Instrinsic relationship among needle morphology, anatomy, gas exchanges and tree growth across 17 Picea species

Abstract

The genus Picea has wide geographical range and includes species with great economic and ecological value in the northern hemisphere. Growth traits, gas exchange parameters and needle morphology and anatomy vary greatly among Picea species, but the instrinsic relationship among these traits has not been well studied for the genus Picea. We thus conducted a common garden experiment to study the relationship for these traits in 13 native and 4 exotic Picea species growing at an experimental site in Tianshui, Gansu, China. Nearly all of these traits were significantly different among the 17 species and most traits were under relatively strong genetic control. The four species introduced from abroad (P. abies, P. pungens, P. glauca and P. mariana) exhibited good growth performance in the experimental site. We found that the growth traits showed significantly positive correlation with branching characteristics. Moreover, the species with good growth performance had a relatively high photosynthetic rate. The correlation analysis based on needle morphological and anatomical traits revealed that needle traits were interrelated and needle anatomical traits might be impacted by needle size due to the increase of mesophyll area and central cylinder area with needle length. Furthermore, the relationship between needle structures and gas exchange parameters may indicate that a higher photosynthetic rate can be attributed to variations in needle structures. In addition, both the cluster analysis and principal component analysis based on needle morphology, anatomy, gas exchanges and growth traits might partially reflect the evolutionary history of the 17 Picea species. Our study represents a comprehensive survey of variation within the genus Picea to date and opens new avenues for exploring the instrinsic relationship among growth traits, needle gas exchange and needle morphology and anatomy.