed coat. Although sulphuric acid (30, 45 and 60 minutes) enhanced the germination of V. karroo seeds, the acid is expensive and hazardous to workers and the environment (Danthu et al., 1992 ; Nasr et al., 2013) . The use of sulphuric acid also requires special equipment, personal protective gear and proper disposal after use (Luna et al., 2009) . Furthermore, seeds can also be damaged by over-soaking in the acid (Nasr et al., 2013) .

3.3 Germination mean time and germination index

Germination mean time and germination index were significantly (p < 0.01) affected by pre-sowing treatments (Table 1). Nicked seeds germinated within two days whereas, seed treated with sulphuric acid (45 and 60 minutes) germinated within 2.3 days, which was significantly lower than the rest. As would be expected, germination index was significantly higher for treatments with higher germination percentages.

Sulphuric acid (45 and 60 minutes) and nicking exhibited more than 70% mean daily germination rate within 2 days whereas, the rest were below 40% (Figure 1). No significant increases in the number of germinated seeds were recorded between 10 to 13 days across treatments. 100.0 90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0

Mean daily germination rate (%) rate germination daily Mean 10.0 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Days

Control Nicking Hot water (24hrs) Boiling water- 30sec Boiling water- 60sec Boiling water- 180sec Boiling water- 300sec Sulphuric acid- 15mins Sulphuric acid- 30mins Sulphuric acid- 45mins Sulphuric acid- 60mins Figure 1. Mean daily germination rate of V. karroo recorded over 20 days.

4. Conclusion

Sulphuric acid (30, 45 and 60 minutes), hot water soaking for 24 hours, nicking and boiling water (30, 60 and 180 seconds) improved the germination of V. Karroo seeds. However, among these treatments, sulphuric acid is not a suitable pre-sowing seed treatment method in tree nurseries because it requires special equipment, personal protective gear and proper disposal after use.

Acknowledgments

We are grateful to Botswana University of Agriculture and Natural Resources for providing research facilities for carrying-out the research. We would like to thank the Department of Tertiary Education Financing, Ministry of Tertiary Education, Research Science and Technology for providing research grant to Gillian Galalea Mmulutsi.

References

1. Ali A., Akhatar N., Khan B.A., Khan M.S., Rasul A.,Khalid N., Waseem K., Mahmood T., Ali L., 2012. Acacia nilotica : a plant of multipurpose uses. Journal of Medicinal Plants Research , 6(9):1492−1496. 2. Aliero B.L., 2004. Effects of sulphuric acid, mechanical scarification and wet heat treatments on germination of seeds of African locust bean tree, Parkia biglobosa. African Journal of Biotechnology , 3(3):179−181. 3. Amusa T.O., 2011. Effects of three pre-treatment techniques on dormancy and germination of seeds of Afzelia Africana (Sm. Ex pers). Journal of Horticulture and Forestry , 3(4):96−103. 4. Aref I.M., 2000. Effects of pre-germination treatments and sowing depths upon germination potential of some Acacia species. Research Bulletin , 95: 5−17. 5. Aref I.M., Atta H.A.E., Shahrani T.A., Mohamed A.I., 2011. Effects of seed pretreatment and seed source on germination of five Acacia spp . African Journal of Biotechnology , 10(71):15901−15910. 6. Azad S.Md., Hasan M.R.,Matin A.Md., 2011. Effect of different pre-sowing treatments on seed germination percentage and growth performance of Acacia auriculiformis . Journal of Forestry Research , 22(2): 183−188. 7. Bamel J.S., Srinivasan K., Saxena S., Uprety M., Bhatnagar N., 2007. Methods for breaking seed dormancy in Acacia species. Indian Journal of Plant Genetic Resources , 20: 28−31. 8. Barnes R.D., Filer D.L., Milton S.J., 1996. Acacia karroo : monograph and annotated bibliography. Tropical Forestry Paper 32. Oxford Forestry Institute, University of Oxford, United Kingdom. 77p.

9. Baskin J.M., Baskin C.C., 2004. A classification system for seed dormancy. Seed Science Research , 14(1): 1-16. 10. Baskin C., Baskin J., 2014. Ecology, biogeography, and, evolution of dormancy and germination. 2 nd Edition. Academic Press, 600p. 11. Ben Zetta H., Amrani S., Nacer A., 2017. Effects of pre-germination treatments, salt and water stress on germination of Acacia ehrenbergiana Hayne and Acacia seyal Del.(Mimosoideae): Two Algerian native species. Applied Ecology and Environmental Research , 15(4): 355−368. 12. Bewley J.D., 1997. Seed germination and dormancy. Plant Cell , 9: 1055-1066. 13. Botsheleng B., Mathowa T., Mojeremane W., 2014. Effects of pre-treatments methods on the germination of pod mahogany ( Afzelia quanzensis ) and mukusi ( Baikiaea plurijuga ) seeds. International Journal of Innovative Research in Science Engineering and Technology , 3(1): 8108−8113. 14. Bradstock R.A., Auld, T.D., 1995. Soil temperatures during experimental bushfires in relation to fire intensity: consequences for legume germination and fire management in south-eastern. Australia. Journal of Applied Ecology , 32:76−84. 15. Chahtane H., Kim W., Lopez-Molina L., 2017. Primary seed dormancy: a temporallymultilayered riddle waiting to be unlocked. Journal of Experimental Botany , 68(4): 857–869. 16. Cirak C., Kevseroglu K., Saglam B., 2004. Physical and physiological dormancy in black henbane (Hyoscyamus niger L.) seeds. Journal of Plant Biology , 47(4): 391−395. 17. Danthu A., Roussel J., Saar J.A., 1992. Effect of different pretreatments on the germination of Acacia senegal seeds. Seed Science and Technology , 20(1): 111−117. 18. Das N., 2014. The effect of seed sources variation and pre-sowing treatments on the seed germination of Acacia catechu and Elaeocarpus floribundus species in Bangladesh. International Journal of Forestry Research , 2014:1−8. 19. de Morais L.F., Almeida J.C.C., Deminicis B.B., de Pádua F.T., Morenz M.J.F., de Abreu , J.R.B., Araujo R.P., de Nepomuceno D.D., 2014. Methods for breaking dormancy of seeds of tropical forage legumes. American Journal of Plant Sciences , 5:1831−1835. 20. Donohue K., Rubio de Casas R., Burghardt L., Kovach K., Willis C.G., 2010. Germination, post germination adaptation and species ecological ranges. Annual Review of Ecology, Evolution, and Systematics , 41: 293−319. 21. Esechie H., 1994. Interaction of salinity and temperature on the germination of sorghum. Journal of Crop Science , 172: 194−199. 22. Finch-Savage W.E., Leubner-Metzger G., 2006. Seed dormancy and the control of germination. New Phytologist , 171: 501−523. 23. Fredrick C., Muthuri C., NgamauK., Sinclair F.,2016. Provenance and pre-treatment ffect on seed germination of six provenances of Faidherbia albida (Delile) A. Chev. Agroforestry Systems , 91(6):1007- 1017. 24. Ghassali F., Salkini A.K., Petersen S.L., Niane, A.A., Louhaichi M., 2012. Germination dynamics of Acacia species under different seed treatments. Range Management and Agroforestry , 33(1): 37−42. 25. Graeber K., Yashi K.N., Miatton E., Leubner- Metzger G., 2012. Molecular mechanisms of seed dormancy. Plant, Cell and Environment , 35(10): 1769−1786. 26. Grubb P.J., Coomes D.A. 1997. Seed mass and nutrient content in nutrient-starved tropical rain forests in Venezuela. Seed Science Research , 7: 269−280. 27. Hanna P.J., 1984. Anatomical features of the seed coat of Acacia kempeana (Mueller) which relate to increased germination rate induced by heat treatment. New Phytologist , 96: 23−29. 28. Herron H., Clemens J., 2001. Seed dormancy and germination in Melicytus ramiflorus (violaceae). New Zealand Journal of Botany , 39(2): 245−249. 29. Himanen K., Nygren, M., Dumroese R.K., 2012. Boiling water scarification plus stratification improves germination of Lliamna rivularis (Malvaceae) seeds. Native Plants , 13(3): 245−254. 30. Holmes P.M., Macdonald I.A.W., Juritz J., 1987. Effects of clearing treatment on seed banks of the alien invasive shrubs Acacia saligna and Acacia cyclops in the southern and south-western Cape, South Africa. Journal of Applied Ecology , 24: 1045−1051. 31. Huang X., Schmitt J., Dorn L., Griffiths C. Effgen S., Takao S., Koornneef M. and Donohue K., 2010. The earliest stages of adaptation in an experimental plant population: strong selection on QTLs for seed dormancy. Molecular Ecology , 19(7): 1335−51. 32. Ibiang Y.B., Ita E.E., Ekanem B.E., Edu N.E., 2012. Effect of different pretreatment protocols on seed germination of Tetrapleura tetraptera (Schum and Thonn). Journal of Environmental Science Toxicology and Food Technology , 2(3): 25−29. 33. Idu M., Omonhinmin A.S., 1999. Effect of oven-heat and boiling on the germination and seedling development of Dichrostachys cinerea (L.) Wight and Arn (Fabaceae). Agronomie , 19: 671−676.

34. Kahaka P., 2017. The effect of pre-sowing treatments on germination of Dichrostachys cinerea,Senegalia erubescens and Vachellia nilotica from Botswana. Unpublished BSc report. Department of Crop Science and Production, Botswana University of Agriculture and Natural Resources, Gaborone, Botswana. 35. Keshtkar A.R., Keshtkar H.R., Razavi S.M., Dalfard S., 2008. Methods to break seed dormancy of Astragalus cyclophyllon . African Journal of Biotechnology , 7(21): 3874−3877. 36. Kheloufi A., Chorfi A., Mansouri L.M., 2017. Germination kinetics in two Acacia karroo Hayne eco-types under salinity conditions. Open Access Library Journal, 4: e3319. http://dx.doi.org/10.4236/oalib.1103319 . 37. Khumbongmayum A.D., Khan M.L., Tripathi R.S., 2005. Survival and growth of seedlings of a few tree species in the four sacred groves of Manipur. Northeast India Current Science , 88: 1781−1788 . 38. Kyalangalilwa B., Boatwright J.S., Daru B.H., Maurin O., Bank M., 2013. Phylogenetic position and revised classification of Acacia s.l. (Fabaceae: Mimosoideae) in Africa, including new combinations in Vachellia and Senegalia . Botanical Journal of the Linnaean Society , 172. 500−523. 39. Lagerwall, D., 2016. Germination and predation of Acacia karroo seedson acid mine drainage polluted soils. Master of Science thesis, Faculty of Science, University of Witwatersrand, Republic of South Africa. 40. Likoswe M.G., Njoloma, J.P., Mwase W.F., Chilima C.Z., 2008. Effect of seed collection times and pretreatment methods on germination of Terminalia sericea Burch. ex DC. African Journal of Biotechnology , 7(16): 2840−2846. 41. Luna T., Wilkinson K., Dumroese R.K., 2009. Seed germination and sowing options-In Nursery manual for native plants: A guide for tribal Nurseries, Vol. 1: Nursery management. Agriculture Handbook 730. Department of Agriculture, Forest Service. Washington, D.C, USA. 163−183. 42. McDonald I., Omoruyi O., 2003. Effect of seed pre-treatment on germination of two surface types of Dialium guianeense. Seed Technology , 25:4−44. 43. Mapongmetsem P.M., Duguma B., Nkongmeneck B.A., Selegny E., 1999. The effect of various seed pretreatments to improve germination in eight indigenous tree species in the forests of Cameroon. Annals of Forest Science , 56: 679−684. 44. Mark K., Ooi J., 2012. Seed bank persistence and climate change. Journal of Seed Science Research, 22: 53−60. 45. Mbalo B.A., Witkowski E.T.F., 1997. Tolerance to soil temperatures experienced during and after the passage of fire in seeds of Acacia karroo , A. nilotica and Chromolaena odorata : a laboratory study. South African Journal of Botany , 63: 421−425. 46. Mojeremane W., Mathowa T., Teketay D., Stimela T., Kopong I., Rampart M., 2017. Presowing seed treatment methods to overcome dormancy in seeds of Vachellia rehmanniana Schinz. Agriculture and Forestry , 63(2): 171−181. 47. Mojeremane W., Mathowa T., Teketay D.,2018. Effects of different pre-sowing treatments on germination of Peltophorum africanum Sond seeds from two provenances in Botswana. Journal of Biodiversity and Environmental Sciences , 12(2): 230−236. 48. Mousavi S.R., Rezaei M., Mousavi A., 2011. A general overview on seed dormancy and methods of breaking it. Advances in Environmental Biology , 5(10): 3333−3337. 49. Mucunguzi P., Oryem-Origa H., 1996. Effects of heat and fire on the germination of Acacia sieberiana D.C. and Acacia gerrardii Benth. in Uganda. Journal of Tropical Ecology , 12: 1−10. 50. Mwase W.F., Mvula T., 2011. Effect of seed size and pre-treatment methods of Bauhinia thonningii Schum. on germination and seedling growth. African Journal of Biotechnology , 10(13): 5143−-5148. 51. Nasr S.M.H., Savadkoohi S.K., Ahmadi E., 2013. Effect of different seed treatments on dormancy breaking and germination in three species in arid and semi-arid lands. Forest Science Practice , 15(2): 130−136. 52. Odirile O., Mojeremane W., Teketay D., Mathowa T., 2019. Responses of seeds of Vachellia erioloba (E. Mey.) P.J.H. Hurter in Botswana to different pre-sowing methods. International Journal of Biology and Biotechnology , 16(1): 181−188. 53. Okunomo K., Bosah, B.O., 2007. Germination response of Acacia senegal (Linn) seeds to various presowing treatments in the nursery. Agricultural Journal , 2(6): 681−684. 54. Ortega-Baes P., De Viana M., Sühring S., 2002. Germination in Prosopis ferox seeds: effects of mechanical, chemical and biological scarifications. Journal of Arid Environments , 50: 185−189. 55. Palgrave K.C., 2002. Trees of southern Africa. Revised and updated by Palgrave, M.C. Struik. Cape Town. Republic of South Africa, 1212p. 56. Sajeevukumar B., Sudhakara K., Ashokan P.K., Gopikumar K., 1995. Seed dormancy and germination in Albizia falcataria and Albizia procera . Journal of Tropical Forest Science , 7(3): 371−382. 57. Salazar A.G.G., Franco A.C., Miralles-Wilhelm, F., 2011. Timing of seed dispersal and dormancy, rather than persistent soil seed-banks, control seedling recruitment of woody plants in geotropically savannas. Journal of Seed Science Research , 21(2): 103−116.

58. Schröder R., Graf M.D., Jochum J., Rode G., Schemmel J., Thimm I., 2013. Testing the effects of a regionalized seed production on the germination behaviour of wild plant species. Ecological Restoration , 31(3): 295−301. 59. Scott S.J., Jones R.A., Williams W.A., 1984. Review of data analysis methods for seed germination. Crop Science , 24: 1192−1199. 60. Setlhabetsi O.T., Mojeremane W., Mathowa T., Teketay, D. 2019. Breaking seed dormancy in Philenoptera violacea (Klotzsch) Schrire using different pre-sowing treatment methods. Journal of Agriculture and Environmental Sciences , 8(1): 104−111. 61. Setshogo M.P., Venter F., 2003. Trees of Botswana: names and distribution. Southern African Botanical Diversity Network Report No. 18. Pretoria. Republic of South Africa, 155p. 62. Shiferaw H., Teketay D., Nemomissa S., Assefa F., 2004. Some biological characteristics that foster the invasion of Prosopis juliflora (Sw.) DC. at Middle Awash Rift Valley Area, north-eastern Ethiopia. Journal of Arid Environments , 58: 135−154. 63. Sosnoskie L.M., Cardina J., 2009. Laboratory methods for breaking dormancy in garlic mustard ( Alliaria petiolata ) seeds. Invasive Plant Science and Management , 2(2): 185−189. 64. Teketay D., 1996. Germination Ecology of twelve indigenous and eight exotic multipurpose leguminousspecies from Ethiopia. Forest Ecology and Management , 80(1-3): 209-223. 65. Teketay D., 1998. Germination of Acacia origena ,A. pilespina and Pterolobium stellatum in response to different pre-sowing seed treatments, temperature and light. Journal of Arid Environments ,38(4):551−560. 66. Teketay D., 2005. Seed and regeneration ecology in dry Afromontane forests of Ethiopia: II. Forest disturbances and succession. Tropical Ecology , 46(1): 45−64. 67. Tigabu M., Oden P.C., 2001. Effect of scarification, gibberellic acid and temperature on seed germination of two multipurpose Albiza species from Ethiopia. Seed Science and Technology , 29: 11−20. 68. Timberlake J., 1980. Handbook of Botswana acacias. Ministry of Agriculture, Gaborone, Botswana. 120p. 69. Travlos I.J., Economou, G., Karamanos A.J., 2007. Germination and emergence of the hard seed coated Tylosema esculentam (Burch) A. Schreib in response to different pre- sowing seed treatments. Journal of Arid Environments , 68: 501−507. 70. Uniyal A.K., Bhatt B.P., Todaria N.P., 2000. Provenance characteristics and pre-treatment effects on seed germination of Grewia oppositifolia Roxb. A promising agroforestry crop of Garhwal Himalaya, India. International Tree Crops Journal , 10(3): 203−213. 71. Van Wyk P., 1990. Field Guide to the Trees of the Kruger National Park. Struik. Cape Town, Republic of South Africa, 272p. 72. VenterF., Venter J.A. 2012. Making the Most of Indigenous Trees. 2nd Ed. Briza. Pretoria, Republic of South Africa, 320p. 73. Walters M., Midgley J.J., Somers M.J., 2004. Effects of fire and fire intensity on the germination and establishment of Acacia karroo , Acacia nilotica , Acacia luederitzii and Dichrostachys cinerea in the field. BMC Ecology , 4: 1−13. 74. Zar J., 2010. Bio-Statistical Analysis. 5 th edition. Prentice-Hall Inc., New Jersey, USA. 944p.

Please cite this Article as: Mmolutsi G.G., Matsuane C., Mojeremane W., Mathowa T. and Teketay D., 2020. Application and Use of Presowing Treatment Methods to Improve Germination of Vachellia karroo (Hayne) Banfi & Galasso. Agric. For. J., 4(1): 47-54.

DOI : https://doi.org/10.5281/zenodo.3837659