Maternal and burial environment determine the physical dormancy release in tropical Senna auriculata(Fabaceae) seeds

In tropical ecosystems,species with an impermeable seed coat,i.e.physical dormancy(PY),are large in number and their seed coat is considered to be an adaptive trait for species persistence and colonization.However,only little is known about their mechanisms for breaking dormancy.The objective of this study was to understand the importance of seed maturation site and burial location in determining the PY release of Senna auriculata.Freshly collected seeds of S.auriculata from Vellore and Coimbatore,Tamil Nadu,India,germinated to 11±1.5%and19±2.5%respectively and remaining seeds did not imbibe water,thus had PY.Germination of seeds from both sites following hot-water treatment for 30 s and mechanical scarification increased significantly and seeds were able to germinate at a wide-range of temperatures(5–35℃)both in light and darkness.When incubated at 15/60℃for 3 months,dormancy release for seeds collected from Coimbatore(72%)was greater than seeds matured in Vellore(53%).Following 1 year of burial at three different locations,seeds from Coimbatore germinated to higher percentage than Vellore seeds at all locations.In particular,the higher temperature sites released dormancy to greater extent than the lower temperature site.Our results suggest that summer temperatures(>60℃)prevailing in the tropics provide appropriate cues for breaking PY,but this could be greatly affected by the initial state of seeds and the burial environment.

Sand-mediated ice seeding enables serum-free low-cryoprotectant cryopreservation of human induced pluripotent stem cells

Human induced pluripotent stem cells(hiPSCs)possess tremendous potential for tissue regeneration and banking hiPSCs by cryopreservation for their ready availability is crucial to their widespread use.However,contemporary methods for hiPSC cryopreservation are associated with both limited cell survival and high concentration of toxic cryoprotectants and/or serum.The latter may cause spontaneous differentiation and/or introduce xenogeneic factors,which may compromise the quality of hiPSCs.Here,sand from nature is discovered to be capable of seeding ice above10◦C,which enables cryopreservation of hiPSCs with no serum,much-reduced cryoprotectant,and high cell survival.Furthermore,the cryopreserved hiPSCs retain high pluripotency and functions judged by their pluripotency marker expression,cell cycle analysis,and capability of differentiation into the three germ layers.This unique sand-mediated cryopreservation method may greatly facilitate the convenient and ready availability of high-quality hiPSCs and probably many other types of cells/tissues for the emerging cell-based translational medicine.