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Seed dormancy can present a significant barrier to restoration outcomes in dryland systems. Physical and combinational (physical + physiological) dormancy are prevalent among seeds of many herbaceous perennials used in restoration of drylands throughout the western United States. Although many techniques designed to alleviate these dormancy traits exist, their efficacy is species specific, may result in embryo damage, and may have limited large-scale application. To identify the most effective means of dormancy alleviation with the potential to be used on an operational scale, we examined the effects of 16 temperature-based techniques (altering temperature and duration of wet heat, freezing and wet heat, and freeze-thaw cycles) and 6 abrasion-based techniques (altering pneumatic scarification length or using a single duration of manual scarification) on the enhancement of seed permeability among two physically dormant (western prairie clover [Dalea ornata{Douglas} Eaton & Wright] and Munro’s globemallow [Sphaeralcea munroana{Douglas} Spach]) and two combinationally dormant species (basalt milkvetch [Astragalus filipesTorr. ex A. Gray] and longspur lupine [Lupinus arbustus{Douglas} ex Lindl.]). We first assessed seed imbibition following exposure to all temperature- and abrasion-based techniques to identify those most successful at promoting seed permeability and then evaluated the effectiveness of those techniques through a series of germination experiments. For combinationally dormant species, we also tested whether exposure to GA3enhanced germination. Abrasion-based techniques were more effective than temperature-based techniques at improving water uptake across all species. Pneumatic scarification significantly improved germination, but optimal treatment durations were species specific. GA3did not enhance germination under the tested conditions. We conclude that pneumatic scarification is a fast, safe, and effective method for alleviating physical seed dormancy with a potential to be scaled up for operational use in restoration.

Phenological patterns including peak flowering and seed production of 19 grass, herb, shrub and tree species were studied in the Pilbara biogeographic region of Western Australia. Each plant population was monitored monthly over an 18-month period. Qualitative data was collected capturing plant phenophases. Plant fecundity was estimated using X-ray analyses to determine the proportion of seeds produced. Two main phenological patterns were established across plant life-forms. Precipitation during the summer wet season provided sufficient soil moisture for grasses to emerge from a dormant vegetative state and rapidly transition into flowering and seed production. In contrast, the deeper-rooted shrubs and herbs commenced flowering before the onset of the summer rains, completing their reproductive cycle before the period of higher moisture availability. The patterns observed indicated that the different plant life-forms co-existing within the Pilbara differentially exploit the available resources of this arid region. The contrasting phenological patterns between plant life-forms across seasons likely represent adaptations to a competitive, arid environment where water is the limiting resource. To meet the increasing demand for native seeds of diverse plant species for ecosystem restoration, plant phenological data will become increasingly important for deriving seed supply strategies from wild or managed plant populations.

We developed a system for time-lapse observation of identified neurons in the central nervous system (CNS) of the Drosophila embryo. Using this system, we characterize the dynamics of filopodia and axon growth of the motorneuron RP2 as it navigates anteriorly through the CNS and then laterally along the intersegmental nerve (ISN) into the periphery. We find that both axonal extension and turning occur primarily through the process of filopodial dilation. In addition, we used the GAL4-UAS system to express the fusion protein Tau-GFP in a subset of neurons, allowing us to correlate RP2's patterns of growth with a subset of axons in its environment. In particular, we show that RP2's sharp lateral turn is coincident with the nascent ISN. © 1998 John Wiley & Sons, Inc. J Neurobiol 37: 607–621, 1998

The embryonic peripheral nervous system of Drosophila contains two main types of sensory neurons: type I neurons, which innervate external sense organs and chordotonal organs, and type II multidendritic neurons. Here, we analyse the origin of the difference between type I and type II in the case of the neurons that depend on the proneural genes of the achaete-scute complex (ASC). We show that, in Notch− embryos, the type I neurons are missing while type II neurons are produced in excess, indicating that the type I/type II choice relies on Notch-mediated cell communication. In contrast, both type I and type II neurons are absent in numb− embryos and after ubiquitous expression of tramtrack, indicating that the activity of numb and the absence of tramtrack are required to produce both external sense organ and multidendritic neural fates. The analysis of string− embryos reveals that when the precursors are unable to divide they differentiate mostly into type II neurons, indicating that the type II is the default neuronal fate. We also report a new mutant phenotype where the ASC-dependent neurons are converted into type II neurons, providing evidence for the existence of one or more genes required for maintaining the alternative (type I) fate. Our results suggest that the same mechanism of type I/type II specification may operate at a late step of the ASCdependent lineages, when multidendritic neurons arise as siblings of the external sense organ neurons and, at an early step, when other multidendritic neurons precursors arise as siblings of external sense organ precursors.

Many plants in fire-prone regions retain their seeds in woody fruits in the plant canopy until the passage of a fire causes the fruit to open and release the seeds. To enable this function, suitable tissues are required that effectively store and protect seeds until they are released. Here, we show that three different species of the Australian genus Banksiaincorporate waxes at the interface of the two valves of the follicle enclosing the seeds, which melt between 45°C and 55°C. Since the melting temperature of the waxes is lower than the opening temperatures of the follicles in all investigated species (B. candolleana, B. serrata, B. attenuata), we propose that melting of these waxes allows the sealing of micro-fissures at the interface of the two valves while they are still closed. Such a self-sealing mechanism likely contributes to the structural integrity of the seed pods, and benefits seed viability and persistence during storage on the plants. Furthermore, we show in a simplified, bioinspired model system that temperature treatments seal artificially applied surface cuts and restore the barrier properties.

A component of the male accessory gland secretion, injected during mating, was responsible for onset of refractory behavior in the female black blow fly, Phormia regina (Meigen). Immediately after mating, two components of the semen were located separately in the bursa copulatrix: sperm were found anteriorly near the opening to the spermathecal ducts, and accessory secretion distended the posterior of the bursa. The accessory secretion disappeared within a day of mating, presumably entering the hemolymph from where it was detected. Scanning electron microscopy of the intromittent organ and phallosome, and reconstruction of the female reproductive tract from serial sections revealed complementary structures in the male and female. A pair of conspicuous flaps on the phallosome clasp a cuticular tonsil in the female, sealing the accessory secretion in the bursa during copulation. Accessory secretion is released at the tip of the phallosome and is redirected to a more proximal release site on the phallosome via a pair of hitherto undescribed accessory ducts, resulting in its deposition posteriorly in the bursa lumen.