Physiological studies on breaking seed dormancy of some trees species and their effects on seedling growth




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g) Root fresh and dry weights ( gm/plant ) :

Fresh and dry weights of roots per plant of Balanites aegyptiaca and Kigelia pinnata as affected by various treatments during 2004 and 2005 seasons are illustrated in Table ( 4 ). It is clear that different seed treatments significantly affected the fresh and dry weights of the roots. The highest value of weight of B. aegyptiaca roots was obtained by treating the seeds with sulphuric acid for 5 min. then soaking in tap water for 24h. On the other hand , soaking seeds of Kigelia pinnata in sulphuric acid for 10 min with immersion in tap water for 24h resulted in the highest fresh and dry weights in comparison with that of the other treatments.



The main aim of presowing treatments of dry dormant seed is to encourage the germination process and possesses that on the quantity and the quality of the obtained seedlings. Prasad and Kandya (1992) revealed that a hard cutinized seed coat completely prevents the imbibition of water and in some cases exchange of gases.

Table 4 : Effect of pregermination treatments on Root Fresh Weight
( R.F.W) and Root Dry Weight ( R.F.W ) of Balanites aegyptiaca and Kigelia pinnata tree seedlings .


Trees

First season ( 2004 )

Second season ( 2005 )

Balanites

Kigelia

Balanites

Kigelia

Treatments

R.F.W

R.D.W

R.F.W

R.D.W

R.F.W

R.D.W

R.F.W

R.D.W

Control

1.54

0.73

4.00

1.16

2.00

1.05

4.34

1.12

Sulphuric (5m.0h)

2.77

1.55

5.82

1.66

2.44

1.33

6.18

1.87

Sulphuric (5m.24h)

2.93

1.49

5.30

1.82

3.04

1.61

6.36

2.18

Sulphuric (10m.0h)

2.42

1.36

6.67

1.98

2.33

1.28

6.40

2.57

Sulphuric (10m.24h)

2.33

1.22

7.39

2.19

3.02

1.53

7.62

2.82

Ethyl (15m. 0h)

2.61

1.35

7.16

1.93

3.06

1.69

6.83

2.46

Ethyl (15m.24h)

2.32

1.22

4.25

1.46

3.02

1.49

5.10

1.75

Ethyl (30m.0h)

1.93

1.14

5.38

1.85

3.06

1.58

6.46

2.22

Ethyl (30m.24h)

2.20

1.50

5.51

1.89

3.05

1.16

6.61

2.27

L. S.D 5%

0.32

0.27

0.56

0.36

0.27

0.29

1.01

0.38

The present results of seedling growth parameters i.e. stem , length ,diameter , fresh and dry weight of the aerial parts , as well as , root fresh and dry weight of seedlings of tested trees indicated that soaking in sulphuric acid for , 10 or 5 min followed by soaking in tap water were the most effective treatments to produce the best seedlings. These results conceded with those obtained by many authors, (Everitt, 1983, Diangana , 1985, Nutumbula et al. ,1990 and Demel, 1994).


II- Cassia javanica and Strychnos nux-vomica :

a) Germination percentage ( G% ):

Table 5 represents germination percentage of the seeds of C. javanica and S. nux-vomica seed trees as affected by mechanical scarification treatments during the 2004 and 2005 seasons. Data revealed that the most effective treatment for C. javanica was scarification of seeds by sand. Meanwhile, the most effective treatment for S. nux- vomica was scarification of seeds by sand with soaking the seeds in tap water for 0 h. and 24 h.



The present results indicated that sand scarification of seed coat induced the maximum germination percentage. These results are in agreement with those obtained by several investigators (Gogue and Emino 1979, Nutumbula et al, 1990 and Fagbayide and Fawusi, 1994).

Table 5 : Effect of pregermination treatments on seed Germination percentag (G%) and Daily seed Germination Speed
(D.G.S) of Strychnos nux-vomica and Cassia javanica tree seedlings .


Trees

First season ( 2004 )

Second season ( 2005 )

Strychnos

Cassia

Strychnos

Cassia

Treatments

G %

DG.S

G %

D.G.S

G %

D.G.S

G %

D.G.S

Control

00.0

0.00

00.0

0.00

00.0

0.00

00.0

0.00

Sand 0 h.

30.0

0.04

23.3

0.05

23.3

0.03

30.0

0.05

Sand 24 h.

30.0

0.05

16.7

0.06

30.0

0.05

16.7

0.06

File 0 h.

13.3

0.06

20.0

0.07

13.3

0.06

16.7

0.06

File 24 h.

16.7

0.07

13.3

0.07

16.7

0.07

13.3

0.07

L.S.D 5%

6.43

0.01

9.1

0.01

8.1

0.03

6.9

0.01


b) Daily Germination speed ( D. G .S.) :

Daily germination speed of C. javanica and S. nux- vomica as affected by pregermination treatments during the 2004 and 2005 seasons are presented in Table 5. It is evident that mechanical scarification of the tested seeds by the steel file then soaking in tap water for24h gave the highest value of daily germination speed in 2004 and 2005 seasons . The second rank of daily germination speed was obtained with using steel file and direct sowing of seeds of C. javanica and S. nux-vomica .



c) Stem length ( cm ):

Data on stem length of C. javanica and S. nux-vomica as affected by pregermination treatments at age of three months during the 2004 and 2005 seasons are shown in Table 6. The pregermination treatments significantly improved stem length of transplants compared to that of the control in both seasons. The tallest transplants for C. javanica and S. nux-vomica resulted from the application of scarification by steel file with direct sowing.



Table 6 : Effect of pregermination treatments on Stem Length ( S.L ) Stem Diameter ( S.D ) and Root Length ( R.L) of Strychnos nux-vomica and Cassia javanica tree seedlings .

Trees

First season ( 2004 )

Second season ( 2005 )

Strychnos

Cassia

Strychnos

Cassia

Treatments

S.L

.D

R.L

S.L

S.D

R.L

S.L

S.D

R.L

S.L

S.D

R.L

Control

00.0

0.00

00.0

00.0

0.00

00.0

00.0

0.00

00.0

00.0

0.00

00.0

Sand 0 h.

15.4

0.20

20.4

24.3

0.21

17.4

20.0

0.22

24.4

29.2

0.24

19.2

Sand 24 h.

14.9

0.21

22.3

28.1

0.24

20.0

19.3

0.24

26.8

33.8

0.27

22.0

File 0 h.

15.6

0.22

23.1

28.8

0.25

19.3

20.3

0.24

27.7

34.6

0.30

21.2

File 24 h.

15.1

0.20

21.9

28.0

0.22

19.3

19.6

0.22

26.3

33.6

0.25

20.9

L.S.D 5%

2.5

0.05

3.7

3.6

0.05

3.3

3.6

0.06

4.4

3.8

0.05

3.9


d) Stem diameter ( cm ) :

Data of the effect of different mechanical scarification treatments of C. javanica and S. nux-vomica seeds on stem diameter during the 2004 and 2005 seasons are shown in Table 6. It is obvious that the highest values of stem diameter for the two species were recorded by using scarification with steel file then the direct sowing compared to other treatments.



e) Root length ( cm ) :

Concerning the effect of the mechanical scarification on root length of the tested trees as shown in Table ( 6 ); the tallest roots of C. javanica were obtained by sand scarification with soaking seeds in tap water for 24 h. in the two seasons . Meanwhile , the most effective treatment for S. nux- vomica was scarification of seeds by steel file then the direct sowing in the two seasons .

These results are in accordance with those obtained; Everitt
(1983), Diangana (1985) , Nutumbula et al (1990) and Demel ( 1994 ).

f) Stem fresh and dry weights (gm) :

The average of fresh and dry weights of aerial parts of C. javanica and S. nux-vomica as affected by pregermination treatments during the 2004 & 2005 seasons are presented in Table 7. It is evident that the highest values of stem weight for C. javanica were obtained with using scarification by sand or steel file followed by the direct sowing of seeds in the two seasons. Meanwhile , using scarification by sand with soaking in tap water for 24h. or steel file (0 h.) in the case of S. nux-vomica resulted in the highest values of stem weight compared to other treatments in the two seasons.



Table 7 : Effect of pregermination treatments on Stem Fresh Weight
( S.F.W ) and Stem Dry Weight ( S.D.W ) of Strychnos nux-vomica and Cassia javanica tree seedlings .


Trees

First season ( 2004 )

Second season ( 2005 )

Strychnos

Cassia

Strychnos

Cassia

Treatments

S.F.W

S.D.W

S.F.W

S.D.W

S.F.W

S.D.W

S.F.W

S.D.W

Control

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

Sand 0 h.

1.35

0.56

2.74

1.37

1.66

0.69

3.40

1.48

Sand 24 h.

1.46

0.61

2.68

1.34

1.80

0.75

3.32

1.45

File 0 h.

1.46

0.61

2.74

1.37

1.79

0.75

3.39

1.47

File 24 h.

1.29

0.54

2.46

1.23

1.59

0.66

3.05

1.32

L.S.D 5%

0.10

0.16

0.22

0.22

0.23

0.20

0.43

0.23


g) Root fresh and dry weights ( gm ):

Data of the effect of some treatments on fresh and dry weights of roots of seedlings of the two tested trees during the 2004 and 2005 seasons are presented in Table 8. It is apparent that sand scarification with soaking in tap water for 24h. produced the heaviest roots of C. javanica compared to other treatments. Whereas, the heaviest roots of S. nux-vomica were due to using steel file on seed with soaking in tap water for 24h. The present results on seedling growth parameters on aerial parts and roots of tested trees clearly indicate that scarification by sand with soaking in tap water for 24h followed by file scarification with soaking in tap water for 24 h. produced the best seedling. These results conceded with those obtained by Everitt (1983) and Demel ( 1994 ).

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