Propagation/Seed in Natural Environments
Stock, W D; Pate, J S; Delfs, J.
Influence of seed size and quality on seedling development under low nutrient conditions in five Australian and
South African members of the Proteaceae.
Journal of Ecology, v.78, n.4, 1990:1005-1020
Abstract: (1) Seedling development under nutrient-deficient conditions was
investigated for five bradysporous members of the Proteaceae to test the
hypothesis that large seed size and high embryo nutritional quality reflect
the outcome of selection favoring propagules suited for establishment in
infertile soils characteristic of those natural environments dominated by
members of the Proteaceae. (2) Seeds of Protea lorifolia, Protea cynaroides,
Leucadendron laureolum, Hakea sericea and Banksia laricina were germinated and
grown on nutrient-deficient sand for 200 days. Every forty days ten seedlings
of each species were harvested to determine growth, allocations patterns and
nurtient use. Seedling parts were dried, weighed and analyzed for N, P, K, Ca
and Mg. (3) Seedlings of all Proteaceae species were able to survive prolonged
periods of nutrient scarcity irrespective of seed size. (4) Rapid germination
of Proteaceae seeds does not appear to be a significant means of increasing
seedling fitness. (5) Seed mass was positively correlated with seedling size.
(6) No correlation between relative growth rates and seed size was found. (7)
Seeds of members of the Proteaceae show selective storage of specific
nutrients (N and P) such that seed chemical compositions is unbalanced for
optimum seedling growth. These elements complement the rich sources of cations
Ca, Mg and K found in soils of post-fire environments when maximal recruitment
of proteoid species occurs.
Gouws, L; Jacobs, G; Strydom, D K.
Factors affecting rooting and auxin absorption in stem cuttings of protea.
Journal of Horticultural Science, v.65, n.1, 1990:59-64
Abstract: The sensitivity of Protea cv. Ivy to supraoptimum concentrations of
NAA resulting in tissue die-back from the basal cut surface was used as an
indirect method of obtaining information on auxin absorption. Most auxin was
absorbed within the first second of treatment, through the basal cut surface
while lateral absorption was approximately 20 times less effective. The
absorption of auxin was also influenced by the physical and chemical
properties of the auxin carriers. The existence of an auxin gradient was
demonstrated, with the highest concentration at the basal treatment area that
decreased to lower concentrations distal from the cut surface. Concentration,
treatment time and depth as well as auxin carrier affected rooting of Protea
Mustart, P J; Cowling, R M.
Impact of Flower and Cone Harvesting on Seed Banks and Seed Set of Serotinous Agulhas Proteaceae
South African Journal of Botany, v.58, n.5, 1992:337-342
Abstract: Inflorescences and cones of serotinous (canopy-stored seed)
Proteacea are extensively harvested by the wildflower industry from natural
stands in fynbos of the Agulhas Plain, South Africa. This study investigated
the impacts of harvesting on seed bank size and seed set of Protea susannae
Phill., P. obtusifolia Beuk ex Meisn., Leucadendron coniferum (L.) Meisn. and
L. meridianum I. Williams. Harvesting of inflorescences or cones by the
stem-cutting method reduced the following seasons's infructescence (called
'cones') production in all species except P. susannae. Remaining current year
cones of the harvested Protea spp. had greater insect predation levels, and
unaltered or lower seed set, than those of unharvested plants. The seed set
findings are not consistent with the hypothesis that seed numbers are
nutrient-limited, since inflorescence harvesting represents a sink removal,
and increased nutrients remaining in the plant would be available for
increased seed set. Since repeated annual harvesting of 70% of current year
inflorescences or fruit was estimated to result in severe seed bank depletion,
it is suggested that lower levels of harvesting (not more than 50% of current
inflorescences or cones) be performed in alternate years.
Yeaton, R I; Bond, W J.
Competition between two shrub species: Dispersal differences and fire promote coexistence.
American Naturalist, v.138, n.2, 1991:328-341
Abstract: Coexistence mechanisms of two co-occurring species of Proteaceae,
Protea lepidocarpodendron and Leucospermum conocarpodendron, were studied.
Both are tall, arborescent shrubs forming the overstory of the fynbos
communities in which they occur. Seeds of L. conocarpodendron are dispersed by
ants while those of P. lepidocarpodendron are dispersed by wind. The seedlings
compete for space made available for periodic fires. Seedlings of the
ant-dispersed species are scarce under the skeletons of the wind-dispersed
species after a fire but relatively common in open sites. In contrast,
seedlings of the wind-dispersed species are densest under their own skeletons
and rare in open sites. Seedlings of the ant-dispersed species are outgrown by
their wind-dispersed competitors and suffer reduced fecundity and increased
mortality when they co-occur. The adult survival of the ant-dispersed species
in light fires is also reduced when it establishes under or next to the
wind-dispersed species. A Markovian model of the system suggests that ant
dispersal of Leucospermum seed reduces the rate of competitive exclusion by
Protea but is not sufficient to explain the persistence of the former in this
system. To persist, Leucospermum requires open space, which is made available
either by adult survival in light fires which set back its Protea competitor
or by survival as seed banks through burns that destroy the seed banks of
Mustart, P J; Cowling, R M.
Seed germination of four serotinous Agulhas Plain Proteaceae.
South African Journal of Botany, v.57, n.6, 1991:310-313
Abstract: Seeds of Protea susannae Phill., P. obtusifolia Beuk ex Meisn.,
Leucadendron coniferum (L.) Meisn. and L. meridianum I. Williams were tested
for their ability to germinate at different temperatures in the laboratory.
Current year seed of all species had more than 90% germination at
10/20.degree. C and 10/10.degree. C. At 15/30.degree. C germination was
negligible (1 - 3%) in all species except Leucadendron coniferum where it was
44.4%. This could enable L. coniferum to germinate in response to warm season
rains after spring burns. In all species canopy-stored seed of increasing age
had similar germination levels (> 89%). Germination rates of older seeds were
slower, however, than those of younger seeds, lagging between 2.5 to 6 days
behind. This is interpreted as a bet-hedging strategy in response to dry
spells after seed release.
Mustart, P J; Cowling, R M.
Seed size: Phylogeny and adaptation in two closely related Proteaceae species-pairs.
Oecologia (Berlin), v.91, n.2, 1992:292-295
Abstract: We studied seed size, seed nutrient status and seedling growth of
two closely related fynbos Proteaceae species-pairs growing on juxtaposed
soils of different nutrient and moisture status. Seeds had a greater mass and
higher phosphorus and nitrogen contents for species occurring on limestone
(higher nutrient and moisture contents) than those on the colluvial sands
(lower nutrients and moisture). This trend was found within, but not across
genera, stressing the importance of phylogeny in interpreting adaptations. It
would be difficult to test for the effects of either nutrients or moisture
separately, since the same advantage of enhanced seedling size, and hence
survival in a stressed environment, applies to both factors. The increased
root: shoot ratios (using lengths) of the Leucadendron species relative to the
Protea species are interpreted as an attempt to overcome a phylogenetic
constraint that results in smaller seed size in the former genus.
Witkowski, E T F.
Growth and competition between seedlings of Protea repens (L.) L. and the alien invasive, Acacia saligna (Labill.) Wendl.
in relation to nutrient availability.
Functional Ecology, v.5, n.1, 1991:101-110
Abstract: Seedlings of Acacia saligna (Labill.) Wendl., an alien invasive
shrub of coastal fynbos, and Protea repens (L.) L., an indigenous shrub, were
grown in pots, as single seedlings and as a mixture. These were amended with
one of a range of treatments representing a broad gradient in nutrient
availability. When grown in isolation, both species displayed increases in dry
mass, and leaf nitrogen and phosphorus contents in response to increasing
levels of nutrient availability. A. saligna however, exhibited a greater
response than P. repens, particularly at high levels of nutrient availability.
No significant differences in root/shoot ratio were found in response to
variation in nutrient availability, but A. saligna consistently allocated a
greater proportion of its total dry mass to below-ground growth. When grown as
a mixture, P. repens exhibited reduced growth at high levels of nutrient
availability in response to competition with A. saligna, which totally
overtopped the indigenous species. In root observation chambers, the depth
penetration of the soil by the tap root of seedlings of A. saligna after
germination was approximately twice as rapid as that of P. repens. Seed
nitrogen and phosphorus contents were significantly linearly related to seed
size, except the phosphorus content of A. saligna. The relatively high
absolute growth rate of A. saligna seedlings, at practically all levels of
nutrient availability found in the fynbos, appears to be one of the key
factors which enables them to compete successfully with P. repens seedlings.
Le Maitre, D C.
The influence of seed aging on the plant on seed germination in Protea neriifolia (Proteaceae).
South African Journal of Botany, v.56, n.1, 1990:49-53
Abstract: Protea neriifolia R. Br. retains its seeds in the canopy in
persistent, woody inflorescences. The effects of ageing on the plant on
percentage germination and germination rates of seeds were examined in a
controlled (light, temperature) environment and in an open environment under
cover. The seeds were classified into the following age classes: current years
crop, previous years crop and all seeds reamining in inflorescences produced
prior to this. The aims of this study were to determine whether the
germination patterns of seeds were influenced by seed age and the conditions
under which the seeds germinated. The percentage germination of seeds did not
decline markedly with increasing seed age but the germination trays took
longer to emerge and appeared less synchronously than seeds placed on the
surface. Seedlings from seeds 3 or more years old will experience a greater
risk of mortality during germination and establishment because they take
longer to emerge and start growing. Successful germination and seedling
establishment in the field may require 4 or more weeks of moist conditions, a
condition which would generally restrict germination to the rainy season.
Midgley, J J; Viviers, M.
The germination of seeds from heated serotinous cones of eight shrubland species.
South African Forestry Journal, n.155, 1990:5-9
Abstract: Freshly picked "cones" of eight serotinous species [Leucadendron
uliginosum, Li salignum, L. eucalyptifollium, L. conicum, Protea repens, Hakea
salicifolia, H. sericea, Widdringtonia cuppressoides.] from firesprone
shrubland ecosystems were exposed to short periods (30, 60, 90s) of high
temperature (650.degree. C). In some species greater numbers of treated seeds
germinated than seeds from the controls. The implications of these results are
briefly discussed in terms of post-free regeneration of shrubs.
Musil, C F.
Seed bank dynamics in sand plain lowland fynbos.
South African Journal of Botany, v.57, n.3, 1991:131-142
Abstract: Seed inputs to the soil, pre- and post-fire non-dormant soil-stored
seed reserves and seedling population densities were compared in one
serotinuous and four non-serotinous species. In all non-serotinous species,
estimated numbers of viable seeds per unit area released annually to the soil
generally exceeded by several orders of magnitude recorded seedling population
densities following an ensuing late spring wild fire. Similar patterns were
evident where estimates of annual viable seed inputs to the soil were compared
with measured non-dormant soil-stored seed reserves. The latter increased up
to 10-fold in soils after fire. In serotinous Protea repens, correction of
measured fire-induced seed input for an observed 72.5% reduction in seed
viability in cones during fire resulted in an estimated seed input similar to
this species's recorded post-fire seedling population density. Data suggest
that dormant seed reserves do not accumulate in fynbos soils between fires.
This may explain localized species population extinctions and sensitivity of
fynbos to disturbance.
Wright, M G; Visser, D; Van der Merwe, E K.
Poor regeneration of Protea magnifica (Proteaceae) after a mid-summer fire in the Cederberg [Cape
Province, South Africa].
South African Journal of Wildlife Research, v.20, n.3, 1990:121-122
Abstract: Regeneration of Protea magnifica, a serotinous species, was
investigated following a mid-summer fire in the Cederberg, Cape Province. Poor
seedling establishment occurred, with 61% of parent plants failing to produce
seedlings. Parent plants produced an average of 0.87 seedlings each. This low
rate of establishment is attributed to low viable seed store in mid-summer and
the long period prior to first post-fire rain. It is suggested that late summer
or autumn fires would be more beneficial to the plant species studied.
Manders, P T.
Seed dispersal and seedling recruitment in Protea laurifolia.
South African Journal of Botany, v.52, n.5, 1986:421-424
Abstract: The pattern of seedling recruitment around a single isolated Protea
laurifolia Thunb, individual after a fire, was determined using a chi-square
goodness of fit test for uniformity and Rayleigh's test for direction.
Recruitment occurred largely to the north-west of the parent plant whereas the
wind after the fire came largely from the south-east, providing some evidence
of the influence of wind on dispersal. The maximum distance of a seeding from
the parent plant was 26.3 m, with 95% of recruitment occurring within 15 m of
the parent. To speed up the rate of migration in areas where the species has
been eradicated the establishment of point seed sources is suggested.
Bond, W J.
Fire survival of Cape Proteaceae: Influence of fire season and seed predators.
Vegetatio, v.56, n.2, 1984:65-74
Abstract: Many Cape Proteaceae store seed reserves in closed cones on the
plant and rely entirely on these reserves for episodic recruitment after
fires. Population size is sensitive to intervals between fires but also on
fire season. Populations can be nearly eliminated by successive winter or
spring fires. Three hypotheses explaining seasonal variation in recruitment
were tested: seeds germinate immediately after fire but seedlings die from
summer drought; seeds remain dormant over summer but the longer the delay
between seed release after fire and germination the greater the competition
between seedlings and resprouts, or the greater the seed losses to predators
and/or decay before germination. Drought-avoiding dormancy occurred in 9 of 11
Cape Proteaceae studied [Protea rouppelliae, P. aurea, P. eximia, P. repens,
P. coronata, P. lovifolia, P. punctata, Leucadendron rubrum, L. conicum, L.
eucalyptifolium, L. uliginosum], all of which delayed germination to autumn or
winter. Seedling emergence and survival was not significant increased after
removal of competitors by methyl bromide poisoning. Seed predation, measured
by exclosures, however, significantly reduced seed reserves before germination
and also number of seedlings emerging. Post emergence seedling predation was
negligible in the burn in contrast to adjacent mature vegetation where
seedling predation was very heavy. The role of germination cues and rodent
behavior in controlling population recruitment is discussed and it is
concluded that a knowledge of both is essential for predicting vegetation
dynamics in this system.
Bond, W J.
Proteas as "tumbleseeds": Wind dispersal through the air and over soil.
South African Journal of Botany, v.54, n.5, 1988:455-460
Abstract: The fruits of the genus Protea have long stiff trichomes forming a
pappus-like structure. In serotinous species the achenes (seeds) are released
only after fire when vegetative barriers to dispersal are minimized. The
dispersal of seed by free-fall from the cones to the ground (phase I) was
compared with subsequent dispersal by rolling over the substrate (phase II).
Seed shadows observed in the field as well as seed release under controlled
conditions suggest that phase I dispersal is seldom more than 30 m. However
phase II dispersal distances measured both from seed shadows and
controlled-release experiments were much greater, frequently exceeding 50 m
with a maximum over 500 m. The most important biological determinant of both
phase I and phase II dispersal was the size of the tuft of hairs and wing
loading of the seed. Substrate roughness was a major physical determinant of
phase II dispersal distance. In rocky areas, phase II dispersal can be
effectively discounted. In smooth areas, previous estimates of Protea
migration rates may be an order of magnitude too low. Other Cape Proteaceae
with hairy seeds and serotinous cones occur in Aulax and a few species of
Leucadendron. This convergence suggests that long-distance phase II transport
may have adaptive value.
Bond, W J.
Canopy-stored seed reserves (serotiny) in Cape [South Africa] proteaceae.
South African Journal of Botany, v.51, n.3, 1985:181-186
Abstract: Many species in several genera of Cape Proteaceae retain seeds in
serotinous cones for a number of years after they have matured. This study is
a report on the contribution of canopy-stored seeds to viable seed reserves.
Cone retention patterns were censused for most of the common serotinous
species in southern Cape fynbos and for Protea nitida, a non-serotinous
species. Germination trials were conducted in an open nursery to determine
age-related variation in seed viability. Significant numbers of viable seeds
were stored for a year or more in all the serotinous species studied but the
contribution of two-year and older cones was small in Protea repens and
Leucadendron conicum. These results suggest that seasonal variation in
pre-burn seed reserves is not sufficient cause for recruitment failure in
stands of serotinous Proteaceae burnt in winter or spring. Adaptive suites of
characteristics associated with serotiny are described and contrasted with
non-serotinous species of fynbos Proteaceae.
Schwilk, D. W.; Keeley, J. E.; Bond, W. J..
The intermediate disturbance hypothesis does not explain fire and diversity pattern in fynbos.
Plant Ecology, v.132, n.1, 1997.:77-84.
Abstract: The intermediate disturbance hypothesis is a widely accepted
generalization regarding patterns of species diversity, but may not hold true
where fire is the disturbance. In the Mediterranean-climate shrublands of
South Africa, called fynbos, fire is the most importance disturbance and a
controlling factor in community dynamics. The intermediate disturbance
hypothesis states that diversity will be highest at sites that have had an
intermediate frequency of disturbance and will be lower at sites that have
experienced very high or very low disturbance frequencies. Measures of
diversity are sensitive to scale; therefore, we compared species richness for
three fire regimes in South African mountain fynbos to test the intermediate
disturbance hypothesis over different spatial scales from 1 m-2 to 0.1
hectares. Species diversity response to fire frequency was highly
scale-dependent, but the relationship between species diversity and
disturbance frequency was opposite that predicted by the intermediate
disturbance hypothesis. At the largest spatial scales, species diversity was
highest at the least frequently burned sites (40 years between fires) and
lowest at the sites of moderate (15 to 26 years between fires) and high fire
frequency (alternating four and six year fire cycle). Community heterogeneity,
measured both as the slope of the species-area curve for a site and as the
mean dissimilarity in species composition among subplots within a site,
correlated with species diversity at the largest spatial scales. Community
heterogeneity was highest at the least frequently burned sites and lowest at
the sites that experienced an intermediate fire frequency.
Effect of smoking treatment on the seed germination of
wild flowers. Kagawa Daigaku Nogakubu Gakujutsu Hokoku, v.49,
n.2, Oct., 1997.:199-205.
Abstract: Seed germination of 36 native Australian, South African and South
American species using smoke was investigated. Smoking treatment stimulated
germination of Anigozanthos humilis, A. manglesii, Banksia prionotes,
Eucalyptus macrocarpa, Hypocalymma robstum, Protea compacta, Thysanotus
multiflorus, Verticordia nitens. On the other hand the smoking suppressed seed
germination of Nuytsia floribunda, Pasithea coerulea, Protea neriifolia, P.
repens, Schizanthus grahamii. Seedling from smoked seeds of Actinostrobus
pyramidalis and Trachymene caerulea showed higher survival compared with those
from non-treated seeds after transplanting to soil containing fertilizer.