Effects of fruit position on fruit mass and seed germination in the ...
Effects of fruit position on fruit mass and seed germination in the ...
Effects of fruit position on fruit mass and seed germination in the ...
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6 L. Moravcová et al. / Acta Oecologica 28 (2005) 1–10<br />
Fig. 4. Mean time to germ<strong>in</strong>ati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> 50% <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>the</strong> <strong>seed</strong> from a r<strong>and</strong>omly chosen<br />
plant, for term<strong>in</strong>al, satellite <strong>and</strong> branch umbels <str<strong>on</strong>g>of</str<strong>on</strong>g> H. mantegazzianum<br />
(n = 210 <strong>seed</strong>s). Different letters <strong>in</strong>side <strong>the</strong> bars <strong>in</strong>dicate significant (p < 0.05)<br />
differences am<strong>on</strong>g umbel types <strong>in</strong> deleti<strong>on</strong> tests. St<strong>and</strong>ard errors are slightly<br />
asymmetrical due to <strong>the</strong> shape <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>the</strong> germ<strong>in</strong>ati<strong>on</strong> curves. v 2 = 14.2; df =2;<br />
p < 0.001. Germ<strong>in</strong>ati<strong>on</strong> rate is <strong>the</strong> time to when 50% <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>the</strong> <strong>seed</strong>s had germ<strong>in</strong>ated,<br />
hence shorter bars <strong>in</strong>dicate faster germ<strong>in</strong>ati<strong>on</strong>. (Note <strong>the</strong> large difference<br />
between <strong>the</strong> mean germ<strong>in</strong>ati<strong>on</strong> rates for <strong>the</strong> two r<strong>and</strong>omly chosen<br />
plants <strong>in</strong> Figs. 3 <strong>and</strong> 4, which dem<strong>on</strong>strates <strong>the</strong> large variati<strong>on</strong> am<strong>on</strong>g plants<br />
<strong>and</strong> sites).<br />
3.2. Effect <str<strong>on</strong>g>of</str<strong>on</strong>g> umbel characteristics <strong>on</strong> <str<strong>on</strong>g>fruit</str<strong>on</strong>g> <strong>mass</strong>,<br />
percentage germ<strong>in</strong>ati<strong>on</strong> <strong>and</strong> germ<strong>in</strong>ati<strong>on</strong> rate<br />
Percentage germ<strong>in</strong>ati<strong>on</strong> was not affected by <strong>the</strong> measured<br />
variables relat<strong>in</strong>g to umbels. Nei<strong>the</strong>r umbel diameter nor <strong>the</strong><br />
tim<strong>in</strong>g <str<strong>on</strong>g>of</str<strong>on</strong>g> flower<strong>in</strong>g (start, end <strong>and</strong> durati<strong>on</strong>) had a significant<br />
effect at any <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>the</strong> sites. Germ<strong>in</strong>ati<strong>on</strong> rate varied unpredictably<br />
with <strong>the</strong> measured umbel characteristics.<br />
Fruit <strong>mass</strong> significantly <strong>in</strong>creased with umbel diameter.<br />
The 95% c<strong>on</strong>fidence <strong>in</strong>tervals <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>the</strong> regressi<strong>on</strong>s <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>fruit</str<strong>on</strong>g> <strong>mass</strong><br />
<strong>on</strong> umbel diameter for <strong>the</strong> different sites overlapped broadly,<br />
<strong>and</strong> <strong>the</strong>se relati<strong>on</strong>ships were <strong>the</strong> same for each umbel type<br />
(deleti<strong>on</strong> test <strong>on</strong> a different regressi<strong>on</strong> slope <strong>on</strong> umbel diameter<br />
for term<strong>in</strong>al, satellite <strong>and</strong> branch: F = 0.35; df = 4, 163;<br />
NS). Comm<strong>on</strong> regressi<strong>on</strong> slope <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>the</strong> <strong>in</strong>crease <strong>in</strong> <str<strong>on</strong>g>fruit</str<strong>on</strong>g> <strong>mass</strong><br />
with umbel diameter is shown <strong>in</strong> Fig. 5.<br />
3.3. Effect <str<strong>on</strong>g>of</str<strong>on</strong>g> plant characteristics <strong>on</strong> <str<strong>on</strong>g>fruit</str<strong>on</strong>g> <strong>mass</strong>,<br />
percentage germ<strong>in</strong>ati<strong>on</strong> <strong>and</strong> germ<strong>in</strong>ati<strong>on</strong> rate<br />
Percentage germ<strong>in</strong>ati<strong>on</strong> was not affected by plant fecundity,<br />
basal diameter or height <strong>and</strong> <strong>the</strong> germ<strong>in</strong>ati<strong>on</strong> rate varied<br />
Fig. 5. Relati<strong>on</strong>ship between <str<strong>on</strong>g>fruit</str<strong>on</strong>g> <strong>mass</strong> <strong>and</strong> <strong>the</strong> size <str<strong>on</strong>g>of</str<strong>on</strong>g> an umbel <strong>in</strong> H. mantegazzianum<br />
based <strong>on</strong> data pooled across all sites. Fruit <strong>mass</strong> = 0.33 + 0.054<br />
umbel diameter. F = 88.73; df =1,163;p < 0.001; R 2 = 0.35.<br />
Table 4<br />
Significant (p < 0.05) effects <str<strong>on</strong>g>of</str<strong>on</strong>g> plant fecundity, height <strong>and</strong> basal diameter<br />
<strong>on</strong> <str<strong>on</strong>g>fruit</str<strong>on</strong>g> <strong>mass</strong> <strong>in</strong> H. mantegazzianum at <strong>in</strong>dividual sites (n = 8 at each site)<br />
Explanatory variable Site Regressi<strong>on</strong> slope ± st<strong>and</strong>ard error<br />
Plant fecundity Arnoltov –0.074 ± 0.023<br />
Plant height Dvorečky –0.044 ± 0.018<br />
Krásná Lípa I –0.10 ± 0.038<br />
Žitný II –0.11 ± 0.032<br />
Plant basal diameter Krásná Lípa I 0.15 ± 0.032<br />
<strong>in</strong>c<strong>on</strong>sistently. At some sites, <strong>the</strong>se characteristics had a significant<br />
effect <strong>on</strong> <str<strong>on</strong>g>fruit</str<strong>on</strong>g> <strong>mass</strong>, which decreased with <strong>in</strong>creas<strong>in</strong>g<br />
fecundity at <strong>on</strong>e site. A negative effect <strong>on</strong> <str<strong>on</strong>g>fruit</str<strong>on</strong>g> <strong>mass</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> plant<br />
height <strong>and</strong> fecundity <strong>and</strong> a positive effect <str<strong>on</strong>g>of</str<strong>on</strong>g> plant basal diameter<br />
were found at three <strong>and</strong> <strong>on</strong>e site, respectively (Table 4).<br />
4. Discussi<strong>on</strong><br />
4.1. Percentage germ<strong>in</strong>ati<strong>on</strong> <strong>in</strong> H. mantegazzianum:<br />
higher than <strong>the</strong> family average<br />
Percentage germ<strong>in</strong>ati<strong>on</strong> <strong>in</strong> H. mantegazzianum was extremely<br />
high. An extensive study <str<strong>on</strong>g>of</str<strong>on</strong>g> germ<strong>in</strong>ati<strong>on</strong> <strong>in</strong> 88 members<br />
<str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>the</strong> family Apiaceae carried out at <strong>the</strong> Institute <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
Botany <strong>in</strong> <strong>the</strong> 1980s (M. Lhotská, unpublished data) allows<br />
<strong>the</strong> results obta<strong>in</strong>ed for H. mantegazzianum to be placed at<br />
wider phylogenetic c<strong>on</strong>text. Seventeen species (i.e., 19% <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
those tested) exhibited 90–100% germ<strong>in</strong>ati<strong>on</strong> under optimum<br />
c<strong>on</strong>diti<strong>on</strong>s. Of <strong>the</strong> three naturalized neophytes (alien<br />
species <strong>in</strong>troduced after <strong>the</strong> discovery <str<strong>on</strong>g>of</str<strong>on</strong>g> America; Richards<strong>on</strong><br />
et al., 2000, Pyšek et al., 2004) <strong>on</strong> <strong>the</strong> list, <strong>on</strong>ly Smyrnium<br />
perfoliatum (92%) has a higher percentage germ<strong>in</strong>ati<strong>on</strong>, <strong>and</strong><br />
for <strong>the</strong> o<strong>the</strong>r two it is lower: Imperatoria ostruthium (74%),<br />
Myrrhis odorata (72%). Heracleum mantegazzianum is <strong>on</strong>e<br />
<str<strong>on</strong>g>of</str<strong>on</strong>g> 24 neophytes bel<strong>on</strong>g<strong>in</strong>g to <strong>the</strong> Apiaceae <strong>in</strong> <strong>the</strong> flora <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>the</strong><br />
Czech Republic (Pyšek et al., 2002) seven <str<strong>on</strong>g>of</str<strong>on</strong>g> which are classified<br />
as naturalized <strong>and</strong> four are <strong>in</strong>vasive (Pyšek et al., 2004).<br />
Published data are available <strong>on</strong>ly for A. archangelica subsp.<br />
archangelica, ano<strong>the</strong>r <strong>in</strong>vasive species, for which <strong>the</strong> percentage<br />
germ<strong>in</strong>ati<strong>on</strong> reaches 82% <strong>and</strong> is enhanced by light (Ojala,<br />
1985).<br />
Good germ<strong>in</strong>ati<strong>on</strong> has also been reported for a number <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
o<strong>the</strong>r species <strong>in</strong> <strong>the</strong> Apiaceae <strong>in</strong> <strong>the</strong> literature, for example<br />
94% <strong>in</strong> A. graveolens (Thomas et al., 1979) <strong>and</strong> 83% <strong>in</strong> P.<br />
sativa (Hendrix, 1984a). Germ<strong>in</strong>ati<strong>on</strong> exceeded 80% <strong>in</strong> 29<br />
(33%) <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>the</strong> 88 species studied by M. Lhotská <strong>and</strong> <strong>the</strong> values<br />
recorded by her for H. mantegazzianum (80%) <strong>and</strong> <strong>in</strong> <strong>the</strong><br />
present study (91%) are higher than <strong>the</strong> average for <strong>the</strong> family<br />
(68.7 ± 23.2%, mean ± S.D., n = 88). An extremely high<br />
percentage <str<strong>on</strong>g>of</str<strong>on</strong>g> germ<strong>in</strong>ati<strong>on</strong> is typical <str<strong>on</strong>g>of</str<strong>on</strong>g> this <strong>in</strong>vasive alien even<br />
with<strong>in</strong> <strong>the</strong> c<strong>on</strong>text <str<strong>on</strong>g>of</str<strong>on</strong>g> its family, <strong>seed</strong>s <str<strong>on</strong>g>of</str<strong>on</strong>g> which generally<br />
readily germ<strong>in</strong>ate <strong>on</strong>ce dormancy is broken (Bask<strong>in</strong> <strong>and</strong><br />
Bask<strong>in</strong>, 1990,1991; Bask<strong>in</strong> et al., 1995).<br />
Percentage germ<strong>in</strong>ati<strong>on</strong> recorded under laboratory c<strong>on</strong>diti<strong>on</strong>s<br />
is not always realized <strong>in</strong> <strong>the</strong> wild. In our study, cold <strong>and</strong>