Seed ecology of dust seeds in situ: a new study technique and its application in terrestrial orchids

Abstract

A method is described by which seeds of terrestrial orchids are sown and retrieved in the field under almost natural conditions. For the first time it is possible to conduct a quantitative study of orchid germination in situ and observe seasonal growth and mortality of seedlings. The technique has also enabled us to investigate the relation between the site where the seeds are sown, the availability of an appropriate fungus to infect the seeds, and seedling establishment in the soil. Five local species were studied. Corallorhiza odontorhiza, Goodyera pubescens, and Galearis spectabilis all began to germinate in May–June, after 23‐30 weeks in the soil. These species differed in their dependency on infection at germination time, but none of the seedlings developed beyond the point of rupturing the testa except when infected. Seeds of Liparis lilifolia and Tipularia discolor did not germinate within the first 12 months of the experiment. The implications and potential uses of this field sowing technique for further studies and for other kinds of minute seeds are discussed.

Symbiotic germination and development of the myco‐heterotrophic orchid Neottia nidus‐avis in nature and its requirement for locally distributed Sebacina spp.

“…They were sown into seed packets constructed from photographic slide mounts and plankton netting of 53 µm pore size (Rasmussen & Whigham, 1993). There were c .…”

“…The development of techniques enabling burial and sequential recovery of these minute seeds from defined habitats (Rasmussen & Whigham, 1993;Masuhara & Katsuya, 1994) has greatly increased the potential for systematic analysis of the early critical events in myco-heterotroph development. In an earlier paper we described the use of these techniques to evaluate the factors influencing germination of the achlorophyllous myco-heterotroph Corallorhiza trifida (McKendrick et al , 2000a).…”

Symbiotic germination and development of myco‐heterotrophic plants in nature: ontogeny of Corallorhiza trifida and characterization of its mycorrhizal fungi

“…An in situ method involving burial and sequential harvesting of seeds sealed in mesh ' packets ' has been employed successfully by Rasmussen & Whigham (1993) who obtained up to 48% germination in the MHP Corallorhiza odontorhiza depending on site, and 31% in the IMHP Goodyera. Using a similar method Masuhara & Katsuya (1994) obtained c. 40% germination in the IMHP Spiranthes sinensis.…”

“…The nylon was folded once and clipped into 2i2i36 mm plastic glassless slide mounts (Rasmussen & Whigham, 1993). A length of coloured nylon cord was attached to each mount to facilitate detection and removal of the packet.…”

Experimental reintroduction of the threatened terrestrial orchid Diuris fragrantissima

“…Ten of the sampled plants were reintroduced with additional inoculum and ten were reintroduced with only the fungi present in the roots at the time of planting. Seed baiting was also conducted (following Rasmussen and Whigham 1993) to determine whether fungi persisted in soil one year after reintroduction in association with host orchids and alone.…”