1998; Baskin and Baskin, 1998) and Storage Effects on Dormancy and Germination harvest season (Norcini et al., 2004, of Native Tickseed Species 2006). One aspect of seed quality that can vary is the percentage of dormant seeds. Although seed laws in some Jeffrey G. Norcini1 and James H. Aldrich states allow dormant seeds to be included in minimum germination specifications, those using seeds in ADDITIONAL INDEX WORDS. after-ripen, Coreopsis, ecotype, Florida, seed, native wildflower, native forb nonarid regions typically desire a high percentage of nondormant seeds to SUMMARY. Fresh seeds of prevariety germplasms of goldenmane tickseed (Coreopsis facilitate quick stand establishment. basalis), florida tickseed (Coreopsis floridana), lanceleaf tickseed (Coreopsis As the length of time over which lanceolata), and leavenworth’s tickseed (Coreopsis leavenworthii) were harvested wildflower seedlings emerge increases, from cultivated plants and stored under dry conditions for 1 to 24 weeks at 15 or there is a greater likelihood that weeds 32 C to alleviate dormancy, that is, to promote after-ripening. The relative humidity (RH) was 33% for all species except lanceleaf tickseed (23% RH). Seeds were will interfere with stand establish- subsequently stored for 24 weeks in a commercial storage facility at 23% RH/17 to ment. Weed interference is one of 19 C to determine whether after-ripened seeds could be stored without loss in the major reasons that wildflowers quality (viability, germination velocity). The only substantial after-ripening stands fail to establish (Doubrova, occurred with seeds of lanceleaf tickseed, although most after-ripening of lanceleaf 1979). tickseed seeds occurred during the 24 weeks of dry storage in the commercial storage Seed dormancy of commercially facility regardless of storage conditions for the previous 24 weeks. After the produced, prevariety germplasm of 24 weeks in commercial storage, germination of lanceleaf tickseed seeds was 48% native wildflower species is more to 80%, but germination was only 2% to 15% after 24 weeks of dry storage at 15 likely to be an issue than for their or 32 C, respectively. Freshly harvested seeds of the other three species were domesticated varieties as Takahashi much more nondormant than seeds of lanceleaf tickseed, but after-ripening effects were still evident because there were increases in germination or germination (1984) concluded for wild and velocity (an indicator of after-ripening). Maintenance of seed quality was domesticated rice (Oryza spp.). In species-dependent. Seed quality of the two upland species, goldenmane tickseed and domesticated flower seed crops, any lanceleaf tickseed, was maintained during the initial 24 weeks of dry storage plus minimal amount of dormancy that the subsequent 24 weeks in the commercial storage facility. In contrast, viability occurs is easily overcome by typical of seeds of the two wetland species, florida tickseed and leavenworth’s tickseed, dry storage conditions used by flower declined to varying degrees either during the initial 24 weeks of after-ripening or seed producers (Geneve, 1998), a during storage in the commercial facility. The greatest decline in quality occurred process referred to as after-ripening. for florida tickseed seeds that were stored for 24 weeks at 32 C and then for Flower seed producers must ensure 24 weeks in the commercial storage facility. their customers, especially plug pro- ducers, that nearly every sown seed verthepast10to20years, western United States (Booth and will germinate within a short period production of prevariety germ- Jones, 2001; Houseal and Smith, of time. Although the end users of Oplasm of native wildflower 2000). Production in the southeast- prevariety germplasm of native wild- seeds has risen dramatically in response ern United States is mainly in Florida flower seeds do not have such strict to the demand for site- or regionally with one full-time grower and 18 germination requirements, relatively specific ecotype seeds for roadside part-time growers. Native ecotype high germination percentages are plantings as well as for ecological wildflower seed production began in very important as noted previously. restoration and revegetation projects Florida in the late 1990s. To the best We are not aware of any published (Booth and Jones, 2001; Harper- of our knowledge, there is only one study in which after-ripening has Lore and Wilson, 1999; Houseal commercial native wildflower seed been formally investigated as a means and Smith, 2000). Researchers and producer each in North Carolina of alleviating dormancy of prevariety practitioners realize that survival, and Alabama. germplasm of native wildflower seeds growth, and flowering of native wild- One challenge facing the indus- produced under cultivated conditions. flower species can be strongly affected try is seed quality, which can often Moreover, research involving by seed origin (Marois and Norcini, vary within a species and even by seed factors that affect seed quality of 2003; Norcini et al., 1998, 2001). origin (Andersson and Milberg, commercially produced, prevariety Demand for prevariety germplasms is being met by a niche industry that is primarily in the midwestern and Units To convert U.S. to SI, To convert SI to U.S., University of Florida, Institute of Food and Agricul- multiply by U.S. unit SI unit multiply by tural Sciences, North Florida Research and Education Center, 155 Research Road, Quincy, FL 32351 29.5735 fl oz mL 0.0338 We thank the Florida Wildflower Advisory Council 3.7854 gal L 0.2642 and Woodhaven Farms, Havana, FL. In addition, we 2.5400 inch(es) cm 0.3937 gratefully acknowledge Ramon Littell for his assis- 25.4000 inch(es) mm 0.0394 tance with the statistical analyses and Barron Riddle, 0.5933 lb/yard3 kgÁm–3 1.6856 Amanda Brock, and Rebecca Riddle for their technical 1 ppm mgÁL–1 1 assistance. ( F – 32) O 1.8 F C (1.8 · C) + 32 1Corresponding author. E-mail: wldflowr@ufl.edu. ( F O 1.8) + 255.37 F K (K – 255.37) · 1.8
• October–December 2007 17(4) 505 RESEARCH REPORTS germplasms is very limited. Nearly all occurs throughout most of the Savage and Leubner-Metzger, 2006). work has centered on ecology of seeds United States, the main exception However, after-ripened seeds might harvested directly from natural stands being the Rocky Mountain states not be sold immediately and would (Baskin and Baskin, 1998). Germina- (USDA, 2006b). The range of this have to be stored. Thus, we also tion and dormancy characteristics of upland species extends southward assessed germination, germination seeds harvested from commercial pro- into central Florida (Wunderlin and velocity, and viability for seeds that duction plots could be substantially Hansen, 2004a). In Florida, lanceleaf had been subjected to dry conditions different from those of seeds har- tickseed is a low-growing, spring- and subsequently stored in a com- vested from natural stands. Under blooming, short-lived perennial. Seed mercial native wildflower seed pro- commercial production conditions, production of goldenmane tickseed, ducer’s cool storage facility. water and nutrition usually are much also an upland species, occurs mainly less limiting compared with natural in Texas and Florida, although gold- Materials and methods conditions, and both factors can enmane tickseed occurs from Texas to SEED ORIGIN. Achenes (hereafter influence germination and dormancy North Carolina and even in Illinois referred to as seeds) of goldenmane (Fenner, 1991; Roach and Wulff, and Connecticut (USDA, 2006c). tickseed and lanceleaf tickseed were 1987). We have noted that freshly This spring-blooming annual, like obtained from Wildflowers of Florida harvested seeds of prevariety germ- lanceleaf tickseed, ranges into central (Alachua, FL) The grower harvested plasms of two native tickseed species Florida (Wunderlin and Hansen, Generation 0 (G0) seeds of golden- grown under cultivated conditions 2004b). Leavenworth’s tickseed cur- mane tickseed from a naturally occur- can possess varying levels of dor- rently is only produced in Florida. It ring population in Suwannee County, mancy. Viable seeds of lanceleaf tick- is nearly endemic to Florida (USDA, FL [American Horticultural Society seed harvested early in the summer 2006d) with the only populations (AHS) Heat Zone 10, USDA Hardi- were nearly 80% dormant, but seeds documented outside of Florida ness Zone 9b]. The origin of lanceleaf harvested later that year were only occurring in two Alabama counties tickseed was a composite of seeds 50% dormant (Norcini et al., (M. Nishino, personal communica- collected in 1996 and 1997 from 2004). Commercially produced leaven- tion). Leavenworth’s tickseed, a fac- natural upland populations located worth’s tickseed harvested in early ultative wetland species that occurs mainly in Leon and Wakulla Coun- Summer 2001 and 2002 were nearly in most Florida counties (Wunderlin ties, FL (both AHS Heat Zone 9 and all dormant (Kabat, 2004). In con- and Hansen, 2004c), tends to be an USDA Hardiness Zone 8b) with trast, seeds of the same prevariety annual in northern Florida and a some seeds from populations in germplasm harvested from container- short-lived perennial in central and Gadsden and Jefferson Counties, FL ized plants exhibited less than 18% southern Florida (authors’ unpub- (both AHS Heat Zone 9 and USDA dormancy (Norcini et al., 2006). lished observations; N. Bissett, per- Hardiness Zone 8b). These G0 seeds Seeds of a prevariety germplasm sonal communication). Flowering were used to establish a seed increase of native tickseeds (Coreopsis spp., occurs mainly in late spring and sum- plot in 1998 at the North Florida Asteraceae)––a genus distributed mer, but it can occur at any time in Research and Education Center throughout North and South southern Florida. Florida tickseed is a (NFREC) in Monticello (Jefferson America (Smith, 1975; Tadesse fall-flowering, short-lived perennial County, FL; AHS Heat Zone 9, et al., 1995)––are being produced in that is endemic (Wunderlin and Hansen, USDA Plant Hardiness Zone 8b). the United States. Of the 28 species 2004d). This species is classified as Seeds provided to Wildflowers of of tickseeds native to the United a facultative wetland species at the Florida, Inc., were harvested in States [U.S. Department of Agricul- state level but as an obligate wetland 2002. Because lanceleaf tickseed is a ture (USDA), 2006a], ecotype seeds species at the federal level (Wunderlin short-lived perennial, the generation of at least eight species are being and Hansen, 2004d). However, flor- of seeds provided to the grower was commercially produced in the United ida tickseed can be successfully es- not known. Seeds of florida tickseed States based on information in seed tablished under landscape conditions (G1) were harvested from an increase catalogs and Internet sites: golden- (Aldrich et al., 2006). Florida tick- plot at the USDA Plant Materials mane tickseed, lanceleaf tickseed, seed mainly occurs in peninsular Flor- Center in Brooksville, FL (Hernando leavenworth’s tickseed, largeflower ida with sporadic occurrences in the County; AHS Heat Zone 10, USDA tickseed (C. grandiflora), stiff tick- Florida panhandle (Smith, 1976). All Hardiness Zone 9a). The origin of seed (C. palmata), star tickseed four of these species are self-incom- florida tickseed was Polk County, FL (C. pubescens), tall tickseed (C. tripte- patible (Smith, 1982). (ASH Heat Zone 11, USDA Hardi- ris), and whorled tickseed (C. verti- In this study, we evaluated ness Zone 9a). Leavenworth’s tick- cillata). Seeds of three other species, changes in germination, germination seed originated (G0) in Orange coastal plain tickseed (C. gladiata), velocity, and viability of seeds of County, FL (AHS Heat Zone 10, florida tickseed, and sickle tickseed prevariety germplasms of these four USDA Hardiness Zone 9b); seeds in (C. falcata), are being increased with native tickseed species when freshly this study (G1) were harvested in the intention of getting them into harvested seeds from cultivated plants 2001 from a production population large-scale seed production within were stored under dry conditions that in Pasco County, FL (AHS Heat the next few years (M. Fiely, personal might result in after-ripening. Germi- Zone 10, USDA Hardiness Zone 9a). communication). The most common nation velocity was evaluated because PLANT CULTURE. Plants were species in production seems to be it can increase as seeds after-ripen (El- grown at the NFREC-Quincy (Gads- lanceleaf tickseed. Lanceleaf tickseed Keblawy and Al-Rawai, 2006; Finch- den County, FL; AHS Heat Zone 9,
506 • October–December 2007 17(4) USDA Hardiness Zone 8b). All period in late May/early June 2004 (33% RH; all other species) (Rock- plants were randomly selected from or mid-Nov. 2004 (florida tickseed land, 1960). The seed-filled contain- the median 90% of the respective only). Seeds of each harvest were ers were tightly sealed and incubated seedling populations to adequately stored separately in a desiccator in the dark at 15 or 32 C. The represent the genetic and phenotyp- [23% relative humidity (RH)] at relative humidities and temperatures ical diversity of the source popula- 72 to 78 F for up to 2 weeks until selected were based on previous stud- tions. On 18 Dec. 2003, seeds of all enough seeds for each species had ies (Carpenter and Ostmark, 1992; species were sown on the surface of been harvested to start the storage J.G. Norcini, unpublished data). At flats containing Metro-Mix 200 (The experiment. Seeds of each harvest 1, 2, 4, 12, and 24 weeks, eight 100- Scotts Co., Marysville, OH). They were pooled, by species, because seed samples were removed. Seeds were covered with 1 to 2 mm of there were no differences in viability from four 100-seed samples were Metro-MixÒ 200 and placed in a among the harvests within a species subjected to viability and germination glasshouse on a propagation mat (data not shown). Viability of these testing as previously described. The (ProGrow Supply Corp., Brookfield, fresh seeds was determined by tetra- other four 100-seed samples were WI) that was set at 21 C. Weekly zolium (TZ) testing [1% TZ at 32 C transferred to a commercial wild- fertilization of seedlings with 100 for 24 h in the dark (Grabe, 1970)] flower seed producer’s cool storage mgÁL–1 of N delivered as 15N– of four 50-seed samples. Extracted unit (17 to 19 C, 23% RH) to 13.2P–12.4K liquid fertilizer (15– embryos that were white, turgid, determine whether viability, germina- 30–15; The Scotts Co.) began on 31 and otherwise appeared normal also tion, and germination velocity were Dec. 2003 and continued through 16 were deemed viable as were such affected by 1) 24 weeks of cool, dry Mar. 2003, except for lanceleaf tick- embryos with only faint pink staining storage, and 2) previous dry storage seed and leavenworth’s tickseed. at the radicle end (Dehgan and of seeds at 15 or 32 C for up to Liquid fertilization of these two spe- Norcini, 2006). Four other 50-seed 24 weeks. These conditions are here- cies was halted on 3 Mar. 2003 samples were subjected to germina- after referred to as ‘‘commercial cool, because seedlings were large and they tion testing under an alternating dry storage’’ (CCDS). Germination could not yet be transplanted to large temperature regime of 15/25 C velocity was assessed based on percent containers and placed outdoors [Association of Official Seed Analysts germination at 7 d. We have observed because of potential frost or freeze (AOSA), 1988; Dehgan and Norcini, that the rate of radicle emergence damage. On 15 Jan. 2004, single 2006; Kabat, 2004] or 20/30 C for greater than 1 mm of relatively non- seedlings of all species were trans- lanceleaf tickseed (AOSA, 1988; dormant seed lots is logarithmic 6 planted to cell packs (2.5 fl oz vol- unpublished data). All seeds were to 8 d after seeds were incubated (J. ume, product no. 1204; Cassco, germinated under an 8-h photoper- G. Norcini, unpublished data). After Montgomery, AL). Goldenmane iod with the warmer temperature 24 weeks in CCDS, seeds were sub- tickseed seedlings were transplanted during the lighted period. A seed jected to viability and germination to larger cups (22 fl oz) on 19 Feb. was deemed germinated if the radicle testing as previously described. 2004. On 17 Mar. 2004, single seed- protruded 1 mm or more. Germina- SEED MOISTURE CONTENT. A lings of all species (50 per species, tion was recorded at 7 and 21 d. follow-up study was conducted to except 46 of goldenmane tickseed) All germinated seeds at 7 d were estimate seed equilibrium moisture were transplanted into a soilless sub- removed. We realize that seeds are contents (EMCs). The seeds used in strate in 1-gal containers. The sub- often termed nondormant when they this study were either seeds not used strate was composed of 3/4-inch germinate at high percentages over a in the original study or seeds har- shaker-screened pine bark (Georgia- wide range of temperatures (Baskin vested from container-grown plants Florida Bark & Mulch, Capps, FL), and Baskin, 1998), but germination at the NFREC-Quincy. Seeds (four Canadian sphagnum peat (Berger tests for each species were conducted 100-seed replications) were incu- Peat Moss Inc., St. Modeste, Quebec, under a single temperature regime bated at 15 or 32 C at 23% RH Canada), and rescreened 6B gravel because germination testing of seeds (lanceleaf tickseed) or 33% RH (all (Martin Aggregates, Chattahoochee, over a wide variety of temperature other species) for 2 weeks. Seed mois- FL) at a ratio of 3:1:1 (by volume). regimes was impractical. ture content was then determined Incorporated into this soilless sub- The remaining seeds of each using the low-temperature oven test strate were Osmocote 18N–2.6P– species were subdivided into 100- method (103 C for 17 h) (Interna- 10K (18–6–12; 8- to 9-month for- seed subsamples, each of which were tional Seed Testing Association, mulation at 21 C; The Scotts Co.) placed into small bags (2 · 2 inches) 1985). at 6.0 lb/yard3 and Micromax (The constructed from polypropylene DATA ANALYSIS. Data for all spe- Scotts Co.) at 1.6 lb/yard3. Pots were mesh (35% open area, product no. cies were analyzed separately. Before placed outdoors on a full sun bed that XN-6065; InterNet, Minneapolis, statistical analyses, germination data was covered in black plastic. Daily MN). These bags of seeds were placed were corrected for the fraction of overhead irrigation (pH 7.8) was on top of an elevated fiberglass screen viable seeds based on results of the 0.35 inch to ensure that substrate in 5.1-L polyethylene containers pregermination TZ tests. All germi- moisture was nonlimiting. Contain- (Multipurpose Specimen Storage nation results are expressed as per- ers were hand-weeded as necessary. Container; Fisher Scientific, Pitts- cent germination of viable seeds. SEED HARVEST. Fully mature burgh) that contained solutions of Percentage data were tested for seeds were hand-harvested directly potassium acetate (23% RH; lanceleaf homogeneity of variance and arcsine from mature seed heads over a 2-week tickseed only) or magnesium chloride transformed, if required, before
• October–December 2007 17(4) 507 RESEARCH REPORTS analyses by general linear model GOLDENMANE TICKSEED. Germi- under CCDS were affected by weeks methods of SAS (version 8.01; nation at week 0 was 87.7% (Table 1). of storage or storage temperature SAS Institute, Cary, NC). Data from Despite this relatively high percent as noted previously (Table 1). Germi- the two parts of the study were ana- germination, seeds appeared to nation at 7 d for CCDS seeds ranged lyzed separately to determine tem- undergo after-ripening during dry from 79.2% to 95.6% regardless of perature and week effects on seeds storage, but mainly only for seeds previous storage conditions (Table 2). that had been stored under CCDS for stored for 4 weeks or more at 32 C. However, for non-CCDS seeds, 24 weeks and seeds that had not. Variability in germination data these percentages were only attained Data from both parts of the study precluded detection of a significant after 12 weeks storage at 32 C were pooled to determine main temperature by weeks of storage (Table 1). Hence, 24 weeks of CCDS and interactive effects involving 24 interaction. However, when data for increased germination velocity (an weeks of CCDS (R. Littell, personal 32 C were analyzed, germination indicator of after-ripening) for all seeds communication). Significant week increased linearly over time (adjusted stored at 15 C and for seeds stored effects (P £ 0.05), as well as interac- R2 = 0.187, P < 0.001), peaking at for less than 12 weeks at 32 C. There tions involving weeks with P £ 0.10 99% (Table 1). When percent ger- was also a significant weeks of storage (R. Littell, personal communication), mination data were pooled by tem- by CCDS interaction. Seeds stored were subjected to sequential, regres- perature, there was a quartic response for up to 24 weeks at 15 or 32 C that sion analyses. The quadratic, cubic, or of germination to weeks of storage did not achieve greater than 98% quartic terms were included in the final (adjusted R2 = 0.208, P < 0.001) with germination eventually attained greater model only if their inclusion was sig- a peak germination rate of 98.1% at than 98% germination after 24 weeks nificant at a = 0.05 and the adjusted week 12. When pooled by week, of CCDS. R2 value improved by at least 0.05. germination at 32 C (90.5%) was In summary, it was evident that Comparisons of individual viability, greater than that at 15 C (87.4%) after-ripening was occurring for seeds germination, and 7-d germination (P £ 0.05). After-ripening also was stored at 33% RH and 15 or 32 C. In means to those of fresh seeds (0 weeks) indicated by a cubic response in ger- addition, there was no loss in viability were determined using least squares mination velocity (germination at for up to 48 weeks after harvest, and means analyses [LSMEANS with 7 d) at both temperatures (Table 1). there was no evidence that 24 weeks PDIFF option (SAS version 8.01)]. Although this response varied by of CCDS caused any loss of vigor. A temperature, percent germination at decline in percent germination at 7 d 7 d at 12 and 24 weeks was much would have indicated vigor loss. Car- Results and discussion greater than that at week 0 and even penter and Ostmark (1992) reported SEED MOISTURE CONTENT. Equi- more so at 32 C (Table 1). There was that storage at low temperatures (at librium seed moisture contents of all no loss in viability after 24 weeks of 5 C/10% to 20% RH or 15 C/20% four species under the different stor- storage at either temperature (Table to 35% RH) for 6 months was more age regimes were 7.3% to 8.6% (data 1). Although there was a significant effective at breaking dormancy of not shown). Our results concurred quartic response for weeks of storage, wild-collected tickseed than storage with EMCs of several native tickseed the relationship was very poor and of at a warmer temperature (25 C/11% species incubated at 50% RH/25 C no practical significance. This quartic to 75% RH), which slightly contrasts (D. Rukuni, personal communica- response was an example of a non- with our results. Contrasting results tion). All seeds used by D. Rukuni practical significant effect resulting in dormancy and germination studies were harvested from cultivated plants. from large sample sizes and concom- involving prevariety germplasm are Equilibrium moisture contents itant high number of degrees of free- not surprising because seed quality ranged from 7.2% for florida tickseed dom for some pooled effects characteristics can vary by season and to 9.2% for a North Carolina ecotype combined with the fact that seeds of germplasm source (Fenner, 1991; of lanceleaf tickseed with EMCs all species were of prevariety germ- Roach and Wulff, 1987); moreover, 0.5% to 2% lower at 23% RH. The plasms and presumably were geneti- our results were based on the per- EMCs of the other Florida ecotypes cally and phenotypically diverse. centage of viable seeds and those of used in our study as determined by Because morphological dormancy Carpenter and Ostmark (1992) were D. Rukuni (personal communication) has not been reported in Asteraceae not. were lanceleaf tickseed, 7.9%; golden- (Baskin and Baskin, 1998), observed FLORIDA TICKSEED. Germination mane tickseed, 8.8%; and leaven- viability means greater than those at at week 0 was 95.5% (Table 1). worth’s tickseed, 7.6%. Schu¨tz et al. week 0, or any observed increases in Despite this high percent germina- (2002) concluded that seed moisture viability, were of no practical value. tion, seeds appeared to undergo a contents of 5% to 12% were appro- Seeds that had been stored in very slight after-ripening regardless priate for after-ripening of native CCDS for 24 weeks all exhibited of storage temperature. This slight Australian Asteraceae species that similar viability (greater than 90%), after-ripening effect was evident in grow in a Mediterranean environ- total germination (greater than 95%), the significant quartic response when ment. A similar range for after-ripen- and 7-d germination (greater than percent germination was pooled by ing was reported by Leopold and 79%) regardless of previous storage temperature (Table 1). Germination Vertucci (1989). Hence, EMCs in our conditions (Table 2). These similar- first increased to 100% by week 2, study likely were in the range at which ities resulted in some significant inter- declined to 82.2% at week 4, and then after-ripening under dry conditions actions involving CCDS seeds because slightly increased to 90.4% by week could occur. characteristics of seeds not stored 24. Although 100% germination at
508 • October–December 2007 17(4) week 2 was not significantly greater
0.10. than that at week 0, the significant £
W increase in 7-d germination provides · evidence that after-ripening was Q* (0.109) 0.05 up to and
£ occurring (Table 1). The gradual decline in both germination and ger- |t| of value for T < P mination velocity after week 2 indi- P
NS cated a loss in seed vigor. In addition, vigor loss at 32 C was greater than that at 15 C as indicated by the sharper decline in 7-d germination (Table 1). There was no concomitant decline in viability, because seed via- C only shown when the bility remained constant over the C*** (0.375) 24 weeks regardless of temperature (Table 1). Decline in seed quality occurred ontransformed means are presented. NS ——— — 0.0001 0.0197 0.0487 0.0197 0.0001 0.4338 0.1417 0.4338 0.0001 0.0494 0.0046 0.0494 during CCDS for seeds that previ- < < < ously had been stored at either tem- perature for 4 weeks or more as evidenced by the substantial drop in
v 7-d germination (Table 2). Loss in ot subjected to dry storage conditions. — seed quality was even greater for seeds 0.0001 < that previously had been stored at 32 C for 24 weeks. After 24 weeks in CCDS, seeds that previously had
NS been stored for 24 weeks at 32 C had 0.0001 0.1672 0.0001 0.1557 0.0001 < < < substantially lower viability, germina- tion, and 7-d germination compared with seeds at week 0. In summary, seeds of freshly harvested florida tickseed were nearly 0.0001 < nondormant but seemed to slightly after-ripen during 2 weeks of dry storage. After 2 weeks of dry storage, germination and germination velocity
0.05 (shown in parentheses) than the preceding lowest order model. All models contained components with declined. Loss of vigor below that of ‡ 0.0001 < freshly harvested seed was clearly evi- 0.05, 0.01, or 0.001, respectively, as determined using LSMEANS with the PDIFF option of SAS (version 8.01; SAS Institute, Cary, NC). value
< dent for florida tickseed seeds in 2 P CCDS that previously had been stored for only 4 weeks at 15 C/ F) on percent viability, germination velocity (percent germination at 7 d), and total percent germination (21 d) 0.0001 33% RH. Hence cool, dry conditions < seem to be sufficient for only short- term seed storage, and cold, dry stor- age seems warranted for maintaining seed quality. 0.0001 1. < = No significant linear (L), quadratic (Q), cubic (C), or quartic (Qt) components. Results of regression analyses for 15 and 32 < LANCELEAF TICKSEED. Unlike the NS C (59.0 or 89.6
other three species, seeds of lanceleaf tickseed were nearly dormant at week 0 because germination was less than 2%. A slight after-ripening effect occurred 0.0001 < z of viable of viable of viable of viable of viable of viable of viable of viable 9.0 ± 2.0 90.2 ± 4.2 81.7 ± 1.0 89.4 ± 2.9* 98.3 ± 1.7 96.2 ± 1.3 0but 4.9 ± 1.9* only 87.9 ± 2.1* 81.3for ± 4.1 seeds 84.2 ± 3.8 stored at 32 C
Germination Germination Germination Germination Germination Germination Germination Germination (Table 1). Germination increased lin- x
Goldenmane tickseed Florida tickseed Lanceleaf tickseed Leavenworth’s tickseed early over time with an after-ripening effect first evident at week 12; after
0.0054 24 weeks at 32 C, germination had <
Qt** (0.124) Qt*** (0.208) — C** (0.204) —increased C** (0.204) — to 15.2%. — The lack of a ) are normalized for the percentage of viable seeds based on results of pregermination tetrazolium tests. Data were transformed before analysis but n
y concomitant increase in germination SE F) w w > C) seeds (%) 7 d (%) 21 d (%) seeds (%) 7 d (%) 21 d (%) seeds (%) 7 d (%) 21 d (%) seeds (%) 7 d (%) 21 d (%) C — — C*** (0.374) — Qt* (0.304) — C — — C*** (0.662) — Qt*** (0.854) — C* (0.151) — L*** (0.613) Q*** (0.471) L*** (0.334) L** (0.188) W 0.7762 0.1921 0.0066velocity 0.3932 based 0.0004 on 0.3932 germination at 7 d is P · Temp Viable seeds at seeds at Viable seeds at seeds at Viable seeds at seeds at Viable seeds atnot seeds at surprising given the minor after- 15 Temp (T) 0.3673 0.0072 0.0002 0.3626 0.0052 0.3626 32 T Model Weeks (W) Model ripening effect. Seed viability was the 24 32 32 94.7 ± 1.2 92.5 ± 1.3 1.8 ± 0.9 23.2 ± 3.3 87.6 ± 1.9 95.8 ± 1.7* 90.1 92.0 ± ± 2.2 1.8* 65.8 ± 5.0 100 ± 0*** 76.1 100 ± ± 5.8*** 0 90.7 ± 1.0** 92.0 ± 2.1* 0 0.5 ± 0.5 1.9 4.4 ± ± 0.8 1.0 84.7 93.4 ± ± 3.6*** 2.2 92.1 ± 3.4** 79.0 ± 0.9 94.4 ± 2.4 87.3 ± 1.3 012 —4 15 92.6 15 ± 0.6 95.5 ± 15 1.21 96.0 ± 0.4 14.4 ± 4.0 93.8 ± 1.2 4.7 ± 1.1 32 0.8 ± 0.3 87.7 3.2 ± ± 97.0 1.4 1.1 ± 0.4** 84.3 ± 3.2 72.7 85.0 ± ± 2.6** 2.1 86.4 ± 3.1 86.0 86.5 ± 2.2 ± 78.0 1.0 ± 1.2 79.6 90.5 ± ± 100 6.2 1.0 ± 0*** 95.5 ± 75.2 2.1 ± 1.0 94.8 100 ± ± 3.3 0 95.3 ± 0.4 88.4 ± 1.3 95.7 ± 0.5 93.4 ± 2.4 0.2 ± 94.5 0.1 ± 1.3 0.3 ± 0.3 1.8 0 ± 0.4 3.9 0 ± 1.6 92.9 ± 0.8 89.8 ± 2.7 2.6 ± 1.3 78.2 ± 3.2 2.0 ± 1.1 85.1 ± 85.8 3.0 ± 2.4** 79.2 ± 87.3 82.8 5.7*** ± ± 1.6 5.8 88.1 ± 88.7 5.5* ± 1.9 96.1 ± 3.6 94.9 ± 4.6 1224 32 32 90.2 ± 2.1 91.0 ± 2.5 84.5 ± 3.2*** 85.7 ± 5.1*** 99.0 ± 0.6** 98.6 ± 1.0** 86.4 ± 3.5 88.2 ± 1.8 57.3 ± 1.1*** 51.0 ± 5.3*** 88.0 ± 2.5 89.5 ± 2.4 96.0 ± 1.3 93.9 ± 1.0 0 0 11.0 ± 2.4*** 15.2 ± 80.0 3.3*** ± 1.8*** 80.3 ± 97.5 2.3*** ± 3.6*** 95.8 ± 1.8*** 98.8 ± 1.0** 96.7 ± 1.6** 1224 15 15 91.5 ± 1.3 94.2 ± 1.1 28.4 ± 5.7* 55.4 ± 0.9*** 97.3 94.0 ± ± 0.9** 3.6 86.5 ± 1.3 87.4 ± 1.2 75.7 ± 6.4 77.5 ± 3.0 87.9 ± 4.1 91.1 ± 3.2 94.5 ± 1.3 93.3 ± 2.2 0.3same ± 0 0.3 at 2.4 ± 0.8 week 1.9 ± 0.5 91.0 ± 1.3 0 88.2 ±as 1.2* 78.5it ± 3.2 85.0 ±was 3.2 at 80.6 ± 2.4 week 91.5 ± 3.5 24 at Dry storage Regression models were fitted sequentially with the model shown having an adjusted R Results (mean ± *,**,***Means, within a column, are significantly different from the 0-week mean at Lanceleaf tickseed seeds stored at 23% relative humidity; seeds of all other species were stored atRegression 33% analysis relative results humidity; omitted fresh seeds because at all 0 means weeks were were n Table 1. Effect of dry storage at 15 or 32 z y x w v Weeks ( Significance ( of native tickseed species seed. including the highest order shown as well as the intercept. either temperature (Table 1).
• October–December 2007 17(4) 509 R 510 ESEARCH Table 2. Effect of 24 weeks of storage at 23% relative humidity at 17 to 19 C (62.6 to 66.2 F) on percent viability, germination velocity (percent germination at 7 d), and total percent germination (21 d) of native tickseed species seeds that had been previously stored dry at 15 or 32 C (59.0 F or 89.6 F) for up to 24 weeks.z Goldenmane tickseed Florida tickseed Lanceleaf tickseed Leavenworth’s tickseed Germination Germination Germination Germination Germination Germination Germination Germination R Dry storagey of viable of viable of viable of viable of viable of viable of viable of viable EPORTS Temp Viable seeds at seeds at Viable seeds at seeds at Viable seeds at seeds at Viable seeds at seeds at Weeks ( C) seeds (%) 7 d (%) 21 d (%) seeds (%) 7 d (%) 21 d (%) seeds (%) 7 d (%) 21 d (%) seeds (%) 7 d (%) 21 d (%) 0x — 92.6 ± 0.6 14.4 ± 4.0 87.7 ± 1.4 85.0 ± 2.1 78.0 ± 1.2 95.5 ± 2.1 95.3 ± 0.4 0.2 ± 0.1 1.8 ± 0.4 92.9 ± 0.8 78.2 ± 2.0 87.3 ± 1.6 1 15 91.2 ± 1.8 81.6 ± 3.1*** 99.5 ± 0.4*** 88.5 ± 1.7 82.5 ± 4.2 89.8 ± 3.4 92.0 ± 1.2* 24.7 ± 2.4*** 76.6 ± 3.8*** 89.3 ± 1.3 82.4 ± 3.9 86.6 ± 2.9 2 15 93.9 ± 0.6 84.4 ± 1.5*** 99.8 ± 0.2*** 91.0 ± 3.1 67.6 ± 4.6 84.1 ± 3.6* 96.2 ± 0.5 59.0 ± 5.3*** 84.7 ± 2.5*** 89.0 ± 1.2 79.8 ± 2.7 84.8 ± 4.4 4 15 93.0 ± 1.8 87.4 ± 1.6*** 99.0 ± 1.0** 86.4 ± 3.3 52.6 ± 1.1*** 79.2 ± 2.6 95.2 ± 1.7 0 62.0 ± 5.5*** 87.8 ± 0.5 86.0 ± 5.9 88.2 ± 5.4 12 15 90.7 ± 0.7 79.2 ± 7.7*** 97.1 ± 1.1* 82.8 ± 4.8 — 84.6 ± 4.9 93.5 ± 1.6 10.7 ± 1.6 47.9 ± 4.3*** 85.8 ± 2.1 81.3 ± 2.6 83.7 ± 2.1 24 15 92.2 ± 2.4 94.7 ± 1.3*** 98.2 ± 0.7** 71.6 ± 2.9** 53.1 ± 5.7*** 88.6 ± 4.8 94.2 ± 1.2 36.6 ± 4.1*** 73.2 ± 3.5*** 80.9 ± 4.4*** 91.5 ± 2.6** 93.3 ± 2.1 1 32 93.6 ± 1.3 89.4 ± 2.7*** 99.4 ± 0.4*** 90.0 ± 3.6 77.8 ± 2.4 86.7 ± 4.9 97.0 ± 0.4 28.3 ± 5.5*** 74.0 ± 5.5*** 85.4 ± 1.0*** 83.8 ± 1.4 85.8 ± 2.2 2 32 92.2 ± 2.0 88.0 ± 3.2*** 99.9 ± 0.1*** 83.9 ± 3.0 73.8 ± 6.4 85.8 ± 5.1* 96.5 ± 0.9 55.3 ± 6.5*** 79.8 ± 3.9*** 91.0 ± 1.8 75.0 ± 5.0 78.9 ± 4.0 4 32 95.0 ± 1.1 84.8 ± 5.1*** 95.7 ± 4.2 90.2 ± 2.2 42.1 ± 6.9*** 81.0 ± 8.3 94.0 ± 1.4 0 74.2 ± 4.2*** 86.5 ± 1.5 89.6 ± 1.5 91.1 ± 1.2 12 32 93.7 ± 1.8 92.0 ± 3.4*** 98.0 ± 1.9** 82.0 ± 2.9 — 73.8 ± 3.6 96.6 ± 1.3 18.9 ± 3.8 65.2 ± 3.5*** 84.5 ± 2.0** 83.2 ± 3.6 87.9 ± 4.7 24 32 95.8 ± 2.3*w 95.6 ± 2.9*** 99.5 ± 0.5** 75.0 ± 3.9* 9.3 ± 1.7*** 81.3 ± 5.2** 95.0 ± 2.3 42.2 ± 2.8*** 80.4 ± 2.6*** 86.3 ± 2.3 86.4 ± 4.4 87.5 ± 4.9 Significance (P > F) (within stored seed)v Temp (T) 0.0758 0.0822 0.8411 0.9963 0.0006 0.2814 0.0238 0.2128 0.0464 0.9239 0.6694 0.6954 Weeks (W) 0.5976 0.0818 0.4483 0.0003 <0.0001 0.3143 0.5464 <0.0001 <0.0001 0.0397 0.0226 0.1688 Model — — — L*** — — — Q*** (0.884) — L** (0.146) Qt* (0.215) — (0.445) T · W 0.5906 0.2395 0.7827 0.3496 <0.0001 0.6482 0.2769 0.4882 0.0727 0.2307 0.8063 0.4768 Model 15 C — — — — Q*** (0.673) — — — Qt*** (0.711) — — — 32 C — — — — Q*** (0.869) — — — NS —— — Significance (P > F) (to determine storage effects)u, v Storage (S) 0.4951 <0.0001 <0.0001 0.0168 <0.0001 <0.0001 0.1609 <0.0001 <0.0001 0.8416 0.2842 0.0086 T · S 0.0408 0.0289 0.0170 0.7664 0.0760 0.7276 0.0531 0.1623 0.3198 0.4879 0.1678 0.4057 W · S 0.0418 0.0006 0.0006 <0.0001 <0.0001 0.2620 0.1774 <0.0001 <0.0001 0.3865 0.6843 0.1959 Model Nonstandard Qt** Q*** L*** C** — — — Qt*** ——— — (0.124) (0.208) (0.436) (0.204) (0.881) Stored NS NS L** L*** — — — Qt*** ——— — (0.147) (0.445) (0.884) T*W*S 0.6516 0.6516 0.2938 0.1270 0.0819 0.3019 0.9560 0.2398 0.0086 0.0078 0.1067 0.0647 Model NI
• t
coe–eebr20 17(4) 2007 October–December (standard) 15 C — — — — Q*** (0.304) — — — Qt*** —— NS (0.702) 32 C — — — — Q*** (0.869) — — — NS —— NS z Results (mean ± SE) are normalized for the percentage of viable seeds based on results of pregermination tetrazolium tests. Data were transformed before analysis but nontransformed means are presented. yLanceleaf tickseed seeds stored at 23% relative humidity (RH); seeds of all other species were stored at 33% RH. x0-week (fresh seeds) data included for comparison only and were not included in regression analyses. These seeds were not stored at 15 or 32 Corat17to19 C. w*,**,***Means, within a column, are significantly different from the 0 week mean at P < 0.05, 0.01, or 0.001, respectively, as determined using LSMEANS with the PDIFF option of SAS (version 8.01; SAS Institute, Cary, NC). vRegression models were fitted sequentially with the model shown having an adjusted R2 value ‡ 0.05 (shown in parentheses) than the preceding lowest order model. All models contained components with P < |t| of £ 0.05 up to and including the highest order shown as well as the intercept. NS = No significant linear (L), quadratic (Q), cubic (C), or quartic (Qt) components. Results of regression analyses only shown when the P values for interactions were £ 0.10. uSignificance of main and interactive effects were based on data from the entire study so as to determine the influence of weeks of storage at 15 or 32 C as well as to determine cool, dry storage effects. tRegression model significances for each temperature are those for stored seed; regression model significances for each temperature for nonstored seed are in Table 1. NI = No significant T · W interaction for seeds stored for 24 weeks at 23% RH and 17 to 19 C. Dormancy was substantially alle- In summary, seed dormancy of greater at 32 C than at 15 C, which viated during 24 weeks of CCDS lanceleaf tickseed was most effectively concurs with the generally accepted regardless of the previous storage alleviated after 25 to 48 weeks at 23% view that after-ripening time is inver- conditions (Table 2). Even more RH under cool conditions without sely related to storage temperature noteworthy was that up to 24 weeks loss of viability. However, dormancy (e.g., see Roberts, 1965). However, at 15 C/23% RH did not alleviate was not completely alleviated so addi- after-ripening of lanceleaf tickseed any dormancy (Table 1), but 1 week tional cool, dry storage would seem to was greatest under long-term cool, at 15 C plus 24 weeks of CCDS be required. Carpenter and Ostmark dry storage. Third, maintenance of substantially reduced dormancy. (1992) noted that dormancy of tick- seed quality after seeds had been Because relative humidities for CCDS seed declined as storage time at 5 C subjected to dry conditions for the and storage conditions before CCDS increased. Dormancy might also be purpose of after-ripening was species- were the same (23%), and cool tem- alleviated by storing seeds at 32 C/ dependent. Interestingly, only seed peratures were nearly the same (15 C 23% RH for more than 24 weeks quality of the two upland species, versus 17 to 19 C), 25 to 48 weeks because there was some after-ripening goldenmane tickseed and lanceleaf of cool, dry storage was an effective under these conditions after 24 weeks. tickseed, was maintained regardless after-ripening treatment, although LEAVENWORTH’S TICKSEED. Ger- of the previous after-ripening temper- dormancy was not completely allevi- mination at week 0 was 87.3% (Table ature to which seeds of these species ated. A less likely but possible explan- 1). However, like goldenmane tick- had been subjected. Hence, we sus- ation was that seeds were exposed to seed and florida tickseed, seeds pect that upland tickseed species ethylene at some point during CCDS. appeared to undergo after-ripening. might have a shelf life greater than Ethylene enhances germination of After-ripening only occurred at 32 C 1 year although tickseed seeds have tickseed (Carpenter and Ostmark, as evidenced by the linear increases in been classified as having a shelf life 1992) and can substitute for after- germination and 7-d germination of less than 1 year if stored under ripening in Asteraceae (Bewley and (germination velocity) (Table 1). ‘‘satisfactory storage conditions’’ Black, 1994). However, common Warm stratification can alleviate dor- (McDonald, 2005). Banovetz and sources of ethylene (fruit, combus- mancy (Kabat, 2004), a conclusion Scheiner (1994b) reported that seeds tion engine exhaust) were absent that does not necessarily conflict with of a midwestern ecotype of lanceleaf based on information provided by results of our current study because tickseed remained viable in the soil for the owner of the CCDS facility. warm temperatures might be the key up to 13 years. Based on evidence in For seeds subjected to 24 weeks to breaking dormancy. Seed moisture our study, McDonald’s (2005) con- CCDS, the response of germination content of seeds at 33% RH/32 C clusion is consistent for the two over previous weeks of storage at was 8% (data not shown), much too wetland tickseed species. 15 or 32 C varied by temperature low for stratification to occur. Viabil- (Table 2). At 15 C, there was a ity of seeds declined slightly as weeks quartic response of germination of storage increased at 15 or 32 C, Literature cited based on weeks of previous storage declines that did not occur in seeds of Aldrich, J.H., G.W. Knox, and J.G. mainly attributable to the decline the other tickseed species (Table 1). Norcini. Florida coreopsis (Coreopsis in germination at 4 and 12 weeks. Under CCDS, there was no evi- floridana): A new fall-flowering peren- Because the 7-d germination exhib- dence of additional after-ripening nial. 2006. Proc. Southern Nursery ited a quartic response similar to because both germination and 7-d Assn. Res. Conf. 51:663–665. the germination response implies germination rates remained relatively Andersson, L. and P. Milberg. 1998. that the length of previous storage constant (Table 2) nor was there any Variation in seed dormancy among at 15 C affected dormancy under additional loss of viability. mother plants, populations, and years of CCDS and might not simply be an In summary, germination of harvest collection. Seed Sci. Res. 8:29–38. artifact. Further research is needed to leavenworth’s tickseed was increased Association of Official Seed Analysts. verify whether these quartic responses by storing seeds at 33% RH/32 C, 1988. Rules for testing seeds. J. Seed represented changes in dormancy. but there was a slight loss in viability. Technol. 12:63–73. There are no reports of changes in Subsequent storage of this seeds dormancy of lanceleaf tickseed stored under CCDS conditions preserved Banovetz, S.J. and S.M. Scheiner. 1994a. Secondary seed dormancy in Coreopsis under cool, dry conditions. Banovetz seed quality for 24 weeks. lanceolata. Amer. Midland Naturalist and Scheiner (1994a) observed sec- 131:75–83. ondary dormancy of imbibed seeds of Conclusions lanceleaf tickseed at 5 C. At 32 C, Several similarities among spe- Banovetz, S.J. and S.M. Scheiner. 1994b. germination was generally similar cies for storage effects on seed quality The effects of seed mass on the seed regardless of length of previous stor- were apparent under the conditions ecology of Coreopsis lanceolata.Amer. Midland Naturalist 131:65–74. age (Table 2). There was no loss in of this study, although this study was seed viability after 24 weeks of CCDS. not designed to compare species. Baskin,C.C.andJ.M.Baskin.1998. We expected the seeds to remain First, there was evidence of dry after- Seeds: Ecology, biogeography, and evo- viable after 48 weeks in dry storage. ripening of all four species, although lution of dormancy and germination. Banovetz and Scheiner (1994b) the only substantial after-ripening Academic Press, San Diego, CA. reported that seeds of a midwestern occurred in lanceleaf tickseed. Bewley, J.D. and M. Black. 1994. Physi- ecotype of lanceleaf tickseed remained Second, after-ripening under dry ology of development and germination. viable in the soil for up to 13 years. conditions for 24 weeks generally was 2nd ed. Plenum Press, New York.
• October–December 2007 17(4) 511 RESEARCH REPORTS
Booth, D.T. and T.A. Jones. 2001. Plants dormancies in three commercially pro- with phyletic interpretations. Bot. Gaz. for ecological restoration: A foundation duced Florida native wildflowers. MS 136:78–86. and a philosophy for the future. Native Thesis, University of Florida, Gainesville. Plants J. 2:12–20. Smith, E.B. 1976. A biosystematic survey Leopold, A.C. and C.W. Vertucci. 1989. of Coreopsis in the eastern United States Carpenter, W.J. and E.R. Ostmark. 1992. Moisture as a regulator of physiological and Canada. Sida 6:123–215. Growth regulators and storage temper- reaction in seeds, p. 51–67. In: P.C. Smith, E.B. 1982. Phyletic trends in ature govern germination of Coreopsis Stanwood and M.B. McDonald (eds.). section Coreopsis in the genus Coreopsis. seed. HortScience 27:1190–1193. Seedmoisture.CropSci.Soc.Amer., Bot. Gaz. 143:121–124. Madison, WI. Dehgan, B. and J.G. Norcini. 2006. Treat- Tadesse, M., D.J. Crawford, and E.B. ment and germination of Florida native Marois, J.J. and J.G. Norcini. 2003. Sur- wildflower seeds for commercial produc- Smith. 1995. Comparative capitular mor- vival of black-eyed susan from different phology and anatomy of Coreopsis L. and tion and natural landscaping. Final report regional seed sources under low and high to the Florida Wildflower Advisory Coun- Bidens L., including a review of generic input systems. HortTechnology 13:161– boundaries. Brittonia 47:61–91. cil. 29 Nov. 2006.
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