Using semi-natural and simulated habitats for seed germination ecology

Simon Kallow1,2,3*, Katrijn Quaghebeur2,3, Bart Panis2,4, Steven B. Janssens3,5, John Dickie1, Lavernee Gueco6, Rony Swennen2,7, Filip Vandelook3
1 Royal Botanic Gardens Kew, Millennium Seed Bank, Wakehurst, Ardingly, Sussex, RH17 6TN, UK
2 Katholieke Universiteit Leuven, Department of Biosystems, Willem de Croylaan 42, 3001, Leuven, Belgium
3 Meise Botanic Garden, Nieuwelaan 38, 1860 Meise, Belgium
4 Bioversity International, Willem de Croylaan 42, 3001, Leuven, Belgium
5 Katholieke Universiteit Leuven, Biology Department, Kasteelpark Arenberg 31, 3001 Leuven, Belgium
6 National Plant Genetic Resources Laboratory, Institute of Plant Breeding, College of Agriculture and Food Science, University of the Philippines, Los Baños, 4031 Laguna, Philippines
7 International Institute of Tropical Agriculture, c/o Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania
Corresponding author: Simon Kallow (S.Kallow@kew.org)
Running title: Seed ecology in non-natural habitats
Word count: 6821

Keywords

Botanic gardens, crop wild relatives, gap detection, seed germination

Abstract

  1. Ecologically meaningful seed germination experiments are constrained by access to seeds and relevant environments for testing at the same time. This is particularly the case when research is carried out far from the native area of the studied species.
  2. Here, we demonstrate an alternative - the use of glass houses in botanic gardens as simulated-natural habitats to extend the ecological interpretation of germination studies. Our focal taxa were banana crop wild relatives (Musa acuminata subsp. burmannica, M. acuminata subsp. siamea and M. balbisiana ), native to tropical and subtropical Southeast Asia. Tests were carried out in Belgium, where we performed germination tests in relation to exposure to sun and foliage-shading, seed burial-depth in different heated glass house compartments, as well as seed survival and dormancy release in the soil. We anchored the interpretation of these studies by also conducting an experiment in a semi-natural habitat in the species native range (M. balbisiana - Los Baños, the Philippines), where we tested germination responses to exposure to the sun and shade. Using temperature data loggers, we determined temperature dynamics suitable for germination in both these settings.
  3. In semi-natural and simulated-natural habitats, seeds germinated in response to exposure to direct solar radiation. Seed burial-depth had a significant but marginal effect by comparison, even when seeds were buried to 7cm in the soil. Temperatures at sun-exposed compared to shaded environments differed by only a few degrees Celsius. Maximum temperature of the period prior to germination was the most significant contributor to germination responses and germination increased linearly above a threshold of 23°C to the maximum temperature in the soil (in simulated natural habitats) of 35°C.
  4. Glass houses can provide useful environments to aid interpretation of seed germination responses to environmental niches.

Introduction

Ideally, seed germination ecology studies are carried out in both natural habitats (NHs) and laboratory conditions (LCs) (Baskin & Baskin 2014). This allows variables affecting germination to be clearly identified and ecologically interpreted. Interpretation is usually made in relation to spatial and temporal niches in NHs, or perhaps semi-natural habitats (Semi-NHs) (Table 1).
Table 1. Descriptions of environments for seed germination studies.