Desiccation tolerance and cryopreservation of seeds of black poplar (Populus nigra L.), a disappearing tree species in Europe

Abstract

Black poplar (Populus nigra L.) is a widely distributed species that plays a crucial role in riparian forest ecosystems. Due to a reduction in its natural habitats and hybridization with introduced poplar species clones, its genetic pool is decreasing and efforts are required to preserve this species. Seeds of black poplar are short-lived and quickly lose viability during conventional storage in gene banks. Therefore, in order to preserve ex situ the genetic diversity of this species, the feasibility of seed cryopreservation in liquid nitrogen (at -196°C, LN) for periods of 24 h and 2 years was investigated. Seeds were harvested from three individual trees (two provenances) and desiccated to different levels of water content (WC) in the range of 0.02-0.35 g g -1 (g H 2 O/g dry mass, g g -1 ) prior to immersion in LN. Seed germination was assessed after each treatment. P. nigra seeds tolerated desiccation to WC 0.07 g g -1 but after severe desiccation to WC\0.05 g g -1 exhibited a significant reduction in germination. Results indicated that all black poplar seeds, regardless of origin, year of harvesting and seed quality, could be cryopreserved for 24 h when their WC was in the range of 0.11-0.17 g g -1 . Physiology of P. nigra seeds showed in this paper is consistent with attributes of intermediate seed storage behavior. This study provides a foundation for using cryopreservation for the ex situ conservation of P. nigra seeds.

Orthodoxy, recalcitrance and in-between: describing variation in seed storage characteristics using threshold responses to water loss

“…2). (Ellis et al 1991a, b;Sacandé et al 2000;Hor et al 2005;Eira et al 2006;Pérez et al 2012); (2) seeds that exhibit anomalous longevity responses to temperatures between ?10 and -30°C (Ellis et al 1991a, b;Hor et al 2005;Eira et al 2006;Crane et al 2006;Pérez et al 2012); or (3) seeds that have short lifespans no matter how they are dried or cooled (Mondoni et al 2010;Michalak et al 2015). Water content thresholds and time for lethal damage to accumulate are cross-cutting parameters used to characterize all seed types.…”

Effect of seed storage temperature on fine root development and mycorrhizal colonization of young Populus nigra seedlings

“…Additionally, fresh seeds that were collected in 2012 were used as a control. Details of the storage protocols were described in Suszka et al (2014) and Michalak et al (2014).…”

“…This requires the development of seed storage methods that can retain the ability of seeds to germinate after many years. Various seed storage temperatures have been reported for P. nigra, which have resulted in the ability to store the seeds for different lengths of time and still retain sufficient levels of seed viability (Stanton and Villar 1996;Tylkowski 2010;Michalak et al 2014;Suszka et al 2014). Thus far in the literature, optimal seed storage conditions have been assessed on the basis of seed germination (Popova et al 2012;Malik et al 2013;Suszka et al 2014) or seedling emergence (Michalak et al 2013;Popova et al 2013).…”

Cryopreservation of Forest Tree Seeds: A Mini-Review

“…Michalak et al (2015) also demonstrated that MC within 0.11-0.17 g g -1 plays an important role in the cryopreservation of black poplar seeds irrespective of its origin, time of harvesting and the seed quality.…”

“…The temperature was sustained at 23 o C and 27 o C for 22 h and 2 h per day, respectively. The use of Jacobsen germinator was also described in the reports of Chmielarz (2010) and Michalak et al (2015). As per their description, the seeds were thawed by keeping in a water bath at 40 o C for 5 min following LN exposure before transferring them in Jacobsen germinator.…”