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The confinement of liquid crystals in geometries with frustrating boundary conditions gives rise to nontrivial effects such as bistability and memory. It is shown that large memory effects arise when nematic liquid crystals are embedded in cubic micrometer-sized scaffolds made by two-photon polymerization. The electric field alignment of the liquid crystals inside the porous medium is maintained when the applied field is above a threshold (approximately 2 V per micrometer of cell thickness). The onset of the memory is an on/off type process for each individual pore of the scaffold, and the memory typically starts emerging in one region of the structure and then propagates. The global memory effects in porous structures with controlled geometry are enhanced with respect to the case of random porous structures. This work is a proof of the 'memory from topology' principle, which was previously suggested by computer simulations. These new materials can pave the way to new types of bistable displays. [ABSTRACT FROM AUTHOR]

•Periods of dormancy in shallow roots allow perennial monocotyledons to establish deep root systems, but we know little about patterns of xylem maturation, water-transport capacities and associated economies in water use of growing and dormant roots. •Xylem development, anatomy, conductance and in situ cellular [K] and [Cl] were investigated in roots of field-grown Lyginia barbata (Restionaceae) in Mediterranean southwestern Australia. Parallel studies of gas exchange, culm relative water loss and soil water content were conducted. •Stomatal conductance and photosynthesis decreased during summer drought as soil profiles dried, but rates recovered when dormant roots became active with the onset of wetter conditions. Anatomical studies identified sites of close juxtaposition of phloem and xylem in dormant and growing roots. Ion data and dye tracing showed mature late metaxylem of growing roots was located ≥ 100 mm from the tip, but at only ≤ 10 mm for dormant roots. Dormant roots remained hydrated in dry soils (0.001–0.005 g g−1). •Effective regulation of growth and water-conserving/obtaining properties permits the survival of shallow roots of L. barbata during summer drought and may represent important strategies for establishing deeper perennial root systems in other monocotyledonous plants adapted to seasonally dry habitats. [ABSTRACT FROM AUTHOR]

• Here, we tested the alternation of root summer dormancy and winter growth as a critical survival strategy for a long-lived monocotyledon (Restionaceae) adapted to harsh seasonal extremes of Mediterranean southwest Western Australia. • Measurements of growth and the results of comparative studies of the physiology, water content, metabolites, osmotic adjustments, and proteomics of the dormant and growing perennial roots of Lyginia barbata (Restionaceae) were assessed in field-grown plants. • Formation of dormant roots occurred before the onset of summer extremes. They resumed growth (average 2.3 mm d−1) the following winter to eventually reach depths of 2–4 m. Compared with winter-growing roots, summer dormant roots had decreased respiration and protein concentration and c. 70% water content, sustained by sand-sheaths, osmotic adjustment and presumably hydraulic redistribution. Concentrations of compatible solutes (e.g. sucrose and proline) were significantly greater during dormancy, presumably mitigating the effects of heat and drought. Fifteen root proteins showed differential abundance and were correlated with either winter growth or summer dormancy. None matched currently available libraries. • The specific features of the root dormancy strategy of L. barbata revealed in this study are likely to be important to understanding similar behaviour in roots of many long-lived monocotyledons, including overwintering and oversummering crop species. [ABSTRACT FROM AUTHOR]

The influence of phosphorus (P) availability on growth and P uptake was investigated in South African Proteaceae: (1) Protea compacta R.Br., endemic on severely nutrient-impoverished colluvial sands; (2) Protea obtusifolia Bueck ex Meissner; and (3) Leucadendron meridianum I. J. Williams, the latter both endemic on comparatively fertile limestone-derived soils. Plants were grown hydroponically in 1000 L tanks at 0.01, 0.1 or 1.0 µm P for 14 weeks. Biomass accumulation was influenced by P availability, doubling as [P] increased from 0.1 to 1.0 µm. Total biomass was greatest for P. compacta, but L. meridianum and P. obtusifolia had two to four times greater relative biomass accumulation at 0.1 and 1.0 µm[P]. Proteoid root clusters developed at both 0.01 and 0.1 µm[P], but were suppressed at 1.0 µm[P]; this was a 10-fold lower [P] than previously reported to inhibit cluster root formation. Rates of net P uptake at 5 µm P decreased in response to increased P availability from 0.01 to 1.0 µm P. Significant between-species differences in rates of P uptake and capacity to down-regulate P uptake were observed: P. compacta < P. obtusifolia < L. meridianum. The species responses are discussed in terms of adaptation to mosaics in soil P availability and the high beta diversity in the natural habitat. [ABSTRACT FROM AUTHOR]

When grown in nutrient solutions of extremely low [P] (≤1.0 µm), the sedge Schoenus unispiculatus Benth. (Cyperaceae) develops dauciform roots, which are short and carrot shaped, and produce dense numbers of long root hairs. It has been suggested that dauciform roots of monocotyledonous sedges function to acquire P from nutrient-poor, P-fixing soils in a manner similar to that of cluster (proteoid) roots developed by some dicotyledonous species, but without evidence to substantiate this claim. To elucidate the ecophysiological role of dauciform roots, we assessed carboxylate exudation, internal carboxylate and P concentrations and O2 uptake rates during dauciform root development. We showed that O2 consumption was fastest [9 nmol O2 g−1 fresh mass (FM) s−1] and root [P] greatest (0.4 mg P g−1 FM) when dauciform roots were young and rapidly developing. Citrate was the most abundant carboxylate in root tissues at all developmental stages, and was most concentrated (22.2 µmol citrate g−1 FM) in young dauciform roots, decreasing by more than half in mature dauciform roots. Peak citrate-exudation rates (1.7 nmol citrate g−1 FM s−1) occurred from mature dauciform roots, and were approximately an order of magnitude faster than those from roots of species without root clusters, and similar to those of mature proteoid (cluster) roots of Proteaceae. Both developing and mature dauciform roots had the capacity to acidify (but not alkalinize) the rhizosphere. Anatomical studies showed that epidermal cells in dauciform roots were greatly elongated in the transverse plane; epidermal cells of parent roots were unmodified. Although structurally distinct, the physiology of dauciform roots in sedges appears to be analogous to that of proteoid roots of Proteaceae and Fabaceae, and hence, dauciform roots would facilitate access to sorbed P and micronutrients from soils of low fertility. [ABSTRACT FROM AUTHOR]

When grown at a low P supply, Hakea prostrata R.Br. (Proteaceae) develops dense clusters of determinate branch roots, termed ‘proteoid’ or ‘cluster’ roots and accumulates Mn in its leaves. The aim of this study was to vary the production of cluster roots and assess the relationship between Mn uptake and cluster-root mass. We collected native soil from a location inhabited by H. prostrata and amended this with ‘high’ and ‘low’ amounts of insoluble or soluble P. After 14 months, we measured the impact of the treatments on cluster-root development and the [P], [Mn], [Fe], [Zn] and [Cu] in young (expanding) and mature leaves. Dry mass and leaf area increased with increasing P availability in the soil, but growth decreased at the highest soluble [P], which caused symptoms of P toxicity. The [P] in young leaves (1.3–2.7 mg g−1 DM) exceeded that in older leaves (0.28–0.85 mg g−1 DM), except when plants were grown with soluble P (3.2–21 mg g−1 DM). Cluster-root formation was inhibited when leaf [P] increased; [P] in young leaves, rather than that in old leaves, appeared to be the factor that determined the proportion of the root mass invested in cluster roots. Old leaves of all treatments had [Mn] from 90 to 120 µg g−1 DM, except for plants grown at high levels of soluble P, when [Mn] decreased below 30 µg g−1 DM. The [Mn] and [Zn] in old leaves and the [Cu] in young leaves were positively correlated with the fraction of roots invested in cluster roots. These findings support our hypothesis that cluster roots play a significant role in micronutrient acquisition, and also provide an explanation for Mn accumulation in leaves of H. prostrata, and presumably Proteaceae in general. [ABSTRACT FROM AUTHOR]

• The incidence of species that develop specialised‘dauciform’ lateral roots, which are hypothesised to be important for phosphorus (P) acquisition, is uncertain. We investigated their occurrence in Australian reed, rush and sedge species, grown at low P concentration in nutrient solution, and studied the response ofSchoenus unispiculatus(Cyperaceae) to a range of P concentrations.• We assessed the fraction of root biomass invested in dauciform roots, their respiration and net P-uptake rate, and the P status of roots and leaves.• Dauciform-root development occurred only in particular genera of Cyperaceae when grown at low P supply. Increased P supply was associated with increased growth ofS. unispiculatusand increased leaf[P]. Dauciform-root growth was reduced by increased P supply, and reduced P uptake co-occurred with the complete suppression of dauciform roots.• The P-induced suppression of dauciform roots in Cyperaceae is similar to that observed for proteoid roots in members of Proteaceae andLupinus albus. The response of dauciform roots to altered P supply and their absence from root systems of some sedge species are discussed in terms of managed and natural systems.New Phytologist(2005)doi: 10.1111/j.1469-8137.2004.01283.x© New Phytologist(2005) [ABSTRACT FROM AUTHOR]

S. M. Eaton and co‐workers report the first experimental proof of the bistability of nematic liquid crystals incorporated in a porous network with a controlled geometry. This configuration, described in detail on page 3990, is specifically designed to enhance memory effects by inducing a regular arrangement of topological defects. The cover image shows this three dimensional porous network, fabricated by femtosecond laser lithography, with the incorporated liquid crystals. This composite material could be exploited for future ultralow‐power bistable displays. [ABSTRACT FROM AUTHOR]

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