|Abstract or Summary
- Meadowfoam (Limnanthes spp.) is a potential oil seed
crop being developed for commercial production in the
Willamette Valley. The seeds are characterized by poor
germination at warm temperatures. It would be desirable
to overcome this temperature-related dormancy problem so
that better stand establishment could be realized from
early fall planting.
The objectives of this study were to determine the
factors influencing seed germination of meadowfoam,
characterize the types of dormancy involved, and develop
methods of overcoming dormancy.
Experiments were carried out with different-aged seed
lots of L. alba 'Mermaid,' L- floccosa Howell and a cross
of L. floccosa x L.. alba. Germination requirements were
investigated by studying seed responses to temperature,
light, oxygen, growth regulators, scarification, and
chemical inhibitors. The most favorable germination temperatures were 10,
5-15 and 10-20°C. No germination occurred above 20°C.
Prechilling 5 days at 5°C promoted germination at higher
temperatures. Potassium and thiourea effectively promoted
germination, while kinetin, gibberellic acid and ethephon
did not. Daily 8-h exposures to light inhibited
germination, particularly at the warmer temperatures.
Increasing the length of the daily light periods resulted
in corresponding decreases in germination. Removal of
portions of the seed coat improved germination, as did
germination at higher concentrations of oxygen. The seed
coat was not a barrier to water uptake by dormant seeds.
Water-soluble extracts from the seeds inhibited
germination of non-dormant seeds.
A number of treatments imposed on meadowfoam seed
overcame dormancy partially or fully, suggesting that
there are several mechanisms regulating seed dormancy.
Evidence from this study suggests that the seed coat is
partially responsible, acting as a barrier to diffusion of
oxygen and because it is a source of germination
inhibitors. Embryo dormancy is also implicated, in that
seeds responded to treatment with potassium nitrate. For
routine germination testing of meadowfoam, it is
recommended that seeds be planted on a substrate moistened
with 1 g L⁻¹ KNO₃ and placed in the dark at 10°C for 14 days. If circumstances warrant, additional germination
of dormant seed lots can be obtained by germination on
substrate of KNO₃ in an atmosphere of 100% O₂.