High Levels Of Germination Research Articles

Effect of Temperature on Conidial Germination of Botryosphaeriaceae Species Infecting Grapevines.

Germination of conidia of eight botryosphaeriaceous fungi infecting grapevines was evaluated after 2, 4, 6, 12, and 24 h incubation under eight different temperatures (5, 10, 15, 20, 25, 30, 35, and 40°C). The effect of temperature on conidial germination was also evaluated in different stages (hyaline versus pigmented conidia) of the species Lasiodiplodia theobromae. Conidial germination of Botryosphaeriaceae species infecting grapevines was significantly affected by temperature. Overall, conidial germination increased significantly with longer incubation times, especially from 2 to 12 h. In most cases, germination of conidia was not significantly different between 12 and 24 h incubation. Conidia of botryosphaeriaceous species did not germinate (with the exception of Botryosphaeria dothidea and Neofusicoccum parvum) at 5°C, and only B. dothidea, Diplodia seriata, and L. theobromae showed high levels of conidial germination at 40°C. Optimum conidial germination temperatures (defined as the temperature in which germination reached at least 50% in the shortest incubation time) were 25°C for B. dothidea and Dothiorella iberica, 25 to 30°C for Spencermartinsia viticola, 30°C for Diplodia corticola, D. mutila, D. seriata, N. parvum, and hyaline L. theobromae, and 40°C for pigmented L. theobromae conidia. Successful conidial germination of species of Botryosphaeriaceae infecting grapevines was always observed between 10 and 35°C with the exception of Dothiorella iberica and pigmented L. theobromae conidia, neither of which germinated at 35 and 10°C, respectively. Results of this study show conidia of botryosphaeriaceous species infecting grapevines to be capable of germination under a broad range of temperatures including those considered to be extreme, which may explain the success of these species as grapevine pathogens throughout most of the grape-growing areas in both Northern and Southern Hemispheres.

Histological responses of host and non-host plants to Hyaloperonospora parasitica

Differences in Hyaloperonospora parasitica development and plant tissue responses were compared for 10 cruciferous hosts (including both resistant and susceptible genotypes), 3 leguminous and 1 graminaceous non-host species. Cotyledons, or true leaves in the case of Triticum aestivum and Pisum sativum, were studied at 2, 8, 24 h and 3, 5, 7 days post inoculation (dpi). The high levels of zoosporangial germination observed on all species tested, as well as on glass slides, suggested that inhibition of germination did not play a significant role in distinguishing host versus non-host resistance. During the early stages of infection, at spore germination and host penetration, there was no evidence of a clear-cut difference between Brassica host species which displayed a hypersensitive, partially resistant or susceptible reaction compared with non-host species. Haustoria formation was the key infection phase for the establishment of biotrophy. Across all tested species, haustoria were initiated inside the epidermal cells. However, there were significant differences in the frequency and timing of haustorial formation and the final size of haustoria among the tested species at early infection stage. Fully developed haustoria were never observed in Raphanus raphanistrum, Triticum aestivum, Lupinus angustifolius nor Trifolium subterraneum. Instead, the haustorium development appears to abort in the penetrated epidermal cells of these species. Although haustoria were formed in the epidermal and mesophyll cells of Sinapsis alba and Pisum sativum, subsequent hyphal growth and/or continued haustoria formation were rare or few, respectively. Hypersensitive reaction was the key resistance response observed among the host and non-host resistant species tested. It is noteworthy that, in the initial stages of pathogenesis, there was no differentiating point that separated the non-host species from those that were hosts.

Screening of maize genotypes for low <i>Striga Asiatica</i> stimulant production using the 'agar gel technique'

One of the best characterized mechanisms of resistance to the parasitic weed ( Striga ) is low germination stimulant exudation by host plants. Using a simple and rapid agar gel assay, 112 maize genotypes were tested for low stimulant production and haustorium initiation of Striga asiatica (L.) Kuntze. Most of the genotypes induced high level of germination of Striga seeds at distances more than 1.3 cm, from the crop seedling root to the furthest germination Striga seed. Germination distance highly correlated with rate of germination and was used as a quick way of determining the level of haustorial germination induced by the test genotypes. Some breeding lines such as PR 91A 496-13 and PR 91A 496-25 induced moderately low germination. B 37.91-952-1 induced the least germination distance (0.87cm). This is comparable to that of highly resistant sorghum varieties. The commercial varieties induced high level of germination. A similar procedure was followed to observe the rate of haustorium initiation. Despite the tendency to stimulate considerably high germination, some entries permitted very low haustorium initiation. The best three lines in terms of low haustorium initiation were PR 496-45, PR 91B 5323 33x34 and PR 91A 496-17. There was no relationship between germination distance and haustorium initiation.

Onset of Dormancy, Dormancy Levels, and Appropriate Seed Production Environment for Two Subspecies ofVernonia galamensis(Cass.) Less

Detailed germination studies were conducted on seeds of two subspecies of Vernonia. galamensis (nairobiensis and afromontana var. gibbosa), a potential industrial oil crop. Plants of both subspecies were grown at two experimental sites in Kenya and sequential harvesting carried out during seed development to determine the best production environment and optimum harvest time for low-dormant, high-quality seed-lots. Seeds harvested at different maturity levels were germinated under different temperature regimes before and after desiccation. The studies revealed that the onset of germinability and desiccation tolerance was achieved during the dry matter accumulation phase of seed development and that seeds developed dormancy 3 to 6 d after acquiring germinability, with high levels of germination only reaching under an alternating temperature regime. The seeds of the subsp. nairobiensis were shown to be more dormant than those of the subsp. afromontana var. gibbosa. Similarly, seeds harvested from a warmer en...

Flower longevity and duration of pistil receptivity in high mountain plants

Flowers of high mountain plants are generally long-lived to compensate for the low frequency of pollinator visits at higher altitudes. However, nothing is known about floral plasticity when pollinators are absent because of unsuitable weather conditions. We investigated both, actual longevity of naturally pollinated flowers and potential flower longevity, the capacity to prolong corolla life-time and pistil receptivity when pollination is retarded. Seven high mountain plant species from different elevations in the European Alps were tested: Gentianella germanica, Ranunculus alpestris and Saxifraga caesia are restricted to the alpine zone, Cerastium uniflorum, Ranunculus glacialis, Saxifraga bryoides and Saxifraga moschata occur from the higher alpine to the glacier zone. Flower longevity differed greatly among species, according to their taxonomic background and their gender sequence type. Actual flower longevity ranged from a few days ( G. germanica, C. uniflorum, R. alpestris) to more than two weeks (saxifrages, R. glacialis). Unpollinated flowers generally increased longevity, but the plasticity of single floral functions was quite different. Stigma receptivity could be maintained longest. Pollen adhesion was enabled during the full stigma life-time. High levels of pollen germination and pollen tube growth were still possible 29 days after anthesis (DAA) in R. glacialis, and 23 DAA in S. bryoides. In the remaining species this ability was gradually lost or, in C. uniflorum, abruptly ended around 10 DAA. The overall pistil receptivity primarily depended on the duration of ovule receptivity, which in most species ended between 16 and 20 DAA. Corolla life-time was significantly prolonged in S. bryoides, S. moschata and G. germanica. In the remainder of species mean corolla longevity did not differ from the actual longevity, and thus any prolongation of female functions over the corolla life-time would not contribute to reproductive success. The maximal potential longevities of individual flowers with fresh corolla and receptive pistils were 21 d in S. moschata followed by S. caesia (19 d), S. bryoides, R. glacialis (18 d) and G. germanica (14 d). R. alpestris (8 d) and C. uniflorum (8 d) exhibited the shortest potential overall flower longevities. Contrary to our expectations, flower longevity did not significantly differ between the alpine and the high-elevation species.

Germination frequency of woody species in exotic plantation and bush fallow land area in Umuahia, Abia State

In a field study involving 21-year old exotic plantations and a bush fallow land use system at Forestry Institute of Nigeria (FRIN) Umuahia, Abia State, the germination of indigenous woody species and litterfall were monitored. Enumeration of indigenous woody species was carried out within a 3.5 x 3.5 quadrat plot. The Pine/Gmelina mixed stand had the highest level of germination among the exotic plantations with a total population of 140 species with 14 families followed by Pine stand with 121 species and 14 families while Gmelina stand had the least germination with 115 species and 11 families. Pine stand was significant (P

A plurality of causal mechanisms explains the persistence or transience of soil seed banks

Annual forbs form short-term persistent soil seed banks whereas perennial grasses form mostly transient ones in the central Monte desert. A conceptual framework predicts that annual forb seeds will have primary dormancy, whereas perennial grasses will have low dormancy levels. We assessed whether the dormancy traits of four annual forb species and five perennial grass species can account for their soil seed bank dynamics. To overcome dormancy, we treated perennial grasses and autumn annual forbs with high temperatures, and spring annual forbs with low temperatures. To force seeds into secondary dormancy we exposed non-dormant perennial grasses to low temperatures. Most of the annual forbs and two perennial grasses ( Setaria leucopila and Sporobolus cryptandrus) showed low germination rates. The remaining perennial grasses presented moderate ( Pappophorum caespitosum and Digitaria californica) or high germination levels ( Trichloris crinita). Low temperatures increased germination in spring forbs ( Chenopodium papulosum and Parthenium hysterophorus), but high temperatures did not break dormancy in autumn forbs ( Sphaeralcea miniata and Phacelia artemisioides). Germination of perennial grasses increased after they had been exposed to high temperatures, but only two species reentered into dormancy under low temperature. Given that in the central Monte desert winter–autumn granivores eat mainly grass seeds, we conclude that high seed dormancy and low consumption may contribute to the persistent soil seed bank of most forbs, and that seed dormancy itself does not explain the transience of grass seed banks.

Habitat-related germination behaviour and emergence phenology in the woodland geophyte Anemone ranunculoides L. (Ranunculaceae) from northern Italy

AbstractThis study examined whether the restricted habitat preference of the spring-flowering woodland geophyte Anemone ranunculoides L., compared with that of A. nemorosa growing in the same woodlands in northern Italy, could be explained by subtle differences in germination preference and emergence phenology. Immediately after harvest, seeds of A. ranunculoides were either sown on agar in the laboratory under simulated seasonal temperatures or placed in nylon mesh sachets and buried in the wild. Embryos, undifferentiated at the time of seed dispersal, grew during summer in the laboratory and in the wild, culminating in radicle emergence in the autumn, when temperatures fell to c. 15°C. Shoot emergence was delayed under natural conditions until soil temperature had dropped further to c. 10°C. Compared with populations of the closely related Anemone nemorosa L. occupying the same woodland habitat, which have been reported to have non-dormant radicles, A. ranunculoides displayed a narrower temperature tolerance for radicle emergence and high levels of germination were possible only after prolonged exposure to summer conditions, indicating physiological dormancy. However, unlike A. nemorosa, shoot emergence in A. ranunculoides was not dependent on winter temperatures, suggesting weaker epicotyl morphophysiological dormancy. Under a regime of diurnal temperature alternation, simulating the microclimate where there is little plant cover, germination failed almost completely; this could explain the absence of A. ranunculoides in open habitats.

Seed dormancy and germination ecology of Lamyropsis microcephala: a mountain endemic species of Sardinia (Italy)

Lamyropsis microcephala only occurs in a very restricted area in the Gennargentu massif (CE-Sardinia, Italy) at 1450-1700 m a.s.l. This rare species has been inserted in the International Union for Conservation of Nature (IUCN) Red Lists under Critically Endangered. In this study, the effect of a pre-chilling period (90 days at 5°C) on germination was investigated as well as the ability of this species to form a soil seed bank. L. microcephala seeds exhibited type 2 non-deep physiological dormancy. Pre-chilling increased the final germination percentages, the germination speed and the temperature range at which high levels of germination were observed. The high optimal germination temperatures (ca. 70% germination at 30°C) demonstrate that this species is well adapted to a temperate climate and the lack of a persistent soil seed bank represents a rarity trait that likely exacerbates the threats to the survival of this species.

Laboratory Methods for Breaking Dormancy in Garlic Mustard (Alliaria petiolata) Seeds

AbstractGarlic mustard seeds are dormant at maturity, and 90 to 105 d of cold-moist stratification at 4 C have been used to induce germination. We studied methods for breaking dormancy and inducing germination without cold stratification, for use in laboratory and greenhouse experiments with garlic mustard. Seeds were collected from large infestations, stored at room temperature, and subjected to chemical and mechanical scarification treatments. For chemical scarification, seeds were immersed in 3% (v/v) H2O2 for 12, 24, or 48 h with constant stirring, or immersed in concentrated (95 to 97%) H2SO4 for 1 or 5 min with stirring. For mechanical scarification, seeds were placed in a sandpaper-lined tumbler for 1 or 3 s. Scarified seeds, along with non-scarified seeds, were placed in petri dishes on germination blotters saturated with gibberellic acid (GA3, 10−3 M) or deionized water, and incubated for 35 d at either 20/10 C or 15/6 C (12 hr/12 hr). None of the non-scarified seeds germinated, regardless of germination solution or temperature. Seeds germinated only following scarification, and only when imbibed in GA3 solutions. Seeds immersed in H2SO4 for 5 min or mechanically scarified for 3 s had the highest level of germination in GA3. Cumulative percent germination after 35 d was greater for seeds stored 30 mo (44 to 83%), than for seeds stored 6 (2 to 60%) or 18 mo (35 to 79%), regardless of scarification treatment. The germination results, along with scanning electron micrographs of seed coats, suggest that the intact garlic mustard seed coat is permeable to water but not GA3; therefore, both scarification and GA3 are needed to break dormancy and induce germination without cold stratification.

Germination Ecology of Chinese Sprangletop (Leptochloa chinensis) in the Philippines

Chinese sprangletop is a grass weed that has the ability to grow in both flooded and upland conditions, which makes it a widespread and abundant weed in rice and many other crops. Experiments were conducted to study the germination of this weed in the Philippines. Germination was strongly stimulated by light and warm fluctuating temperatures, suggesting high emergence of Chinese sprangletop on bare ground such as a crop seedbed. A high level of germination (95%) immediately after seed harvest suggests that the soil seed bank of this species could be depleted by stale-seedbed strategies. Seed burial depth in soil strongly influenced emergence of this weed, and no seedlings emerged from seeds buried at depths of ≥ 0.5 cm. Maximum emergence (80%) from seeds placed on the soil surface suggests that no-till practices would enhance the emergence of seedlings. Seedling emergence from surface-sown seeds was similar (80 to 82%) between saturated and aerobic-moist soil, demonstrating that this weed does not require a saturated soil and that it can emerge from a moist soil. Flooding, even though not continuous or deep, had a suppressive effect on the emergence and dry matter of Chinese sprangletop. Germination responses to light and seed burial depth were different between our study in the Philippines and the study conducted with seeds of an Italian population, suggesting that Chinese sprangletop might be polymorphic. The implications of this information for weed management strategies are discussed.

The combined effects of high pressure and nisin on germination and inactivation ofBacillusspores in milk

The aim of this work was to investigate the germination and inactivation of spores of Bacillus species in buffer and milk subjected to high pressure (HP) and nisin. Spores of Bacillus subtilis and Bacillus cereus suspended in milk or buffer were treated at 100 or 500 MPa at 40 degrees C with or without 500 IU ml(-1) of nisin. Treatment at 500 MPa resulted in high levels of germination (4 log units) of B. subtilis spores in both milk and buffer; this increased to >6 logs by applying a second cycle of pressure. Viability of B. subtilis spores in milk and buffer was reduced by 2.5 logs by cycled HP, while the addition of nisin (500 IU ml(-1)) prior to HP treatment resulted in log reductions of 5.7 and 5.9 in phosphate buffered saline and milk, respectively. Physical damage of spores of B. subtilis following HP was apparent using scanning electron microscopy. Treating four strains of B. cereus at 500 MPa for 5 min twice at 40 degrees C in the presence of 500 IU ml(-1) nisin proved less effective at inactivating the spores of these isolates compared with B. subtilis and some strain-to-strain variability was observed. Although high levels of germination of Bacillus spores could be achieved by combining HP and nisin, complete inactivation was not achieved using the aforementioned treatments. Combinations of HP treatment and nisin may be an appealing alternative to heat pasteurization of milk.

The Effects of Tannery Wastewater on the Development of Different Plant Species and Chromium Accumulation in Phragmites australis

Toxicity tests were performed to assess the effect of tannery wastewater with different treatment levels on two wetland plants, Phragmites australis and Typha latifolia, which are frequently used in constructed wetlands (CWs) for water treatment, and thus deepen the knowledge on their capacity to withstand the application of industrial wastewater. Trifolium pratense, a plant generally used as an indicator in toxicity tests, was included as a control. End points measured were germination percentage, shoot length, root elongation, and biomass growth of the plants. When tannery effluent, with a low treatment level, was supplied to the wetland plants germination occurred even at effluent concentrations of 100%, whereas germination of T. pratense was completely inhibited, almost invariably, at effluent concentration of 50%. Higher germination levels were achieved when the plants were exposed to effluent originating from the outlet of constructed wetland pilot units, allowing germination of all tested plants, indicating a significant decrease in its toxicity level. Experiments conducted with the same plants using different growing substrata as the germination matrix, namely expanded clay aggregates (Filtralite MR 3-8 and Filtralite NR 3-8) and two types of sand (fine gravel and standard sand) have shown that higher germination levels were achieved in standard sand and that P. australis was the plant species showing higher germination in all cases, reinforcing the robustness of this plant to environmental stress. The phytoextraction potential of P. australis, was evaluated by subjecting the plant to tannery wastewater supplemented with 50 and 150 mg Cr/L. After 6 weeks of exposure, levels up to 4825, 883, and 627 mg Cr/kg were found in the rhizome, shoot, and leaves, respectively, although phytotoxic signs in the plant were evident. This plant might not be considered a chromium hyperacumulator, but the potential to extract and accumulate this metal on its rhizomes is high.

Laboratory germination of seeds from 10 British species of Potamogeton

Factorial laboratory germination experiments were carried out on fruits from 10 British species of Potamogeton (Potamogetonaceae). Fruits had all been placed in a dry-room maintained at 15% RH and 15 °C for 3–6 months from the time of collection. Maximum levels of germination ranged from 13% ( P. polygonifolius) to 90% ( P. berchtoldii). Whilst for some species, there was some germination across all the conditions tested, for others germination was significantly increased under specific conditions. The single most important factor for promoting germination was cold stratification prior to placing at the germination temperature. Logistic regression analysis indicated that there was a positive effect of applying a cold stratification treatment in P. filiformis, P. gramineus, and P. natans. Scarification (removal of some of the fruit) also resulted in increases in the number of seeds that germinated for all species. It is suggested that the initial conditions which should be tried for germinating seeds from temperate Potamogeton species are 15–20 °C with a 12 h photoperiod, anaerobic conditions, following a cold stratification treatment. If high levels of germination are not observed, the fruits should be scarified to remove the mechanical restriction of the fruit coat.

Seed morphology and ultrastructure in Citrus garrawayi (Rutaceae) in relation to germinability

Combinational traits of seed size and seed-coat hardness in Citrus garrawayi (F.M.Bailey) (syn. of Microcitrus garrowayi) were investigated as markers for estimation of seed morphological and physiological maturity. Seed size (length) and coat hardness correlated well with changes in seed coat and embryo morphological development, dry-weight accumulation, decreases in moisture content and a significant increase in germinability. Seed moisture content decreased from 82 ± 1% in immature seeds to 40 ± 1% at seed maturation. The outer integument of immature seeds consisted of thin-walled epidermal fibres from which outgrowths of emerging protrusions were observed. In comparison, mature seed coats were characterised by the thickening of the cell walls of the epidermal fibres from which arose numerous protrusions covered by an extensive mucilage layer. Immature seeds, with incomplete embryo and seed-coat histodiffereniation, had a low mean germination percentage of 4 ± 4%. Premature seeds, with a differentiated embryonic axis, were capable of much higher levels of germination (51 ± 10%) before the attainment of mass maturity. Mature seeds, with the most well differentiated embryonic axis and maximum mean dry weight, had the significantly highest level of germination (88 ± 3%).

Ecology and conservation of the endangered quillwort Isoetes sinensis in China

Isoetes sinensis Palmer is an East Asia endemic fern that faces impending extirpation from the expansive area of Mainland China. Presently, only two natural populations are known to exist in this vast region. Both populations have decreased by about 50% within the last 4 years. This reduction is most probably related to the decline in the size of the wetlands since reproductive activity, spore production, and recruitment were noticeably lower at the microsites occurring in smaller ponds. The decline in population size seems to be associated with succession from marsh to dry land at the habitats of both populations. The study revealed that individuals in both populations produced copious numbers of spores suggesting adequate fecundity, furthermore high levels of spore germination were obtained in laboratory experiments. However, inefficient spore dispersal appears to have contributed to the limited spread of the species. The sex ratio in both populations was male‐biased. Several factors are identified here as posing a threat to Isoetes sinensis populations in China, chiefly the loss of habitat due to infrastructure construction and competition with adventive weed species for establishment on available sites. Disturbance by introduced mammals during browsing and trampling by livestock farm workers, as well as tourists, further contribute to the diminishing numbers of Isoetes sinensis at the study sites. Present address: Robert Wahiti Gituru, Botany Department, Jomo Kenyatta University of Agriculture and Technology, P. O. Box 62000‐00200, Nairobi, Kenya.

The changing window of conditions that promotes germination of two fire ephemerals, Actinotus leucocephalus (Apiaceae) and Tersonia cyathiflora (Gyrostemonaceae).

Following a period of burial, more Actinotus leucocephalus (Apiaceae) and Tersonia cyathiflora (Gyrostemonaceae) seeds germinate in smoke water. The main aim of this study was to determine whether these fire-ephemeral seeds exhibit annual dormancy cycling during burial. This study also aimed to determine the effect of dormancy alleviation on the range of light and temperature conditions at which seeds germinate, and the possible factors driving changes in seed dormancy during burial. Seeds were collected in summer, buried in soil in mesh bags in autumn and exhumed every 6 months for 24 months. Germination of exhumed and laboratory-stored (15 degrees C) seeds was assessed at 20 degrees C in water or smoke water. Germination response to light or dark conditions, incubation temperature (10, 15, 20, 25 and 30 degrees C), nitrate and gibberellic acid were also examined following burial or laboratory storage for 24 months. In the laboratory seeds were also stored at various temperatures (5, 15, 37 and 20/50 degrees C) for 1, 2 and 3 months followed by germination testing in water or smoke water. The two species exhibited dormancy cycling during soil burial, producing low levels of germination in response to smoke water when exhumed in spring and high levels of germination in autumn. In autumn, seeds germinated in both light and dark and at a broader range of temperatures than did laboratory-stored seeds, and some Actinotus leucocephalus seeds also germinated in water alone. Dormancy release of Actinotus leucocephalus was slow during dry storage at 15 degrees C and more rapid at higher temperatures (37 and 20/50 degrees C); weekly wet/dry cycles further accelerated the rate of dormancy release. Cold stratification (5 degrees C) induced secondary dormancy. By contrast, no Tersonia cyathiflora seeds germinated following any of the laboratory storage treatments. Temperature and moisture influence dormancy cycling in Actinotus leucocephalus seeds. These factors alone did not simulate dormancy cycling of Tersonia cyathiflora seeds under the conditions tested.

Selfing and resource allocation in Schiedea salicaria (Caryophyllaceae), a gynodioecious species

Abstract Levels of selfing and resource allocation patterns were investigated in Schiedea salicaria (Caryophyllaceae), a gynodioecious species with high levels of inbreeding depression and nuclear control of male sterility. Selfing levels were higher in hermaphrodites than females, especially when adjusted for early acting inbreeding depression. The sexes of S. salicaria were similar in most allocation patterns including number of flowers and capsules per inflorescence, seeds per flower, and seed mass. Seeds produced by females had higher levels of germination than seeds of hermaphrodites, a likely result of high selfing levels and the expression of inbreeding depression in the progeny of hermaphrodites. Invasion of females in populations of S. salicaria is probably related to the expression of inbreeding depression at germination and in later life history stages. Comparisons with related species of Schiedea that also have nuclear control of male sterility suggest that reallocation of resources in hermaphrodites to male function occurs as females increase in frequency, but that resource reallocation is not important for the success of females when they first invade populations.

Grazing by Kangaroos Limits the Establishment of the Grass Trees Xanthorrhoea gracilis and X. preissii in Restored Bauxite Mines in Eucalypt Forest of Southwestern Australia

Abstract This study examined factors affecting germination, survival, and growth of the grass trees Xanthorrhoea gracilis and X. preissii on newly rehabilitated bauxite mine pits in the jarrah forest of southwestern Australia. Grazing by kangaroos (Macropus fuliginosus) was the major factor in reducing survival and growth of both species during the first 2 years. Provision of artificial grazing protection increased survival and growth (plant mass) of both species by 3‐fold. Grazing by native vertebrates has not previously been identified as affecting mine restoration in Western Australia. Initial germination rates from sown seeds of X. preissii at eight replicate sites ranged from 25 to 64% with a mean of 42%. Corresponding figures for X. gracilis were 5–42% with a mean of 17%. Germination of X. gracilis was greater on heavier, moister soils, but X. preissii germinated better on sandier soils. High levels of initial germination did not ensure high survival. Plants of both species grew bigger and survived better on the lighter, sandy soils. Xanthorrhoea seedlings located in the depressions created by the ripping process grew larger than seedlings on the slopes of the riplines. The presence of plants of other species did not have a significant effect on survival. However, these plants facilitated the growth of both species when artificial grazing protection was unavailable. Plants of other species reduced the growth rates of Xanthorrhoea seedlings where artificial grazing protection was provided. Artificial shade by itself had no significant effect on growth of either species. In rehabilitated bauxite mines in the jarrah forest, the provision of grazing protection is recommended to ensure successful establishment and early survival of Xanthorrhoea spp.

Comparison of a common and rare species of Mimosa (Mimosaceae) in Central Brazil

Abstract The aim of this study was to verify differences in the biology of a common widespread species (Mimosa claussenii Benth.) and three rare endemics (Mimosa decorticans Barneby, M. heringeri Barneby, and M. setosissima Taub.). We studied three populations of M. claussenii and one population of each rare species at four localities in central Brazil. We compared the population structure, phenology, fruit set, seed predation, germination, establishment and root/shoot ratio in these six populations. The endemic species occurred in higher densities and smaller individuals were more abundant. When in sympatry, the rare and common species showed a significant negative correlation of density. Mimosa claussenii occurred in drier and rocky environments, whereas M. decorticans and M. setosissima occurred in moister habitats. Rare species had higher levels of fruit set, more viable seeds per individual, and heavier seeds. Mimosa setosissima had the highest level of germination and establishment rate, but did not survive away from its endemism centre. The common species had a higher root/shoot ratio. Overall, the biological aspects studied indicated an advantage in reproductive biology for the rare in relation to the common species. The small geographical range of the rare species may be related to edaphic isolation and climatic changes in the Quaternary.