Vincent S Pan1,2, Cecilia Girvin1, Eric F LoPresti1. 1. Department of Plant Biology, Ecology, and Evolution, Oklahoma State University, 421 Physical Sciences, Stillwater, OK, USA. 2. Department of Integrative Biology, Michigan State University, 288 Farm Lane, East Lansing, MI, USA.
Abstract
BACKGROUND AND AIMS: Seed mucilage is a common and highly diverse trait shared among thousands of angiosperm species. While it has long been recognized that mucilage allows seeds to anchor to substrates (antitelechory), resisting abiotic and biotic dislodgement, we still lack a mechanistic understanding of this process. METHODS: We propose a mechanistic model of how mucilage affects substrate anchorage and fluid resistance, ultimately contributing to dislodgement resistance. To test this model, we subjected mucilaginous seeds of 52 species, varying in eight measured seed traits, to 7 d of continuous water flow at a range of dislodgement potentials. KEY RESULTS: Supporting our model, mucilage mass increased the force necessary to dislodge both dry and wet seeds; our measurement of the dislodgement force of dry mucilage explained time to dislodgement well. The effect size was remarkably large; increasing the standardized mucilage mass by 1 s.d. resulted in a 280-fold increase in the time to dislodgement. Fluid resistance was largely dependent on the speed of water flow and the seed's modified drag coefficient, but not seed traits. Neither mucilage expansion speed nor mucilage decay rate explained dislodgement potential well. CONCLUSIONS: Our results suggest that the degree of anchorage to a substrate, measured with a simple dislodgement force assay, is highly predictive of mucilaginous seed retention in highly erosive environments. In contrast, we found that other seed and mucilage traits are of lesser importance to anchorage.
BACKGROUND AND AIMS: Seed mucilage is a common and highly diverse trait shared among thousands of angiosperm species. While it has long been recognized that mucilage allows seeds to anchor to substrates (antitelechory), resisting abiotic and biotic dislodgement, we still lack a mechanistic understanding of this process. METHODS: We propose a mechanistic model of how mucilage affects substrate anchorage and fluid resistance, ultimately contributing to dislodgement resistance. To test this model, we subjected mucilaginous seeds of 52 species, varying in eight measured seed traits, to 7 d of continuous water flow at a range of dislodgement potentials. KEY RESULTS: Supporting our model, mucilage mass increased the force necessary to dislodge both dry and wet seeds; our measurement of the dislodgement force of dry mucilage explained time to dislodgement well. The effect size was remarkably large; increasing the standardized mucilage mass by 1 s.d. resulted in a 280-fold increase in the time to dislodgement. Fluid resistance was largely dependent on the speed of water flow and the seed's modified drag coefficient, but not seed traits. Neither mucilage expansion speed nor mucilage decay rate explained dislodgement potential well. CONCLUSIONS: Our results suggest that the degree of anchorage to a substrate, measured with a simple dislodgement force assay, is highly predictive of mucilaginous seed retention in highly erosive environments. In contrast, we found that other seed and mucilage traits are of lesser importance to anchorage.
Authors: Amy E Zanne; David C Tank; William K Cornwell; Jonathan M Eastman; Stephen A Smith; Richard G FitzJohn; Daniel J McGlinn; Brian C O'Meara; Angela T Moles; Peter B Reich; Dana L Royer; Douglas E Soltis; Peter F Stevens; Mark Westoby; Ian J Wright; Lonnie Aarssen; Robert I Bertin; Andre Calaminus; Rafaël Govaerts; Frank Hemmings; Michelle R Leishman; Jacek Oleksyn; Pamela S Soltis; Nathan G Swenson; Laura Warman; Jeremy M Beaulieu Journal: Nature Date: 2013-12-22 Impact factor: 49.962