The relationship between seed mass and mean time to germination for 1037 tree species across five tropical forests

Abstract

Summary 1.Theoretical models predict that large-seeded species should germinate more rapidly than smallseeded species, since large seeds are more likely to have higher post-dispersal seed predation than small seeds. A prompt germination strategy would therefore enable large seeds to reduce risks of mortality. 2. To assess this predicted relationship between seed mass and mean time to germination (MTG), we used a meta-analysis of published data sources. Our data base contained information for these two traits for 1037 tree species from five tropical areas worldwide (Brazil, India, Ivory Coast, Malaysia and Panama). Both cross-species analyses and phylogenetically independent contrasts (PIC) were conducted on the log-transformed values of seed mass and MTG. 3. Log-seed mass was a significantly phylogenetically conserved trait in all five data sets. Log-MTG was significantly phylogenetically conserved in all sites except for Malaysia and India. 4. Log-MTG and log-seed mass were significantly positively correlated in all sites except for Malaysia. PIC analyses showed a significantly positive relationship in Brazil, India and Ivory Coast but not in Malaysia and Panama. When all sites were combined, PIC analyses indicated a significant positive relationship between these two traits. 5. Our findings do not support the hypothesis that large seeds germinate faster than small seeds, but rather that small seeds germinate faster. We interpret our results in light of phylogenetic and biophysical constraints. We propose four alternative mechanisms that could account for the observed pattern, including developmental constraints, water absorption and investment to physical defences.

Limites térmicos para a germinação em função da origem de sementes de espécies de Eugenia (Myrtaceae) nativas do Brasil

“…Estudos com sementes de Aesculus hippocastanum L. e Acer pseudoplatanus L. coletadas em diferentes localidades demonstraram que há estreita relação entre as fl utuações térmicas e a temperatura basal e, também, entre o somatório de GD e o aumento de massa seca (Daws et al 2004;. Há, ainda, relação entre a massa seca e a velocidade de germinação (Norden et al 2009). Os resultados apresentados por Daws et al (2004;, associados com os resultados apresentados pelas sementes de Eugenia pyriformis neste trabalho, demonstram que as condições ambientais, principalmente a temperatura do ar, exercem grande infl uência nas características germinativas das sementes.…”

phenoSeeder - A Robot System for Automated Handling and Phenotyping of Individual Seeds

“…This might be true even when considering that the type of reserves, such as proteins, carbohydrates, or lipids (Rolletschek et al, 2015), and also different seed tissues, such as seed coat, embryo, or endosperm, may contribute differently to seed mass (Alonso-Blanco et al, 1999). While seed mass and time to germination (radicle protrusion) do not necessarily correlate (Norden et al, 2009), in particular under greenhouse conditions, higher seed mass may be advantageous for seedling establishment under adverse environmental conditions (Moles et al, 2005). For example, shade-tolerant species showed largely higher seed masses than cogeneric species growing in open habitats, indicating that seedlings under low-light conditions need more reserves than under good light (Salisbury, 1974).…”

Towards an Understanding of Factors Controlling Seed Bank Composition and Longevity in the Alpine Environment

“…The relatedness of taxa in alpine systems therefore has the potential to explain some of the variation in seed size and morphology, dispersal strategy, dormancy mechanisms and response to germination cues, all of which affect the composition of seed banks. Links between phylogeny and traits affecting seed bank membership have been made in temperate systems (Mazer 1989;Leishman et al, 1995), tropical communities (Norden et al, 2009) and alpine/subalpine vegetation (Bu et al, 2007a;Bu et al, 2008;Xu et al, 2014;Zhang et al, 2004). More generally, Finch-Savage and Leubner-Metzger (2006) highlight the common evolutionary path for dormancy that means it is present throughout the higher plant families with only a few exceptions, and in all major climate zones.…”