Seed Technology An International Journal Serving Seed Scientists and Technologists
Volume 28, Number 1 • 2006
Published jointly by:
Association of Official Seed Analysts Society of Commercial Seed Technologists Editor: Wayne R. Guerke Georgia Department of Agriculture P.O. Box 1507, 3150 U.S. Hwy. 41 South Tifton, GA 31793-1507 USA Associate Editors: Sabry Elias, Oregon State University, Corvallis, OR, USA Tim Loeffler, Seminis, Inc., Oxnard, CA, USA Miller McDonald, Jr., The Ohio State University, Columbus, OH, USA Deborah Meyer, California State Seed Laboratory, Sacramento, CA, USA Amanda Patin, Mid-West Seed Svcs., Brookings, SD, USA Fawad Shah, Washington State Dept. of Agriculture, Yakima, WA, USA Dennis TeKrony, University of Kentucky, Lexington, KY, USA Denise Thiede, BioDiagnostics, River Falls, WI, USA Michael Thompson, BioDiagnostics, River Falls, WI, USA Richard Vierling, Indiana Crop Improvement Assn., Lafayette, IN, USA
issn: 1096-0724
Printed in the USA by Allen Press, Lawrence, KS
Germination Properties of Some Wild Medicinal Plants from Iran Mohammad Bannayan,* Farsad Nadjafi, Mehdi Rastgoo and Leila Tabrizi ABSTRACT Germination properties, including germination rate, germination percentage and cardinal temperatures, of eight wild medicinal species from Iran were studied. The seeds of the eight medicinal plants were exposed to germination temperature treatments ranging from of 5 to 35 °C consisting of seven constant and three alternating temperature regimes. A linear model was applied to describe the germination rate-temperature relationship. The species studied using constant germination temperatures showed the highest germination percentages in the range of 20–30 °C for Nepeta binaludensis and Nepeta crassifolia, 15–20 °C for Zataria multiflora, 20–25 °C for Nepeta glomerulosa, 25–30 °C for Dysphania botrys and 15–30 °C for Thymus kotschyanus, Rubia tinctorum and Achillea millefolium ssp. elburensis. The highest germination percentage and germination rate were observed at alternating temperatures of 20–30 °C for Nepeta binaludensis, 10–20 °C for Zataria multiflora, Thymus kotschyanus, Nepeta glomerulosa and Nepeta crassifolia, and, 10–20, 20–30 °C, for Dysphania botrys. The various species showed clear differences in the temperature requirements of their seed for germination. Both germination percentage and rate were higher at constant than alternating temperatures. The highest base (Tb °C) and optimum temperatures (To °C) were observed in Dysphania botrys, while the highest critical temperature (Tc °C) was recorded for Rubia tinctorum. There was a positive linear relation between temperature at which the highest germination percentage was obtained at To , but this relationship was negative for Tb. INTRODUCTION
Due to over-exploitation and habitat degradation, a number of wild medicinal and aromatic plants are facing possible extinction. The mounting demand for these plants necessitates domesticating and propagating them on a large scale (Lambert et al., 1997; Pushpangadan, 1992). Cultivation is frequently advocated as a measure to remove pressure from wild stocks, especially for species collected in large quantities for trade (FAO, 1998; Lange and Schippmann, 1996). Over 8000 species of higher plants have been recorded in Iran (FAO, 1999), and nearly 13% of these are reported to have medicinal value (Bagheri and Reghan 1994). The wide array of medicinal plants requires many different techniques for production, harvesting and storage, yet the requirements of these species are poorly documented and often unsuccessful (Uniyal, et al., 2000). To increase the success rate and reduce the cost of restoration Mohammad Bannayan, Farsad Nadjafi, Mehdi Rastgoo and Leila Tabrizi, Ferdowsi University of Mashhad, School of Agriculture, P. O. Box 91775-1163, Mashhad, Iran; Mohammad Bannayan, Present address: Biological and Agricultural Engineering Department, University of Georgia, Griffin, GA 30223, USA. *Corresponding author (
[email protected]). Received 25 January 2006.
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operations, it is essential to have a good understanding of their germination requirements (Sy et al., 2001). Temperature can affect the percentage and rate of germination (Roberts, 1988). Therefore, the objective of this paper was to characterize the germination properties of some medicinal species to facilitate their potential cultivation and propagation. MATERIALS AND METHODS The mature seeds of eight wild medicinal species, including Nepeta binaludensis Jamzad, Nepeta glomerulosa Boiss., Nepeta crassifolia Boiss. & Buhse, Zataria multiflora Boiss., Thymus kotschyanus Boiss. & Hohen., Dysphania botrys (L.) Mosyakin & Clemants, Rubia tinctorumu L. and Achillea millefolium L. ssp. elburensis Hub.-Mor. were collected in 2003 from their natural habitats in Iran. After collection, immature and insect-damaged seeds were removed. Seeds were surface sterilized by soaking in 1% sodium hypochlorite (NaOCl) for 5 min and subsequently thoroughly rinsed with sterilized water. All germination experiments were conducted using three replicates of 50 seeds for each treatment. Seeds were placed on double layered Whatman no.1 filter paper moistened with 5 ml distilled water in sterilized petri dishes. The effects of seven constant temperatures, including 5, 10, 15, 20, 25, 30 and 35 °C and three alternating temperatures, including 5–15, 10–20 and 20–30 °C were studied using dark germinators with 70–75% relative humidity for 21 d. Due to the scarcity of Achillea millefolium ssp. elburensis seeds, alternating temperatures were not applied to this species. Germinated seeds were counted and removed every 24 h. A seed was considered germinated when the tip of the radicle had grown free of the seed coat (Auld, et al., 1988; Wiese and Binning, 1987). If no seed germinated for three consecutive d, the test was terminated. The germination rate was calculated according to Burget and Burnside (1972) as follows: Germination rate = Germination % /Length of test (d) After Arcsin transformation, the percentage of germination was subjected to an analysis of variance. The data were analyzed by a randomized complete design with three replications and means separated using Duncan’s new multiple range test (LSR). The following linear model (Summerfield et al., 1991) was used to calculate the cardinal temperatures. f = B (T – Tb ) if: T < To f = C (Tc – T) if: T > To Where f is the daily development rate (per d), T is the temperature in °C (Tb < T
