Context. Most gymnosperms are dioecious (no self-pollination). It was not known if Wollemia nobilis (monoecious) could produce viable seeds via self-pollination. Aims. In the nearly 30 years since its scientific discovery Wollemia nobilis (Araucariaceae) has been the focus of considerable scientific attention. While this includes several aspects of sexual reproduction, many features of ovulate cone morphology and seed biology have not been investigated. Methods. Various aspects of ovulate cone morphology were quantified, as were seed morphology and germination (e.g. seed moisture content and rate of imbibition), in material from an isolated tree of Wollemia nobilis. Seeds of Agathis microstachya and Araucaria cunninghamii were also examined to allow comparisons across the Araucariaceae. Key results. In Wollemia nobilis most seeds were empty (no formation of a megagametophyte and embryo (M + E)). Empty and filled seeds were morphologically very similar. On average, the fresh weights (FW) of empty and filled seeds were 6.2 and 33.1 mg, respectively. On average, the FW of the M + E was 25.8 mg (78% of seed mass, the other 22% was testa). The average moisture content (FW basis) of the testa and the M + E were 9.6% and 7.0%, respectively. The M + E imbibed water relatively slowly and imbibed, on average, to similar to 110% increase in FW after 48 h. In Agathis robusta and Wollemia nobilis the seeds separated freely from the cone scales. In Araucaria cunninghamii the M + E was an integral part of the bract/scale complex. Conclusions. The seeds examined in this study came from an isolated, almost certainly self-fertilised tree. The seeds were of approximately the same dimensions as those from the wild populations of Wollemia nobilis, while average filled seed FW was greater and less variable. The filled seeds had a high viability and an excised M + E could germinate rapidly. This study shows that Wollemia nobilis can produce large, viable seeds via self-fertilisation. Successful self-fertilisation may be a factor in the low genetic diversity detected in the wild population. Implications. Based on evidence from a single tree it would appear that Wollemia nobilis can produce large, viable, vigorous seeds via self-fertilisation. This has implications for the population structure of this species.

In a recent paper in Southern Forests, Jaganathan and co-workers indicated that the low constant-temperature drying method (LCTDM) (103 degrees C for 17 h) is satisfactory for determining moisture content (MC) in seeds with physical dormancy (PY). Would this recommendation apply to Acacia, a large genus (1000+ species) with a seed coat so strong that seeds in the soil can maintain high viability for many decades? MC was assessed, using the LCTDM, in six Australian Acacia species by comparing intact seeds with those cut in half. Halved seeds of all species lost moisture rapidly and their mass had largely stabilised after about 2-3 h. Intact seeds had a wide variation in moisture-loss patterns. In some species, the testa was morphologically unchanged after 24 h at 103 degrees C and this was associated with a relatively slow moisture loss. In other species, the testa had completely shattered after 8 h, leading to a rapid moisture loss. If the LCTDM is used to determine MC in Acacia species, it is advisable to employ a technique that substantially disrupts the testa.

Our analyses of data in Luna et al. (Fire Ecology 19:52, 2023) do not support the proposal that dormancy release of the hard seeds in 12 species of Cistaceae is a “two-step process” involving high summer temperatures followed by fire-type heat. The reverse is true: subjection to a month of daily alternating temperatures of 50/20 °C (summer heat) is more likely to induce dormancy among initially soft seeds or secondary dormancy among those softened by fire heat or reduce the ability of fire heat to soften the seeds. The need to inspect seeds for the presence of an open “water gap” following various heat treatments, and using more realistic summer temperatures in future studies, is clear.

Acacia implexa, Eucalyptus rossii and Exocarpos cupressiformis are native plants of Australia, which were used by the First Peoples for medicinal purposes. In this study, 70% aqueous ethanol crude extracts were prepared from A. implexa bark and leaves, E. rossii leaves and E. cupressiformis leaves, and partitioned via sequential extraction with n-hexane, dichloromethane (DCM), ethyl acetate and ethanol. The crude extracts and fractions were screened for antioxidant activity using a novel, high-throughput lipid-based antioxidant assay, as well as the aqueous ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) assay and the Folin–Ciocalteu test for total phenols. In the lipid-based assay, non-polar n-hexane and DCM fractions showed higher antioxidant activity against the formation of peroxides and thiobarbituric acid reactive substances (TBARS) than the other fractions, whereas the non-polar fractions were not effective in aqueous assays. This illustrates that the high potential of the lipid-soluble n-hexane and DCM fractions as antioxidants would have been missed if only aqueous-based assays were used. In addition, the potent antioxidant compounds were putatively annotated using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-qTOF-MS). Gallic acid, (+)-catechin, (−)-epicatechin and tannins were found in most crude extracts.

In a recent issue of New Phytologist, Schoonderwoerd & Friedman (2021) indicated that woody angiosperms with naked buds (buds that lack cataphylls) that can survive freezing temperatures are more common than was previously thought. A commentary on this paper titled ‘… we really don't know [buds] at all …’ was also published in the same issue (Jones, 2021). Naked buds in temperate areas (i.e. exposed to freezing temperatures) were found in at least 87 genera in 42 angiosperm families (Schoonderwoerd & Friedman, 2021). Included in these 87 genera was Eucalyptus (Myrtaceae). The eucalypts are composed of c. 800 species, in three closely related genera, Angophora, Corymbia and Eucalyptus (González-Orozco et al., 2014). Probably all eucalypts have naked buds (e.g. Jacobs, 1955; Chattaway, 1958a; Cremer, 1972; Burrows, 2013), but before considering how the buds of this group were classified by Schoonderwoerd & Friedman, the structure and function of these axillary buds needs to be reviewed. There are three main features of these buds. First, the buds do not look particularly bud-like. Before expanding into a shoot, they consist of a very slender structure with very few leaf primordia (see Cremer, 1972 and Figs 1-3). The shoot apical meristem is located at the tip of an elongated stem (Fig. 1b), thus the meristem receives no protection from the base of the petiole, as occurs in some Myrtaceae genera (Burrows et al., 2008). Second, under favourable conditions the naked buds can allow for rapid expansion of the shoot system (see the large arrow in Fig. 2a); however, nearly all naked buds are abscised shortly after formation (Jacobs, 1955; Chattaway, 1958a; Cremer, 1972; Carr, 1998; Burrows, 2013). This leaves a circular scar in the leaf axil (Figs 1c, 2c,d, 3b,f). For example, Chattaway (1958a) examined the leaf nodes of 44 eucalypt species and recorded that naked buds occurred in every axil, but most were shed in the first hot dry spell. Third, while many plant species have only a single bud in a leaf axil, the eucalypts have additional buds (accessory buds) at the base of the naked bud. After naked bud abscission, it appears externally that the axil no longer possesses any regeneration potential, but these well-protected accessory buds and meristems (Fig. 2d; Burrows, 2000: figs 2–5, 2013: fig. 3; Burrows et al., 2008: figs 1–4; Waters et al., 2010: figs 1, 3) allow regeneration after minor damage (e.g. fire scorch, low-level drought, insect herbivory, severe frost). They are also the progenitors of the eucalypts' epicormic strands, which have remarkable resprouting capacity after crown fire (Burrows, 2013). Cremer (1972, p. 185) noted of 20 eucalypt species from the Australian Capital Territory (within the Southern Tablelands of New South Wales (NSW) and one of the colder parts of Australia) ‘… very few primary buds had survived the winter and a large proportion of the shoots growing in spring had come from accessory buds located on the previous year's shoots.’ This would also be my general observation of c. 20 eucalypt species from around Wagga Wagga, NSW. Thus, in the eucalypts the naked buds can lead to a rapid expansion of the shoot system but in the main are ‘expendable’, while the important bud reserve is the accessory buds. The three monotypic genera (Arillastrum, Allosyncarpia, Stockwellia) closest to the eucalypts have compact, long-lived primary buds and a series of accessory buds at surface level (Burrows et al., 2008). While the above is a general description of eucalypt naked buds, some variation has been recorded. Cremer (1972) notes that for Eucalyptus regnans in Tasmania, shoot growth in spring mainly came from primary buds that survived the winter. Cremer also noted that the overwintering primary buds of Eucalyptus pauciflora (snow gum, often found lining the runs in Australian ski fields) were covered by a single pair of cataphylls. Combined with my observations of what appear to be bud scales for one Angophora species (Fig. 3d,e; see also Carey, 1931) there is some variability in the structure and behaviour of eucalypt primary buds. With c. 800 eucalypt species, it is possible that further variation is yet to be described. Schoonderwoerd & Friedman classified naked buds into six morphological categories, four with exposed buds (archetypal, heteroblastic, nonenveloping, caducous) and two with unexposed buds (recessed, stipular). They indicated that Eucalyptus had archetypal naked buds. Archetypal buds have three main features: the ‘… outermost preformed leaves in the resting bud are exposed directly to the aerial environment during summer, autumn and winter.’ (p. 526); ‘… considerable preformation of foliage leaves …’ occurs (p. 526); and no scale leaves are formed, not even those that are nonenveloping or caducous. While eucalypts definitely have naked buds, two issues exist with classifying eucalypt naked buds as archetypal. First, as noted, eucalypt naked buds are usually slender, delicate structures with few leaf primordia (Figs 1b, 2b, 3a,f). A ‘considerable preformation of leaves’ does not occur. Second, if the eucalypt naked buds do not immediately develop into a branch they will be abscised; thus, primary resting buds are not exposed to freezing temperatures (although see Cremer's comments on E. regnans). Schoonderwoerd & Friedman did not have access to living eucalypt material (pers. comm.), and herbarium specimens might not show the developmental sequence illustrated in Figs 1a and 2a. Over 60 yr ago, Chattaway (1958b, p. 45) noted that the regenerative powers of the eucalypts were ‘distinctive and unique’, with the structure and function of the naked and concealed (accessory) buds not as well-known as they should be. It is not stated how many eucalypt species Schoonderwoerd & Friedman included in their study. For the climate and tree height analyses, they note (p. 525) ‘… Eucalyptus spp. were excluded to avoid phylogenetic biases introduced by a single species-rich clade …’ and ‘when the species-rich Eucalyptus radiation in Australia is excluded …’ (p. 529). Combining the data of González-Orozco et al. (2014) on spatial patterns of eucalypt richness with the Australian Bureau of Meteorology's map of potential frost days, it appears that several hundred eucalypt species in southern Australia would be exposed to freezing temperatures. The area where the inclusion of eucalypts as having archetypal naked buds might have the greatest influence on their paper is their fig. 4a,b, where it appears that the coastal and tableland regions of southeast Australia have the world's greatest number and relative richness of species with exposed naked buds (among freezing-tolerant woody angiosperms). Much of this richness might be from the inclusion of eucalypt species. As the eucalypt naked buds are probably not present when frosts occur, this figure could be considered misleading. Also, many of the darkly coloured cells in their fig. 4a,b are in southeast Queensland, where frosts rarely occur, and some coloured cells extend well into the tropics, where frosts would never occur. Carey (1930), from a study of 140 woody species of NSW, recorded naked buds in several families not listed by Schoonderwoerd & Friedman. Carey recorded 22 families with naked buds, 11 of which were in Schoonderwoerd & Friedman's study, while the remaining 11 were not included. In short, there may be still more to be discovered about naked buds, especially away from the well described European and North American woody floras. Jones (2021) considered that the recent study of naked buds and cold was an example of renewed interest in a subject that had been dormant for decades. It is not surprising that Schoonderwoerd & Friedman's study would generate some additional contributions to the topic. The title of Jones' commentary ‘… we really don't know [buds] at all …’ was perhaps somewhat prophetic? In summary, the eucalypts are possibly the largest group of woody plants that form naked buds. They are probably the only group of woody plants in which most primary buds are abscised soon after formation and deeply buried accessory buds form the resprouting reserve. This unusual combination of axillary structures is apparently quite consistent across this large and diverse group. While the eucalypts have naked buds they are not archetypal and possibly require an expansion of Schoonderwoerd & Friedman's classification system. It could be argued that eucalypts have two types of naked bud – exposed and nonexposed. The accessory buds could be an extreme form of naked recessed bud, although their initial leaf primordia (Fig. 2d) may be cataphylls to protect the bud as it pushes through the overlying tissues. These two very different axillary buds give the eucalypts the ability to rapidly expand shoots whenever the conditions are suitable, while also having an excellent protected bud reserve. All new data are available in the three figures.

Anthocyanins are naturally occurring water-soluble plant pigments belonging to the flavonoids chemical class. The red, blue and purple colours of leaves, flowers and fruits of plants confirm that they are rich sources of anthocyanins. Many in vivo and in vitro studies reveal that anthocyanins have different health beneficial effects such as antioxidant, antidiabetic, anti-inflammatory, anti-obesity, antihypertensive and anticancer properties. Major benefits of anthocyanin administration are owing to their potent anti-inflammatory and antioxidant activities. Recent investigations have revealed that anti-inflammatory activities of anthocyanins follow the inhibitory pathways of NF-кB-mediated decline of inflammatory cytokines production. Inhibition of the anti-inflammatory pathways also influences the modulation of arteriolar disorders and cardiovascular complications due to anthocyanin administration. Moreover, anthocyanins improve diabetes, obesity and cancer pathology by inhibiting NF-кB-mediated inflammatory pathways. However, considerable variations in activities do exist among structurally diverse anthocyanins. This review appraises the recent literature regarding the health benefits of anthocyanins and their molecular mechanisms in various oxidative stress related pathophysiological conditions.

In a unique study, Luna (Luna, Sci Rep 10:1–10, 2020) examined the viability and germination of 12 hard-seeded Cistaceae in the Mediterranean Basin by alternating a prolonged summer-type temperature (50/20 °C at 12 h cycles) treatment with a fire-type heat pulse. A re-analysis of their data shows that the summer treatment applied before the heat pulse was superfluous as similar high levels of germination under ambient conditions were attained with the heat pulse only. Additional tests using the hard seeds of Acacia showed that the water gap opened at once in the presence of dry heat such that contact with moisture is not required to complete the process of softening. The abundance of hard seeds remaining when the summer treatment was applied after the heat pulse is better explained by ungerminated seeds having become hard again under such dry conditions rather than remaining dormant, i.e., acquiring secondary physical dormancy, and thus becoming ‘desensitized’ to their environment. While this response may be adaptive, such a retarding effect will be limited in practice as most fires are expected in autumn, at least historically, and are thus close to the start of optimal winter conditions for germination. Future studies should concentrate on the fate of the water gap plug during such alternating treatments and also ensure that realistic summer temperature regimes are used.

Half-butt eucalypts (genera: Eucalyptus and Corymbia) have both thick outer bark at the stem base (half-butt) conferring resistance to surface fire, and thin photosynthetic canopy bark that reduces moisture stress. Here we examine how the functional ecology of dual outer bark types influences the wide distribution of Australian half-butt species. We evaluate the proposition that half-butts should predominate in semi-arid environments prone to surface fires. We measured the bark thickness, butt height relative to flame/fire char height and tree height, height of first branch, and the location and prevalence of epicormic resprouting of co-occurring Eucalyptus miniata (half-butt) and E. tetrodonta (fibrous bark only) individuals, across 15 sites with contrasting fire frequencies (2000-2015) in the Darwin region. Total tree height was compared with butt height for all E. miniata individuals. The survival of half-butt and other eucalypt species, as well as non-eucalypts, was investigated at three sites affected by intense gamba grass (Andropogon gayanus) fire. The proportion of half-butt species in each of Australia's 85 bioregions was calculated from geographic distribution records of 618 eucalypt species. Mean annual fire frequency (1997-2010), fire type (crown or surface fires) and climate in each bioregion was determined from satellite-derived records. Butt height at a site, including gamba grass sites, was not induced by flame height or affected by fire frequency and was approximately half the canopy height of the tree, suggesting it is internally regulated. The half-butt E. miniata and full-bark eucalypts were similarly resilient (survival) under surface fire conditions. Half-butt species predominated in arid and semi-arid bioregions characterised by surface fire, consistent with our proposition that half-butt bark is an adaptation to surface fire, and thin photosynthetic outer canopy bark reduces moisture stress, accounting for the wide distribution of half-butt eucalypts in arid and seasonally dry regions of Australia.

Gymnosperms are generally regarded as poor resprouters, especially when compared to angiosperms and particularly following major disturbance. However, is it this clear-cut? This review investigates two main aspects of gymnosperm resprouting: (i) various papers have provided exceptions to the above generalization—how frequent are these exceptions and are there any taxonomic trends?; and (ii) assuming gymnosperms are poor resprouters are there any anatomical or physiological reasons why this is the case? Five of six non-coniferous gymnosperm genera and 24 of 80 conifer genera had at least one species with a well-developed resprouting capability. This was a wider range than would be expected from the usual observation ‘gymnosperms are poor resprouters’. All conifer families had at least three resprouting genera, except the monospecific Sciadopityaceae. Apart from the aboveground stem, buds were also recorded arising from more specialised structures (e.g., lignotubers, tubers, burls and underground stems). In some larger genera it appeared that only a relatively small proportion of species were resprouters and often only when young. The poor resprouting performance of mature plants may stem from a high proportion of apparently ‘blank’ leaf axils. Axillary meristems have been recorded in a wide range of conifer species, but they often did not form an apical dome, leaf primordia or vascular connections. Buds or meristems that did form often abscised at an early stage. While this review has confirmed that conifers do not resprout to the same degree as angiosperms, it was found that a wide diversity of gymnosperm genera can recover vegetatively after substantial disturbance. Further structural studies are needed, especially of: (i) apparently blank leaf axils and the initial development of axillary meristems; (ii) specialised regeneration structures; and (iii) why high variability can occur in the resprouting capacity within species of a single genus and within genera of the same family.

In a unique study, Luna (2020) examined the viability and germination of 12 hard-seeded Cistaceae in the Mediterranean Basin by alternating a prolonged summer-type-temperature (50/20°C at 12 h cycles) treatment with a fire-type heat pulse. A re-analysis of their data shows that the summer treatment applied before the heat pulse was superfluous as similar high levels of germination under ambient conditions were attained with the heat pulse only. The abundance of hard seeds remaining when the summer treatment was applied after the heat pulse is better explained by ungerminated seeds having become hard again rather than not responding, i.e., showing secondary physical dormancy, and thus became ‘ de sensitized’ to their environment. While this response is adaptive, such a retarding effect will be limited in practice as most fires are expected in autumn, at least historically, and are thus close to the start of optimal winter conditions for germination. Future studies should concentrate on the fate of the water-gap plug during such alternating treatments and also ensure that realistic summer temperature regimes are used.

Small diameter branchlets and smooth barked stems and branches of most woody plants have chloroplasts. While the stems of several eucalypt species have been shown to photosynthesise, the distribution of chloroplasts has not been investigated in detail. The distribution of chloroplasts in branchlets (23 species) and larger diameter stems and branches with smooth bark (14 species) was investigated in a wide range of eucalypts (species of Angophora, Corymbia and Eucalyptus) using fresh hand sections and a combination of bright field and fluorescence microscopy. All species had abundant stem chloroplasts. In both small and large diameter stems, the greatest concentration of chloroplasts was in a narrow band (usually 100–300 μm thick) immediately beneath the epidermis or phellem. Deeper chloroplasts were present but at a lower density due to abundant fibres and sclereids. In general, chloroplasts were found at greater depths in small diameter stems, often being present in the secondary xylem rays and the pith. The cells of the chlorenchyma band were small, rounded and densely packed, and unlike leaf mesophyll. A high density of chloroplasts was found just beneath the phellem of large diameter stems. These trees gave no external indication that green tissues were present just below the phellem. In these species, a thick phellem was not present to protect the inner living bark. Along with the chlorenchyma, the outer bark also had a high density of fibres and sclereids. These sclerenchyma cells probably disrupted a greater abundance and a more organised arrangement of the cells containing chloroplasts. This shows a possible trade-off between photosynthesis and the typical bark functions of protection and mechanical strength.

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder with an unclear cause. It appears that multiple factors participate in the process of neuronal damage including oxidative stress and accumulation of the protein amyloid β (Aβ) in the brain. The search for a treatment for this disorder is essential as current medications are limited to alleviating symptoms and palliative effects. The aim of this study is to investigate the effects of mint extracts on selected mechanisms implicated in the development of AD. To enable a thorough investigation of mechanisms, including effects on β-secretase (the enzyme that leads to the formation of Aβ), on Aβ aggregation, and on oxidative stress and apoptosis pathways, a neuronal cell model, SH-SY5Y cells, was selected. Six Mentha taxa were investigated for their in vitro β-secretase (BACE) and Aβ-aggregation inhibition activities. Moreover, their neuroprotective effects on H2O2-induced oxidative stress and apoptosis in SH-SY5Y cells were evaluated through caspase activity. Real-time PCR and Western blot analysis were carried out for the two most promising extracts to determine their effects on signalling pathways in SH-SY5Y cells. All mint extracts had strong BACE inhibition activity. M. requienii extracts showed excellent inhibition of Aβ-aggregation, while other extracts showed moderate inhibition. M. diemenica and M. requienii extracts lowered caspase activity. Exposure of SH-SY5Y cells to M. diemenica extracts resulted in a decrease in the expression of pro-apoptotic protein, Bax, and an elevation in the anti-apoptotic protein, Bcl-xL, potentially mediated by down-regulation of the ASK1-JNK pathway. These results indicate that mint extracts could prevent the formation of Aβ and also could prevent their aggregation if they had already formed. M. diemenica and M. requienii extracts have potential to suppress apoptosis at the cellular level. Hence, mint extracts could provide a source of efficacious compounds for a therapeutic approach for AD.

With an increase in the longevity and thus the proportion of the elderly, especially in developed nations, there is a rise in pathological conditions that accompany ageing, such as neurodegenerative disorders. Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive and memory decline. The pathophysiology of the disease is poorly understood, with several factors contributing to its development, such as oxidative stress, neuroinflammation, cholinergic neuronal apoptotic death, and the accumulation of abnormal proteins in the brain. Current medications are only palliative and cannot stop or reverse the progression of the disease. Recent clinical trials of synthetic compounds for the treatment of AD have failed because of their adverse effects or lack of efficacy. Thus, there is impetus behind the search for drugs from natural origins, in addition to the discovery of novel, conventional therapeutics. Mints have been used traditionally for conditions relevant to the central nervous system. Recent studies showed that mint extracts and/or their phenolic constituents have a neuroprotective potential and can target multiple events of AD. In this review, we provide evidence of the potential role of mint extracts and their derivatives as possible sources of treatments in managing AD. Some of the molecular pathways implicated in the development of AD are reviewed, with focus on apoptosis and some redox pathways, pointing to mechanisms that may be modulated for the treatment of AD, and the need for future research invoking knowledge of these pathways is highlighted.

Mentha (mint) is a genus in the Lamiaceae with a worldwide distribution. It has a complex classification due to frequent hybridisation at the interspecific level, variation in basic chromosome number and the occurrence of polyploidy (diploid to nonaploid). Although there have been many studies of Mentha leaf micromorphology, usually only a few taxa were described. The aim of this study was to characterise the micromorphology of Mentha leaves. Nineteen Mentha taxa, covering all four sections of the genus, were grown under controlled conditions and adaxial and abaxial leaf surfaces were examined using stereo and scanning electron microscopes. This study included examination of the previously uninvestigated Australian species, M. australis and M. diemenica. The study revealed that average lamina length varied from 3 mm (M. requienii) to 34 mm (M. × niliaca) and leaves were sessile (M. spicata) to where petiole length was 50% of total leaf length (M. requienii). Peltate and capitate glandular trichomes were found on the adaxial and abaxial leaf surfaces of almost all taxa. Most taxa were hypostomatous. A few taxa had amphistomatous leaves which was interesting given that Mentha is a mesophytic genus naturally found in moist environments beside streambanks and lake shores. Average guard cell length varied from 14 µm (M. suaveolens) to 27 µm (M. × piperita f. citrata ‘Basil’) with larger guard cell length correlated with larger DNA content and chromosome number. Two species in section Pulegium (M. requienii and M. pulegium) had small laminas, relatively long petioles and high adaxial stomatal density which distinguished them from taxa in the other three sections. Larger DNA content in plants can be associated with larger cell size. Most studies of Mentha leaf micromorphology make no mention of ploidy. The present study indicates this should be considered when comparing relative cell size between species.

AbstractThe seeds of most Australian acacias have pronounced physical dormancy (PY). While fire and hot water (HW) treatments cause the lens to ‘pop’ almost instantaneously, for many Acacia species the increase in germination percentage can be gradual. If PY is broken instantly by HW treatment, why is germination often an extended process? Control and HW treatments were performed on seeds of 48 species of Acacia. Seeds were placed on a moist substrate and imbibition was assessed by frequently weighing individual seeds. In the two soft-seeded species all control seeds were fully imbibed within 6–24 h, while in hard-seeded species very few control seeds imbibed over several weeks. In 10 species over 50% of the HW-treated seeds imbibed within 30 h, but mostly the percentage of imbibed seeds gradually increased over several weeks. Some seeds in a replicate would imbibe early, while others would remain unimbibed for many days or weeks then, remarkably, become fully imbibed in less than 24 h. While HW treatment broke PY almost instantaneously, it appeared that in many Acacia species some other part of the testa slowed water from reaching the embryo. This process of having staggered imbibition may be a way of ensuring not all seeds in a population germinate after small rain events. Thus it appears the lens acts as a ‘fire gauge’ while some other part of the seed coat acts as a ‘rain gauge’.

Acacia sensu lato is a large and widespread genus of the family Fabaceae with more than 1350 species. Taxonomically, this genus is complex and has undergone substantial controversial revisions recently. Acacia have been used as folk medicines for the treatment of a wide range of disorders including gastrointestinal, respiratory, eye, skin, teeth, blood, uterine, and endocrine problems. Gums (heteropolysaccharides) and condensed tannins (flavan-3-ol derivatives) are the most commonly reported constituents in Acacia. Pharmacological studies, at least in vitro, have demonstrated antioxidant, analgesic, antihypertensive, antidiabetic, anti-Alzheimer's, and antimalarial effects of Acacia extracts. A number of secondary metabolites including phenols, alkaloids, and terpenoids, some with useful biological activities, have been reported in acacias. Very few species have been investigated for their phytochemical composition and biological activities. Hitherto, Acacia is largely an untapped resource of valuable secondary plant metabolites that have not gained enough scientific attention. This review aims to survey and critically appraise current literature on Acacia to provide sufficient baseline information for future work and potential commercial exploitation of Acacia.

Acacia s. str. (Mimosoideae, Fabaceae) is the largest plant genus in Australia (~1000 species). Its seeds have physical dormancy from a hard, water-impermeable testa. Heat from fire (natural systems) and hot water (nursery production) can break this dormancy. It is often reported that these treatments ‘soften’ or ‘crack’ the seed coat, but in practice they only affect a minute part of the seed coat, the lens. We examined lens structure in a wide range of Acacia species to determine what diversity of testa and lens structure was present, if there were differing responses to a hot water dormancy breaking treatment and if there were structural differences between soft- and hard-seeded species. Seed morphology, testa and lens structure were examined before and after hot water treatment (~90°C for one minute), in 51 species of Australian Acacia from all seven sections, from all states and territories of Australia and from a wide range of environments. Five of the species had been noted to produce non-dormant seed (‘soft-seeded’ species). Average seed mass per species ranged from 3.1 to 257.9 mg (overall average 24.2 mg, median 13.8 mg). Almost all species had a relatively thick seed coat (average 132.2 µm) with well-developed palisade cells (average 41.5 µm long) and a lens which ‘popped’ in response to hot water treatment. For 44 species ranging in average seed mass from 3.1 to 43.9 mg (×14 range), the unpopped lens area only ranged ×3 (11480–36040 µm2). The lens was small (in 88% of species the average length of the unpopped lens was <300 µm) and the unpopped lens area was a minute proportion of seed surface area (average 0.10%). A. harpophylla (soft-seeded species) had a thin testa (37.3 µm) without obvious palisade cells and did not have a functional lens. In hard-seeded species the morphology of the popped lens varied widely, from a simple mound to complete detachment. A functional lens is not a universal feature in all genera of the Mimosoideae, including several species in a genus (Senegalia) previously included in Acacia s. lat. On the basis of the 51 investigated species a lens was present in all Australian acacias, although non-functional in two soft-seeded species. Although the lens was, on average, only ~1/1000th of the surface area of an Acacia seed and thus easily overlooked, it can have a profound influence on imbibition and germination. An assessment of lens structure, before and after heat treatment, can be of considerable use when interpreting the results of Acacia germination experiments.

High daytime temperatures during the grain filling stage in rice have negative impacts on milling quality traits. In this study, we used growth chambers to evaluate the influence of high daytime temperature (33 degrees C) during grain filling, together with grain moisture content at harvest (26%, 18% and 15%), on grain fissure formation. Varietal susceptibility to fissure formation was also evaluated by exposing grains to high temperature at different grain filling stages (milky, dough, maturing). Two fissure resistant varieties: Cypress (long-grain) and Reiziq (medium-grain) and susceptible varieties: YC53-00-7 (long-grain) and Baru (medium-grain) were compared. The average head rice yield (HRY) of Cypress declined from 62.7% at 25 degrees C to 53.5% at 33 degrees C, while Reiziq declined from 56.2% (25 degrees C) to 47.4% (33 degrees C). Both were significantly higher than the HRY of YC53-00-7 (39.2% and 24.9%) and Baru (39.3% and 31.7%) at 25 degrees C and 33 degrees C, respectively. When grains were drier at harvest (15% cf. 26%) there was a greater reduction in HRY. When the four varieties were exposed to high temperature, the highest average reduction of HRY was recorded at 21 days after heading. It is important to choose an optimal sowing date to avoid coincidence of the final grainfilling stage with high temperatures, in order to minimize milling quality losses. (C) 2017 Elsevier Ltd. All rights reserved.

Citrullus lanatus (camel melon) is an important summer weed of Australian fallows, and can rapidly develop monocultural stands in sandy soils receiving adequate soil moisture. As a general review on the biology of C lanatus, this paper reviewed the current published literature (including our recent published studies) and also summarised extensive field and laboratory studies performed on its biology, phenology and management in the South-West Slopes of New South Wales. Recent population genetics studies conducted in Australia have shown that the species is monotypic, and was introduced as a single colonisation event in the mid 1800's. Our studies showed genetic diversity in C. lanatus to be nonexistent across Australia and invasive ranges and highest in the native range in Africa. Further genetic analyses have shown the species in Australia is identical to Citrullus lanatus var. citroides, the citron melon, native to Africa and now naturalised across Africa, Asia and North America, where it is a weedy nuisance or occasionally a food source for livestock and humans. Although limited genotypic diversity may facilitate potential biocontrol strategies for Citrullus lanatus in Australia, biocontrol may be difficult due to its close genetic similarity to commercial watermelon, a major horticultural crop in Australia and more globally. In Australia, field germination was observed to occur during a two to three-month period between late spring and summer, when warm soil temperatures occurred and field establishment was typically observed after significant rainfall events and was associated with soil moisture availability. Controlled environment seed dormancy findings indicated that dormancy was significantly reduced by storage at ambient laboratory temperatures over eighteen months. Seed dormancy was transient and appeared to be both physical and physiological in nature, and was dependent on the period of after ripening during the post-harvest period. Key reproductive attributes, including high seed production, self-compatibility and pollination facilitated by several non-specific pollinators have likely resulted in increased spread of this weed in Australia and more globally. Management of C lanatus is achieved using IWM strategies including pre and post-emergent applications of herbicides as well as limiting fruit production by cultural practices including mowing, grazing and cultivation. (C) 2017 Elsevier Ltd. All rights reserved.