Correlates of inter-specific variation in germination response to water stress in a semi-arid savannah

Kos, Martijn; Poschlod, Peter

doi:10.1016/j.baae.2007.10.005

Cited by 38 publications

(42 citation statements)

References 29 publications

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“…However, these results may not be universal. Kos and Poschlod (2008), studying 28 species from a semi-arid savanna region of the Kalahari Desert, found that species in sandy soils with small seeds (<0.5 mg) only germinate at high water potentials.…”

Section: Discussionmentioning

confidence: 98%

Germination biology and seedling growth of Clusia hilariana Schltdl., a dominant CAM‐tree of drought‐prone sandy coastal plains

Cavalcante

Braz

Mattos

2010

Ecological Research

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The spatial and temporal fluctuations of water availability can be an obstacle for recruitment of many species in the restinga and might restrict seed germination and seedling growth in specific regeneration safe-sites. Clusia hilariana is one of the most dominant species of Restinga de Jurubatiba. This species has a high proportion of seedling establishment occurring inside the tanks of soil bromeliads underneath vegetation patches. Given the thin seed coats, the fast germination time and seed dispersal of C. hilariana during the dry season, we hypothesized that their major regeneration niche (the tanks of soil bromeliads) is related to susceptibility of seed germination and also seedling growth to low water availability. To test this hypothesis, seeds were germinated under decreasing water potentials using PEG 6000 solutions and seedlings were grown under varying water regimes. The percentage of seed germination progressively decreased at lower water potentials. After 38 days in À1.0 MPa no seeds germinated. However, approximately 90% of seeds germinated when transferred to W = 0 MPa. The relative growth rates of seedlings of C. hilariana did not differ between water treatments. Thus, the major regeneration niche of C. hilariana is not a consequence of a high sensitivity of seeds and seedlings to water shortage. Nonetheless, C. hilariana showed an array of seed and seedling traits that may help to overcome establishment constraints of the harsh environment of restingas.

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Section: Discussionmentioning

confidence: 98%

Germination biology and seedling growth of Clusia hilariana Schltdl., a dominant CAM‐tree of drought‐prone sandy coastal plains

Cavalcante

Braz

Mattos

2010

Ecological Research

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“…Germination behaviour is often described as adaptive in relation to habitat characteristics. Ignoring variation in seedling functional traits in such studies, which is commonly done, may not always be justiWed (Kos and Poschlod 2008). Comparative germination studies that aim to demonstrate adaptation to habitat should consider that traits evolve in the context of both the environment and other traits.…”

Section: Discussionmentioning

confidence: 99%

“…Data for the median base potential for germination 50 were extracted from Kos and Poschlod (2008) and were not available for Trianthema parvifolia.…”

Section: Germination and Root Measurementsmentioning

confidence: 99%

Why wait? Trait and habitat correlates of variation in germination speed among Kalahari annuals

Kos

Poschlod

2009

Oecologia

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The longer soil has to stay moist to allow germination the more likely that seedlings experience favourable moisture conditions. Since theory predicts that fitness variance-reducing traits will be negatively correlated, we tested the hypothesis that time to germination is negatively correlated with the ability of radicle growth to keep up with the drying front. We measured time to germination and root elongation rate (RER) in 14 Kalahari annuals. We controlled for habitat (canopy association and sand content), germinability, median base water potential for germination (psi(50)), seed mass and seed shape as a persistence surrogate. For species and phylogenetically independent contrasts (PICs), we did not find a relationship between time to germination and RER. However, we found a negative relationship of time to germination with RER for PICs when controlling for sand content and psi(50). Seed shape increased with time to germination which can be explained by reduced opportunities for germination in slow-germinating species that select for persistence. We found a positive relationship between time to germination and psi(50), suggesting a continuum of risky to cautious germination. psi(50) was not correlated with RER suggesting that variation in psi(50) reflects different drought-adapted traits. Probably the relationship of time to germination with RER is not mediated by seed mass, which was not correlated with time to germination as found by others, though RER was positively correlated with seed mass. Instead of the seed size-seed number trade-off, a trade-off with resource capture may explain variation in RER: more root hairs or rootlets may increase resource capturing surface while reducing RER. For habitat, we found a (positive) relationship with time to germination only for canopy association. This may be explained by maximization of resource capture at the expense of RER being favoured by the higher nutrient and water availability under canopies. Future studies should clarify which trade-offs govern variation in time to germination, focussing on a possible resource capture-RER trade-off.

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“…In conclusion, suitable conditions including temperature and humidity are necessary for seed germination, emergence and seedling survival [47][48][49]. R. ludovici-salvatoris has shown a low ability for seed germination at 5-15ºC temperature regimes, as well as a low ability to emerge seedlings when compared with other temperature regimes and both populations of R.alaternus, even from shallow burials.…”

Section: Seed Germination Seedling Emergence and Regeneration Abilitymentioning

confidence: 99%

Seed germination at different temperatures and seedling emergence at different depths of Rhamnus spp

Aou-ouad¹,

Medrano

Lamarti

et al. 2014

Open Life Sciences

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Rhamnus alaternus and R. ludovici-salvatoris, two Mediterranean shrubs with different geographic distributions, have shown important differences in seedling recruitment capacity. The objectives of this work were to determine the ability of these species to germinate seeds under different temperature ranges, as well as the capacity of seedlings to emerge from different burial depths, in order to better understand their regeneration processes. Two different experiments were performed. In the first one, seed germination was studied in Petri dishes and in the dark at different temperature regimes: a) 5–15°C, b) 10–20°C and c) 15–25°C (12h/12h). In the second experiment, seedling emergence capacity from different burial depths (0.5, 2 and 5 cm) was tested. R. ludovici-salvatoris showed a significantly higher final germination rates, a lower dormancy period, and average time response at 10–20°C than at other temperature ranges, although differences were much greater when seeds were subjected to the 5–15°C temperature regime. By contrast, R. alaternus did not show significant differences between treatments (5–15°C and 10–20°C) in germination behavior. Seedling emergence of both species was lower and slower when seeds were buried at 5 cm. However, R. ludovici-salvatoris always showed a lower seedling emergence capacity than R. alaternus at any burial depth. The low ability of R. ludovici-salvatoris to germinate seeds and emerge between 5–15°C, even from shallow depths, is discussed in relation to its low regeneration capacity and declining geographic distribution.

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Correlates of inter-specific variation in germination response to water stress in a semi-arid savannah

Cited by 38 publications

References 29 publications

Germination biology and seedling growth of Clusia hilariana Schltdl., a dominant CAM‐tree of drought‐prone sandy coastal plains

Germination biology and seedling growth of Clusia hilariana Schltdl., a dominant CAM‐tree of drought‐prone sandy coastal plains

Why wait? Trait and habitat correlates of variation in germination speed among Kalahari annuals

Seed germination at different temperatures and seedling emergence at different depths of Rhamnus spp

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