No abstract

Recalcitrant seeds are intolerant of desiccation and cannot be stored in conventional seed banks. Cryopreservation allows storage of the germplasm of some recalcitrant seeded species, but application to a wide range of plant diversity is still limited. The present work aimed at understanding the stresses that accompany the first steps in cryopreservation protocols, wounding and desiccation, both of which are likely to lead to the formation of reactive oxygen species (ROS). Extracellular ROS production was studied in isolated embryonic axes of sweet chestnut (Castanea sativa). Axis excision was accompanied by a burst of superoxide (O(2)(*-)), demonstrated by a colorimetric assay using epinephrine, electron spin resonance and staining with nitroblue tetrazolium. Superoxide was immediately produced on the cut surface after isolation of the axis from the seed, with an initial 'burst' in the first 5 min. Isolated axes subjected to variable levels of desiccation stress showed a decrease in viability and vigour and increased electrolyte leakage, indicative of impaired membrane integrity. The pattern of O(2)(*-) production showed a typical Gaussian pattern in response to increasing desiccation stress. The results indicate a complex interaction between excision and subsequent drying and are discussed with a view of manipulating ROS production for optimisation of cryopreservation protocols.

No abstract

Team supervision of PhDs is increasingly the norm in Australian and UK universities; while this model brings many improvements on the traditional one-on-one research supervision, it also introduces new complexities. In particular, many students find the diversity of opinions expressed in teams to be confusing. Such diversity in supervisor feedback is often experienced as unsettling, and the study indicates that students generally seek consensus from their supervisory team. The power dynamics existing in the relations between team members in this situation need to be carefully considered, and supervisors must be alert to the ways in which doctoral students can be effectively and productively inducted into the norms of academic debate and collaborative research projects. The paper explores the implications of diversity in feedback in relation to developing a pedagogy of supervision.