STRIDER (Sildenafil TheRapy in dismal prognosis early onset fetal growth restriction): An international consortium of randomised placebo-controlled trials

Background: Severe, early-onset fetal growth restriction due to placental insufficiency is associated with a high risk of perinatal mortality and morbidity with long-lasting sequelae. Placental insufficiency is the result of abnormal formation and function of the placenta with inadequate remodelling of the maternal spiral arteries. There is currently no effective therapy available. Some evidence suggests sildenafil citrate may improve uteroplacental blood flow, fetal growth, and meaningful infant outcomes. The objective of the Sildenafil TheRapy In Dismal prognosis Early onset fetal growth Restriction (STRIDER) collaboration is to evaluate the effectiveness of sildenafil versus placebo in achieving healthy perinatal survival through the conduct of randomised clinical trials and systematic review including individual patient data meta-analysis.  Methods: Five national/bi-national multicentre randomised placebo-controlled trials have been launched. Women with a singleton pregnancy between 18 and 30 weeks with severe fetal growth restriction of likely placental origin, and where the likelihood of perinatal death/severe morbidity is estimated to be significant are included. Participants will receive either sildenafil 25 mg or matching placebo tablets orally three times daily from recruitment to 32 weeks gestation.  Discussion: The STRIDER trials were conceived and designed through international collaboration. Although the individual trials have different primary outcomes for reasons of sample size and feasibility, all trials will collect a standard set of outcomes including survival without severe neonatal morbidity at time of hospital discharge. This is a summary of all the STRIDER trial protocols and provides an example of a prospectively planned international clinical research collaboration. All five individual trials will contribute to a pre-planned systematic review of the topic including individual patient data meta-analysis

Ecology and ecophysiology of southwestern Australian hakea species with contrasting leaf morphology and life forms.

Members of the genus Hakea (Proteaceae) are sclerophyllous, evergreen perennial shrubs or small trees endemic to Australia, with 65% of species confined to the South-West Botanical Province (southwestern Australia). Southwestern Australian Hakea species possess two contrasting leaf morphologies (broad or terete leaves) and fire-related life forms (non-sprouting (fire-killed) or resprouting (fire-surviving)), with each species representing one of four leaf morphology-life form groups.Representative species within each group were studied to determine whether they display similar distribution and ecophysiological patterns at both the adult and seedling stages. The distribution of species within these groups was best based on averages and variations in annual temperature and rainfall. The highest percentage of terete leaved non-sprouters (25 species) occurred in areas of low-moderate rainfall with large annual temperature ranges, whereas terete leaved resprouters (14 species) displayed a patchy distribution. Broad leaved resprouters (28 species) dominated areas of strongly seasonal rainfall, with few species occurring in the drier regions. Broad leaved non-sprouters (33 species) were best represented in areas of low annual temperature. The distribution of non-sprouters/resprouters may be due to the effect of climatic factors on seedling recruitment and/or fire frequencies. Leaf morphology appears to have a more direct influence on species distribution, as broad leaves are favoured in regions of medium-high, seasonal rainfall (less stressful habitats) while terete leaves are better adapted to tolerate hot, dry environments.Terete leaves are either simple (needle-like) or 2-3 pronged, and, apart from their narrow width, are characterised by their greater leaf thickness (> 1 mm), smaller projected area and mass, higher leaf mass per area (a measure of sclerophylly) and a lower density than broad leaves. Broad leaves are much more variable in their shape. Increased leaf thickness and sclerophylly in terete leaves can be partially attributed to the presence of a central parenchyma core and increased palisade thickness. This core is surrounded a compact network of fibre-capped vascular bundles. Thickness and sclerophylly were good indicators of relative nutrient content in terete, but not broad leaves. Both leaf types have a thick cuticle (> 20 mu m) and sunken stomates, with terete leaves possessing a greater stomatal density than broad leaves. Broad leaves are bilateral and hence amphistomatous. Adult and seedling leaves (of a similar leaf type) differed in morphology, but not anatomy, with some species producing broad seedling leaves and terete adult leaves.Seedlings growing under optimal growth conditions (full sunlight, well watered) in pots showed no relationship between rate of growth and ecophysiology with respect to the four species groupings, although seedlings of non-sprouters and broad leaved species had higher transpiration and photosynthetic rates than seedlings of resprouters and terete leaved species respectively. In response to high air temperatures (> 35°C), leaf temperatures close to or lower than the surrounding air temperature only occurred for terete leaved species possessing small individual and total leaf areas. By maintaining leaf photosynthesis rates during periods of relatively high air temperatures, terete leaved seedlings were able to produce more biomass per leaf area while retaining a low leaf area per seedling mass. When subjected to periods of water stress (withholding water), differences in water relations were most evident between seedlings of non-sprouters and resprouters, with resprouter seedlings showing an ability to minimise the decrease in relative water content for a given decrease in XPP. Although terete leaves possess many xeromorphic attributes, terete leaved seedlings were not necessarily superior at avoiding/tolerating drought. Terete leaves in seedlings may have alternative heat dissipation and/or anti-herbivore properties.Seasonal water relations of adult plants were monitored for over a year, including a period of prolonged summer drought at four sites (two on laterite (rocky substrate) and two on deep sand). The eight species inhabiting the lateritic sites were more stressed (more negative xylem pressure potentials (XPP)) in summer than the eight species on sandy soils, with lower conductances and higher leaf specific resistivity (XPP/area-based transpiration, LSR). Broad leaved species had higher transpiration rates and LSR, and more negative midday XPP throughout the study than terete leaved species. When spring (predrought) and summer (drought) data were compared, non-sprouters had lower XPP in summer, and lower transpiration rates and conductances in both seasons than resprouters. Non-sprouters on lateritic sites had the lowest water relations values in summer (drought tolerators). There was a tendency for broad leaved resprouters on sandy soils to have higher summer water relations values (drought avoiders). Broad leaved non-sprouters on lateritic soils could be considered the most water stressed group, with substantial plant death during the summer period. Terete leaved species on sandy soils were the most conservative in their water usage

LMA, density and thickness: recognizing different leaf shapes and correcting for their nonlaminarity

Leaf thickness (t) and dry bulk density (D) are now considered to be the two major components of leaf structure that, when multiplied, give leaf mass per unit area (LMA = tD), or its inverse, leaf-specific-area (tD−1)..

Green cotyledons of two Hakea species control seedling mass and morphology by supplying mineral nutrients rather than organic compounds

•Hakea species dominate shrubby vegetation on seasonally dry, nutrient impoverished soils in Australia. We hypothesized that the exposed cotyledons control growth of the young seedling by providing it with mineral nutrients rather than C-based compounds. • Two representative species with differing seed masses were tested. Cotyledon removal caused large reductions in plant mass and dimensions, but little effect on specific leaf area. Cotyledons expanded markedly on germination although their chlorophyll content was much lower than the first leaves. Shading the cotyledons or applying a C-storage compound (inositol) to the soil had no consistent effect on seedling properties. • Cotyledon removal greatly reduced seedling P (especially), N, K, Ca, Mg and Cu, but not Fe or Mn, whereas shading the cotyledons had no effect. Transfer of mineral nutrients from the embryos to the seedlings in their natural soils varied from 90 to 2% (for P and Ca, respectively), and accounted for 79% of total content (P) to negligible (K, Ca, Fe) at 3 months. Cotyledons indirectly increased soil nutrient uptake. Addition of P, N or P + N after cotyledon removal had no benefit but addition of P + N + K + Mg + S restored morphology and nutrient content. • In nutrient and water-limited habitats with abundant light, cotyledons in Hakea spp. might serve to maximize supply of mineral nutrients to the shoots, which then maximize C-supply to the rapidly elongating roots

Regional and local effects on reproductive allocation in epicormic and lignotuberous populations of Banksia menziesii

Reproductive allocation (RA) is a measure of how resources (biomass, nutrients) are partitioned between reproductive structures and the rest of the plant. For plants that resprout after fire, the percentage of resources allocated to reproduction may vary depending on their resprouting ability. Our study examines the percentage RA (biomass, N, P, K) and nutrient content of current season’s growth in southern (Swan Coastal Plain) epicormic and northern (Eneabba Plain) lignotuberous resprouter populations of Banksia menziesii (Proteaceae), a species endemic to nutrient-impoverished sandplains of southwestern Australia. Within each population, plants along road edges were compared with plants not associated with road edges. There was no difference in total nutrient content of current year’s growth between both resprouting types, except that total K in the shoots of lignotuberous populations was >2 times that in the epicormic populations. Non-road lignotuberous plants allocated twice the biomass, N and P, and 13.5 times the K, to reproduction as non-road epicormic plants. Lignotuberous populations had the highest RA (17–34% of biomass, N, P, K), with non-road epicormic populations the lowest RA (3–15%). This can be viewed as an adaptive (ultimate) response to the poorer postfire survival and recruitment conditions where the lignotuberous populations occur.Total biomass and nutrient content of road-edge plants was 2–3 times that of non-edge plants. Lignotuberous populations in both road positions allocated the same fraction of biomass, N and P to reproduction, whereas road-edge populations allocated 10% less K than non-road. Road-edge epicormic populations allocated 5–10% more biomass, N, P and K to reproduction than non-road populations. This can be viewed as an ecophysiological (proximate) response to the better growing conditions created by the roadways that may also ultimately have an adaptive explanation

Phosphorus accumulation in Proteaceae seeds: a synthesis

The family Proteaceae dominates the nutrient-poor, Mediterranean-climate floristic regions of southwestern Australia (SWA) and the Cape of South Africa. It is well-recognised that mediterranean Proteaceae have comparatively large seeds that are enriched with phosphorus (P), stored mainly as salts of phytic acid in protein globoids. Seed P can contribute up to 48% of the total aboveground P, with the fraction allocated depending on the species fire response. For SWA species, 70–80% of P allocated to fruiting structures is invested in seeds, compared with 30–75% for Cape species, with SWA species storing on average 4.7 times more P per seed at twice the concentration. When soil P is less limiting for growth, seed P reserves may be less important for seedling establishment, and hence plants there tend to produce smaller seeds with less P. For Australian Hakea and Grevillea species the translocation of P from the fruit wall to the seed occurs in the days/ weeks before final fruit dry mass is reached, and accounts for 4–36% of seed P. Seed P content increases with the level of serotiny, though it decreases marginally as a fraction of the total reproductive structure. The greater occurrence of serotiny and higher seed P content within the Proteaceae in SWA supports the notion that SWA soils are more P-impoverished than those of the Cape