Abstract
Abstract Key message Seed storage temperature influences root anatomy of the endangered Populus nigra, and consequently may alter nutrient absorption. A lower temperature during seed storage (−20 and −196 °C) may preserve the potential for a suitable root system development after germination. Context Seed storage conditions can be an important determinant of later seedling growth of Populus nigra L., an endangered tree species. Aims We tested whether long-term seed storage temperature, −10, −20 or −196 °C, affects the pattern of seedling root traits responsible for resource acquisition as compared to seedlings of fresh seeds. Methods We analysed the morphology, anatomy, degree of mycorrhizal colonization, and biochemical composition of roots developed from seed stored for 24 months at five different temperatures (from 3 to −196 °C) commonly used to preserve genetic resources. Results Except for root anatomy, we found no relationship between seed storage temperature and the root traits of seedlings. Among the various storage conditions, the proportion of roots with primary development in the first four orders was similar in seedlings developed from fresh seeds of from seeds stored at −196 or −20 °C. Nitrogen content in the roots was positively correlated with the proportion of (i) roots with primary development and (ii) the cortex width in the root diameter. Conclusions Higher temperatures during seed storage reduced the proportion of roots with absorptive function (with primary development). Therefore, for preservation of P. nigra seeds we recommend lower temperatures such as −20 and −196 °C.
Highlights
Populus nigra L. is a species that occurs within a riparian ecosystem and is widely distributed throughout the northern hemisphere, with a geographical range from Central and South Europe to Central Asia and North Africa (Storme et al 2004)
The specific environmental conditions in natural habitats have favored the evolution of preferential root development of P. nigra during the first few years of seedling growth to ensure anchorage and resource acquisition via fine roots (Braatne et al 1996; Hodge et al 2009), what is essential in biomass production (FernándezMartínez et al 2014)
When root anatomy was studied, seed storage temperature turned out to have a significant impact on the proportion of roots with primary development (Tables 2 and 3)
Summary
Populus nigra L. is a species that occurs within a riparian ecosystem and is widely distributed throughout the northern hemisphere, with a geographical range from Central and South Europe to Central Asia and North Africa (Storme et al 2004). In Europe, approximately 99% of the riparian forests are projected to disappear by human use and the regulation of river systems (Lefèvre et al 1998; Hughes and Rood 2003). The life cycle of riparian black poplar is adapted to hydrogeomorphological conditions (Corenblit et al 2014). These morphological, physiological, and biochemical adaptations ensure growth in a disturbed, unstable, and fluctuating environment (Lytle 2001). The specific environmental conditions in natural habitats have favored the evolution of preferential root development of P. nigra during the first few years of seedling growth to ensure anchorage and resource acquisition via fine roots (with diameter
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