Effects of Boiled Water Pre-Sowing Treatment on the Germination and Early Growth Performance of Faidherbia albida in Three Ecological Zones of Ghana

(1)

_____________________________________________________________________________________________________ *Corresponding author: E-mail: sakpalu2@gmail.com, seakpalu@yahoo.com;

Effects of Boiled Water Pre-Sowing Treatment on the

Germination and Early Growth Performance of

Faidherbia albida

in Three Ecological Zones of

Ghana

Stephen Edem Akpalu

1*

, Evans Lawrence Dawoe

2

and Akwasi Adutwum Abunyewa

2

1

CSIR-Forestry Research Institute of Ghana, Bolgatanga, Upper East Region, Ghana. 2_{Department of Agroforestry, Kwame Nkrumah University of Science and Technology, Kumasi,} Ghana.

Authors’ contributions

This work was carried out in collaboration among all authors. Author SEA identified the need for this study, wrote the concept note, proposal and protocols for the entire study. He also did the data collection, statistical analysis, wrote the first draft of the manuscript and managed the literature searches. Author ELD refined the protocol of the study, made very significant suggestions to the data collection protocols, managed literature searches and did proof reading of the manuscript. Author AAA assisted in the statistical analyses of the data and the presentation and discussion of the results as well as proof reading of the manuscript. All authors read and approved the final manuscript.

Article Information

DOI: 10.9734/AJRAF/2019/v4i330065 Editor(s): (1)Dr. Lucia Bortolini, Assistant Professor, Department of Land, Environment, Agriculture and Forestry, University of Padova, Italy. Reviewers: (1)Schirley Costalonga, Universidade Federal do Espírito Santo, Brazil. (2)Zdzisław Kaliniewicz, University of Warmia and Mazury in Olsztyn, Poland. Complete Peer review History:http://www.sdiarticle4.com/review-history/51951

Received 05 August 2019 Accepted 10 October 2019 Published 21 October 2019

ABSTRACT

Aims: To identify an appropriate boiled water pre-sowing treatment regime for improved germination, survival and early growth performance of Faidherbia albida (Delile) A. Chev., in three ecological zones of Ghana.

Study Design: The design was a Completely Randomized Block Design (CRBD) in three replicates, where the three different ecological zones were considered as blocks.

(2)

Place and Duration of Study: The study was conducted in Bolgatanga (Guinea Savannah Zone), Abofuor (Forest-Savannah Transitional Zone), and Kumasi-Mesewam (Moist Semi-deciduous Forest Zone) between April 2017 and April 2018.

Methodology: Matured seeds of F. albida were harvested, dried and cleaned. For each treatment replicate, one hundred F. albida seeds were immersed in boiled water (100ºC) for 0, 30, 60, 120, 180 and 300 seconds and then, soaked in water at room temperature for 24 hours. Seeds were then sown in drills on well prepared seed beds, and then observed for germination. Watering was done to keep the soil moist until the onset of germination.

Results: There were significant interactive effects between ecological zones and pre-sowing treatments with respect to Final germination percentage (P<0.001), Germination rates (P<0.001) and Survival percentage (P=0.007). Root length (P=0.040), total plant length (P=0.040) and Number of leaves (P<0.001) also exhibited significant interactive effects due to ecological zones and pre-sowing treatments. Roots were significantly longer in the GSZ than in the more humid ecological zones whereas stems were significantly longer in the MSFZ than in the drier GSZ. Conclusion: Different durations of F. albida seeds in boiled water had different effects on germination and growth in the different ecological zones.

Keywords: Germination; imbibition; dormancy; survival rate; dry matter partitioning; shoot to root ratio.

1. INTRODUCTION

Faidherbia albida belongs to the sub-family Mimosoideae [1] and is monotypic within the tribe Ingeae and sub-tribe Acaceae [2]. It is a useful traditional agroforestry tree species, commonly found on parklands in the arid and semi-arid regions across Africa [3]. By virtue of its reverse phenology, its demand for growth resources is usually out of tandem with that of major field crops in these areas. Furthermore, it adds a significant amount of nutrients to the soil for use by field crops. The pods, which are rich in crude proteins and carbohydrates [4], serve as feed for livestock in the dry season. These beneficial roles of the tree make it a preferred candidate in the choice of tree species for domestication especially in Africa, where affordability for inorganic fertilizers is the lowest [5], and livestock feed availability in the dry season is of major concern [6].

Germination is key to the successful regeneration and propagation of plants. However, for germination to occur physical and environmental factors would need to be favourable. The condition where an intact, viable seed fails to germinate under favourable conditions is known as dormancy [7]. Dormancy has been classified as physical, chemical, physiological, photo- or thermo-dormancy [8] or physiological, morphophysiological, physical, and a combination of physical and physiological [9]. The intensity of dormancy could be

influenced by the species, genome and the type of dormancy [10]. Most leguminous tree

seeds, including F. albida, are noted for their hard seededness [11-13], resulting in their

resistance to imbibition, a very crucial process required for the initiation of germination

[14,15]. Common methods that have been suggested to break physical dormancy in seeds

include scarification by nicking [16], hot water and acid treatments [17], stratification [18].

To overcome the challenge of seed dormancy, various studies have recommended hot water treatment but with varying durations of exposure to the hot water. According to [19], pre-sowing treatment methods need to be easy to apply even under local conditions and easy for the local farmer to adopt. Hot water treatments should therefore be considered as alternative to sulphuric acid (which poses danger to the farmer), nicking (which is laborious), and seed gun (which requires expertise and precision). The commonest pre-sowing treatment for F. albida seeds among smallholder farmers is to keep the seeds in boiled water for 3 to 5 minutes followed by soaking in tap water for 24 hours [13]. This method has, however, been noted to have variable effects in different locations and in different seasons [13]. Missanjo et al. [17], compared the effects of different pre-sowing treatment methods on the germination of Acacia polyacantha, and observed that immersing seeds in boiling water for 5 minutes and soaking in cold water for 24 hours resulted in 76.2% germination rates whiles immersing in concentrated sulphuric acid resulted in 74.8%, both significantly higher than that of the control (42.4%).

(3)

determination of an appropriate duration of F. albida seeds in boiled water will improve germination and early growth, and will subsequently contribute tremendously to the successful domestication and upscaling of the tree.

This study compared the effects of different durations of seed immersion in boiled water (1000C), and later in tap water for 24 hours, on the germination and early growth performance of F. albida seedlings in three different ecological zones of Ghana. It is expected to help identify the optimal time required for improved germination and growth of F. albida seedlings to upscale the population of the tree in the Guinea Savannah, Forest-Savannah Transitional and Moist Semi-deciduous Forest Zone parkland tree species.

This study sought to provide answers to the following research questions:

 Will the different durations of immersion of seeds in boiled water (100°C) significantly affect germination and early growth performance of F. albida?

 Will the germination and early growth performance of F. albida seedlings differ significantly in the respective ecological zones?

 Will the pre-treatment methods and ecological differences affect the distribution of dry matter in different (below and above ground) portions of seedlings?

2. METHODOLOGY

2.1 Study Sites

The study was carried out in Bolgatanga, Guinea Savannah Zone (GSZ), located at Latitude 10°47'8" North and Longitude 0°51'5" West at 191m above sea level, in Abofuor, Forest-Savannah Transitional zone (FSTZ) located at Latitude 7°8'0" North and Longitude 1°45'0", and Kumasi-Mesewam, Moist Semi-deciduous Forest Zone (MSFZ), located at Latitude 6°41'0" North and Longitude 1°37'0" West at 270m above sea level.

The vegetation in the GSZ is the Guinea Savannah woodland type, characterized by short scattered drought resistant trees with undergrowth of grass that serves as fuel for bushfires in the long dry season. Common economic fruit trees include Vitellaria paradoxa (Shea), Parkia biglobosa (Dawadawa),

Adansonia digitata (Baobab) and Faidherbia albida [20]. The area is characterized by one raining season, which occurs between May/June and September/October. Mean annual rainfall is between 800 and 1,000mm and the rains are generally erratic in terms of frequency and intensity. There is a long dry season that extends from November to April/May. Temperatures range between 14ºC during the harmattan (December to February) and 42ºC in April [21]. Soils are generally shallow and low in major soil nutrients and organic matter content, and prone to erosion. Due to the short raining season, only short-term annual crops such as millet, sorghum, maize, rice, cowpea, groundnut, Bambara groundnut, soybean, pepper, onions and leafy vegetables are grown.

The Forest-Savannah Transitional Zone (FSTZ) is bordered to the north by the GSZ and in the south by the MSFZ. Mean annual rainfall ranges between 1,200mm and 1,300mm with marked variability, whiles mean annual temperature is about 28ºC [22]. The soils are underlain by the Voltaian sandstones, shales and granites with the presence of iron pans at shallow depths, resulting in poor ground water infiltration in most places. Soils are generally loamy and do not easily dry up due to the presence of thick layers of humus. Farming is small-scale and rain-fed agriculture, producing a wide variety of crops including cocoa, citrus, oil palm, plantain, yam, maize, cassava, cowpeas and vegetables [23].

(4)

2.2 Seed Collection and Treatment

Matured F. albida pods were collected from a matured tree in the GSZ, where it occurs naturally, in February 2017. The pods were shelled and seeds extracted.

The following treatments were used in each of the three ecological zones. T1 (0/0) where F. albida seeds were sown directly without being immersed in boiled (100°C) water nor soaked in tap water; T2 (0/24) where seeds were soaked in tap water for 24 hours; T3 (30/24) where seeds were immersed in boiled water for 30 seconds and then soaked in tap water for 24 hours; T4 (60/24) where seeds were immersed in boiled water for 60 seconds and then soaked in tap water for 24 hours; T5 (120/24) where seeds were immersed in boiled water for 120 seconds and then soaked in tap water for 24 hours; T6 (180/24) where seeds were immersed in boiled water for 180 seconds and then soaked in tap water for 24 hours; and, T7 (300/24) where seeds were immersed in boiled water for 300 seconds. The seven lots of F. albida seeds, each comprising one hundred (100) seeds were sown in drills at 15 cm spacing on the seedbeds and watered regularly to keep the soil moist until germination commenced. In each ecological zone, each treatment was replicated three times.

2.3 Data Collection and Analysis

Data was collected on the number of seeds that germinated at 3 days intervals. Germination in this context means the emergence of the radicle above the soil surface.

Germination parameters assessed in this study included

(i) Final Germination Percentage (FGP), (ii) Germination Rate (GR),

(iii) Germination Index (GI), (iv) Mean Germination Time (MGT)

(v) Seedling Survival Rates/Percentage (SP) and

(vi) Days to final germination (DFG).

FGP = (Final number of seeds germinated in seed lot/ Total number of seeds in seed lot) x 100

GR = ∑n/t,

where, n is the number of germinated seeds in day t

GI = (∑TiNi)/S,

where, Tiis the number of days after sowing, Ni is the number of germinated seeds in that day, and S is the total number of seeds sown.

MGT = ∑f *x/∑f

where f is the number of seeds germinating on day x.

Survival Rate/Percentage (SP) = {(Total germinated seedlings – Dead seedlings)/ Total germinated seedlings}x 100

Days to final germination (DFG) = No. of days between date of germination experiment (sowing) and the last day of seed germination.

Data on total seedling length, shoot height, collar diameter, root length and number of leaves were collected on 120 and 165 days after sowing (DAS). Total seedling length, shoot height and root length were measured with measuring tape, whiles collar diameter was measured with digital callipers. The dry matter of seedlings and the various components was determined after they were oven-dried to constant weight and then weighed with a laboratory electronic scale.

For each measured variable normal distribution was tested using the Shapiro-Wilks W-test for homogeneity of variances. Variables that conformed to normal distribution were analysed using two-way analysis of variance (ANOVA) using GenStat (12th edition). Where significant differences were observed, treatment means were separated using Tukey’s Honestly Significant Difference (HSD) test at the 5% probability level. Similarly, seedling height, collar diameter, root length and number of leaves for each treatment were also subjected to ANOVA and Tukey’s HSD after the appropriate normality tests.

3. RESULTS

3.1 Germination

3.1.1 Independent/main and interaction effects of pre-sowing treatment and ecological zones on germination parameters

(5)

these factors. However, pre-sowing treatment method and ecological zone significantly influenced Final Germination (FGP), Germination Rate (GR) and Survival Percentage (SP) [Table 1].

3.1.2 Effects of boiled water pre-sowing treatment on Final Germination Percentage (FGP) in three ecological zones in Ghana

The different pre-sowing treatment methods had varying effects on FGP in the different ecological zones. T4(60/24), which produced the highest FGP in the FSTZ produced the least in the MSFZ together with T5(120/24) and T3(30/24). Whereas T3(30/24) and T7(300/24) in GSZ produced significantly higher FGPs than the control, T3(30/24), T4(60/24) and T5(120/24) produced significantly higher FGPs than the control in FSTZ and T6(180/24) produced the highest FGP in MSFZ (Fig. 1).

3.1.3 Effects of boiled water pre-sowing treatment on Germination Rate (GR) in three ecological zones

Boiled water pre-sowing treatment had both interactive and main effects similar effects on Germination rate across all ecological zones, and the trends were similar to those of the FGP (Fig. 2).

3.1.4 Interactive effects of boiled water pre-sowing treatment and ecological zone on Survival Percentages

Survival percentages (SP) were generally high and similar in all three ecological zones. It was generally lower in MSFZ than the other two ecological zones. In FSTZ, the highest survival percentage was observed in T1(0/0) (control) and T4(60/24). In the MSFZ the highest survival percentage was observed in T2(0/24) and T6(180/24) treated seeds, whiles the least was

Table 1. Summary of analysis of variance indicating P-values of effects of pre-sowing treatments and ecological zone on various germination parameter of F. albida seeds

Parameters FGP GR GI MGT DFG SP

Pre-sowing treatment ˂.001 ˂ .001 0.72 0.75 0.36 0.05

Ecological zone ˂.001 ˂.001 0.89 0.95 0.10 ˂.001

Pre-sowing treatment x Ecological zone interaction

˂.001 ˂.001 0.62 0.89 0.59 0.007

FGP = Final Germination Percentage; GR = Germination Rate; GI = Germination Index; MGT = Mean Germination Time; DFG = Days to Final Germination; SP = Survival Percentage

Fig. 1. Effects of boiled water pre-sowing treatment on Final Germination Percentage (FGP) of F. albida in three ecological zones

GSZ = Guinea Savannah Zone, FSTZ = Forest-Savannah Transitional Zone and MSFZ = Moist Semi-deciduous Forest Zone. T1(0/0), T2(0/24), T3(30/24), T4(60/24), T5(120/24), T6(180/24), T7(300/24). Error bars are

standard errors

0 10 20 30 40 50 60 70 80 90

T1 T2 T3 T4 T5 T6 T7

Fi

n

al

G

er

m

in

at

io

n

P

er

ce

n

ta

ge

(

%

)

Pre-sowing treatments

(6)

observed in T4(60/24). In the GSZ, T3(30/24), T6 and T7 resulted in the highest survival percentage (Fig. 3).

3.2 Growth

3.2.1 Effects of boiled water pre-sowing treatment and ecological zones interaction on growth parameters of F. albida seedlings

Pre-sowing treatment significantly influenced seedling height, root length, total seedling length and collar diameter (Table 2). These growth parameters were significantly influenced in each ecological zone. However, the interactive effects of pre-sowing x ecological zones significantly

influenced only root length, total seedling length and number of leaves (Table 2).

3.2.2 Effects of boiled water pre-sowing treatment methods on root length in the three ecological GSZ, FSTZ and MSFZ

Apart from T4(60/24) and T6(180/24) treated seedlings, roots of seedlings in GSZ were significantly longer with all pre-sowing treatments than those in the FSTZ and MSFZ, both of which were rather similar. The T6(180/24) seedlings had the longest roots in GSZ whiles those of T1(0/0), T2(0/24), T3(30/24) and T4(60/24) were similar. The T3(30/24) seedlings produced the longest roots in both FSTZ and MSFZ and T4(60/24) produced the shortest roots in the two ecological zones(Fig. 4).

Fig. 2. Effects of boiled water pre-sowing treatment on Germination Rate (GR) of F. albida in three ecological zones

standard errors

Table 2. Summary of Analysis of Variance (ANOVA) indicating P-values of effects of pre-sowing treatments on various growth parameters of F. albida seeds in three ecological zones

in Ghana

Seedling height

Root length

Total seedling length

Collar diameter

No. of leaves

Pre-sowing treatment 0.003 0.004 <0.001 0.014 <0.001 Ecological zone <0.001 <0.001 0.013 <0.001 <0.001 Pre-sowing treatment x

Ecological zone interaction _0.297 _0.040 _0.040 _0.146 _<0.001

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

T1 T2 T3 T4 T5 T6 T7

G

er

m

in

at

io

n

R

at

e

Pre-sowing treatments

(7)

Fig. 3. Effects of boiled water pre-sowing treatment on Survival Percentage (SP) of F. albida in three ecological zones

standard errors

Fig. 4. Effect of pre-sowing treatments on seedling root length of F. albida seedlings in three ecological zones

standard errors

3.2.3 Effects of boiled water pre-sowing treatment methods on total seedling length in the three ecological zones

Pre-sowing treated seedlings T4(60/24) were significantly longer in the GSZ than those in FSTZ but similar to those in the MSFZ. The

T6(180/24) treated seedings in the GSZ were also significantly longer than those in both FSTZ and MSFZ whiles seedlings in both

FSZ and MSFZ were statistically similar in length. The T1(0/0), T2(30/24), T3(60/24), T5(120/24) and T7(300/24) affected total seedling length similarly in all ecological zones. 0

20 40 60 80 100 120

T1 T2 T3 T4 T5 T6 T7

Su

rv

iv

al

P

er

ce

n

ta

ge

(

%

)

Treatments

(LSD = 21.60) GSZ FSTZ MSFZ

0 5 10 15 20 25 30 35 40

T1 T2 T3 T4 T5 T6 T7

R

o

t

le

n

gt

h

(

cm

)

Pre-sowing treatment

(8)

The T4(60/24) treated seedlings were the

shortest in all ecological zones. In the GSZ the longest seedlings were produced by

T6(180/24) whereas T3(30/24) produced the longest seedlings in both FSTZ and MSFZ (Fig. 5).

3.2.4 Effects of boiled water pre-sowing treatment methods on number of leaves in the three ecological zones

In general, the mean number of leaves on each seedling ranked in the order of MSFZ > FSTZ > GSZ (Fig. 6). In GSZ, the highest number of leaves was in T3(30/24), followed by T5(120/24), T1(0/0), T6(180/24), T7(300/24) and T2(0/24) in decreasing order. In MSFZ, T2(0/24) and T3(30/24) seedlings had significantly more leaves than all the other treatments. In FSTZ, T6(180/24) was similar to T2(0/24), T3(30/24), and T7(300/24) but had significantly more leaves than T1(0/0), T4(60/24) and T5(120/24) [Fig. 6].

3.2.5 Effects of boiled water pre-sowing treatments in three ecological zones on seedling height and collar diameter in GSZ, FSTZ and MSFZ

Seedling heights observed due to effect of T3(30/24) was significantly higher than those of T4(60/24) and T5(120/24) but similar to all other pre-sowing treatments. Generally, seedling heights in FSTZ and MSFZ were similar in height

but significantly taller than those of GSZ (Table 3). Collar diameter of seedlings due to the effects of T3(30/24) was significantly higher than those of T1(0/0), but similar to all other treatments. Collar diameter of seedlings in GSZ and FSTZ were similar and significantly thicker in collar diameter than those observed in MSFZ (Table 3).

3.3 Dry Matter Partitioning

3.3.1 Effects of pre-sowing seed treatment x ecological zones interactions on seedling growth parameters

There were significant pre-sowing and ecological zone interaction effects on shoot growth rates, root growth rates and shoot to root growth rates at both 120 and 165 days after sowing (DAS) [Table 4].

3.3.2 Effects of boiled water pre-sowing treated seeds on dry matter accumulation in their seedlings in GSZ, FSTZ and MSFZ

Shoot dry weights measured 120 and 165 days after sowing (45 days intervals) showed a relatively slower dry matter accumulation in stems of seedlings in GSZ than in FSTZ and MSFZ. On both 120 and 165 DAS, shoot dry weight increased with increasing duration of immersion in boiled water (i.e. 0 to 60 seconds).

Fig. 5. Effect of pre-sowing treatments on total seedling length of F. albida seedlings in three ecological zones

standard errors

0 5 10 15 20 25 30 35 40 45 50

T1 T2 T3 T4 T5 T6 T7

To

ta

l s

ee

d

lin

g

le

n

gt

h

(

cm

)

LSD = 5.71

(9)

Fig. 6. Effect of pre-sowing treatments on number of leaves on F. albida seedlings in three ecological zones

standard errors

Table 3. Main effects of pre-sowing treatment and ecological zone on seedling height and collar diameter of F. albida

Pre-sowing treatment Seedling/shoot height (cm) Collar diameter (mm)

T1 (0/0) 14.41ab 1.06b

T2 (0/24) 15.30ab 1.17ab

T3 (30/24) 17.11a 1.42a

T4 (60/24) 12.08b 1.27ab

T5 (120/24) 12.94b 1.34ab

T6 (180/24) 14.99ab 1.27ab

T7 (300/24) 14.59ab 1.17ab

P-value 0.003 0.014

LSD 2.39 0.20

Ecological zone

GSZ 8.32b 1.30a

FSTZ 17.49a 1.35a

MSFZ 17.65a 1.08b

P-value <0.001 <0.001

LSD 1.56 0.13

Pre-sowing treatments: The numerator in parenthesis represents the number of seconds seeds were immersed in boiled water, denominator represents number of hours seeds were soaked in tap water.

Ecological zones: Guinea Savannah zone (GSZ), Forest-Savannah Transitional zone (FSTZ), Moist Semi-deciduous Forest zone (MSFZ)

Further increases in duration of immersion in boiled water resulted in reduced shoot dry weight (120 to 300 seconds). As at 120 DAS, shoot dry weights of all boiled water pre-sowing treated seeds in the MSFZ were highest among the ecological zones except T5(120/24), with the least shoot dry weights recorded in GSZ except T1(0/0). The T4(60/24) treated seeds produced

the highest shoot dry weight in all ecological zones (Fig 7). Similar trends in response to boiled water treatments and ecological zones were observed at 165 DAS, with varying degrees of increase in shoot dry weight over DAS values. Generally, shoot dry weight was in the order MSFZ > FSTZ > GSZ, except for T1(0/0) where seedlings in all ecological zones were 0

10 20 30 40 50 60

T1 T2 T3 T4 T5 T6 T7

N

u

m

b

er

o

f

le

av

es

(10)

statistically similar in shoot dry weight and in T5(120/24) where seedlings in FSTZ were significantly higher than those of MSFZ and GSZ (Fig. 8).

3.3.3 Effects of boiled water pre-sowing treated seeds on root dry weight in GSZ, FSTZ and MSFZ

Like shoot dry weight, root dry weight of seedlings increased with increasing duration of immersion in boiled water between 0 and 60 seconds (T1(0/0) to T4(60/24)) and then decreased with further longer duration of

immersion in boiled water (T5(120/24) to T7(300/24)) at 120 DAS. Among T1(0/0), T2(30/24) and T6(180/24) treated seedlings the highest root dry weights were produced by seeds in GSZ whereas MSFZ produced roots with the highest dry weights in T3(30/24) and T4(60/24), with FSTZ producing roots with the highest dry weight in T7(300/24) [Fig. 9]. Similar trends were observed 165 DAS with MSFZ producing seedlings with the highest root dry weights in T2(0/24), T3(30/24), T4(60/24) and T7(300/24), and GSZ producing seedlings with the highest root dry weights in T5(120/24) and T6(180/24) [Fig. 10].

Table 4. Summary of Analysis of Variance (ANOVA) indicating P-values of effects of F. albida seed pre-sowing treatments on shoot dry weight, root dry weight and shoot to root ratio in

three ecological zones in Ghana

Parameters Shoot dry weight Root dry weight Shoot/root ratio 120 DAS 165 DAS 120 DAS 165 DAS 120 DAS 165 DAS Pre-sowing treatment ˂0.001 ˂0.001 ˂0.001 ˂0.001 ˂0.001 ˂0.001 Ecological zone ˂0.001 ˂0.001 ˂0.001 ˂0.001 ˂0.001 ˂0.001 Pre-sowing treatment x

Ecozone

˂0.001 ˂0.001 ˂0.001 ˂0.001 ˂0.001 ˂0.001

Fig. 7. Shoot dry weight of seedlings of seeds that were subjected to different boiled water treatments after 120 DAS in three ecological zones

standard errors

0 50 100 150 200 250 300

T1 T2 T3 T4 T5 T6 T7

D

ry

w

t

(m

g)

Pre-sowing treatment

LSD = 10.41

GSZ

FSTZ

(11)

Fig. 8. Shoot dry weight of seedlings from seeds that were subjected to different boiled water treatments165 DAS in three ecological zones

standard errors

Fig. 9. Root dry weight of seedlings from seeds that were subjected to different boiled water treatments after 120 DAS in three ecological zones

standard errors

3.3.4 Effects of boiled water pre-sowing treated F. albida seeds on shoot to root ratio in GSZ, FSTZ and MSFZ

At 120 and 165 DAS, shoot to root ratios in the three ecological zone ranked in the order of MSFZ > FSTZ > GSZ (Fig. 11). As at 165 DAS the trend was similar. However, the difference

between values for MSFZ and FSTZ decreased whiles the difference between values in these two ecological zones and GSZ were more pronounced, (i.e. the shoot to root ratio of seedlings in GSZ reduced with time). The least shoot to root ratios were produced by T3(30/24) [Fig. 12].

0 50 100 150 200 250 300

T1 T2 T3 T4 T5 T6 T7

Sh

o

t

d

ry

w

ei

gh

t

(m

g)

LSD = 25.23

GSZ

FSTZ

MSFZ

0 50 100 150 200 250 300 350 400 450 500

T1 T2 T3 T4 T5 T6 T7

R

o

t

d

ry

w

ei

gh

t

(m

g)

LSD = 17.69

GSZ

FSTZ

(12)

Fig. 10. Root dry weight of seedlings from seeds that were subjected to different boiled water treatments165 DAS in three ecological zones

standard errors

Fig. 11. Shoot/root ratio of seedlings of different boiled water pre-treated seeds of F. albida 120 DAS in three ecological zones

standard errors

4. DISCUSSION

Germination is an important developmental phase in the life cycle of a plant since it marks the onset of the plant’s life. Identifying processes that could enhance this process is therefore of utmost importance.

There was a general improvement in final germination percentages using the boiled water pre-sowing treatments for different periods over the control (where the seeds were sown directly without immersing in boiled (1000C) water and soaking in tap water overnight) in the different ecological zones especially in the FSTZ, where 0

50 100 150 200 250 300 350 400 450 500

T1 T2 T3 T4 T5 T6 T7

R

o

t

d

ry

w

ei

gh

t

(m

g)

LSD = 48.79

GSZ

FSTZ

MSFZ

0 0.2 0.4 0.6 0.8 1 1.2

T1 T2 T3 T4 T5 T6 T7

Sh

o

t-ro

o

t

ra

ti

o

LSD = 0.04

GSZ

FSTZ

(13)

immersion in boiled water for between 30 and 180 seconds yielded significantly higher FGPs. This finding corroborates that of [25] who found out that apart from sulphuric acid, hot water treatment was also effective in breaking dormancy in some Acacia species. [11] also identified hot water pre-treatment to be the most effective method for improving upon the germination percentage in four tree species belonging to the Leguminosae (Fabaceae) family, including Bauhinia variegate, Cassia fistula, Delonix regia and Peltophorum pterocarpum. This improvement in seed germination could be due to increased permeability of the seed coat induced by the hot water. The findings of this study however, conflict with the findings of [15], who, in comparing hot water, nicking and combination of hot water and nicking, found out that hot water produced the least cumulative percentage. [26], in a germination experiment on F. albida, observed that sulphuric acid, manual scarification and hot wire scarification achieved better germination rates (over 90% in 8 days) than hot water pre-treatment which showed less than 20% after 16 days. The germination percentage of hot water treated F. albida seeds is noted to rather increase with time and show a more extended germination period (days to final germination ranging between 42 and 74 days) as was demonstrated in this study. Such staggered germination pattern has the advantage of spreading the recruitment of seedlings into saplings and adult trees and insurance against species extinction [27]. Though [17] also found nicking to be most effective in breaking dormancy in Acacia polyachanta, immersing seeds in boiling water (100°C) for 5 minutes was next to nicking in all germination and growth parameters considered. They however, did not report on germination percentages beyond the 16-day period. It is necessary to assess germination and early growth parameters over a considerably longer period because staggered germination is an adaptation which could enable plants in the drier zones to escape drought conditions and also maintain the seed bank for continuous regeneration [28]. In an experiment to assess the effects of a wide variety of pre-sowing treatment methods on the germination of some agroforestry tree species, [19] observed that the immersion of seeds in boiling water gave reliable and improved germination in most of the species tested. It was however evident that, the appropriate duration of immersion in the hot water was crucial, as seeds of Sesbania sesban

completely failed to germinate after being immersed in boiling water for 8 minutes. As observed in this study, immersing seeds in boiling water for 30 to 120 seconds before soaking in tap water for 24 hours (T3(30/24) - T5(120/24)) produced the best germination percentage in the Forest-savannah transitional zone (FSTZ), whiles immersing seeds in boiled water for 180 seconds before soaking in tap water for 24 hours (T6(180/24)) was the most effective pre-sowing treatment method in the Moist Semi-deciduous Forest zone (MSFZ). In the Guinea savannah zone (GSZ) however, immersing seeds in boiled water for 30 seconds or 300 seconds and soaking in tap water for 24 hours was more effective than direct seed sowing. These results corroborate the observation of [13] that, hot water pre-sowing treatments have variable effects on the same F. albida seed lots in different ecological zones, and therefore suggest that specific boiled water pre-sowing treatments should only be recommended for each specific ecological zone.

The survival and growth of tree seedlings after seed germination is of great importance to the successful establishment of agroforestry programmes. Though [29] asserted that seedlings from boiling water pre-treatments resulted in high mortality rates, survival rates in this study were generally high as at about six months after sowing. In a similar study, [15], determined the effects of nicking, hot water treatment and a combination of nicking and hot water treatments on the germination and survival of F. albida, recorded survival rates of 93.3% for nicking, 80.7% for hot water treatment, 77.1% for the combination of nicking and hot water and 63.4% for the control.

(14)

Fig. 12. Shoot/root ratio of seedlings of different boiled water pre-treated seeds of F. albida 165 DAS in three ecological zones

standard errors

The balance between the relative growth rates of shoots and roots of plants is key to the understanding of the mechanisms by which plants adapt to their habitats, and explain the variations in dry matter partitioning [32]. Shoot to root ratio is the quotient of the dry weight of the shoots produced during a given growth period divided by the dry weight of the roots. Results from this study indicate that seedlings in the Guinea savannah zone concentrated more of their dry matter in the roots than in the shoots, whiles the reverse occurred in the Forest-savannah transitional and Moist Semi-deciduous Forest zones. The relatively higher root growth in the drier semi-arid zone than the more humid zones agrees with [33], who observed that the deep rooting habit of F. albida was dependent on ecological factors. These trends were observed in the root length, shoot height and the shoot to root ratios. The tree (F. albida) is known to respond to dry soil conditions by developing roots at a fast rate towards the water table, a trait that makes it to be classified among phreatophytes [34]. [29], corroborated this finding when he observed that the primary roots rapidly elongated in search of a suitable moisture zone, and that 6 months old seedlings were only 8 cm tall and yet had tap roots up to 70 cm long. In a study to compare the growth characteristics of 16 provenances collected from all naturally occurring F. albida across the African continent,

[35] observed that the semi-arid West African provenances were characterized by slow shoot growth and collar diameter. Though, the relative dry matter accumulation in the roots and shoots of a plant is mainly genetically controlled, environmental factors could play significant roles in the eventual architecture of the plant. Generally, shoot to root ratios for all treatments at 120 DAS ranked in the order; MSDFZ > FSTZ > GSZ, with only slight variations in this trend at 165 DAS. The higher shoot to root ratios observed in the moist semi-deciduous forest zone compared to those in the other two drier zones suggests a developmental pattern that allows seedlings to grow through their most vulnerable stages, and confers an adaptive advantage on tree seedlings in drier/arid zones. This strategy seems apparent where seedlings in drier areas invest a higher proportion of photosynthetic material for relatively rapid root growth, to a decline in shoot to root ratio. According to [32], such adaptive mechanisms are important for post-transplanting survival. Favourable carbon concentrations will lead to an increase in biomass partitioning towards the roots whiles an increase in nitrogen concentration should also favour biomass partitioning towards the shoot [36]. Moreover, root systems in dry soil conditions tend to increase in volume to obtain more water whiles leafing is reduced to minimize transpiration [37]. 0

0.2 0.4 0.6 0.8 1 1.2

T1 T2 T3 T4 T5 T6 T7

Sh

o

t-ro

o

t

ra

ti

o

LSD = 0.06

GSZ

FSTZ

(15)

This could be responsible for the comparatively lower leaf numbers in the GSZ as compared to the more humid ecological zones, and the lower shoot to root ratio in the GSZ than the more humid ecological zones. The study also corroborated the observation of [17] that pre-sowing treatment regime could influence the post germination development of plants. It was demonstrated that some boiled water pre-sowing treatments (immersing in boiled water for between 60 and 180 seconds) could result in increased plant (shoot + root) growth in the Guinea Savannah zone. Immersing seeds in boiled water for 60 seconds also favoured the growth and retention of leaves of seedlings in the MSFZ.

5. CONCLUSION

Boiled water pre-sowing treatment was found to be effective in enhancing the seed germination, survival and growth of F. albida seedlings respectively, at varying degrees in different ecological zones. In the GSZ, immersing seeds in water at 1000C for 30 seconds or 300 seconds before soaking in tap water for 24 hours (T3(30/24) and T7(300/24)) were effective in improving upon final germination percentage. In the FSTZ, seeds should be immersed in boiling water for between 30 and 120 seconds for improved germination. In the MSFZ, immersing seeds in boiled water at 100°C was effective in improving final germination percentage in F. albida seeds. Hot water pre-sowing treatments have variable effects on different seed lots in different ecological zones. These observations presuppose that seeds of the same species (F. albida) would respond in varying degrees to different boiling water pre-sowing treatments in different ecological zones in terms of their germination, survival and early growth. Future studies should look at the survival rates for at least three years to be able to establish a more conclusive survival rates of seedlings subjected to different pre-sowing treatments. The faster above-ground seedling growth in the more humid ecological zones could lead to better leaf litter production to improve upon soil fertility, whiles the faster root growth in the drier zones could also enable the plant to reach underground water reserves and leached nutrients in good time to encourage nutrient cycling and also build the plant’s resilience to moisture deficiencies during droughts. Moreover, the growth and retention of more leaves in the more humid ecological zones could result in better plant assimilation and improved physiological developments that will

eventually culminate into better dry matter accumulation and hence growth. This retention of leaves in the more humid ecological zones, could also affect the reverse phenology trait exhibited by F. albida in the drier semi-arid zone.

There is the need for a longer-term study to be able to compare the growth, dry matter partitioning into the various components, as well as the phenology of the tree in the different ecological zones. A long-term study will also ascertain or disprove the soil improvement capacity of F. albida in the more humid ecological zones and hence justify, or otherwise, the need for its introduction and domestication in these ecological zones. There is the need to research into the leaf phenology of F. albida in these new ecological zones to provide the basis for its introduction into agroforestry systems either among tree crops like cocoa and coffee, or annual crops such as maize, cassava, yam etc.

COMPETING INTERESTS

Authors have declared that no competing interests exist.

REFERENCES

1. Fagg C. Faidherbia albida: Inverted phenology for dry zone agroforestry. NFT Highlights. 1995;95-06.

2. Dangasuk OP, Seurei, Gudu S. Genetic variation in seed and seedling traits in 12 African provenances of Faidherbia albida (Del.) A. Chev. at Lodwar, Kenya. Agroforestry systems, 1997;37(2):133-141. 3. Depommier D. The tree behind the forest: Ecological and economic importance of traditional agroforestry systems and multiple uses of trees in India. Tropical Ecology. 2003;44(1):63-71.

4. Hassan L, Umar K, Yuguda H. Nutritional evaluation of Faidherbia albida seeds and pulp as source of feeds for livestock. African Journal of Food, Agriculture, Nutrition and Development. 2007;7(5). 5. Morris ML. Fertilizer use in African

agriculture: Lessons learned and good practice guidelines: World bank Publications; 2007.

6. Adzitey F. Animal and meat production in Ghana-An overview. The Journal of World’s Poultry Research. 2013;3(1):1-4. 7. Bewley JD. Seed germination and

(16)

8. Schmidt L, Jøker D. Glossary of seed biology and technology. Danida Forest Seed Centre; 2001.

9. Baskin JM, Baskin CC. A classification system for seed dormancy. Seed science research, 2004;14(1):1-16.

10. Zoghi Z, Azadfar D, Kooch Y. The effect of different treatments on seeds dormancy breaking and germination of Caspian Locust (Gleditschia caspica) Tree. Annals of Biological Research, 2011;2(5):400- 406.

11. Sinhababu A, Banerjee A. Optimization of seed germination of some multipurpose tree legumes by seed treatments. The Journal of Plant Physiology. 2013;114(7): 170-175.

12. Nasr SMH, Savadkoohi SK and Ahmadi E. Effect of different seed treatments on dormancy breaking and germination in three species in arid and semi-arid lands. Forest Science and Practice. 2013;15(2): 130-136.

13. Jøker D. Faidherbia albida (Del.) A. Chev. Seed Leaflet-Danida Forest Seed Centre. 2000:(28).

14. Van der Burg J, De Freitas J, Debrot D. Seed germination methods for native Caribbean trees and shrubs. Plant Research International, part of Wageningen UR, Business Unit Agrosystems Research. 2014;551:8-11. 15. Chuyong G, Acidri T. Combining

Pre-sowing Treatments in Faidherbia albida (Delile) A. Chev. does not Imply Better Germination Success. Methodology; 2014. 16. Mwase WF, Mvula T. Effect of seed size

and pre-treatment methods of Bauhinia thonningii Schum. On germination and seedling growth. African Journal of Biotechnology. 2011;10(26):5143-5148. 17. Missanjo E, Chioza A, Kulapani C. Effects

of different pretreatments to the seed on seedling emergence and growth of Acacia polyacantha. International Journal of Forestry Research. 2014.

18. Vandenbeldt R. Problems with range-wide provenance trials of Faidherbia albida on sandy soils in Niger. Faidherbia albidn in the West African Semi Arid Tropics: Proceedings of a Work-shop, ICRISAT-ICRAF. 1992:83-86.

19. Shapo HE. The effects of presowing treatments on seed germination of some agroforestry tree species; 2015.

20. Michel A. Trees, Shrubs and Lianas of West African Dry Zones. CIRAD, MARGRAF Publishers GMBH; 2004. 21. Siaw DE. State of forest genetic resources

in Ghana. Forest Genetic Resources Working Papers (FAO); 2001.

22. Dickson BK, Benneh G. A new geography of Ghana : Longman Group. 1977;173. 23. Ayivor JS, Ntiamoa-Baidu Y. Assessing

the socio-economic stressors of Ghana’s only Strict Nature Reserve–Kogyae. Parks. 2015;21(2):85-100.

24. Arthur MB. The effect of Compost and NPK fertilizers on growth performance of Tectona grandis Linn. F. seedlings in the nursery. Ghana Journal of Forestry. 1999; 8:31-35.

25. Hossain M, et al. Effects of seed treatments on germination and seedling growth attributes of Horitaki (Terminalia chebula Retz.) in the nursery. Research Journal of Agriculture and Biological Sciences. 2005;1(2):135-141.

26. Diallo I, et al. Effects of different pretreatments on the germination of Faidherbia albida (Del.) A. Chev. seeds. International Tree Crops Journal. 1996; 9(1):31-36.

27. Soriano D. et al. Effects of burial and storage on germination and seed reserves of 18 tree species in a tropical deciduous forest in Mexico; 2013.

28. Khurana E, Singh J. Ecology of seed and seedling growth for conservation and restoration of tropical dry forest: A review. Environmental conservation. 2001;28(1): 39-52.

29. Wickens GE. A Study of Acacia albida Del. (Mimosodeae). Kew Bulletin, 1969;23(2): 181-202.

30. Marziliano PA, et al. Estimating belowground biomass and root/shoot ratio of Phillyrea latifolia L. in the Mediterranean forest landscapes. Annals of forest science. 2015;72(5):585- 593.

31. Amanullah, Stewart B. Shoot: Root differs in warm season c-4-cereals when grown alone in pure and mixed stands under low and high water levels. Pakistan Journal of Botany. 2013;45:83-90.

(17)

33. Vandenbelt R. Rooting systems of western and southern African Faidherbia albida (Del.) A. Chev.(syn. Acacia albida Del.)—A comparative analysis with biogeographic implications. Agroforestry Systems. 1991; 14(3):233-244.

34. Roupsard O, et al. Reverse phenology and dry‐season water uptake by Faidherbia albida (Del.) A. Chev. in an agroforestry parkland of Sudanese west Africa. Functional ecology. 1999;13(4):460- 472.

35. Dangasuk O, Gudu S, Okalebo J. Early growth performance of sixteen populations of Faidherbia albida in semi arid Baringo

district of Kenya. in 10th international soil conservation organization conference on sustaining the global farm, Purdue University, West Lafayette, Indiana, USA; 1999.

36. Marschner H, Kirkby E, Cakmak I. Effect of mineral nutritional status on shoot-root partitioning of photoassimilates and cycling of mineral nutrients. Journal of Experimental Botany. 1996;47(suppl_1): 1255-1263.

37. Bolinder M, et al. Root biomass and shoot to root ratios of perennial forage crops in eastern Canada. Canadian Journal of Plant Science. 2002;82(4):731-737. _________________________________________________________________________________ © 2019 Akpalu et al.; This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Peer-review history: