Germination Responses to Water Potential in Neotropical Pioneers Suggest Large-seeded Species Take More Risks

Matthew I. Daws, Lora M Crabtree, James W. Dalling, Christopher Mullins, David Francis Robert Philip Burslem

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

In neotropical forests, very small-seeded pioneer species (< 0.1 mg seed mass) recruit preferentially in small tree fall gaps and at gap edges, but large-seeded pioneers do not. Since water availability is related to gap size, these differences in microsite preference may reflect in part species-specific differences in germination at reduced water potentials.

For 14 neotropical pioneer species, the hypothesis is tested that small-seeded species, with shallow initial rooting depths, reduce the risks associated with desiccation by germinating more slowly and at higher water potentials than large-seeded species.

Germination occurred both more quickly and at lower water potentials with increasing seed mass. For example, Ochroma pyramidale (seed mass 5.5 mg) had a time to 50 % germination (T-50) of 2.8 d and a median base potential for germination (psi(b50)) of -1.8 MPa while Clidemia quinquenervia (seed mass 0.017 mg) had a T-50 of 17.6 d and psi(b50) of -1.1 MPa.

These data suggest that small-seeded species germinate only in comparatively moist microsites, such as small canopy gaps, which may reduce the risk of drought-induced mortality. Conversely, large-seeded species are able to germinate in the drier environment of large gaps, where they benefit by enhanced seedling growth in a high irradiance environment. The positive association of seed size and canopy gap size for optimal seedling establishment is maintained by differential germination responses to soil water availability coupled with the scaling of radicle growth rate and seed size, which collectively confer greater drought tolerance on large-seeded species.

Original languageEnglish
Pages (from-to)945-951
Number of pages7
JournalAnnals of Botany
Volume102
Issue number6
Early online date7 Oct 2008
DOIs
Publication statusPublished - Dec 2008

Keywords

  • tropical forest
  • gao size
  • seedling establishment
  • dessication tolerance
  • soil
  • temperature
  • plants
  • trees
  • regeneration
  • persistence
  • germination
  • seed size
  • Panama
  • neotropical
  • pioneer
  • water potential

Cite this

Germination Responses to Water Potential in Neotropical Pioneers Suggest Large-seeded Species Take More Risks. / Daws, Matthew I.; Crabtree, Lora M; Dalling, James W.; Mullins, Christopher; Burslem, David Francis Robert Philip.

In: Annals of Botany, Vol. 102, No. 6, 12.2008, p. 945-951.

Research output: Contribution to journalArticle

Daws, Matthew I. ; Crabtree, Lora M ; Dalling, James W. ; Mullins, Christopher ; Burslem, David Francis Robert Philip. / Germination Responses to Water Potential in Neotropical Pioneers Suggest Large-seeded Species Take More Risks. In: Annals of Botany. 2008 ; Vol. 102, No. 6. pp. 945-951.
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title = "Germination Responses to Water Potential in Neotropical Pioneers Suggest Large-seeded Species Take More Risks",
abstract = "In neotropical forests, very small-seeded pioneer species (< 0.1 mg seed mass) recruit preferentially in small tree fall gaps and at gap edges, but large-seeded pioneers do not. Since water availability is related to gap size, these differences in microsite preference may reflect in part species-specific differences in germination at reduced water potentials.For 14 neotropical pioneer species, the hypothesis is tested that small-seeded species, with shallow initial rooting depths, reduce the risks associated with desiccation by germinating more slowly and at higher water potentials than large-seeded species.Germination occurred both more quickly and at lower water potentials with increasing seed mass. For example, Ochroma pyramidale (seed mass 5.5 mg) had a time to 50 {\%} germination (T-50) of 2.8 d and a median base potential for germination (psi(b50)) of -1.8 MPa while Clidemia quinquenervia (seed mass 0.017 mg) had a T-50 of 17.6 d and psi(b50) of -1.1 MPa.These data suggest that small-seeded species germinate only in comparatively moist microsites, such as small canopy gaps, which may reduce the risk of drought-induced mortality. Conversely, large-seeded species are able to germinate in the drier environment of large gaps, where they benefit by enhanced seedling growth in a high irradiance environment. The positive association of seed size and canopy gap size for optimal seedling establishment is maintained by differential germination responses to soil water availability coupled with the scaling of radicle growth rate and seed size, which collectively confer greater drought tolerance on large-seeded species.",
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T1 - Germination Responses to Water Potential in Neotropical Pioneers Suggest Large-seeded Species Take More Risks

AU - Daws, Matthew I.

AU - Crabtree, Lora M

AU - Dalling, James W.

AU - Mullins, Christopher

AU - Burslem, David Francis Robert Philip

PY - 2008/12

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N2 - In neotropical forests, very small-seeded pioneer species (< 0.1 mg seed mass) recruit preferentially in small tree fall gaps and at gap edges, but large-seeded pioneers do not. Since water availability is related to gap size, these differences in microsite preference may reflect in part species-specific differences in germination at reduced water potentials.For 14 neotropical pioneer species, the hypothesis is tested that small-seeded species, with shallow initial rooting depths, reduce the risks associated with desiccation by germinating more slowly and at higher water potentials than large-seeded species.Germination occurred both more quickly and at lower water potentials with increasing seed mass. For example, Ochroma pyramidale (seed mass 5.5 mg) had a time to 50 % germination (T-50) of 2.8 d and a median base potential for germination (psi(b50)) of -1.8 MPa while Clidemia quinquenervia (seed mass 0.017 mg) had a T-50 of 17.6 d and psi(b50) of -1.1 MPa.These data suggest that small-seeded species germinate only in comparatively moist microsites, such as small canopy gaps, which may reduce the risk of drought-induced mortality. Conversely, large-seeded species are able to germinate in the drier environment of large gaps, where they benefit by enhanced seedling growth in a high irradiance environment. The positive association of seed size and canopy gap size for optimal seedling establishment is maintained by differential germination responses to soil water availability coupled with the scaling of radicle growth rate and seed size, which collectively confer greater drought tolerance on large-seeded species.

AB - In neotropical forests, very small-seeded pioneer species (< 0.1 mg seed mass) recruit preferentially in small tree fall gaps and at gap edges, but large-seeded pioneers do not. Since water availability is related to gap size, these differences in microsite preference may reflect in part species-specific differences in germination at reduced water potentials.For 14 neotropical pioneer species, the hypothesis is tested that small-seeded species, with shallow initial rooting depths, reduce the risks associated with desiccation by germinating more slowly and at higher water potentials than large-seeded species.Germination occurred both more quickly and at lower water potentials with increasing seed mass. For example, Ochroma pyramidale (seed mass 5.5 mg) had a time to 50 % germination (T-50) of 2.8 d and a median base potential for germination (psi(b50)) of -1.8 MPa while Clidemia quinquenervia (seed mass 0.017 mg) had a T-50 of 17.6 d and psi(b50) of -1.1 MPa.These data suggest that small-seeded species germinate only in comparatively moist microsites, such as small canopy gaps, which may reduce the risk of drought-induced mortality. Conversely, large-seeded species are able to germinate in the drier environment of large gaps, where they benefit by enhanced seedling growth in a high irradiance environment. The positive association of seed size and canopy gap size for optimal seedling establishment is maintained by differential germination responses to soil water availability coupled with the scaling of radicle growth rate and seed size, which collectively confer greater drought tolerance on large-seeded species.

KW - tropical forest

KW - gao size

KW - seedling establishment

KW - dessication tolerance

KW - soil

KW - temperature

KW - plants

KW - trees

KW - regeneration

KW - persistence

KW - germination

KW - seed size

KW - Panama

KW - neotropical

KW - pioneer

KW - water potential

U2 - 10.1093/aob/mcn186

DO - 10.1093/aob/mcn186

M3 - Article

VL - 102

SP - 945

EP - 951

JO - Annals of Botany

JF - Annals of Botany

SN - 0305-7364

IS - 6

ER -