SEED VIABILITY AND GERMINATION BEHAVIOR OF THE DESERT SHRUB ENCELIA FARINOSA TORREY AND A. GRAY (COMPOSITAE)

8 Pages·1999·5.8 MB·English

by  Pamela E Padgett

Madrono, Vol. 46, No. 3, pp. 126-133, 1999
SEED VIABILITY AND GERMINATION BEHAVIOR OF THE DESERT
SHRUB ENCELIA FARINOSA TORREY AND A. GRAY (COMPOSITAE)
Pamela E. Padgett1
Pacific Southwest Forest and Range Experiment Station, USDA-FS, Forest Fire
Laboratory, 4995 Canyon Crest Dr., Riverside, CA 92507
Lucia Vazquez
NY
Department of Plant Biology, Cornell University, Ithaca, 14853
Edith B. Allen
Department of Botany and Plant Sciences, University of California, Riverside,
CA 92521-0124
Fax: [phone]
Abstract
Restoration and revegetation ofarid and semi-arid landscapes requires an understanding ofthe targeted
environmental conditions, physiological requirements ofthe plant species, andhorticulturaltoolsavailable
tocomplete the project. Enceliafarinosa Torrey & A. Gray is ashrub widely adaptedtodesertandcoastal
sage shrublands. It is often included in seed mixes intended for revegetation of disturbed arid lands.
However, the successful establishment of shrubs in wild lands and the ability to grow Enceliafarinosa
under horticultural conditions has been hampered by poor germination percentages, typically 2-5%. In
this study, we endeavored to establish the source ofgermination failure and to testmethods forincreasing
germination. We found that nearly halfthe seeds collected from field sites or donated from a commercial
sourcewere not viable. The seedcoats wereeithercompletelyemptyorcontainedembryosandendosperm
unresponsive to the metabolic indicator Triphenyl-tetrazolium chloride, indicative ofdead tissues. Ofthe
remaining seeds, soaking seeds in gibberellic acid, a well-known germination stimulant, enhanced ger-
mination. The ecological significance of such a large number of non-viable seeds is not understood, but
for restoration purposes, the data suggests pretreatment with gibberellic acid may increase establishment
of genetically mixed stands.
Enceliafarinosa Torrey & A. Gray (Compositae) nated this species, little is known about the reesta-
is an arid-zone shrub with floral structures that are blishment of natural stands.
typical of the family. The seeds are flattened The understanding of restoration and revegeta-
achenes similar in appearance to small sunflower tion processes in disturbed arid and semi-arid hab-
seeds. The edges of the achenes are ciliate and the itats is becoming more important as human utili-
faces are slightly pubescent which may aid in ani- zation and the intrinsic value of arid ecosystems
mal dispersion (Keator 1994). This species is native continue to increase. Adjustments in desert man-
to the deserts of California, Utah, Arizona, and agement such as abandonment of military installa-
New Mexico as well as parts ofnorthwestern Mex- tions, curtailing ofmining operation, restrictions in
ico (Clark 1993). It is also a common component livestock utilization and heightened interest in the
in the drier sites of the Mediterranean coastal sage recreational value of deserts have increased the in-
scrublands of southern California and tends to oc- terest in reestablishment ofnative desert vegetation
cupy alluvial fans and rocky aprons, especially on (Bainbridge et al. 1995). In related semi-arid eco-
south facing slopes (Clark 1993; Keator 1994). En- systems such as coastal sage scrub, the listing of
celia farinosa is facultatively drought deciduous, many plant and animal species as rare, threatened,
normally loosing its leaves during dry summers. It and endangered has driven legal requirements to
will, however, remain evergreen orflush new leaves restore appropriate habitats (Bowler 1990; Minnich
when even small amounts of rainfall or irrigation and Dezzani 1998). However, re-establishment and
are introduced (Smith and Nobel 1986; Ehleringer management ofnative arid and semi-aridvegetation
and Cook 1990). The ecophysiology of this plant has proved challenging due to severeenvironmental
is among the best studied ofthe desert-adapted spe- stresses such as water limitations and high temper-
cies. This is, in part, because of its abundance in atures. (Mooney 1982; Call and Roudy 1991; Bain-
nature and its large and accessible leaves (Nobel et bridge et al. 1995). Many unique adaptations allow-
al. 1998). However, where disturbance has elimi- cionngdiptliaonntss htaovegeervmoilnvaetde. Aanmdonsgurvtihvoeseuanddaeprtattihoensse
are germination strategies designed to inhibit or
1 To whom correspondence should be addressede-mail: trigger emergence depending on environmental
[email protected] conditions (Went 1948; Bowers 1994).
1999] PADGETT ET AL.: GERMINATION OF ENCELIA FARINOSA 127
The reported germination percentages for Ence- from each source were selected for intact, uniform
liafarinosa are typically 2-5% under ordinary hor- appearance and then divided into 10 replicates of
mM
ticultural conditions (Emery 1988; Szarek et al. 20 seeds. The seeds were soaked in a 1 CaCL
1996). Although some work has been published re- solution at 37°C for 1 hr to initiate imbibition and
garding germination under natural field conditions then dissected for TZ staining.
(Went 1948; Bowers 1994), less is known for hor- For evaluation of viability after the petri dish
ticultural approaches. The ability to raise seedlings germination trial, the ungerminated seeds were
under horticultural conditions for scientific study, scored for the presence or absence of fungal con-
ornamental use, or for restoration purposes is im- tamination and the uncontaminated seeds dissected
portant for progress in these endeavors. It may be for TZ staining. In the post-germination viability
even more important in restoration projects where tests, the seeds were scored by the following cri-
natural germination and seedling survival is poor, teria: fungal contamination, presence or absence of
or where rapid revegetations is preferred. Encelia embryo and endosperm, and viability stain. A sim-
farinosa is easily propagated from stem cuttings ilar approach of scoring ungerminated seeds from
(JoshuaTree Nursery personal communication), but the vermiculite pots studies was attempted in order
concerns about overly uniform genetic backgrounds to compare the differences in germination between
in clonal populations makes this a less desirable these studies. Howeverretrieval ofthe ungerminated
option in fragmented habitats where loss ofgenetic seeds from the vermiculite pot studies was unsuc-
diversity could lead to local extinctions. cessful.
The objectives of this work are twofold: 1) to Triphenyl-tetrazolium chloride (TZ) staining is
determine the causes of low germination in seeds an indicator ofmetabolic activity. The method used
from natural populations and from commercial was adapted from Das and Sen-madi (1992). For
sources and 2) to identify readily available seed staining, the seed coats were removed from each
treatments for enhancing germination. seed and the exposed embryo and endosperm were
placed into a solution of 0.5% TZ dissolved in 0.1
mM
Materials and Methods CaCL. Stain-treated seeds were incubated in a
water bath at 50°C for 30 minutes and then inspect-
Seed collection and storage. Three seed sources
ed under a dissection microscope. Viable seeds in-
were used: two collected from local populations
dicated metabolic activity by the presence of a
and one donated from a commercial source. The
strong pink/red coloring of the embryo. Occasion-
locally collected populations were from two coastal
nsearg,easpiptreso,xiBmoaxtelSypr7i0ngksmMoaupanrttaiinnRainvderLsiadkeeCSokuinn-- walalsy sotbasienrivnegdo.fWthheeenndtohisspeorcmc,urbruetdntohtetsheeeedmsbrwyeor,e
ty, CA. The collected seeds from each site were not scored as viable. The intensity and degree of
pooled from many individuals in the population. staining varied markedly from seed to seed, but
The commercially available seed was acquired there did not seem to be any correlation between
from S&S Seed in Carpinteria, CA and consisted magnitude of staining and the seed source, age, or
ofa mixed population ofindividuals collected from germination potential.
southern California. Harvesting and storage of the Germination percentages on differentsubstrates.
S&S seed is presumed to be optimal for commer- Germination percentages were determined by two
cial purposes. Seeds from the three different methods, petri dishes lined with germination blotter
sources were divided into two groups; one was paper and in pots containing sterile vermiculite.
stored in a standard refrigerator at about 5°-10°C The petri dish method is typical of standard ger-
and the other group was stored in the dark at room mination tests and vermiculite is typically used for
temperature. The seeds were stored in paper bags
seedling establishment prior to transplanting into
and were neither cleaned nor sorted prior to stor- potting soil. Seeds to be tested in petri dishes were
age.
transferred after visual inspection to disposable pe-
Prior to planting, each seed was selected individ- tri dishes lined with 2 layers of blotter paper. The
ually after visual inspection under a dissecting mi-
croscope. Seeds containing obvious defects, signs bmloMtteCrapCalpearnwdaasnyprsetmaonidsitnegnesodlutotisoantuwraastiroenmwoivtehd.1
ofpredation orthose smalleror largerthan the pop- 2
Twenty seeds were placed in each dish and the
ulation means were rejected. Acceptable seeds were
dishes were sealed with parafilm to reduce evapo-
pooled and redistributed as required for each ex-
ration. The petri dishes were placed in an incubator
periment. m
under low light (approximately 50 |xmol 2 s~')
Viability determination. Seed viability was tested at a constant temperature of 25°C. Each dish was
in the bulk population prior to germination testing, opened every two days to enumerate germinated
and in the ungerminated seeds following the ger- seeds and to replace the CaCl when necessary.
2
mination tests using a Triphenyl-tetrazolium (TZ) Emergence of the radical was scored as germina-
staining technique. For the evaluation of embryo tion and once counted, the germinated seed was
viability in the bulk seed populations (Box Springs, removed. The evaluations typically ran 10 days af-
Lake Skinner and S&S Seed), 200 uniform seeds ter which further germination was infrequent. At
MADRONO
128 [Vol. 46
LakeSkinner BoxSpringsMt S&S(Commercial)
Fig. 1. Percent viability as determined by tetrazolium staining. Three bulk populations were evaluated: two collected
locally and one donated by a commercial source. The seeds were stored at 5-10°C for6 months prior to testing. Letter
designations denote significant differences at the P < 0.01 level and error bars indicate SEM.
the conclusion of the evaluations, the remaining fatal in most cases (data not shown). Germination
seeds were inspected as described above. trials using native soils or potting media produced
To estimate the germination percentages in ver- poor results regardless of the treatments applied,
miculite, following visual inspection seeds were therefore experiments were conducted using stan-
transferred to 4 inch pots partially filled with moist, dard petri dish and vermiculite techniques only.
sterile, expanded vermiculite (McConkey Co., Once the parameters were established, the experi-
Sumner, WA). The pots were kept in a glasshouse ments described were conducted once for the lo-
with an average light level of two-thirds full sun- cally collected seed source and twice for the com-
light and a temperature regime of 80°F days, 65°F mercially available seeds. Data shown are from
nights. Complete germination generally required 2 commercial source experiments, because the results
weeks. Seedlings were not removed until the end would be easiest to replicate by others.
of the experiment whereupon they were transplant-
ewdasin1t0o0p%o.tting soil. The success of transplanting werSteatisatniaclaylzeadnalybsyis.onGee-rmwianyatiAoNnOpVerAcentuasgiensg
SigmaStat, version 2.0 by Jandel Scientific Soft-
Germination responses to chemical treatments. ware (San Rafael, CA, USA). Statistical signifi-
Seeds were treated with the following chemical so- cance of the differences were generally set at P <
lutions that have been reported tomeMnhance germi- 0.01, but the specific rejection criteria of each ex-
nmaMtioCnaiCn0somaendpl1a0n0t psppemciegsi:bb0e.r5elic aciCda.(ONn0e3)m2,M1 periment is indicated in the text.
3,
CaCL was used as a control (Bewley and Black Results
1994). Some experiments included a combined 0.5- —
mM
Ca(N03)2 and gibberelic acid treatment. Each Seed viability untreated seeds. Dissection and
experimental unit contained 20 seeds and was rep- TZ staining indicated that a large proportion ofthe
licated 5 times per treatment using both petri dishes Enceliafarinosa seeds were either empty (absence
and vermiculate as substrates. of endosperm) or contained a dead embryo (Fig.
Preliminary experiments investigated chemical 1). A comparison of the three seed sources indi-
treatment, incubation temperature, and duration and cated no significant difference in the percent of
appropriate germination substrate. For determina- seeds with a dead embryo, approximately one-third
tion of exposure time, seeds were soaked in solu- of the total. However, seeds collected from Lake
tions at room temperature or at 37°C for 0.5, 1, 3 Skinner had a significantly greater (P < 0.01) per-
or 6 hours. The elevated temperature proved more centage of empty seeds than the other two sources
reliable than room temperature (data not shown) even though the outer appearance of the seed was
and soaking the seeds for more than 3 hours was normal. No significant difference in the percentage
1999] PADGETT ET AL.: GERMINATION OF ENCELIA FARINOSA 129
Cacl2 Gibberelin(GA) GA&Ca(N03)2 Ca(NQ3
TreatmentSolution
Fig. 2. Comparison of the effects of storage temperature on germination response to four common seed treatments.
Data shown is from seeds donated by S&S Seeds, but all seed sources indicated similar responses. Seeds were soaked
30minutes at room temperature in each ofthe solutions indicated. Please referto the materials and methodsforsolution
details. Letter designations denote significant differences at the P < 0.01 level and error bars indicate SEM.
ofempty seeds was found between the Box Springs or from seeds receiving gibberellic acid, Ca(N03)2
Mt and the commercial seed sources (18% and 14% or a combination of gibberellic acid and Ca(N0
3)2.
respectively). Seeds collected from Lake Skinner Seeds stored under cold conditions (shaded bars)
showed the lowest percentage ofviable seeds com- exhibited germination percentages that fell into two
pared to the Box Springs and commercial sources. classes. Mean germination percentages were iden-
On average, only 35% of the seeds collected from tical for untreated seeds and seeds treated with
LcaokmeparSkeidnntoerslwigohutllydmboereextpheacnt5ed0%tofrgeormmtihneatoetheasr oCraCaL.comSbeiendastisoonakoefdbionthCaso(lNut0i3o)n2s, gsihbobwereedliacnaacvi-d
two sources. erage of 50% greater germination than those un-
treated or soaked in CaCL. Analysis of variance
Effectofstorage temperature andchemicaltreat-
identified significant differences between the ger-
ment on germination. Germination was significant-
mination percentages of untreated seeds and seeds
ly affected by storage conditions. Seeds stored for soaked in gibberellic acid, Ca(N0 or a combi-
; psirxoxmiomnattehlsy i5n° tao s1t0a°nCdaerxdhirbeiftreidgetrwatoortohtehlrdeettoimaeps- cnaotnifoindeonfcegibibneterrevlalli.c aNcoiddainffderCean(ceN30)i2n3)2geatrmtihnea9ti5o%n
greater germination percentages than seeds stored between the untreated seeds and the CaCL treated
at room temperature (Fig. 2). Under both storage seeds was noted, and there was no difference
regimes, seeds were placed in paper bags, kept as among the gibberellic acid and N0 treatments.
dry as possible and were not deliberately stratified — 3
(Emery 1988; Bewly and Black 1994). Chemical treatments petri dish tests. Soaking
The response to commonly used germination seeds in commonly used germination stimulants re-
stimulants indicated trends of greater germination sulted in a mix of germination responses (Fig. 3).
with chemical treatment under both room temper- Seeds were selected from the refrigerator-stored
ature and cold storage regimes. Seeds stored at batches, and soaked for 30 minutes, 1 or 3 hours
room temperature (black bars, Fig. 2) germinated at 37°C. In the treatments using CaCL and
at significantly higher percentages (P < 0.01) when Ca(N0 differences in the soaking times did not
soaked in gibberellic acid, Ca(N03)2 or a combi- result i3n)2a,ny significant differences (P < 0.01) in
nation of gibberellic acid and Ca(N0 The CaCL germination percentages. In the treatments using
3)2.
treatment resulted in an intermediate response that CaC0 and gibberellic acid, however, an increase
3
was not significantly different from untreated seeds, in the soaking time suggested a trend in increased
MADRONO
130 [Vol. 46
None CaCI, Ca(N03)2 CaC02 Gibberelin
TreatmentSolution
Fig. 3. Evaluation of chemical treatments and exposure times for enhanced germination of Enceliafarinosa seeds
incubated in petri dishes. Data shown are from commercially available seeds stored under cold conditions. Similar
responses were observed for seeds collected from local sites.
germination. On average, gibberellic acid doubled dish trials, there was no a clear pattern ofincreased
germination as compared to CaCl CaC0 and germination rate with increased soaking times in
2, 3,
Ca(N03)2. Germination percentages among these the different chemical treatments. Germination in
three calcium salts were not significantly different. general, however, was better in vermiculite than in
Contrary to the results shown in the storage tem- the petri dishes. On average, vermiculite produced
perature experiment (at 5°C; Fig. 2), Ca(N03)2 did a 50% increase in germination in the CaCl2 treat-
not result in any clear, significant increases in ger- ment, a 3-fold increase in CaC0 a 3-fold increase
mination as compared to the CaCl2 treatment. A in Ca(N03)2 treatment, and a littl3e, more than 2-fold
comparison of germination percentages in seeds increase in the gibberellic acid treated seeds over
tinreaatseidgnwiiftihcaCntaCdlif2foerreCncae(Nat0t3h)e2 fPor<10h.o1ulrevreelsuslutge-d tshigenipfeitcriantdliyshhiggehremrinaintiotnhes.giGbebremrielnlaitcioancirdemtareianteedd
gesting a slight, but inconsistent response to nitrate. seeds, but the trend was for seeds soaked for 3
Maximum germination even in the gibberellic hours to yield less than seeds soaked for 1 hour.
acid treatment was still less than 20% and between Seeds soaked in CaCl2 for 3 hours had significantly
5% and 10% for most of the other treatments. This lower germination percentages than most of the
is considerably less than the 50% maximum ger- other treatments.
mination indicated by evaluating the bulk seedpop-
ulations (Fig. 1). Discussion
—
tesStseepderfvioarbmieldityon suenegderthmaitndaitdednotsegeedrsm.inVaitaebialfitteyr minEantcieolniabfararriienrossasuicshnaost tkhnoosewnretpoorhtaevdefaornymagenry-
5th0e%10andday6s0%inopfettrhiosdeissheeesdsincdoinctaatiendedthaatdbeeatdweeme-n arid and semi-arid species (Emery 1988; De Hart
bryo and between 5% and 10% of the seeds coats o1f9924;toK5ig%elar1e99t5y)p,icaelvleynentchoouungthergeedr.miTnhaetiloonwrgaetre-s
fwreorme esmeepdtybo(rFinge. s4p).orFesu,ngcallaiimnfeedct2io0n,%ptroes3u0m%abloyf mination rate of Enceliafarinosa has made sexual
the seeds, leaving approximately 5% of those un- propagation of this species problematic for nurser-
ies and restoration projects. The source ofthis poor
germinated seeds with—viable embryos. germination response has not been identified. How-
Chemical treatment vermiculitepots. The over- ever the data presented here clearly sh—ows that a
all pattern of enhanced germination with chemical significa—nt portion ofthe seed population as much
treatment observed in the petri dish trials was rep- as 65% will never germinate because they lack
licated in the pot studies (Fig. 5). As with the petri embryonic or endosperm tissues, or the embryos
1999] PADGETT ET AL.: GERMINATION OF ENCELIA FARINOSA 131
TreatmentSolutions
Fig. 4. Status of ungerminated seeds after chemical treatment and 10 day incubations. Ungerminated seeds were
scored forfungal contamination. Seeds with little orno contamination were dissected andtreated with 0.5% tetrazolium
ofdetermination ofembryo viability.
are not metabolically active. Under horticultural portion of the seeds identified as viable prior to
conditions, a significant portion of the population planting, lost viability during the germination test.
also succumbed to fungal infection. It is possible The reason for this remains unclear.
that infection was enhanced by the absence of vi- Cool storage temperatures significantly increased
able embryo. The data further suggest that some germination of seeds that had been held for 6
None CaCI, Ca(N03)2 CaCO, Gibberelin
TreatmentSolution
Fig. 5. Evaluation of chemical treatments and exposure times for enhanced germination of Enceliafarinosa seeds
planted in vermiculite and grown in the glasshouse. Data shown are from commercially available seeds stored under
cold conditions. Similar responses were observed for seeds collected from local sites.
MADRONO
132 [Vol. 46
months or more. Cool storage serves two functions: development exogenous applications of gibberellic
the reduced temperatures slow metabolic activity of acid stimulates cell elongation (Metraux 1988).
both seeds and infectious microbes and secondly, Given the observation that Encelia farinosa does
cool temperatures contain less water. The dryer the not respond to stratification, nor seems to have any
atmosphere, the longer a seed retains its dormant specific light requirements, it seems reasonable to
condition (Bewley and Black 1994). When seeds surmise that the germination responses to gibber-
are exposed to cool, moist conditions such as re- ellic acid is due to induced enzyme activity.
frigeration storage in damp peat moss, stratification The germination rate was clearly better in ver-
can occur. This common seed treatment is most ef- miculite as compared to petri dishes (Figs. 3 and
fective for temperate species and is thought to pre- 5), but both methods were superior to the germi-
clude early germination until the correct environ- nation percentages ofseeds planted in artificial pot-
mental signal is received to indicate spring (Bewley ting media or native soils (data not shown). There
and Black 1994). Enceliafarinosa is not known to were many environmental differences between
respond to stratification, and because seeds were these two methods, and as a rule the goals of these
not stored in this manner, we do not believe that two methods were different. Vermiculite provides
the enhanced germination of the cold-stored seed no substantial nutrient source (Troeh and Thomp-
was due to stratification. However, the possibility son 1993), but the greenhouse environment provid-
ofa dry chilling requirement in this species has not ed more light, better aeration, and most likely more
been evaluated andcannot be ruled out at this point. compatible moisture regime suitable for transplant-
Of the seeds stored under cool conditions a con- ing germinated seedlings for establishment. While
sistent 30% from each of three pooled populations petri dish methods are rarely used forestablishment
contained seeds with non-viable embryos. Signifi- of potted plants, they are often used to estimate
cant portions of the remaining seeds were only viable seed content. We did not attempt to optimize
empty seed coats leaving the viable population be- the incubator conditions used for the experiments
tween 30% and 50%. It should be noted, however, and it is likely that other parameters may have in-
that this determination was made from a visually creased seedling yield. In any event the relative re-
inspected and uniform population of seeds. These sponses to the seed treatments remain consistent
populations were specifically selected as undam- between the two methods even if the total germi-
aged, and representative of the healthy population nation varied.
mean in terms of size and weight. The seeds that We found that it was nearly impossible, based on
were rejected during inspection were not accurately microscopic observation of undissected seeds or
counted, but we estimate a percentage of about mass of dried seeds, to predict which individuals
25% were unsuitable because of insect predation, would contain a viable embryo. The dried seeds,
broken seed coats, or size and mass outside of the when harvested oras released fromthe flowerhead,
population mean. When this is taken into account are very flat but swelled rapidly with imbibition.
(and assuming that the rejected seeds would not Unfortunately, even seeds without an embryo or an
have germinated), maximum germination percent- endosperm often swelled with imbibition. Also,
ages from the bulk population are expected to be there was no consistent relationship between seed
between 20% and 40%, ifevery viable seed sprout- viability and position on the flower head (data not
ed. shown). Many of the outer-most and innermost
Untreated germination percentages were about seeds were underdeveloped, but these were usually
5% for seeds tested in petri dishes and 12% for eliminated during visual inspection. We could de-
seeds evaluated in vermiculite (control bars in Figs. vise no method for identifying and selecting viable
3 and 5). Gibberellic acid significantly increased seeds prior to planting.
the germination percentages in all of the experi- The adaptive advantage ofthis poor seed set un-
ments under all conditions. The application of the der natural conditions is unclear. A typical Encelia
plant growth regulators gibberellin, cytokinin, and farinosa shrub produces tens ofthousands ofseeds.
ethylene to break dormancy is widely recognized Perhaps by hiding the "good" seeds among the
(Powell 1988). Ofthe three, gibberellin is the most "bad" seed, the viable seeds are more likely to es-
commonly used and frequently substitutes for other cape predation. It seems unlikely that this is the
germination signals such as light and chilling re- result of environmental conditions because of the
quirements. However, not all plants respond to gib- two field sites. Box Springs Mt. is the more highly
berellin (Powell 1988, Bewley and Black 1994). In disturbed and influenced by urban pollution (Allen
cereal grains, applications of gibberellic acid stim- et al. 1997). Yet, Box Springs Mt. had the more
ulate the activity of several enzyme systems in- viable population ofviable seeds. Although the his-
cluding the initiation ofhydrolysis of starch to glu- tory of the commercial seeds is unknown, we as-
cose. Other plant families seem to respond to ap- sume that they were collected from relatively pris-
plications of gibberellic acids with changes in en- tine desert populations. Other than the greater per-
zyme activity, but the numbers of species centage of empty seed coats observed from the
investigated is quite limited (Jacobsen and Chan- Lake Skinner seeds, all three sources behaved re-
dler 1988, Bewley and Black 1994). During cell markably similarly.
1999] PADGETT ET AL.: GERMINATION OF ENCELIA FARINOSA 133
In conclusion: the most significant cause of the De Hart, J. 1994. Propagation secrets for California na-
poor germination in Enceliafarinosa is lack of vi- tive plants. Self Published: 237 Seeman Dr., Encini-
able embryos in nearly 50% of the seeds tested. tas, CA.
Storage at 5° to 10°C resulted in better germination Ehleringer, J. R. and C. S. Cook. 1990. Characteristics
percentages than seeds stored at room temperature. otrfanEsnpcierlaitiaonspreactieesunddiefrferciongmmionnlegaafrdreefnleccotnadnicteioannsd.
Soaking the seeds in 0.1% gibberellic acid for 30 Oecologia 82:484-489.
minutes to 1 hour at 37°C improved germination by Emery, D. A. 1988. Seed propagation ofnative California
about 2 fold as compared to no treatment. And fi- plants. Santa Barbara Botanic Garden, SantaBarbara.
nally germination in horticultural vermiculite fol- CA.
lowed by transplantation into sterile potting media Jacobsen, J. V. and P. M. Chandler. 1988. Gibberillin
resulting in about 30% germination and a success- and abscisic acid in germination cereals, in P. J. Da-
fully reared population of seedlings. vies (ed.), Plant hormones and their role in plant
growth and development. Kluwer Academic Publish-
Acknowledgments ers, Dordrecht, The Netherlands.
Keator, G. 1994. Complete garden guide to the native
Support for this work was partially funded by USDA- shrubsofCalifornia. Chronicle Books, San Francisco,
NRI grant #95-3701-1700. The authors thank Nancy CA.
Storms, Elise Focht, and Jane Wahrman for all of their Kigel, J. 1995. Seed germination in arid and semiarid
hard work in completion of this project. We are grateful regions, in J. Kigel and G. Galili (ed.), Seed devel-
to S&S Seeds for the generous donation of seeds. opment and germination. Marcel Dekker, New York.
Metraux, J.-P. 1988. Gibberellins and plant cell elonga-
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