For morphological observation and floral development, about 600 buds or shoot tips displaying a similar growing condition were selected and tagged as they were sprouting, the self-pruning time of these shoot tips was recorded, the time span of self-pruning was analyzed based on these spring shoots self-pruning time.
The shoot attained its maximum length, the tip changed from green to yellow and lobular of some shoot tips begin to fall at 3 days before self-pruning; the separation layer was visible as self-pruning began; and an obvious necrosis commenced in surrounding AZ at 7 days after self-pruning.
In the lateral bud, CiFLC showed relatively high transcript level at 20 days after self-pruning compared with the levels at 3 days before self-pruning.
Based on these results, we conclude that a high expression level of three flowering time genes might help to maintain the terminal buds in a dormant state before self-pruning, whereas the down-regulation of these genes after self-pruning induction might be closely related to the shift of cell activity or the change in flowering competence of spring shoot lateral buds.
Our results from terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and transmission electron microscopy (TEM) analyses suggest that PCD occurs systematically at shoot tips during the self-pruning process, and ROS-induced PCD may be involved in the process of self-pruning.
Interestingly, three homologs of citrus flowering related genes, which encode three MADS-box TFs (CiAP1, CiFLC and CiSP) and regulator of self-pruning process of sweet orange spring shoots, were down-regulated in shoot tips before self-pruning, and up-regulated in lateral buds after self-pruning.
However, it must be noted that wild cherry is a tree species that does not self-prune well (Pryor 1988); therefore, dead branches remain attached to the stem.
The construction of the multicast-tree can also occur at run-time (self-pruning).
In self-pruning, only a subset of nodes forward the message based on certain forwarding rule.
Self-pruning is one of such broadcast algorithm that received much attention from the research community.
The lower part of the trees shows no branch-scars; therefore, self-pruning would have been present.
