Abstract Detail

Developmental and Structural Section

Little, Stefan [1], Cooper, Ranessa [2], Jernstedt, Judy [1].

Developmental anatomy of branch architecture in Ginkgo biloba.

Ginkgo biloba is notable in having highly dimorphic shoots. Long shoots produce elongate axes with leaves separated by internodes several centimeters long. Spur shoots/short shoots are produced in the axils of leaves of long shoots, and can occur as the ultimate shoot tip of a branch. Short shoots often persist for several years, producing leaves with crowded internodes, and either axillary pollen strobili in male trees or axillary ovulate structures in female trees. In investigations of experimentally induced vegetative branching of short shoots, we (and others)have noted the relatively narrow diameter of axes bearing several year-old short shoots. Analysis of tree architecture and branch anatomy reveals that short shoots have highly divergent development and structure compared to that of long shoots. Typical pycnoxylic wood with several growth increments is found in long shoots, but only a single increment of xylarytissue is found in short shoots. Short shoot axes do not widen appreciably with age, and the xylem is constructed more like that of a manoxylic cycad axis. Relating the age of short shoots to the growth increments in their subtending long shoots reveals cryptic growth rings that can be very narrow. In especially long-lived branches that bear only short shoots (both laterally and terminally), the hypothesized 1:1 ratio ofshort shoot age to subtending long shoot growth rings appears to be decoupled;branches that are 20+ years old may only bear 3-10 annual rings in long shootwood, and only 1-2 apparent rings in short shoot steles. Short shoot development bears anatomical signatures of both primary thickening and radially aligned metaxylem, another similarity to axes of cycadophytes. Xylem of short shoots is mainly primary unless shoots convert to long shoot growth. Results suggest, therefore, another line of evidence that Ginkgo short shoots are analogous to the pachycaul axes of cycads. Supported in part by a Katherine Esau Postdoctoral Fellowship (SAL).

Broader Impacts:

1 - University Of California Davis, Department Of Plant Sciences, Davis, CA, 95616-8515, USA
2 - HILLSDALE COLLEGE, 33 E COLLEGE ST, HILLSDALE, MI, 49242, USA

Keywords:
tree architecture
cycadophyte
development
ginkgophyte
seed plants
shoot branching
secondary growth.

Presentation Type: Oral Paper:Papers for Sections
Session: 24
Location: Waterman Room/Chase Park Plaza
Date: Tuesday, July 12th, 2011
Time: 8:45 AM
Number: 24004
Abstract ID:417