Blandfordia Grandiflora Research Articles

Why do flowers wilt?

Resources salvaged when flowers wilt on a perennial plant could promote reproduction by, in preference order, the same flowers (Hypothesis 1), adjacent flowers on the same plant (Hypothesis 2), or during the next flowering season by the same plant (Hypothesis 3). We tested the above hypotheses for Blandfordia grandiflora, a perennial species, where some plants included flowers that were allowed to wilt, while equivalent flowers on other plants were prevented from wilting. The abilities of these plants to produce seed were determined by liberally pollinating all flowers. To test Hypotheses 1 and 2, seed set per flower and per plant were compared between plants with and without wilting flowers. To specifically test Hypothesis 3, reproduction was prevented in all flowers. For each experiment, flowering was monitored in the same plants during the next flowering season, thus also enabling Hypothesis 3 to be tested. The results were consistent with Hypothesis 3, but not with Hypotheses 1 and 2. Hence, we verified, for the first time, that plants may benefit from salvaging resources from wilting flowers and re-using these resources for subsequent reproduction. However, contrary to expectations, plants re-used these resources to promote reproduction during subsequent flowering, and not during current flowering by either the same flowers or other flowers on the same plant. The plants must have transferred resources from wilting flowers to underground corms and roots, which provided resources necessary for subsequent flowering. This is likely part of a general plant strategy to salvage resources invested in reproduction during one flowering season and reuse these resources during subsequent flowering.

Patterns of floral nectar standing crops allow plants to manipulate their pollinators

‘Pollination syndromes’ involving floral nectar have eluded satisfactory evolutionary explanation. For example, floral nectars for vertebrate-pollinated plants average low sugar concentrations, while such animals prefer high concentrations, perplexing pollination biologists and arousing recent controversy. Such relationships should result from evolutionary games, with plants and pollinators adopting Evolutionarily Stable Strategies, and nectar manipulating rather than attracting pollinators. Plant potential to manipulate pollinators depends on relationships between neighbouring flowers within plants, for all nectar attributes, but this has not been investigated. We measured nectar volume, concentration and sugar composition for open flowers on naturally-growing Blandfordia grandiflora plants, presenting classic bird-pollinated plant syndrome. To evaluate potential pollinator manipulation through nectar, we analysed relationships between neighbouring flowers for nectar volume, concentration, proportion sucrose, log(fructose/glucose), and sugar weight. To evaluate potential attraction of repeat-visits to flowers or plants through nectar, we compared attributes between successive days. Nearby flowers were positively correlated for all attributes, except log(fructose/glucose) as fructose≈glucose. Most relationships between nectar attributes for flowers and plants on successive days were non-significant. Nectar-feeding pollinators should therefore decide whether to visit another flower on a plant, based on all attributes of nectar just-obtained, enabling plants to manipulate pollinators through adjusting nectar. Plants are unlikely to attract repeat pollinator-visits through nectar production. Floral nectar evolution is conceptually straightforward but empirically challenging. A mutant plant deviating from the population in attributes of nectar-production per flower would manipulate, rather than attract, nectar-feeding pollinators, altering pollen transfer, hence reproduction. However, links between floral nectar and plant fitness present empirical difficulties.

Flowering of Blandfordia grandiflora (Christmas bells) in response to fire frequency and temperature

Blandfordia grandiflora (Blandfordiaceae) is a resprouting perennial herb in wet heathland of coastal and tableland habitats on mainland eastern Australia. It has attractive turbinate flowers of considerable horticultural value. Blandfordia grandiflora is reported to have an enhanced flowering response in the first post-fire flowering season, and management prescriptions advocate frequent fire as beneficial for the species. Nonetheless, the present study appears to be the first to document the flowering response and fate of individual plants exposed to a range of fire frequencies (3-, 6- and 9-year intervals) over an extended period. We also examined the flowering response in unburnt habitat. High survival rates (>95%) were observed for B. grandiflora plants in heathland that had remained unburnt for a minimum of 30 years. Flowering after experimental burns was found to peak in the second post-fire flowering season rather than the first, and there was no clear fire frequency effect. Maximum levels of flowering during the second post-fire season reached 38 to 56% of individuals, although in some years post-fire flowering during this peak season was as low as 23%. Comparatively few plants flowered during the second-year peak season after every fire, and ~34% of individuals in both the 6- and 9-year burn treatments failed to flower at any time. Inter-fire flowering was also observed, and in some instances this flowering was not significantly different to the level achieved during the peak post-fire flowering season. For example, ~9% of individuals flowered 5–7 times over a 12-year period despite being burnt on only four occasions. Flowering after vernalisation (winter-chilling) was observed in unburnt heathland, and the level of this response was not significantly different to peak post-fire flowering in some years. The findings are examined in the context of evolutionary and habitat processes within a climate change framework. Future studies should focus on the complex interactions between climate, fire and soil for not only B. grandiflora, but more importantly for the diverse assemblage of plant species in wet heathland.

Effect of Environment on the Magnitude of Inbreeding Depression in Seed Germination in a Partially Self-Fertile Perennial Herb (Blandfordia grandiflora, Liliaceae)

Inbreeding depression, the decreased fitness of progeny derived from self-fertilization compared to outcrossing, is affected by the environmental conditions in which it is examined, often being greater in adverse environments than in benign environments. We germinated selfed and outcrossed seeds from the same Blandfordia grandiflora plants and estimated inbreeding depression in germination under benign laboratory conditions and adverse field conditions. In both environments, more outcrossed seeds germinated than did selfed seeds. In the laboratory, only 7.7% more outcrossed seeds germinated than did selfed seeds (98.4% ± 0.6 vs. 90.7% ± 3.9), whereas in the field the difference was 22.1% (92.5% ± 1.9 vs. 70.4% ± 5.0). The decrease in germination between the laboratory and field was only 5.9% for outcrossed seeds, but was 20.8% for selfed seeds. Germination of selfed seeds was more variable than of outcrossed seeds in both environments (coefficients of variation, selfed seeds vs. outcrossed seeds: laboratory, 13.6% vs. 1.9%; field, 22.5% vs. 6.5%). Germination success varied significantly among maternal plants, except for outcrossed seeds in the laboratory. In the laboratory, 60% of plants expressed inbreeding depression, whereas in the field all plants expressed inbreeding depression. The magnitude of inbreeding depression was significantly greater in the field than in the laboratory (0.242 ± 0.156 vs. 0.078 ± 0.130). Inbreeding depression of individual plants was positively related between the two environments (r = 0.69). The greater inbreeding depression in the field indicated that selfed seeds were unable to cope with the physiological demands that were imposed by the more adverse field environment.

No Evidence for Demographic Costs of Seed Production in the Pollen-Limited Perennial Herb Blandfordia grandiflora (Liliaceae)

Increased seed production in pollen-limited plants may result in decreases in future fecundity, growth, and/or survival, indicating that resources limit seed set in the long term. In pollen-limited Blandfordia grandiflora populations, I generated high- and low-reproductive-effort plants to examine whether increased seed production resulted in demographic costs over a 3-yr period. I used similar treatments to examine whether trade-offs occurred between seed production and corm mass within a flowering year. To examine how demographic costs might be avoided, I compared masses of leaves, roots, and corms of flowering + fruiting and nonflowering plants. I also examined whether seed production was resource limited by comparing seed abortion, production, and mass in early and late opening flowers on cross-pollinated plants and assessed the magnitude of reproductive effort (RE) in open- and cross-pollinated plants. Seed abortion, set, and mass did not differ between early and late fruits, indicating that sufficie...

Inbreeding Depression and Pollinator Availability in a Partially Self-Fertile Perennial Herb Blandfordia grandiflora (Liliaceae)

In partially self-fertile populations of Blandfordia grandiflora, inbreeding depression and pollinator abundance were examined as factors influencing the evolution of self-fertility. Inbreeding depression at several life-cycle stages was estimated by comparing the performance of crossed and selfed progeny from field-pollinated plants. Seed set was greater and seed abortion was less after crossing than after selfing. Seed weights did not differ. In the glasshouse, crossed progeny outperformed selfed progeny for seed germination, speed of germination, seedling dry weight, relative growth rate and survival. Cumulative inbreeding depression, estimated from seed set, seed germination, seedling dry weight and survival, was 0.69 + 0.03, and was significantly greater than 0.50, the threshold level of inbreeding depression below which selfing should evolve. The availability of avian pollinators was assessed for 3 yr in five different populations. Low numbers of birds were observed on transects (peak flowering in January, 0.6-2.3; end of flowering in March, 0.3-1.0), and a low percentage of flowers were visited by birds (January, 21%; March, 1%). Nectarivorous birds were not important pollinators. Despite variation in abundance of and visitation by birds, natural seed set was similar within and among years (48.958.5%), and seed set of plants from which birds were excluded did not differ from control plants (both about 53%). Selection for reproductive assurance due to the paucity of avian pollinators would have favoured self-fertility in B. grandiflora, despite high inbreeding depression.

Ant Pollination of the Perennial Herb Blandfordia grandiflora (Liliaceae)

Blandfordia grandiflora plants are self-compatible, but do not self-pollinate autonomously. Worker ants of an unidentified Iridomyrmex sp. self-pollinated flowers. Seed-set was about 17%, which was significantly greater than autonomous self-pollination (< 1%), but less than experimental self-pollination (40%). Seed-set of emasculated flowers visited by ants was only 0.1%, indicating that ants do not cross-pollinate flowers. Differences in anther-stigma seperation did not affect seed-set ; seed-sets of flowers with exserted or included stigmas were 1% for autonomous self-pollination and 21% for ant-pollination treatments. Ants possessed thoracic metapleural glands, suggesting that antibiotic secretions that inhibit pollen function are produced. Although significantly fewer pollen grains germinated after thoracic contact compared to control pollen, the difference was only 6% (72.7% vs 78.7%). Seed-set of flowers that were cross-pollinated with pollen that either had been in contact with ants or had not did not differ significantly (78.3% vs 76.3%), suggesting that, if secretions are produced, they only marginally affect pollen function. Pollen loads of ants were small ; individual ants carried about 28 pollen grains, 50% of which were carried on the legs and, hence, away from potential metapleural gland secretions. Ants were observed more often on bagged flowers from which introduced honeybees were excluded than on unbagged flowers ; honeybees probably removed floral nectar from unbagged flowers before ants could recruit to them. In B. grandiflora, avian pollinators infreqeuntly visit flowers. By assuring reproduction, ant-mediated self-pollination may have been an important factor in the evolution of self-compatibility, and may have reduced selection for autonomous self-pollination.

Ovule pre-emption and pollen limitation in a self-fertile perennial herb (Blandfordia grandiflora, Liliaceae).

The extent, frequency and causes of pollenlimited seed production were examined in partially selffertile populations of Blandfordia grandiflora for 2 years. Percentage seed set of open-pollinated plants (50-57%) did not differ within or between years, and was about 19% less than experimentally cross-pollinated plants (70-75%). Floral visits by honeybees did not differ through the flowering season and the number of pollen grains deposited on stigmas within 12 h of flowers opening exceeded the number of ovules per flower, indicating that the quality rather than the quantity of pollination limited seed set. Pollen limitation was caused by concurrent self- and cross-pollination and the subsequent abortion of some selfed ovules due to inbreeding depression. Natural seed set (55%) was intermediate between selfed (43%) and crossed (75%) flowers and was not increased when flowers that had been available to pollinators for 24 h were hand cross-pollinated, suggesting that ovules were already fertilized. Similarly, experimental pollination with both cross and self pollen within 24 h of flowers opening did not increase seed set relative to natural seed set, indicating that both cross- and self-fertilizations had occurred. In contrast, when selfing followed crossing by 48 h, or vice versa, seed set did not differ from crossed-only or selfed-only flowers, respectively, indicating that ovules were pre-empted by the first pollination. Collectively, these results indicate that under natural conditions self pollen pre-empts ovules, rendering them unavailable for cross-fertilization. This selfing reduces fecundity by 50%, as estimated from the natural production of cross seeds when selfing was prevented. Consequently, selection should favour floral traits, such as increased stigma-anther separation or protandry, that reduce interference between male and female functions that leads to selfing.

The control of flowering in Blandfordia grandiflora

The control of flowering of Blandfordia grandiflora (Liliaceae) has been studied in wild populations in the field and in seedlings in the laboratory. In the field flowering was observed at three locations on the coast of eastern Australia, namely Williamtown, Port Macquarie and Wooli. These locations encompass much of the geographic range of the species. Flower initiation began in October, with flowering 5–6 weeks later. Analysis of the weather data at each site indicated that flower initiation in the field occurred when the plants had received over 500 chilling hours below 10 °C, and once the mean ambient temperature was above 16 °C. In general, flowering rhizomes were heavier, wider and deeper in the soil than vegetative rhizomes. Vegetative rhizomes were found with weights down to 1 g, but no flowering rhizomes were smaller than 16 g fresh weight. Plant growth (fresh weight gain) was fastest with a temperature of 27 22 °C (day/night) compared with 15 10 , 18 13 , 21 16 , 24 19 or 30 25 °C , and 50% shade compared with 0, 10 or 70%. In the laboratory, floral initiation could be induced in 3-year-old plants by subjecting them to a cold period of 4–6 weeks at temperatures between 2 and 8 °C. Treatment at 10 °C did not induce flowering. Ten percent of 2-year-old plants could be forced to flower by vernalisation below 9 °C for 5 weeks. The percentage flowering could be increased to 80% with 3-year-old plant material. Thus, the induction of flowering seems to require that plants reach a suitable size and then be vernalised, and shows similarities with other summer flowering bulbs from the same family.

Causes and Consequences of Seasonal Variation in Pollen Limitation of Seed Production in Blandfordia grandiflora (Liliaceae)

Natural seed set was consistently pollen-limited for 5 yr in the perennial herb Blandfordia grandiflora. The extent of pollen limitation varied within seasons, depending on when individual plants lowered. In all years, percent seed set was greatest in January (36-41%) and least in March (12-14%). Seed set of hand-pollinated fruits did not differ within lowering seasons (46-52%), indicating that pollination factors caused natural seed set to vary. Variation in natural seed set was positively correlated with frequency of visits to lowers by nectarivorous birds, but not their abundance in the area. Bird abundance increased during the lowering season, but floral visits decreased. B. grandiflora lowers received about 2 visits in December, 3 in January, fewer than 1 in February and none in March. In February and March, B. grandiflora plants coflowered and competed for bird pollinators with Banksia serrata. In these months, birds preferentially foraged at Banksia serrata inflorescences which produced about 10-fold more nectar per 24 h. The consistently greater natural seed set in January suggests that optimizing selection would favour plants that lower in this month

Breeding Systems of Disjunct Populations of Christmas Bells (Blandfordia grandiflora R.Br., Liliaceae): Variation in Self-Fertility and an Ovular Mechanism Regulating Self-Fertilisation

The breeding systems of disjunct tableland and coastal populations of Christmas bells were determined using hand-pollination experiments. In both populations, 90% or more of self-pollinated plants produced seeds. Tableland plants were significantly more self-fertile than coastal plants (ratio of self seed set to cross seed set: tableland, 0.55 ± 0.03; coast, 0.08 ± 0.02). Significant variation among plants for self-fertility was found in both populations. Autofertility was 1.6% or less in both populations indicating that pollen vectors are necessary for seed set. Seed set by agamospermy in both populations was less than 0.1%. Percentage seed abortion was greater in self-pollinated plants than cross-pollinated plants in both populations. In both self- and cross-pollinated plants, seed abortion was twice as great in the coastal population than in the tableland population. No evidence was found for stigmatic or stylar self-incompatibility. Self and cross pollen adhered to and germinated equally well on stigmas in both populations (72 - 77% germination). Similarly, there were no differences between pollination treatments or populations in the percentage of ovules penetrated by pollen tubes (82 - 89% penetration). When self-pollination preceded cross-pollination by 24 h or longer seed set was significantly reduced compared to flowers that were cross-pollinated only, suggesting ovules were pre-empted by self pollen tubes. Collectively these results strongly suggest that self seed set was reduced by a mechanism operating at the ovule level, such as early-acting inbreeding depression due to recessive seed-aborting genes, although incomplete late-acting self-incompatibility cannot be ruled out. For coastal plants, this ovular mechanism largely prevents selfing, indicating plants were predominantly outcrossing although most produced some self seed. For tableland plants, substantial seed set by selfing may occur under natural conditions.

Floral Morphology, Biology and Sex Allocation in Disjunct Populations of Christmas Bells (Blandfordia grandiflora, Liliaceae) With Different Breeding Systems

Evolutionary shifts in breeding systems are often accompanied by changes in reproductive attributes such as floral morphology and biology, and pre- and post-zygotic allocation patterns. The effects of breeding system variation on several such attributes were examined in self-fertile tableland and outcrossing coastal populations of Blandfordia grandiflora R. Br. In general, overall flower size was similar in both populations, although pedicel and pistil stipe diameters were greater in coastal plants, and pistil length and stigma-anther separation were greater in tableland plants. Although all floral parts from coastal flowers weighed more, proportional biomass allocation to floral parts was similar in both populations. Daily nectar production per flower was similar in both populations. Tableland flowers produced more ovules but fewer pollen grains than did coastal flowers. Pollen-ovule ratios were 11 500 in coastal flowers and 5600 in tableland flowers. Open-pollinated tableland fruits produced more seeds than coastal fruits, but individual seeds weighed less; total seed biomass of tableland fruits was greater than coastal fruits. Prezygotic relative male biomass did not differ significantly between populations. Relative male biomass, estimated from stamen and seed weights, was 5% greater in coastal plants, although populations did not differ significantly. Similarly, relative biomass allocation to pollinator attraction (i.e. coralla and nectar) did not differ between populations. The onset and duration of stigmatic receptivity and pollen longevity of flowers from the two populations were similar. The large differences in ovule, seed and pollen production supports sex allocation theory which predicts that in self-fertile plants resource allocation should be female biased whereas in outcrossing plants, allocation should be male biased. The lack of differences between the Christmas bell populations in other aspects of floral morphology, allocation pattterns and biology suggests that changes in ovule and pollen production precedes changes in other traits during the evolution of autonomous selfing. Overall, these findings suggest that tableland plants may have evolved self-fertility only recently and selection has had insufficient time to change floral traits. Alternatively, self-fertility may not have evolved recently and floral traits promoting outcrossing have been maintained by selection, imposed by inbreeding depression and/or overdominance.

In vitropropagation ofBlandfordia grandiflora(Liliaceae)

SummaryMultiple shoots were obtained when single shoot tips of Blandfordia grandiflora were exposed to different concentrations of kinetin, N6~ benzylaminopurine (BAP) and N6- isopentenylaminopurine (2iP). The best multiplication results were obtained when explants were subjected to kinetin at 8 (iM BAP at 0.5,2 and 8 (iM and 2iP at 2,8,32 and 128 |iM. Preliminary rooting trials were performed with three different auxins: indo- lebutyric acid (IB A), naphthalene acetic acid (NAA) and indole acetic acid (I A A). IB A at a concentration of 8 |iM and IAA at a concentration of 32 |xM gave highest root number, but when transplanted to the glasshouse, the best surviving plantlets were those treated with 2 |xM of IBA or 0.5 μM of IAA.

Nutritional Studies of Christmas Bell

Eighteen-month-old seedlings of Christmas Bell (Blandfordia grandiflora Sm.) in 800-ml containers were top dressed with 8- to 9-month Osmocote controlled-release fertilizer 18N-2.6P-10K at 0, 0.625, 1.25, 2.5, 5.0, or 10 kg·m-3. Other plants were fertilized once or twice weekly with a complete liquid fertilizer supplying 100 mg N/liter based on an N : K ratio of either 1:0.6 or 1:1.5. The former ratio was the same as the Osmocote while the latter was the N : K ratio in tops of healthy wild-growing plants of B. grandiflora. The highest fresh weights occurred at the Osmocote rate of 5 kg·m-3 and with the once-weekly liquid feed of 1 N : 1.5 K ratio. Plants fertilized with low rates of Osmocote were pale green but had extensive root systems that were white and predominantly fibrous. As the rate of Osmocote was increased, plants became greener and produced smaller root systems in which fleshy storage organs were predominant over fibrous roots.