The Urticaceae comprise about 500 species of herbaceous plants, shrubs, and trees within about 40 genera, of which Boehmeria nivea (L.) Gaud. (ramie) is grown for fibre and Urtica spp. provide leaf vegetables or flavourings. The fruits are usually dry, small, achenes and are likely to be enclosed within the calyx. Seed storage behaviour is orthodox. For example, Boehmeria polystachya and Urtica pilulifera are maintained in the long-term seed store at the Wakehurst Place Gene Bank.
SEED DORMANCY AND GERMINATION
Detailed information on seed dormancy and germination in the Urticaceae is limited to the genus Boehmeria including synonyms within Urtica). In order to develop techniques for difficult accessions, the RBG Kew Wakehurst Place suggests, as a first step, testing seeds at a constant temperature of 16°C with light applied for 12h/d. If this regime is unsatisfactory, then experiment with further treatments. Clues to likely promotory treatments can be obtained from the information on Boehmeria.
BOEHMERIA
|
B. nivea Gaud. [Urtica niveaL.] |
ramie, rhea, China grass |
I. Evidence of dormancy
Seeds of B. nivea are reported to exhibit dormancy (2).
II. Germination regimes for non-dormant seeds
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III. Unsuccessful dormancy-breaking treatments
Light: dark (2)
IV. Partly-successful dormancy-breaking treatments
Light: white, at 25°C (2)
GA3: co-applied, 100 ppm (2)
V. Successful dormancy-breaking treatments
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VI. Comment
Germination of seeds of B. nivea requires light (2), but treatment with gibberellins appears to substitute for the light requirement and promote germination in the dark (2). It is suggested that the seeds of Boehmeria spp. be tested for germination on top of filter papers in petri dishes (1,2) at a constant temperature of 25°C in diffuse light - see Chapter 6. Seeds should begin to germinate within about 4 days and germination may be complete after 21 days (1). It is suggested that co-application of gibberellins at a low concentration (see above) be used as an additional stimulus to germination when required.
VII. References
1. Fierro, A.F. and Redondo, B.D.A. (1980). [Evaluation of 3 methods of propagating ramie for agro industrial use.] Acta Agronomica, 30, 99-109.
2. Nakamura, S., Watanabe, S. and Ichihara, J. (1960). Effect of gibberellin on the germination of agricultural seeds. Proceedings of the International Seed Testing Association, 25, 433-439.
