Chapter 3: The effects of oil on morphological characteristics in Avicennia marina,
3.3 Results
3.3.2 Second rhizotron study
3.3.2.1 Shoot growth and morphology
76
Fig. 3.15 Effects of oiling on root growth in R. mucronata, after two months. Note the necrosis on the propagule (arrow).
77
Shoot length was highest in the control and significantly lower in the sediment and propagule oiled treatments by 80% and 82%, respectively (Fig. 3.16). There was no significant difference in shoot length between the oiled treatments (Fig. 3.16).
In the oiled treatments, the length of the first - fifth internode was significantly lower by 86% compared to the control (Fig. 3.18). There was no significant difference in the length of each internode between the oiled treatments (Fig. 3.18).
Number of leaves (Fig. 3.20), leaf area (Fig. 3.22) and chlorophyll content (Fig. 3.24) were highest in the control and significantly lower in the sediment oiled treatment by 80%, 81% and 79%, respectively. In the propagule oiled treatment, number of leaves, leaf area and chlorophyll content were significantly lower by 80%, 82% and 80%, respectively, compared to the control.
In both the sediment and propagule oiled treatments, there was 67% plant mortality after four weeks. Sixty seven percent of propagules in the oiled treatments produced roots, but shoots were absent (Figs. 3.37 and 3.38).
B. gymnorrhiza
Shoot length was highest in the control and significantly lower in the oiled treatment by 88% (Fig. 3.17A).
In the oiled treatment, the length of the first - fourth internode was significantly lower by 84% compared to the control and there were only four internodes in seedlings (Fig.
3.19A).
Number of leaves (Fig. 3.21A), leaf area (Fig. 3.23A) and chlorophyll content (Fig.
3.25A) were highest in the control and significantly lower in the oiled treatment by 93%, 94% and 81%, respectively.
After four weeks, there was 67% plant mortality in the oiled treatment.
78 R. mucronata
Shoot length was highest in the control and significantly lower in the oiled treatment by 43% (Fig. 3.17B).
In the oiled treatment, the length of the first – third internode was significantly lower by 65% compared to the control while the fourth was absent (Fig. 3.19B).
There was no significant difference in number of leaves between treatments (Fig.
3.21B). In the oiled treatment, leaf area (Fig. 3.23B) and chlorophyll content (Fig.
3.25B) were significantly lower than the control by 44% and 32%, respectively.
Fig. 3.16 Effects of oiling on shoot length in A. marina. Measurements were taken after 409 days, C = control, SO = sediment oiled, O = propagule oiled. Means ± standard error are given, n = 3. Bars with different letters are significantly different at P ≤ 0.05 using Tukey-Kramer multiple comparisons test.
0 5 10 15 20 25
C SO O
Shoot length (cm)
b b
a
A. marina
79
Fig. 3.17 Effects of oiling on shoot length in B. gymnorrhiza (A) and R. mucronata (B).
Measurements were taken after 409 days, C = control, O = sediment oiled. Means ± standard error are given, n = 3 (B. gymnorrhiza) and n = 2 (R. mucronata). Bars with different letters are significantly different at P ≤ 0.05 using Tukey-Kramer multiple comparisons test.
0 5 10 15 20 25 30 35
C O
Shoot length (cm)
A a
b
B. gymnorrhiza
0 5 10 15 20 25
C O
Shoot length (cm)
a B
b
R. mucronata
80
Fig. 3.18 Effects of oiling on length of each internode in A. marina. Measurements were taken after 409 days, C = control, SO = sediment oiled, O = propagule oiled.
Means ± standard error are given, n = 3. Bars with different letters are significantly different at P ≤ 0.05 using two-way ANOVA and Tukey’s multiple comparisons test.
0 2 4 6 8 10
1 2 3 4 5 6
Length of each internode (cm)
C SO O b
c b
c
c c
b b
c a
c c c c c c c c
Internode
A. marina
81
Fig. 3.19 Effects of oiling on length of each internode in B. gymnorrhiza (A) and R.
mucronata (B). Measurements were taken after 409 days, C = control, O = sediment oiled. Means ± standard error are given, n = 3 (B. gymnorrhiza) and n = 2 (R.
mucronata). Bars with different letters are significantly different at P ≤ 0.05 using two- way ANOVA and Tukey’s multiple comparisons test.
0 2 4 6 8 10
1 2 3 4 5 6 7
Length of each internode (cm) A
a
a
c b
d a
c c c
d d
Internode B. gymnorrhiza
□ C
■ O
0 2 4 6 8 10
1 2 3 4
Length of each internode (cm) B
b
c a
b
d
c c
b
Internode R. mucronata
□ C
■ O
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Fig. 3.20 Effects of oiling on number of leaves in A. marina. Measurements were taken after 409 days, C = control, SO = sediment oiled, O = propagule oiled. Means ± standard error are given, n = 3. Bars with different letters are significantly different at P
≤ 0.05 using Tukey-Kramer multiple comparisons test.
Fig. 3.21 Effects of oiling on number of leaves in B. gymnorrhiza (A) and R. mucronata (B). Measurements were taken after 409 days, C = control, O = sediment oiled. Means
± standard error are given, n = 3 (B. gymnorrhiza) and n = 2 (R. mucronata). Bars with different letters are significantly different at P ≤ 0.05 using Tukey-Kramer multiple comparisons test.
0 4 8 12
C SO O
Number of leaves
A. marina
b b
a
0 5 10 15 20
C O
Number of leaves A
B. gymnorrhiza b a
0 2 4 6 8 10
C O
Number of leaves B
R. mucronata a
a
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Fig. 3.22 Effects of oiling on leaf area in A. marina. Measurements were taken after 409 days, C = control, SO = sediment oiled, O = propagule oiled. Means ± standard error are given, n = 3. Bars with different letters are significantly different at P ≤ 0.05 using Tukey-Kramer multiple comparisons test.
Fig. 3.23 Effects of oiling on leaf area in B. gymnorrhiza (A) and R. mucronata (B).
Measurements were taken after 409 days, C = control, O = sediment oiled. Means ± standard error are given, n = 3 (B. gymnorrhiza) and n = 2 (R. mucronata). Bars with different letters are significantly different at P ≤ 0.05 using Tukey-Kramer multiple comparisons test.
0 20 40 60 80
C SO O
Leaf area (cm²)
A. marina
b b
a
0 50 100 150 200 250
C O
Leaf area (cm²)
A
B. gymnorrhiza a
b
0 40 80 120 160 200
C O
Leaf area (cm²)
B
R. mucronata a
b
84
Fig. 3.24 Effects of oiling on chlorophyll content index (CCI) in A. marina.
Measurements were taken after 409 days, C = control, SO = sediment oiled, O = propagule oiled. Means ± standard error are given, n = 3. Bars with different letters are significantly different at P ≤ 0.05 using Tukey-Kramer multiple comparisons test.
Fig. 3.25 Effects of oiling on chlorophyll content index (CCI) in B. gymnorrhiza (A) and R. mucronata (B). Measurements were taken after 409 days, C = control, O = sediment oiled. Means ± standard error are given, n = 3 (B. gymnorrhiza) and n = 2 (R.
mucronata). Bars with different letters are significantly different at P ≤ 0.05 using Tukey-Kramer multiple comparisons test.
0 5 10 15 20 25 30 35
C SO O
CCI
a
b b
A. marina
0 20 40 60 80
C O
CCI
B. gymnorrhiza a A
b
0 30 60 90
C O
CCI
B
b a
R. mucronata
85