The Earliest Stages of Tree Growth: Development, Physiology and Impacts of Microclimate [chapter]

Daniel M. Johnson, Katherine A. McCulloh, Keith Reinhardt
2011 Tree Physiology  
Although the germinant and young seedling life stage of trees has the highest mortality rates, our understanding of their fundamental physiology is surprisingly limited in naturally-occurring environments. Field measurements for this life stage are particularly important because of the uniquely harsh environment these small trees experience: their proximity to the soil surface results in an exceptionally dynamic microclimate with large daily shifts in such parameters as temperature, humidity
more » ... rature, humidity and radiation. The impact of these changing conditions is discussed with respect to seedling survival. Our current knowledge of anatomical and morphological responses of early seedlings to variation in light and water conditions is also reviewed. For example, research has shown that differences in light intensity result in divergence in vessel diameters and number in Eucalyptus grandis seedlings. Using these data, we calculated the theoretical hydraulic conductivity for high and low light-grown seedlings. This comparison showed that after 7 weeks the differences in xylem anatomy would result in the high light seedlings having two times the theoretical leaf-specific hydraulic conductivity of the low light seedlings. Future research in this field should include developing new techniques specific to the unique fragility and size of seedlings, determining the adaptive nature of different cotyledon structures, and better quantifying the physiological and developmental characteristics of early germinants.
doi:10.1007/978-94-007-1242-3_3 fatcat:qehx4gwmczgvbpxbrliqde7bwu