Viability assessment and estimation of the germination potential of charophyte oospores: testing for site and species specificity

Figures & data

Table 1. Triphenyltetrazolium chloride (TTC) viability test of Chara oospores.

TTC conc.	Colour	Chara contraria	Chara globularis	Chara canescens	Chara vulgaris
0.5%	Red coloured	40.5	81.2	52.5	36.8
	Partially red coloured	27.1	9.4	25	39.5
	Colourless	32.4	9.4	22.5	23.7
1.0%	Red coloured	52.6	60.0	45.0	30.4
	Partially red coloured	18.5	15.0	37.5	23.9
	Colourless	28.9	25.0	17.5	45.7
2.0%	Red coloured	63.1	43.9	52.5	48.7
	Partially red coloured	21.7	26.8	22.5	17.9
	Colourless	15.2	29.3	25.0	33.3

The numbers are the percentage of oospores tested vital (red coloured and partially red coloured) and non-vital (colourless) at 0.5%, 1.0% and 2.0% concentrations of TTC. The oospores of C. vulgaris (n = 120) and C. canescens (n = 120) were taken from the sediment samples; the oospores of C. contraria (n = 120) and C. globularis (n = 134) were taken directly from the field-grown plants.

Table 2. Results of the χ² test.

Species	Concentration (%)	Colour	χ^2	p (two-tailed)
Chara contraria	0.5	Red	2.52	0.112
		Partially red	0.184	0.668
		Colourless	5.789	0.016*
	1	Red	0.23	0.88
		Partially red	0.195	0.659
		Colourless	0.237	0.626
	2	Red	5.393	0.02*
		Partially red	0	0.997
		Colourless	1.069	0.301
Chara globularis	0.5	Red	10.968	0.001*
		Partially red	1.444	0.23
		Colourless	1.702	0.192
	1	Red	0.449	0.503
		Partially red	0.054	0.816
		Colourless	0.169	0.681
	2	Red	7.511	0.006*
		Partially red	1.946	0.163
		Colourless	2.927	0.087
Chara canescens	0.5	Red	0.073	0.787
		Partially red	1.102	0.294
		Colourless	1.57	0.21
	1	Red	0.593	0.441
		Partially red	0	0.988
		Colourless	0.467	0.494
	2	Red	0.232	0.63
		Partially red	1.024	0.311
		Colourless	0.249	0.618
Chara vulgaris	0.5	Red	1.111	0.292
		Partially red	2.894	0.089
		Colourless	1.868	0.172
	1	Red	0.038	0.845
		Partially red	0.36	0.548
		Colourless	1.894	0.169
	2	Red	1.628	0.202
		Partially red	4.971	0.026*
		Colourless	0.016	0.9

Standard p = 0.05 was used for significance (*).

Table 3. Comparison of tested oospores and the combinations influencing dormancy, as well as the germination-inducing conditions and resulting percentage of germination.

Species; site	n (Oospores)	Germination (%)	T	M	D	Sediment
			Pretreatment	Pretreatment	Pretreatment	Germination process
			A	B	C	α
Chara canescens; Neusiedler Seewinkel, Austria	40	0	5	0	1	0
Chara canescens; Baltic Sea, Germany	40	0	15	1	1	0
Chara baltica; Mallada, Spain	10	0	−5	0	0	1
Chara baltica; Mallada, Spain	10	0	5	0	0	1
Chara baltica; Mallada, Spain	10	0	15	0	0	1
Chara hispida; Gummanz, Germany	30	0	–	0	0	1
Chara hispida; Gummanz, Germany	30	0	–	1	0	1
Chara hispida; Gummanz, Germany	30	0	−5	1	0	1
Chara hispida; Gummanz, Germany	30	0	−5	1	0	1
Chara hispida; Gummanz, Germany	15	0	5	0	0	1
Chara hispida; Gummanz, Germany	15	0	5	1	0	1
Chara papillosa; Röblingen, Germany	25	0	5	0	0	1
Chara canescens; Neusiedler Seewinkel, Austria	25	0	−5	1	0	1
Chara canescens; Baltic Sea, Germany	15	0	15	0	0	1
Chara papillosa; Röblingen, Germany	25	0	20	0	1	1
Chara canescens; Baltic Sea, Germany	15	0	15	0	1	1
Chara papillosa; Röblingen, Germany	25	12	5	0	0	2
Chara canescens; Baltic Sea, Germany	15	20	15	1	0	2
Chara canescens; Neusiedler Seewinkel, Austria	25	32	5	0	0	2
Chara canescens; Baltic Sea, Germany	15	33	15	1	1	2
Chara canescens; Baltic Sea, Germany	15	40	15	1	1	2
Chara papillosa; Röblingen, Germany	25	44	20	0	1	2
Chara canescens; Neusiedler Seewinkel, Austria	25	48	5	0	1	2
Chara papillosa; Röblingen, Germany	25	60	20	0	1	2

Pretreatments: T = temperature; M = microbial; D = desiccation; 0 = no microbial/not desiccated; 1 = microbial active phase/desiccation of oospores. Germination process: 0 = agar; 1 = washed sea sand and phosphorus; 2 = washed sea sand and phosphorus with organic addition.

Table 4. Total numbers of germinated oospores from natural sediments of seven locations under three light intensities.

Location	Replicates	Light irradiance	Total number of germlings	Lychnothamnus barbatus	Chara contraria	Nitellopsis obtusa	Chara globularis	Nitella flexilis/opaca	Nitella mucronata	Chara canescens	Chara filiformis	Tolypella glomerata	Lamprothamnium papulosum	Chara baltica/liljebladii
Lake Balsys	10	1	33	–	3.3 ± 2.5	–	0.7 ± 1.4	–	–	–	–	–	–	–
	10	2	30	2.6 ± 1.7	–	0.2 ± 0.6	–	–	–	–	–	–	–	–
	10	3	5	–	–	–	0.2 ± 0.4	–	–	–	–	–	–	–
Stoßdorfer See	7	1	142	–	–	2.4 ± 2	–	–	–	–	–	–	–	–
	7	2	11	–	–	0.9 ± 0.8	3.4 ± 4.7	–	–	–	–	–	–	–
	7	3	38	–	–	1 ± 1.4	3.4 ± 3	–	14.4 ± 6.6	–	–	–	–	–
Borkener See	10	1	89	–	9.3 ± 9.5	–	1.7 ± 1.4	–	–	8.6 ± 11.2	3.6 ± 3.1	–	–	–
	10	2	28	–	2.4 ± 3.9	–	0.1 ± 0.4	0.5 ± 1.1	–	16.7 ± 11.5	–	–	–	–
	10	3	36	–	4.5 ± 4.9	–	0.6 ± 1.4	1 ± 1.8	–	10.9 ± 11.7	–	3.1 ± 4.8	–	–
Obersee bei Lanke	7	1	13	–	0.9 ± 8.6	–	0.7 ± 1.4	–	–	–	–	–	–	–
	7	2	8	0.5 ± 1	1.3 ± 1.5	–	0.6 ± 0.7	–	–	–	–	–	–	–
	7	3	0	–	–	–	–	–	–	–	–	–	–	–
Großer Goitzschesee	10	1	164	–	11 ± 6.4	–	5.7 ± 4.8	–	–	–	–	–	–	–
	10	2	153	–	10.5 ± 7.5	–	2.5 ± 2	0.5 ± 1.5	–	–	–	–	–	–
	10	3	197	–	16.7 ± 8.6	–	1.1 ± 0.6	5 ± 5.4	–	–	–	–	–	–
Fastensee	10	1	77	–	–	–	–	–	–	0.1 ± 0.3	–	–	11 ± 9.9	–
	10	2	2	–	–	–	–	–	–	1.7 ± 1.9	–	–	0.3 ± 0.7	–
	10	3	0	–	–	–	–	–	–	0.9 ± 2	–	–	–	–
Grabow	7	1	145	–	–	–	–	–	–	0.4 ± 1	–	–	–	20.3 ± 23.7
	7	2	35	–	–	–	–	–	–	0.4 ± 0.7	–	–	–	4 ± 10.6
	7	3	78	–	–	–	–	–	–	–	–	–	–	10.7 ± 14
Generative (oospores) (%)		1	312	0	31	0	25	0	0	31	100	0	97.5	–
		2	239	63	16	0	16	0	0	47	0	0	2.5	–
		3	283	0	21	1	7	0	26	22	0	0	0	–
Vegetative (bulbils, stem-tuber or root nodes) (%)		1	100	0	5	25	34	0	0	0	0	0	0	–
		2	103	37	14	9	5	8	0	0	0	0	0	–
		3	167	0	13	65	13	92	74	0	0	100	0	–

Light intensity: 1 = 15–20 µmol photons s⁻¹ m⁻²; 2 = 30–40 µmol photons s⁻¹ m⁻²; 3 = 110–130 µmol photons s⁻¹ m⁻². Species-specific and site-specific mean values are listed with standard deviations, as well as the fractions of generative and vegetative reproduction.

Table 5. Statistical analyses (Mann–Whitney U test).

Species	Groups of light irradiances
	1–2		2–3		1–3
	U	p (two-tailed)	U	p (two-tailed)	U	p (two-tailed)
Lychnothamnus barbatus	−2.673	0.008*	−2.536	0.011*	−0.014	0.989
Chara contraria	−0.629	0.529	−2.462	0.014*	−1.61	0.107
Nitellopsis obtusa	−0.332	0.74	−0.458	0.647	−0.183	0.855
Chara globularis	−1.434	0.152	−3.211	0.001*	−1.837	0.066
Nitella flexilis/opaca	−0.786	0.432	−2.376	0.017*	−2.874	0.004*
Nitella mucronata	−1.478	0.140	−3.351	0.001*	−3.343	0.001*
Chara canescens	−1.671	0.095	−1.556	0.12	−0.067	0.946
Chara filiformis	0.000	1	−2.357	0.018*	−2.46	0.014*
Tolypella glomerata	−0.971	0.331	−1.361	0.173	−0.333	0.739
Lamprothamnium papulosum	−1.296	0.195	−1.867	0.062	−2.241	0.025*
Chara baltica/liljebladii	−2.241	0.025*	−2.245	0.025*	−0.799	0.424

The U values and the significance level p are listed. Standard p = 0.05 was used for significance (*).