Phytotoxicity induced by Phragmites australis: an assessment of phenotypic and physiological parameters involved in germination process and growth of receptor plant

Figures & data

Figure 1. Effect of aqueous extracts (5%) of different organs of P. australis on liquid imbibitions of lettuce seeds expressed in fresh weight [mg. (100 mg seed)⁻¹] throughout 32 h. Values are mean±standard error (n=3). ***, ** and * indicate significant differences from control at P ≤ 0.001, P ≤ 0.01 and P ≤ 0.05 respectively after Dunnett's test.

Figure 2. Effect of aqueous extracts (5%) of different organs of P. australis on (a) total carbohydrates (mg g⁻¹) and (b) water soluble carbohydrates (mg g⁻¹) of lettuce seeds at 0, 8 and 32 h imbibition. Values are mean±standard error (n=3). ***, ** and * indicate significant differences from control at P ≤ 0.001, P ≤ 0.01 and P ≤ 0.05 respectively after Dunnett's test.

Figure 3. Dose-response relationships for effects of aqueous extracts of different organs of P. australis on (a) germination percentage, (b) speed of germination, and (c) radicle length of lettuce seeds. Values are mean±standard error (n=3). Horizontal lines indicate LC₅₀ concentration and values along arrows indicate LC₅₀ of different organs extracts. r=correlation coefficient.

Table 1. Results of two way ANOVA (F-ratios) showing the effects of different organ materials (M) of P. australis, extract concentration (C) and their interaction (M×C) on germination indices, biometric, and biochemical parameters in lettuce.

Parameter	M	C	M× C
Germination indices
Percentage of germination	F4,82=458.14*	F6,82=707.20*	F24,82=71.15*
Speed of germination	F4,82=497.33*	F6,82=745.98*	F24,82=55.28*
Biometric parameters
Radicle length	F4,76=315.69*	F6,76=276.26*	F22,76=23.85*
Hypocotyl length	F4,76=24.19*	F6,76=9.54*	F22,76=26.02*
Radicle weight	F4,73=28.89*	F6,73=36.92*	F21,73=3.45*
Hypocotyl weight	F4,76=43.86*	F6,76=3.27*	F22,76=14.78*
Biochemical parameters
H2O2 content	F4,62=77.43*	F6,62=116.23*	F20,62=8.05*
Enzyme activity	F4,71=46.41*	F6,71=510.85*	F20,71=14.68*
Membrane injury	F4,71=131.99*	F6,71=215.25*	F20,71=12.83*
Lipid peroxidation	F4,62=144.70*	F6,62=196.76*	F20,62=21.39*

Note: Level of significance: *P<0.0001.

Figure 4. Effects of aqueous extracts of different organs of P. australis at different concentrations on (a) H₂O₂ content (nmol g⁻¹ FW) and (b) dehydrogenase enzyme activity (% of control) in treated plantlets of lettuce. Values are mean±standard error (n=3). r=correlation coefficient.

Figure 5. Effects of aqueous extracts of different organs of P. australis at different concentrations on (a) membrane injury (% of total leakage) and (b) lipid peroxidation (nmol MDA g⁻¹ FW) in treated plantlets of lettuce. Values are mean±standard error (n=3). r=correlation coefficient.

Table 2. Effect of osmotic potential at various concentrations on germination, growth, and physiological parameters of lettuce. Values are mean±standard error (n=3).

Osmotic potential (bar)	Germination (%)	Speed of germination	Radicle length (% of control)	Membrane injury (% of total leakage)	Dehydrogenase enzyme activity (% of control)
0	100±0	12.50±0	100±0	5.12±0.03	100±0
0.11	97.33±1.33^ns	10.82±0.70^ns	100±7.38^ns	4.55±0.30^ns	96.33±1.93^ns
0.17	97.33±1.3^ns	10.89±0.36^ns	97.16±3.60^ns	4.56±0.21^ns	94.50±2.76^ns
0.22	94.67±1.3^ns	10.99±0.15^ns	100.44±3.74^ns	5.01±0.10^ns	93.04±2.22^ns
0.27	94.67±2.6^ns	10.22±0.43*	97.60±5.69^ns	4.26±0.12^ns	88.64±2.86*
0.37	94.67±1.33^ns	10.42±0.32*	93.22±1.52^ns	5.90±0.29^ns	57.14±2.28***
0.45	97.33±1.33^ns	10.69±0.44*	79.45±2.65*	6.47±0.33*	42.12±1.93***
0.57	74.67±2.67***	6.56±0.52***	57.16±2.47***	6.89±0.37**	34.79±1.93***
0.67	62.67±3.53***	5.48±0.48***	52.46±1.89***	7.23±0.28***	27.47±1.26***
0.77	18.67±2.67***	0.43±0.04***	34.43±1.68***	–	–
0.87	12.00±2.31***	0.31±0.03***	24.92±1.62***	–	–
0.97	5.33±1.33***	0.19±0.03***	13.55±1.08***	–	–

Note: ***, **, * and ^ns indicate significant difference from control at P ≤ 0.001, P ≤ 0.01, P ≤ 0.05 and non-significant respectively after applying the Dunnett's test.

Table 3. Results of paired t-tests showing the effects of different organ of P. australis and extract concentration considering osmotically adjusted control on germination indices, biometric and physiological parameters in lettuce.

Organ/concentration (%)	Germination	Speed of germination	Radicle length	Membrane injury	Dehydrogenase enzyme activity	Lipid peroxidation
Inflorescence
1.25	NS	NS	ST	NS	NS	NS
2.5	NS	NS	ST	NS	**	*
5.0	NS	NS	**	*	**	NS
10.0	NS	NS	**	*	***	*
15.0	NS	NS	*	**	*	NS
20.0	NC	NC	NC	**	NC	NC
Leaf
1.25	NS	NS	*	*	**	*
2.5	NS	*	**	*	*	*
5.0	***	***	**	*	*	**
10.0	***	***	***	**	*	**
15.0	–	–	–	–	–	–
20.0	–	–	–	–	–	–
Stem
1.25	NS	NS	NS	NS	**	NC
2.5	NS	NS	NS	*	*	NC
5.0	NS	NS	NS	*	**	NC
10.0	*	*	**	NS	**	NC
15.0	*	*	**	*	**	NC
20.0	NC	NC	NC	NC	–	–
Rhizome
1.25	NS	NS	*	**	NS	NS
2.5	NS	NS	**	**	NS	NS
5.0	NS	NS	*	**	**	*
10.0	**	**	*	**	**	*
15.0	**	**	**	*	**	**
20.0	NS	NS	NC	–	–	–
Root
1.25	NS	NS	NS	**	**	NC
2.5	NS	NS	NS	*	**	NC
5.0	NS	NS	NS	*	***	*
10.0	**	*	NC	**	NC	NC
15.0	NS	NS	NC	–	–	–
20.0	NC	NC	NC	–	–	–

Note: Level of significance: *, **, ***, and NS at P<0.05, P<0.01, P<0.001 and not significant; NC=not calculated due to high effects by osmotic potential rather than plant extracts and ST=stimulation. Units are as same as Table 2.

Figure 6. Effects of root exudates of P. australis on (a) germination (%), (b) root and shoot length (cm), and (c) root and shoot weight (mg/plant) in lettuce grown alone, or together with P. australis either with or without activated carbon (AC) in the soil. Values are mean±standard error (n=3). Means with different letters were significant different in pairwise comparison (P>0.05).

Figure 7. Effects of root exudates of P. australis on (a) membrane injury of root (% of total leakage) and (b) total chlorophyll (mg L⁻¹) in lettuce grown alone, or together with P. australis either with or without activated carbon (AC) in the soil. Values are mean±standard error (n=3). Means with different letters were significant different in pairwise comparison (P>0.05).