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AN ECOLOGICALLY BASED STUDY OF GERMINATION REQUIREMENTS AND DORMANCIES IN THREE COMMERCIALLY PRODUCED FLORIDA NATIVE WILDFLOWERS
... Viable seeds of lanceleaf tickseed harvested early in the summer were nearly 80% dormant, but seeds harvested later that year were only %50% dormant (Norcini et al., 2004). Commercially produced leavenworth's tickseed harvested in early Summer 2001 and 2002 were nearly all dormant (Kabat, 2004). In contrast, seeds of the same prevariety germplasm harvested from containerized plants exhibited less than 18% dormancy . ...
... Extracted embryos that were white, turgid, and otherwise appeared normal also were deemed viable as were such embryos with only faint pink staining at the radicle end (Dehgan and Norcini, 2006). Four other 50-seed samples were subjected to germination testing under an alternating temperature regime of 15/25°C [Association of Official Seed Analysts (AOSA), 1988; Dehgan and Norcini, 2006;Kabat, 2004] or 20/30°C for lanceleaf tickseed (AOSA, 1988;unpublished data). All seeds were germinated under an 8-h photoperiod with the warmer temperature during the lighted period. ...
... After-ripening only occurred at 32°C as evidenced by the linear increases in germination and 7-d germination (germination velocity) ( Table 1). Warm stratification can alleviate dormancy (Kabat, 2004), a conclusion that does not necessarily conflict with results of our current study because warm temperatures might be the key to breaking dormancy. Seed moisture content of seeds at 33% RH/32°C was %8% (data not shown), much too low for stratification to occur. ...
Fresh seeds of prevariety germplasms of goldenmane tickseed (Coreopsis basalis), florida tickseed (Coreopsis floridana), lanceleaf tickseed (Coreopsis lanceolata), and leavenworth's tickseed (Coreopsis leavenworthii) were harvested from cultivated plants and stored under dry conditions for 1 to 24 weeks at 15 or 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 subsequently stored for 24 weeks in a commercial storage facility at 23% RH/17 to 19°C to determine whether after-ripened seeds could be stored without loss in quality (viability, germination velocity). The only substantial after-ripening occurred with seeds of lanceleaf tickseed, although most after-ripening of lanceleaf tickseed seeds occurred during the 24 weeks of dry storage in the commercial storage facility regardless of storage conditions for the previous 24 weeks. After the 24 weeks in commercial storage, germination of lanceleaf tickseed seeds was 48% to 80%, but germination was only 2% to 15% after 24 weeks of dry storage at 15 or 32°C, respectively. Freshly harvested seeds of the other three species were much more nondormant than seeds of lanceleaf tickseed, but after-ripening effects were still evident because there were increases in germination or germination velocity (an indicator of after-ripening). Maintenance of seed quality was species-dependent. Seed quality of the two upland species, goldenmane tickseed and lanceleaf tickseed, was maintained during the initial 24 weeks of dry storage plus the subsequent 24 weeks in the commercial storage facility. In contrast, viability of seeds of the two wetland species, florida tickseed and leavenworth's tickseed, declined to varying degrees either during the initial 24 weeks of after-ripening or during storage in the commercial facility. The greatest decline in quality occurred for florida tickseed seeds that were stored for 24 weeks at 32°C and then for 24 weeks in the commercial storage facility.
... Interestingly, despite the second peak in germination at 5/20 °C in May 2002, speed of germination in light declined at 5/20 °C from January to May (Figure 3). As the temperature regimes increased, this delay in germination gradually abated to the point that at regimes of 15/25 °C and greater, most germination occurred at 7 d in both light and dark (results not shown; Kabat 2004). ...
... Similar to the 2001 study, at the temperature regimes of 15/25 °C and higher, the overwhelming percentage of seeds germinated at 7 d in both light and dark (results not shown; Kabat 2004). ...
... The total number of viable seeds (number germinated + number of viable nongerminated seeds as determined by the TZ test) for a given month should have been equal regardless of the regime under which seeds were germinated. This was not the case, however, for several months of the 2002-2003 study (Kabat 2004). Within a given month, the figure used when calculating the percentage germination of viable seeds was the temperature/light regime treatment that had the highest value for total number of viable seeds. ...
Commercially produced, source identified, natural track seeds of Leavenworth's tickseed (Coreopsis leavenworthii Torr. & Gray [Asteraceae]) harvested in late June expressed a type of physiological dormancy in which seeds became nondormant first at cooler temperatures and then at warmer temperatures. In 2 studies, fresh seeds were buried about 7 cm (3 in) deep in sand in 3.8-l (1-gal) containers, irrigated once per week, and exposed to ambient temperatures. Seeds were excavated monthly during 10 mo in the 2001–2002 study and 9 mo in the 2002–2003 study. Seeds became nondormant in late fall to early winter, approximately 5 to 6 mo after they were buried. Coreopsis leavenworthii showed that it was well-adapted to Florida's climate because its seeds germinated under a wide variety of temperatures typical in Florida during late fall and early winter at shallow seeding depth (light enhanced germination) in sites typical of C. leavenworthii's moist habitat. While C. leavenworthii most closely resembled a facultative winter annual, it also showed the potential to germinate to some degree under temperatures typical of Florida's subtropical summer. No buried seeds germinated, indicating that C. leavenworthii has the potential to form at least a short-term seedbank.
Effects of season and fertilization on seed production were investigated for a central Florida ecotype of Leavenworth's coreopsis (Coreopsis leavenworthii Torr. & A. Gray) grown in containers. Since container-grown ecotypes of native, herbaceous species are frequently grown using nutrient regimes lower than those for production of typical garden plants, Osmocote 18N–2.6P–10K (18–6–12;8–9 month formulation) was incorporated into the soilless substrate at one-half the low, low, and medium label rates for container-grown herbaceous plants [1.8, 3.6, and 5.4 kg/m3 (3.0, 6.0, and 9.0 lb/yd3], respectively. Seed were harvested from mature heads (capitulescences) in late May to mid-July, and then again from late July to late October after plants had been cut back and reflowered. Seed yield and quality were greatest for the May–July harvest. Averaged over fertilizer rate, there were 3-fold more filled seed per mature head for the May–July harvest than during July–October. Mature head production was most responsive to increases in fertilizer rate during May–July. Percent germination of viable seed was nearly 90% or more for both harvests, but there were more viable seed for May–July than for July–October (75 vs. 57%). Seed also ripened much more uniformly during May–July then during July–October. Based on these conditions and results, the best time to harvest seed was from May to early July.
Seeds of Coreopsis tinctoria Nutt., Ipomopsis rubra (L.) Wherry, Linum perenne L., and Asclepias tuberosa L. were germinated under constant light at 155 ± 10 μEm ⁻² sec ⁻¹ on a thermogradient plate to determine optimum temperatures for germination. Optimum temperatures were 30°C for C. tinctoria , 25° for L. perenne and 30° for A. tuberosa . I . rubra exhibited poor germination at all temperatures in light. C. tinctoria, L. perenne and A . tuberosa germinated within temperature ranges of 15° to 35°, 15° to 25°, and 25° to 35°, respectively. A. tuberosa was the slowest germinating of the 3 species.
Growth, flowering, and survival of black-eyed susan (Rudbeckia hirta L.) from three seed sources - Northern Florida (NFL), central Florida (CFL), and Texas (TEX) - Were evaluated under low input conditions for one growing season at four sites in Florida. Two sites were in American Horticultural Society (AHS) Heat Zone 9 while the other two were in AHS Heat Zones 10 and 11. Growth, onset date of flowering, and number of flowers at peak flowering varied by site. With few exceptions, plants tended to reach peak flowering at about the same time. Flower diameter varied by seed source with TEX>NFL>CFL. While TEX plants were perceived as the showiest, NFL and CFL plants persisted longer under the low input conditions in Florida, and hence provided some evidence of adaptation to regional site conditions.
1 hybrids. In order to assess the ease with which crop-to-wild introgression can proceed, we compared characteristics of F1 wild-crop progeny with those of purely wild genotypes. Two nontransgenic, cultivated varieties were crossed with wild plants from three different regions— Texas, Kansas, and North Dakota. Seed burial experiments in the region of origin showed that wild-crop seeds had somewhat higher germination rates (less dormancy) than wild seeds from Kansas and North Dakota, while no differences were seen in seeds from Texas. Progeny from each type of cross were grown in outdoor pots in Ohio and in a weedy field in Kansas to quantify lifetime fecundity and flowering phenology. Flowering periods of hybrid and wild progeny overlapped consid- erably, especially in plants from North Dakota and Texas, suggesting that these hybrids are very likely to backcross with wild plants. In general, hybrid plants had fewer branches, flower heads, and seeds than wild plants, but in two crosses the fecundity of hybrids was not significantly different from that of purely wild plants. In Ohio, wild-crop hybrids from North Dakota appeared to be resistant to a rust that infected 53 % of the purely wild progeny, indicating a possible benefit of ''traditional'' crop genes. In summary, our results suggest that F 1 wild-crop hybrids had lower fitness than wild genotypes, especially when grown under favorable conditions, but the F1 barrier to the introgression of crop genes is quite permeable.
We examined physical and physiological factors that control germination in the herbaceous perennial, Coreopsis lanceolata L. (Asteraceae). Seeds stored in paper envelopes for 6 to 18 months at room temperature were tested for germination on moistened filter paper in petri dishes. Germination percentages were greatest at 15 and 25 C and 12 h light/dark cycles. Germination percentages of imbibed seeds were not affected by previous storage at -10 C. Imbibed seeds subjected to 5 C entered a secondary dormancy that could not be broken by subsequent warmer temperatures, light/dark cycles or freezing temperatures. This study is the first of which we are aware documenting secondary dormancy in a perennial species. Secondary dormancy in C. lanceolata may be a mechanism for spreading the risk of recruitment.
Biparental inbreeding is thought to be a common feature of plant populations with restricted pollen dispersal. It is generally assumed that the inbreeding depression frequently observed to accompany self-fertilization can be extrapolated to the lesser degrees of consanguinity involved in biparental inbreeding, but this is virtually untested. To test this assumption, seeds collected from a single natural population of the self-incompatible annual Gaillardia pulchella were used to generate full-sib families derived by crossing either noninbred full-sibs (inbred families) or noninbred nonrelatives (outbred families). Members of each family were divided between high-stress and low-stress treatments that differed in soil volume and nutrient level. Inbred seedlings had a lower chance of survival, were more likely to be morphologically abnormal, and grew more slowly than outbred seedlings, indicating the presence of biparental inbreeding depression. Stress treatment had no significant effect on inbreeding depression, and no family stress-environment interactions were detected. Inbreeding did not increase the among-family variance in growth rate, suggesting that inbreeding depression of growth rate is caused by many genes with small individual effects. Relative to direct estimates of inbreeding depression, observed levels of near-neighbor outcrossing depression, presumed to be biparental inbreeding depression, are surprisingly high in many plant species.
The storage and germination environments were evaluated to determine the cause of low total germination percentages and highly irregular germination of Coreopsis lanceolata L. seed. Highest total germination and most rapid and uniform germination of seed occurred at constant 15C, other constant temperatures and all alternating temperature regimes caused lower total germination or delayed it. Seeds tolerated -20C during storage, but total germination was reduced below -5C. Recently harvested seeds had 44% total germination, but 54% to 81% germination was achieved after 6 hours of soaking seeds in 1000 ppm GA 3 , 1000 ppm ethephon, or 25 ppm kinetin alone or in combination. Growth regulators reduced the number of days to 50% of final germination (T 50 ), and the span in days between 10% and 90% of germination (T 90 - T 10 ). Storing fresh seeds without chemical treatment for > 6 months at 5C and 10% to 20% relative humidity (RH), or 15C at 20% to 35% RH, increased total germination to 75% and 80%, respectively. Ten days were required to achieve T 50 after 5 to 6 months of storage at 5C and 10% to 20% RH or 15C and 10% to 40% RH, with longer periods to T 50 at other storage durations and RH levels. The germination spans (T 90 - T 10 ) were lengthened the higher the seed storage temperatures between 5 to 25C, with longer spans as seed storage durations and relative humidities increased. Total germination was similar after storing seeds at 5 or 15C and 10% to 30% RH and after soaking recently harvested seeds in GA 3 + ethephon, but the days to T 50 and T 90 - T 10 were shorter after growth regulator treatment. Chemical names used: (2-chloroethyl) phosphonic acid (ethephon); gibberellic acid (GA 3 ); 6-furfurylaminopurine (kinetin).
Significant research has been conducted on wildflower sod, but the reasoning behind the production system methods is not clear. The purpose of this research was to determine the influence of mowing height on the subsequent leaf growth and root biomass distribution in a wildflower sod production system. Rudbeckia hirta was grown in sand in polyvinyl chloride (PVC) tubes in simulating field conditions. Plants were either not mowed (control) or hand-clipped to 5.1, 7.6, or 10.2 cm to simulate mowing. After the initial mowing, plants were mowed at ≈7-day intervals. Total root depth, number of root axes in the top 2.5 cm, root : shoot ratio, total root dry weight, and root dry weight at depths of 0.0– 2.5, 2.5–21.7, 21.7–40.8, and 40.8–60.0 cm were measured at the end of the study. Comparing the total root dry weight of all segments indicates that mowing significantly reduces root biomass. As mowing height increased, the depth of longest root increased linearly. Plants not mowed or plants mowed to 10.2 cm produced significantly more root axes in the top 2.5 cm of sand than did mowing heights of 5.1 or 7.6 cm. Root dry weight in the top 2.5 cm was considerably greater in nonmowed plants. Increased root axes in sod with higher mowing heights indicated a greater root density, which may also increase wildflower sod stability.
Survival of black-eyed susan (Rudbeckia hirta) from three regional seed sources was evaluated after inoculation with the pathogenic fungus Fusarium oxysporum in the greenhouse, and after they were planted in fumigated or nonfumigated and irrigated or nonirrigated field plots. The three seed sources were northern Florida (NFL), central Florida (CFL), or Texas (TEX). Plants from the three seed sources were inoculated individually under greenhouse conditions with four isolates of F. oxysporum originally isolated from the roots of diseased black-eyed susan grown in ecotype trials near Monticello, Fla. About 20% of the inoculated plants developed symptoms similar to those observed in the field, but no consistent ecotype or isolate effects were observed. In the field trial, planting beds were fumigated with methyl-bromide and chloropicrin and irrigated with drip irrigation (high input), not fumigated and irrigated, fumigated and not irrigated, or not fumigated and not irrigated (low input). During the first month of the trial, treatment and seed source had a significant effect on survival due to the low initial survival of NFL in the nonfumigated-nonirrigated plots. After the first month, only seed source had a significant effect on survival, with TEX decreasing rapidly and the NFL population decreasing to a lesser degree. The decline of TEX could not be directly attributed to pests or climatic effects.
Seeds of tickseed (Coreopsis lanceolata L.) and purple coneflower [Echinacea purpureo (L.) Moench] were primed in aerated solutions of a 50 m m potassium phosphate buffer at 16C. C. lanceolata seeds were primed for 3 or 6 days; E. purpurea seeds were primed for 6 or 9 days. Seeds were vacuum-stored for 2 months immediately after priming. Identical treatments were imposed on open-stored seeds just before the termination of the storage duration, thus producing four treatments: a vacuum-stored control, an open-stored control, primed vacuum-stored seed, and seed primed after open storage. Although priming significantly improved the performance of C. lanceolata seed, vacuum storage alone also significantly increased the speed of germination and final germination. The advantage of priming was diminished during 2 months of vacuum storage of E. purpurea, but priming enhanced germination as compared with the open-stored nonprimed control. There was little difference between the performance of E. purpurea seeds both primed and vacuum-stored. and the vacuum-stored control.
Seeds from nine species of desert annuals native to the Mojave and Sonoran Deserts were stored at constant temperatures of 4@?, 20@?, 50@?, and 75@?C. All species except one, when stored at 50@?C, reached maximum germination within the first 5 weeks of storage. Seeds stored at 75@?C failed to germinate while seeds stored at 4@?C gave poor germination, equivalent to fresh seeds. Seeds stored at room temperature (20@?C) need 5 months' maturation to achieve comparable germination percentages. The prevalent high temperatures in the following seed dispersal probably promote seed maturation in desert plants.
Strobilanthinae comprise approximately 350 species from south and southeast Asia and Melanesia. Three main classifications of Strobilanthinae have been advocated, differing markedly in the number of groups recognised, their circumscription, and the rank assigned to them. But there remains no consensus concerning the best approach to the classification of the group. To investigate this issue, a morphological cladistic analysis of the southern Indian and Sri Lankan Strobilanthinae, comprising 66 species, is described. The results of the analysis demonstrate significant limitations of all three historical approaches to the classification of the group and, furthermore, suggest that any attempt to provide an informative formal classification of Strobilanthinae will be problematic. The only satisfactory approach consistent with these results is to place all previously recognised taxa in synonymy of an expanded Strobilanthes and to recognise informally those infrageneric monophyletic groups that can be clearly diagnosed.
Plantings of six native wildflower species—Cassia fasciculata Michx. (partridge-pea), Coreopsis ianceoiata L. (lanceleaf coreopsis), Gaillardia pulchella Foug. (blanketflow er), Ipomopsis rubra(L.) Wherry (standing cypress), Rudbeck ia hirta L. (black-eyed susan), and Salvia lyrata L. (lyreleaf sage) —were established during winter 1997 at five sites in Jef ferson County, Florida. Seeds of each species were derived from native populations (local ecotype) and purchased from commercial sources outside of Florida (nonlocal ecotype). Plantings were irrigated as needed up until early April to en sure germination but received no supplemental fertilizer. No pesticides were applied except to control weeds on the perim eter of the plantings and fireants; plots were handweeded as necessary. Plants were evaluated once per month from June to October 1997. It was clearly evident from these evaluations that the local ecotypes generally were better adapted to north Florida conditions than were the nonlocal ecotypes. The most noteworthy differences were as follows: 1) local ecotypes of black-eyed susan and blanketflower had longer flowering peri ods than their nonlocal counterparts; 2) the local ecotype of lanceleaf coreopsis flowered profusely while flowering of the nonlocal ecotype was sparse; 3) the local ecotypes of lanceleaf coreopsis and lyreleaf sage had less disease incidence than nonlocal ecotypes; 4) flower color and blooming date of stand ing cypress ecotypes varied substantially.
Low-vigor seeds of black-eyed Susan ( Rudbeckia fulgida Ait.) primed in aerated -1.3 MPa KNO 3 for 7 days at 30C in darkness had double the total germination percentage at 30C and one-half the mean time of germination as nonprimed seeds. Priming the seeds in polyethylene glycol rather than KNO 3 generally resulted in lower total germination percentage and longer mean time of germination. Osmotic priming increased total germination percentage and germination rate of seeds germinated at 21.9 to 32.2C, but the priming benefit on total germination percentage was greater at ≤27.6C. Total germination percentage of primed and nonprimed seeds was highest at 28.8 to 32.2C.
A study was conducted on 20 species of prairie forbs collected from Illinois tallgrass prairie to determine their levels of germination without treatment of the seed and to determine their expected higher levels of germination with various seed treatments. The present assay of forb seed germination was made to aid those engaged in prairie restoration. Seed fill was visually and physically determined. Seed viability was determined by use of triphenyl tetrazolium chloride, which turns living embryos red. Germination was done on moist filter paper inside petri plates in darkness at constant temperature. From tests on 20 species only three germinated without treatment; 12 germinated under 2 months of moist-cold treatment; and four germinated with scarification. When treated with rootone, five species germinated. Three species germinated with single application of .005% potassium gibberellate spray. These results suggest most of the 20 species could be planted with success with the proper preparation or treatment of the seed.
Patterns of change in temperature requirements for germination of achenes of four Texas winter annual Asteraceae were investigated as they afterripened at simulated summer habitat temperatures. In addition, temperature requirements for after-ripening were determined. In Gaillardia pulchella, Krigia gracilis, and Pyrrhopappus multicaulis, the maximum temperature for germination increased during afterripening (type 1 response pattern). This is the first report of a type 1 pattern in the Asteraceae. In Hymenoxys linearifolia, the maximum and minimum temperatures for germination increased and decreased, respectively, increasing to two the number of winter annuals with a type 3 response pattern. As in winter annuals in other plant families, achenes of the four species required exposure to moderately high temperatures (25:15, 30:15 °C) to gain the ability to germinate to high percentages at autumn temperatures in autumn. Of the 32 species of Asteraceae whose afterripening pattern has been investigated, 3 have type 1, 22 have type 2, and 7 have type 3. Evidence suggests that types 1 and 3 and types 2 and 3 are more closely related physiologically than are types 1 and 2. Key words: winter annuals, Asteraceae, achenes, seed germination, afterripening.
Three germination attributes (lag time, maximum germination rate, and final germination proportion) were measured. Environmental conditions approximated the drawdown environment known to stimulate germination in wetland plants: a period of cold stratification followed by position of the seed on the surface of wet, but not inundated, substrate in the presence of light and with a 20/30°C daily temperature cycle. Average seed weight was not correlated with any of the 3 germination attributes studied. Seedling relative growth rate was negatively correlated with time to initiation of germination. Species capable of setting seed their 1st year initiated germination sooner, a larger proportion germinated per day once germination began, and a larger proportion of seeds had germinated by the end of the experiment in comparison with species which require >1 yr to set seed. The time to initiation of germination could accurately classify 89% of the perennial species as being either facultative annuals or obligate perennials. -from Authors
A cladistic study of all 44 species of North AmericanCoreopsis was performed using 35 characters. The resulting cladogram indicated that all 11 sections are monophyletic. At the intersectional level, two lineages were revealed, one consisting of six sections occurring almost exclusively in Mexico and California, and another comprising five sections restricted largely to the eastern and southeastern United States. The cladogram is similar to phylogenies produced by less explicit methods but it differs in two major respects: the monotypic sect.Silphidium is placed with other sections from the southeastern United States rather than with Mexican sections, and sect.Anathysana from Mexico is more closely allied with the three California sections than with sect.Electra from Mexico.
Enzyme electrophoresis was employed to examine genetic variation within and among the three diploid (n=12) species comprisingCoreopsis sectionCalliopsis: C. leavenworthii, C. paludosa andC. tinctoria. Twelve enzymes specified by 20 genes were included, and those isozymes localized in the plastids were identified for several
of the enzymes. Mean genetic identities calculated for pair-wise comparisons of 22 populations (four ofC. leavenworthii, one forC. paludosa, and 17 ofC. tinctoria) reveal no genetic differentiation betweenC. leavenworthii andC. tinctoria, whereasC. paludosa exhibits lowered values with the other two taxa. These results are in general agreement with concepts of relationships inferred
from morphological and biosystematic data. That is,C. paludosa has been viewed as more distinct fromC. leavenworthii andC. tinctoria than the latter two are from each other. The high similarity betweenC. leavenworthii andC. tinctoria is somewhat unexpected, however, given the several morphological features that serve consistently to distinguish them.
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