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Agroforestry SystemsAn International Journal incorporatingAgroforestry Forum ISSN 0167-4366 Agroforest SystDOI 10.1007/s10457-016-9974-3

Provenance and pretreatment effect onseed germination of six provenances ofFaidherbia albida (Delile) A. Chev

Charity Fredrick, Catherine Muthuri,Kamau Ngamau & Fergus Sinclair

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Provenance and pretreatment effect on seed germinationof six provenances of Faidherbia albida (Delile) A. Chev

Charity Fredrick . Catherine Muthuri .

Kamau Ngamau . Fergus Sinclair

Received: 3 July 2015 / Accepted: 30 May 2016

� Springer Science+Business Media Dordrecht 2016

Abstract A nursery experiment was conducted to

determine the effects of seed pretreatment methods on

the germination of Faidherbia albida at ICRAF,

Nairobi from six provenances consisting of Awassa,

Taveta, Lake Koka, Maseno, Chinzombo and Wagin-

gombe. Seeds were subjected to five pretreatment

methods namely nicking, soaking in acid, hot water,

cold water and control. Germination percentages (GP),

mean germination time (MGT) and germination index

(GI) were calculated and the data was subjected to

ANOVA. The study revealed significant (p B 0.05)

differences in seed treatments among provenances in

all studied parameters. Highest germination among

pretreatments in Awassa (99 %) and Wagingombe

(80 %) was observed in nicked seeds, Chinzombo

(81 %) in nicked and acid treated seeds, Lake Koka

(90 %) in acid treated seeds and Taveta (28 %) and

Maseno (64 %) in cold water treated seeds. Nicking

gave the highest cumulative GP (69.67) while lowest

GP was observed in hot water treated seeds (23.17).

Acid treatment exhibited lowest MGT (8.85 days) and

highest GI (2.29) while highest MGT (24.35 days) and

lowest GI (0.31) were observed in control and hot

water treatment respectively. Although acid treatment

gave a high GP and lowest MGT and GI, nicking and

soaking in cold water for 24 h is being recommended

as cheaper and less hazardous pretreatment methods to

improve germination in F. albida since sulphuric acid

is expensive and requires proper handling techniques.

Significant correlation between geo-climatic data and

germination parameters of seeds subjected to different

pretreatments indicates that provenances are as impor-

tant as pretreatments in germination of the species.

Keywords F. albida � Provenances � Pre-germination treatments � Germination percentage �Germination mean time � Germination index

Introduction

Faidherbia albida (Del.) A. Chev. (Syn. Acacia albida

Del.), commonly referred to as Apple-ring acacia

(Barnes and Fagg 2003), is a multipurpose leguminous

tree species belonging to the mimosoideae subfamily

(Dangasuk et al. 2011). It is widespread and com-

monly found in all tropical Africa from Senegal to

Sudan and as far as Natal or Angola (Danthu et al.

2002). It grows at low to medium altitudes

C. Fredrick (&)

University of Port Harcourt, P.M.B. 5323 Port Harcourt,

Rivers State, Nigeria

e-mail: charity_nwaogwugwu@yahoo.com;

charity.fredrick@uniport.edu.ng

C. Muthuri � F. SinclairWorld Agroforestry Centre, United Nations Avenue,

Gigiri, P.O. Box 30677-00100, Nairobi, Kenya

C. Fredrick � K. Ngamau

Jomo Kenyatta University of Agriculture and Technology,

P.O. Box 62000-00200, Nairobi, Kenya

123

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DOI 10.1007/s10457-016-9974-3

Author's personal copy

(270–2700 m) in areas of low to medium rainfall

(250–1200 mm/year) and mean temperatures from 18

to 30 �C (WAC 2004). It is also known to grow on the

banks of seasonal and perennial rivers and streams on

sandy alluvial soils or on flat land where Vertisols

predominate. It is very important for agro-silvo-

pastoral as well as soil conservation and soil fertility

improvement throughout the arid and semi-arid areas

(Dangasuk et al. 2011).

Its unique phenology of shedding its leaves during

the rainy season and retaining it in the dry season

improves soil structure, stability and permeability and

also provides shade and mulch which reduces evap-

oration thereby conserving available soil moisture

(Dangasuk et al. 2001). The leaves remain green

during the dry season due to its long tap root

(30–35 m) which is able to utilize deep underground

water (Dupuyl and Dreyfus 1992). Due to its capacity

to fix atmospheric nitrogen, and with its reversed

phenology, F. albida plays an important role in the

protection and improvement of soils as well as in the

increase of crop yield (Danthu et al. 2002). This makes

it an ideal agroforestry tree for use in combination with

crops (Wood 1992). The species is also known to have

high medicinal values; it provides food, furniture, fuel

and can be used for making fences; it also provides

shade and a highly nutritious fodder for livestock

(Kiros et al. 2009). The importance of this species in

agroforestry has made it an important subject for

research. F. albida is mainly propagated by seeds; an

attempt to use artificial regeneration by means of

seedling was not very successful due to poor survival,

slow and variable early growth of the planted trees

(Ibrahim et al. 1997).

Many seeds have difficulty in germination such

that their propagation is adversely affected by seed

coat dormancy which leads to poor growth potential

(Falemara et al. 2014). Botsheleng et al. (2014)

noted that seeds of most arid and semi-arid tree

species cannot germinate promptly when subjected

to conditions favourable for germination due to

impermeable seed coat to water. Also most Acacia

spp have hard seed coats which are impervious to

water (Walters et al. 2004; Aref et al. 2011). Clode

(2011) also noted that many leguminous trees have

hard seed coats and Faidherbia albida is no

exception. Seed dormancy has evolved differently

across species due to adaptation to a prevailing

environment (Botsheleng et al. 2014), it is said to be

a temporary failure of a mature viable seed to

germinate under environmental conditions that

would normally favour germination (Ibiang et al.

2012). The conditions necessary to allow seeds to

‘‘break’’ dormancy and germinate can be highly

variable among species, within a species, or among

seed sources of the same species (Luna et al. 2009).

Several studies have shown that pretreatment may

significantly enhance seed germination of various

tree species (Hossain et al. 2005). Seeds of species

with hard seed coat need to be subjected to some

physical or chemical treatment to break dormancy

and obtain uniform germination (Botsheleng et al.

2014). Different pre-sowing treatment have been

used by different Researchers to enhance seed

germination of different species including Faidher-

bia albida (Diallo et al. 1996), Acacia spp (Aref

et al. 2011); Grewia oppositifolia (Uniyal et al.

2000); Vitellaria paradoxa (Iroko et al. 2013);

Terminalia chebula (Hossain et al. 2005); Te-

trapleura tetraptera (Ibiang et al. 2012); Afzelia

quanzensis (Botsheleng et al. 2014), and Adansonia

digitata (Falemara et al. 2014). However, There are

around 132 provenances of F. albida in Africa all

displaying differences in germination characters and

therefore recommending which pretreatment is suit-

able for which provenance (s) is a big challenge

(Fredrick et al. 2015). There is paucity of informa-

tion on the effect of pre- sowing treatment on

germination of F. albida seeds and also lack of

information on the effect of provenances and

pretreatment on germination of seeds subjected to

different pretreatments. Due to its hard seed coat,

there is poor and prolonged germination of the

species. Diallo et al. (1996) noted that F. albida

produces seeds with hard and impermeable tegument

which becomes an obstacle for it to germinate.

Barnes and Fagg (2003) also reported that F. albida

seeds requires pretreatment to stimulate rapid and

uniform germination. A study to improve the

germination of F. albida by some selected pre-

sowing treatment will help in selecting the most

suitable method to break water impermeable seed

coat of F. albida provenances so as to obtain rapid

and uniform germination of seedlings for application

in agroforestry systems. The objective of this study

was to investigate the effects of provenance char-

acteristics (seed source) and five pre-treatment

techniques on germination response of seeds of F.

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albida in order to identify the most suitable pretreat-

ment method that will increase germination of F.

albida provenances namely Awassa, Chinzombo,

Lake Koka, Maseno, Taveta and Wangingombe,.

Materials and methods

Experimental site

The study was carried out at the World Agroforestry

Centre (ICRAF) nursery in a greenhouse with a

temperature range of 27 and 40 �C, between July and

August, 2014. ICRAF is located about 20 km south-

east of Nairobi, Kenya; at latitude 1�330S and longi-

tude 37�140E, with an average elevation of 1700 m

above sea level. The mean annual rainfall ranges

between 930 and 1500 mm and the annual tempera-

ture range is 16–24 �C.

Seed materials

The seeds of F. albida provenances, namely, Awassa,

Chinzombo, Lake Koka, Maseno, Taveta, and Wagin-

gombe used in this study (Table 1) were obtained from

the ICRAF germplasm laboratory. The seeds were

collected by Oxford Forest Institute for international

provenance trials in 1990 (Fredrick et al. 2015). After

collection, seeds were cleaned and dried immediately

before storage. Seeds were placed in cotton bag and

stored in a cool, dry, and dark place with good air

circulation at -20 �C (WAC 2013). During collec-

tion, 25 mother trees spaced 100 m apart to avoid

collection from related individuals were selected to

represent a provenance (Fredrick et al. 2015). The

samples were representative of the entire natural

distribution range of the species in East and Southern

Africa (EA and SA respectively). In this study, the

term provenance denotes the original geographic zone

from which seeds were collected (Loha et al. 2006).

The location and geographical descriptions of the

different provenances are given in Fig. 1 and Table 1.

Experimental design

The experiment was laid out in a randomized complete

block design consisting of 500 randomly selected

seeds per provenance for the five different scarifica-

tion methods. 25 seeds replicated four times (100

seeds) for each provenance were subjected to a

scarification method giving a total of 3000 seeds (i.e.

25 seeds 9 4 replicates 9 5 scarification meth-

ods 9 6 provenances = 3000 experimental units).

Each treated seed was directly sown in a germination

tray measuring 17 9 13 9 3.5 cm and filled with

sterilized sharp sand and were kept moist by watering

daily. Seeds were germinated under a 50 % light shade

net. No fertilizers or bacterial and/or mycorrhizal

inoculation was used.

Scarification treatments

To investigate the effect of different scarification

methods on the selected provenances, five methods of

scarification were used. These included acid scarifi-

cation, mechanical scarification (nicking), hot water

Table 1 Geographic locations and climatic conditions of the six provenances used in this study (Fredrick et al. 2015)

Provenance Country Zone Geographical location

Lat.–Long.

Altitude (m) Rain (mm) Temp (�C)

Chinzombo Zambia SA 13�080S–32�450E 550 958 24.0

Wangingombe Tanzania EA 08�510S–34�380E 1450 819 20.6

Taveta Kenya EA 03�240S–37�420E 760 545 23.5

Maseno Kenya EA 00�010S–34�600E 1503 119 21.1

Lake Koka Ethiopia EA 08�200N–38�590E 1600 742 10.0

Lake Awassa Ethiopia EA 07�030N–38�280E 1650 961 19.6

EA East Africa, SA Southern Africa

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treatment, cold water treatment and control (untreated

seeds).

Pretreatment procedure

Acid scarification (T1)

In the acid treatments, seeds were placed in heat

resistant non-corrosive glass beaker and concentrated

sulphuric acid (98 %) was poured slowly on the side of

the beaker until all the seeds were covered (50 ml)

(Botsheleng et al. 2014) and left for 30 min during

which they were frequently stirred. Thereafter, treated

seeds were rinsed thoroughly with tap water to remove

all the acid and finally air dried before sowing for

germination (schelin et al. 2004; Asinwa et al. 2012).

Mechanical scarification (T2)

The effect of mechanical scarification was investi-

gated by carefully nicking the seed coat at the distal

end with nail clipper.

Hot water treatment (T3)

In hot water treatments, seeds were placed in fabric

bags and immersed in preheated water at 80 �C and

left to cool gradually at room temperature for 24 h.

Pretreated seeds were air dried before they were sown

for germination (Schelin et al. 2004).

Cold water treatment (T4)

In cold water treatments, seeds were soaked in clean tap

water at ambient temperature (28 �C) for 24 h (Fale-

mara et al. 2013) and air dried before they were sown.

Control (T5)

For control, seeds were not treated. It was conducted to

be able to compare the effect of no pretreatment of F.

albida seeds on germination.

Germination assessment

Germination was recorded daily from the day of

sowing by counting the number of germinated seeds;

Fig. 1 Sources of the

different provenances of

Faidherbia albida used in

this study (Fredrick et al.

2015)

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seedlings were pricked-out after counting to avoid

error. Germination was allowed to proceed for 50 days

after which the experiment was termination. A seed

was considered to have germinated when the hypoco-

tyls hook is evident above the soil surface (Fandohan

et al. 2010). Data collected on germination was used to

calculate germination percentage GP, mean germina-

tion time (MGT) and germination index (GI) for each

treatment using the equation below.

Germination Capacity ðGCÞ

¼ Total germinated seeds

Total seeds sown� 100

1ð1Þ

Germination Index ðGIÞ ¼ G1

1

� �þ G2

1

� �þ ::::::

þ Gx

x

� �

ð2Þ

where G is the germination day 1, 2…, and x

represents the corresponding day of germination

(Botsheleng et al. 2014).

MeanGermination Time ðMGTÞ ¼P

ðtiXniÞPni

ð3Þ

where ti is the number of days starting from the date of

sowing and ni is the number of seeds germinated at

each day (Bewley and Black 1994).

Statistical analysis

Data collected were statistically analyzed using SPSS

statistical software (SPSS version 16.0, SPSS Inc.) to

explore possible treatment variation (Hossain et al.

2005). Analysis of variance was carried out to test the

effect of seed treatments on provenances and Dun-

can’s multiple range test at p B 0.05 level of signif-

icance was used for mean separation (Aref et al. 2011)

after ensuring main effects were significant. All graphs

were plotted using Microsoft excel.

Results

Effect of seed treatment on germination

of F. albida provenances

Seed pretreatment significantly (p B 0.05) affected

germination percentage, mean germination time and

germination index of seeds of F. albida from different

provenances (Table 2). In Chinzombo, mechanically

scarified seeds and seeds treated with acid produced

highest germination percentage (81 %) when com-

pared to hot water immersion (39 %), cold water

immersion (16 %), and control seeds (13 %) which

had the lowest germination percentage (Table 2).

Mean germination time varied among treatments from

7.77 to 37.92 days Highest mean germination time

was observed in control seeds (37.92 days) followed

by hot water immersion (27.34 days) and lowest in

seeds treated with acid (7.77 days). Also Chinzombo

exhibited highest germination index in acid treatments

(2.92) and lowest in control seeds (0.09) (Table 2).

In Wagingombe, mechanically scarified seeds

exhibited highest germination percentage (80 %),

followed by seeds treated in cold water (71 %) while

seeds treated in hot water had the lowest germination

percentage (15 %). Mean germination time ranged

from 7.95 to 22.71 days withcontrol seeds

(22.71 days) exhibiting highest mean germination

time and acid treated seeds lowest (7.95 days),

followed by mechanically scarified seeds (9.83 days).

Germination index was higher in acid and mechani-

cally scarified seeds (2.37 and 2.24 respectively), and

lower in seeds immersed in cold water, control seeds

and hot water, (1.40, 0.79 and 0.25 respectively)

(Table 2).

Taveta exhibited poor germination in all treatments

including control. Germination percentage ranged

from 6 to 28 %. Highest germination percentage was

observed in seeds immersed in cold water (28 %)

followed by mechanically scarified seeds (26 %) and

lowest germination percentage in hot water treated

seeds (6 %). Mean germination time ranged from 9.05

to 22.58 days. Highest mean germination time was

observed in control seeds (22.58 days) while mechan-

ically scarified seeds exhibited lowest mean germina-

tion time. Similarly, germination index ranged from

0.06 to 1.01. Seeds immersed in hot water showed

lowest germination index (0.06) while highest germi-

nation index was observed in mechanically scarified

seeds (1.01) (Table 2).

In Maseno, germination percentage ranged from 29

to 64 %. Seed treated in cold water was highest (64 %)

followed by control seeds (63 %), acid treated seeds

(61 %) and mechanically scarified seeds (55 %),

while seeds immersed in hot water was lowest

(29 %). Mean germination time was significantly

Agroforest Syst

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lower for seeds treated in acid and mechanically

scarified seed (8.56 and 8.73 days respectively) than in

seeds immersed in hot water (24.58 days), cold water

(16.84 days) and control (23.14 days). Germination

index ranged from 0.36 to 2.01 with acid treated seeds

exhibiting highest germination index (2.01 days)

followed by mechanically scarified seed 1.76 days)

while lowest germination index was found in seeds

immersed in hot water (0.36). Note, seeds immersed in

hot water exhibited lowest germination percentage

(29 %), highest mean germination time (24.58 days)

and lowest germination index (0.36) (Table 2).

In Lake Koka, Germination percentage ranged from

27 to 90 %. Seeds treated in acid and control seeds

produced higher germination percentage (90 and 82

respectively) while germination percentage was low-

est for seeds treated in hot water (27 %). Mean

germination time ranged from 7.78 to 19.67 days.

Mechanically scarified seed had the lowest mean

germination time (7.78) followed by seeds treated in

acid (8.09 days) while control seeds had the highest

mean germination time (19.67 days). Germination

index was highest in acid treated seeds (3.06) and in

seeds immersed in hot water (0.40) (Table 2).

Awassa exhibited an excellent germination in all

pretreatments except for hot water treatment. Germi-

nation percentage ranged from 23 to 99 %. Highest

germination percentage occurred in mechanically

scarified seed (99 %), followed by control seeds

(92 %), acid treated seeds in (89 %) and seeds

immersed in cold water (87 %) and lowest in seeds

immersed in hot water (23 %). Mean germination time

ranged from 8.30 to 20.11 days. Highest mean

germination time was observed in control seeds

(20.11 days) while lowest mean germination time

was observed in acid treated seeds (8.33 days).Ger-

mination index ranged from 0.35 to 2.89. The highest

germination index was observed in acid treated seeds

(2.89) followed by mechanically scarified seed (2.86),

while lowest germination index was recorded in seeds

immersed in hot water (0.35) (Table 2).

Correlation between seed geo-climatic variables

and germination parameters in various treatments

Correlation between germination percentage and geo-

climatic data of seed collection sites showed a highly

significant correlation between altitude and germina-

tion percentage in seed pretreated with cold water (T4)

and control seeds (T5), a significant correlation in seed

pretreated with acid (T1) and nicked seeds (T2) and an

inverse non-significant correlation in seeds pretreated

with hot water (T3). Rainfall had a significant

correlation with germination percentage in seeds

Table 2 Effects of seed

pretreatment on mean

germination parameters of

the six F. albida

provenances

Means followed by the

same letter in a row are not

significantly different at

p B 0.05

GP germination (%), GI

germination index, MGT

mean germination time

(days)

Provenances Parameters Acid Nicking Hot water Cold water Control P value

Chinzombo GP (%)

MGT (days)

GI

81c

7.77a

2.92d

81c

10.94a

2.01c

39b

27.34b

0.45b

16a

25.37b

0.18a

13a

37.92c

0.09a

0.000

0.000

0.000

Wagingombe GP (%)

MGT (days)

GI

63b

7.95a

2.37c

80c

9.83a

2.24c

15a

16.23b

0.25a

71bc

14.43b

1.40b

57b

22.71c

0.79a

0.000

0.000

0.000

Taveta GP (%)

MGT(days)

GI

22b

12.41ab

0.50b

26b

9.05a

1.01c

6a

20.25b

0.06a

28b

18.10ab

0.43ab

21b

22.58b

0.27ab

0.002

0.049

0.001

Maseno GP (%)

MGT (days)

GI

61b

8.56a

2.01c

55b

8.73a

1.76c

29a

24.58c

0.36a

64b

16.84b

1.10b

63b

23.14c

0.79b

0.000

0.000

0.000

Lake Koka GP (%)

MGT (days)

GI

90c

8.09a

3.06d

77bc

7.78a

2.73c

27a

17.19b

0.40a

65b

17.10b

1.03b

82c

19.67c

1.23b

0.000

0.000

0.000

Awassa GP (%)

MGT (days)

GI

89bc

8.33a

2.89c

99c

9.34a

2.86c

23a

19.11c

0.35a

87b

15.99b

1.60b

92bc

20.11c

1.37b

0.000

0.000

0.000

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pretreated with acid (T1) and nicked seeds (T2) and a

non-significant correlation with seeds treated in hot

water (T3), cold water (T4) and control seeds (T5).

Temperature had an inverse correlation with germi-

nation percentage in all treatments. Mean germination

time was inversely correlated with altitude and

positively correlated with temperature while correla-

tion with rainfall was not significant. Also germination

index had a highly significant correlation with altitude

in seed treated in nicked seeds (T2), cold water (T4)

and control seeds (T5) and a non-significant correla-

tion in acid (T1) and hot water (T3). Germination

index was positively correlated with rainfall and

inversely correlated with temperature in all treat-

ments. This information is given in Table 3.

Discussion

Seed coat hardness is an important factor that affects

germination in seed (Aref et al. 2011). Seed dormancy

is known to occur in many tropical tree species

(Amusa 2011), most Acacia spp have hard seed coats

which are impervious to water (Aref et al. 2011).

Uniyal et al. (2000) stated that seed pretreatment are

species specific and that no one type of treatment has

been reported to be universally effective. Therefore

breaking the seed dormancy by softening the seed testa

to allow water imbibition is crucial for any afforesta-

tion programs (Aref et al. 2011).

The results of this study showed that all treatment

significantly (p B 0.05) affected various germination

parameters (germination percentage, mean germina-

tion time, and germination index) in all provenances

studied. Mechanical and chemical scarification were

more effective in rendering seeds of F. albida

permeable, leading to a mean germination of up to

69.67 and 67.67 % respectively. Mechanical scarifi-

cation which recorded highest germination percentage

is known to break physical dormancy of hard seed

coats by enhancing gases and water uptake especially

in Acacia species (Missanjo et al. 2014). The enhanced

germination observed in the mechanical treatment

could be attributed to water uptake by the quiescent

dry seed, which ended up with the elongation of the

embryonic axis (Botsheleng et al. 2014). Chemical

scarification also enhanced germination of F. albida

seeds and exhibited lowest mean germination time and

highest germination index. Reduced mean Table

3Pearsoncorrelationcoefficient(r)betweengerminationparam

etersofvariouspretreatm

entandgeo-climatic

variables(m

eanaltitude,

meanannual

rainfallandmean

annual

temperature)ofseed

origin

ofsixF.albidaprovenances

Param

eters

Germinationpercentage

Meangerminationtime

Germinationindex

T1

T2

T3

T4

T5

T1

T2

T3

T4

T5

T1

T2

T3

T4

T5

Altitude

0.425*

0.424*

-0.047

0.937**

0.938**

-0.382

-0.515**

-0.366

-0.750**

-0.733**

0.373

0.613**

0.165

0.892**

0.902**

Rainfall

0.477*

0.657**

0.111

-0.009

0.015

-0.307

0.386

-0.136

0.237

0.256

0.494*

0.499*

0.191

0.020

0.077

Tem

perature

-5.13*

-0.305

-0.093

-0.479*

-6.73**

0.311

0.622**

0.341

0.343

0.509*

-0.462*

-0.590**

-0.260

-0.378

-0.685**

T1Acid,T2Nicking,T3Hotwater,T4Cold

water,T5Control

*Significant,**highly

significancesat

the0.05and0.01levelsrespectively

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germination time in acid treated seeds implies that the

period of dormancy in seeds was reduced due to

pretreatment of seeds in sulphuric acid. It is reported

that acid treatment is an efficient method of enhancing

seed germination of species with hard impermeable

seed coat (Mcdonald and Omoruyi 2003; Likoswe

et al. 2008). It stimulates prompt and uniform germi-

nation of seeds (Agbogidi et al. 2007). Sulphuric acid

is known to disrupt the seed coat thereby exposes the

lumens of the macrosclereids cells, permitting imbi-

bitions of water which triggers germination (Amusa

2011). Agbogidi et al. (2007) also stated that acid

treatment of seeds removes waxy layer of the seed coat

by chemical decomposition of seed coat component

which is similar to breakdown process that occurs

during microbial attack. Hot water treatment exhibited

a low germination percentage (below 40 %) for all

provenances. It was observed that hot water treatment

was not found to be suitable in improving germination

of F. albida provenances. Amusa (2011) stated that

poor germination in hot water treatment could be due

to death of seed embryo as a result of prolonged

contact with hot water. Cold water treatment of F.

albida gave a fair germination percentage and a

reduced mean germination time when compared to hot

water treatment and control. This also implies that

soaking in cold water could also reduce dormancy

period in seeds of F. albidawhen compared to control.

This result concurs with earlier report of Emerhi and

Nwiisuator (2010) and Falemara et al. (2013) which

shows that soaking in cold water is a feature that

enhances germination in seeds of tropical trees. The

control treatment exhibited a lower germination

percentage than cold water and the highest mean

germination time when compared with other

treatments.

This study is in conformity with the work carried

out at the Eden Foundation on how best to establish a

healthy population of F. albida by direct sowing,

without the use of plant nurseries, irrigation or

inorganic fertilizers (Beckman 1990) which reported

that the physical scarification techniques provided the

best results when compared with other treatments.

Jemutai (2011), Barnes and Fagg (2003), Diallo et al.

(1996), Sniezko and Gwaze (1987), Bebawi and

Mohamed (1985) and Halliday and Nakao (1984) also

reported that mechanical and acid scarification gave

the highest germination percentage in seeds of F.

albida. Aref et al. (2011) reported that seeds from four

Acacia species germinated better and faster after

scarification (abrasion and acid treated) when com-

pared to hot water and no treatment. Botsheleng et al.

(2014) and Asinwa et al. (2012) also reported that

mechanical scarification gave the highest germination

percentage in seeds of A. quanzensis and Leucaena

leucocephala respectively and concluded that seed

scarification was the most effective method of

improving seed coat permeability. Poor germination

of F. albida due to hot water treatment has been

reported by Eden Foundation (Beckman 1990). Diallo

et al. (1996) also observed less than 20 % germination

in F. albida seeds subjected to hot/boiling water

methods after 16 days. Bebawi and Mohamed (1985)

warned that boiling water treatment for acacia seeds

was particularly detrimental and could kill most of the

seeds. Similar results have been reported in other

species such as Lupinus hispanicus (Centenera et al.

1999) where poor germination was reported with hot

water treatment when compared to mechanical scar-

ification and immersion in sulphuric acid and A.

quanzensis (Botsheleng et al. 2014) where hot water

treatment had a low germination percentage not

exceeding 40 %. Amusa (2011) also noted that hot

water pretreatment is not an appropriate pretreatment

technology in the seeds of A. africana. Although

Diallo et al. (1996) suggested the use of seed gun

method to treat large quantity of seed quickly since

nicking individual seeds could be labour intensive,

Barnes et al. (1996) concluded that despite the very

large number of seedlings of F. albida to be raised, it

was practicable to nick every seed before germination.

The subsequent increase in the germination per-

centage, decrease in mean germination time and

increase in germination index when subjected to

different pretreatment methods is an indication that

the hard seed coat is responsible for the dormancy in F.

albida. Significant correlation between altitude and

germination percentage in seeds treated in acid,

nicking, cold water and control indicates that seeds

collected from provenances with higher altitude had

higher germination percentage than those with lower

altitudes. Temperature is known to decrease as altitude

increases (Uniyal et al. 2000); this explains the inverse

correlation between temperature and germination

percentage in all treatments. Also provenances with

higher rainfall exhibited higher germination percent-

age in acid treated and nicked seeds. Inverse signif-

icant correlation between mean germination time and

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altitude indicates that provenances with higher altitude

had a lower mean germination time i.e. rapid germi-

nation while provenances with higher temperature had

higher mean germination time in nicked and control

seeds. Non-significant correlation between rainfall

and mean germination time indicates that rainfall does

not have any effect on mean germination time in all

treatments. Significant correlation between altitude

and germination index indicates that seeds from

provenances with higher altitude also exhibited higher

germination index in nicked, cold water treated and

control seeds while seeds from provenances with

higher rainfall had higher germination index in nicked

treated seeds. This implies that seed provenance is as

important as pretreatment, therefore seed collection

should be done at an appropriate altitude, rainfall and

temperature since seed germination can be affected by

climatic condition of seed source.

This finding agrees with the findings of Uniyal et al.

(2000), who also noted that seed source is as important

as pretreatment in seeds of Grewia oppositifolia. The

different response of F. albida provenances to differ-

ent pretreatments shows that seeds of a particular

species collected from different locations will differ in

germination indicating that seed source plays an

important role in the response of seeds subjected to

different pre-sowing treatment. This result is in

agreement with the statement by Luna et al. (2009)

‘That the conditions necessary to allow seeds to

‘‘break’’ dormancy and germinate can be highly

variable among species, within a species, or among

seed sources of the same species’. Differences in

germination of a species from different provenances

subjected to the same pretreatment methods have been

reported by Webb and Farmer (1968) and Uniyal et al.

(2000).

Conclusion

Seeds of most arid and semi-arid tree species areas

cannot germinate promptly when subjected to condi-

tions favourable for germination due to impermeable

seed coat to water. It is also noted that many

leguminous trees have a hard seed coat and F. albida

is no exception. Since the seed coat of F. albida is

hard, it takes more time to germinate with lower

germination percentage in nursery establishment. The

nature and dimension of hard seed coat dormancy in

different species is not fully understood. Therefore,

pre-germination treatments are needed to break phys-

ical dormancy caused by hard seed coat. The objective

of this study was to investigate the effect of different

pretreatment methods on F. albida provenances so as

to determine the most suitable pretreatment that would

enhance and increase germination.

The study revealed the existence of considerable

variation in germination among provenances with

respect to germination percentage, mean germination

time and germination index when subjected to differ-

ent pretreatment methods. Although pretreatment is

not very relevant to reach high final germination

percentage in F. albida provenances (excluding

Chinzombo), it may reduce mean germination time

and increase germination index of F. albida seeds.

Mechanical scarification and acid treatments are the

most effective methods in improving seed germination

of F. albida species by increasing germination

percentage and reducing dormancy period (mean

germination time) but nicking or soaking in cold

water for 24 h is being recommended as cheaper and

less hazardous pretreatment methods to improve

germination in F. albida since sulphuric acid is

expensive and requires proper handling techniques.

Also combined nicking and soaking for 3–12 h could

be used to achieve rapid and maximum germination.

This study also revealed that provenances are as

important as pretreatments. Therefore seed collection

should be done at an appropriate altitude, rainfall and

temperature to enhance germination since seed ger-

mination can be affected by climatic condition of seed

source. The findings of this study will enable selection

of the most suitable pretreatment method for the

different provenances and raising seeds of Faidherbia

albida for easy propagation, domestication and plan-

tation establishment, which will enhance and improve

performance and growth potential of the F. albida

seeds. We recommend that since nicking individual

seeds could be labour intensive, soaking in cold water

for 12–24 h could be used but both methods (nicking

and cold water treatment) are cheap and efficient for

poor farmers although nicking is the best practicable

method to treat every F. albida seed before

germination.

Acknowledgments Authors are thankful to the World

Agroforestry Centre (ICRAF, Nairobi) for providing the

necessary materials for this work. This work was carried out

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under the ‘trees for food security’ project led by ICRAF and

funded by the Australian Centre for International Agriculture

Research (ACIAR). The project is operating in Ethiopia,

Rwanda, Uganda and Burundi and F. albida is one of the

important tree species being studied under the project. We also

want to thank Lucy Mwaura of the ICRAF seed laboratory for

availing the seeds and Julius Njoroge, Agnes Gachuiri, Julius

Kimani and Valentine Gitonga for their support in setting up the

experiment.

Compliance with ethical standards

Conflict of interest The authors declare that they have no

conflict of interest.

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