Branch architecture in Ginkgo biloba: wood anatomy and long shoot-short shoot interactions.
OBJECTIVE
Ginkgo, centrally placed in seed plant phylogeny, is considered important in many phylogenetic and evolutionary studies. Shoot dimorphism of Ginkgo has been long noted, but no work has yet been done to evaluate the relationships between overall branch architecture and wood ring characters, shoot growth, and environmental conditions. •


METHODS
Branches, sampled from similar canopy heights, were mapped with the age of each long shoot segment determined by counting annual leaf-scar series on its short shoots. Transverse sections were made for each long shoot segment and an adjacent short shoot; wood ring thickness, number of rings, and number of tracheids/ring were determined. Using branch maps, we identified wood rings for each long shoot segment to year and developmental context of each year (distal short shoot growth only vs. at least one distal long shoot). Climate data were also analyzed in conjunction with developmental context. •


RESULTS
Significantly thicker wood rings occur in years with distal long shoot development. The likelihood that a branch produced long shoots in a given year was lower with higher maximum annual temperature. Annual maximum temperature was negatively correlated with ring thickness in microsporangiate trees only. Annual minimum temperatures were correlated differently with ring thickness of megasporangiate and microsporangiate trees, depending on the developmental context. There were no significant effects associated with precipitation. •


CONCLUSIONS
Overall, developmental context alone predicts wood ring thickness about as well as models that include temperature. This suggests that although climatic factors may be strongly correlated with wood ring data among many gymnosperm taxa, at least for Ginkgo, correlations with climate data are primarily due to changes in proportions of shoot developmental types (LS vs. SS) across branches.
Department of Plant Sciences, One Shields Avenue, University of California, Davis, California 95616, USA.
Stefan A
SA
Little
Brooke
B
Jacobs
Steven J
SJ
McKechnie
Ranessa L
RL
Cooper
Michael L
ML
Christianson
Judith A
JA
Jernstedt
D000704:Analysis of Variance; D002980:Climate; D020441:Ginkgo biloba / Q000033:anatomy & histology* / Q000254:growth & development / Q000648:ultrastructure; D016015:Logistic Models; D018520:Plant Shoots / Q000033:anatomy & histology* / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D013696:Temperature; D014197:Trees / Q000033:anatomy & histology / Q000254:growth & development; D014934:Wood / Q000033:anatomy & histology* / Q000648:ultrastructure
Ginkgo biloba; Ginkgoaceae; branch architecture; climate; mean annual maximum temperature; mean annual minimum temperature; mean annual precipitation; shoot dimorphism; wood development