Submitted to: Plant Dormancy Symposium
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2000
Publication Date: 3/2/2000
Citation: Horvath, D.P., Anderson, J.V. 2000. The effect of photosynthesis on underground adventitious shoot bud dormancy/quiescence in leafy spurge (Euphorbia esula). 2nd International Symposium on Plant Dormancy: Short Communications. J-D Viemont and J.J. Crabbe eds., Presses de l'University d'Angers, 30-34.n ISBN: 2-903075-81-6. (Invited Book Chapter). Interpretive Summary: Leafy spurge is an invasive and non-indigenous perennial weed of the Northern Great Plains. This weed maintains perennial growth through the formation and selective growth of a prodigious number of underground axillary buds on its extensive root system. This paper details the two new findings on the control of root bud growth in leafy spurge. One is that root buds of leafy spurge require more than 24 hours to begin active growth following plant defoliation. The other is that even on isolated root sections, at best only 50% of the root buds appear capable of growth. This last finding illuminates the possibility that some root buds of leafy spurge are truly dormant rather than having their growth inhibited by external signals from other plant organs or the environment.
Technical Abstract: Abstract Leafy spurge is a perennial weed that propagates vegetatively through an abundance of underground adventitious shoot buds located on the subterranean portion of the stem (crown) and lateral roots of the plant. After these buds form, they enter a quiescent state and cease growth. Growth is not resumed until the buds are separated from the aerial portion of the plant. Initial experiments indicated that either the presence of mature leaves or growing axillary buds could prevent growth. The signal from the expanding axillary buds can be blocked by application of the polar auxin transport inhibitor NPA. However, NPA could not block the growth inhibiting signal produced in mature leaves. As few as three mature leaves can reduce the growth rate of root buds by more than 50%. The presence of 12 or more leaves results in complete inhibition of growth by underground adventitious shoot buds. The morphology of the growth inhibited buds is reminiscent of GA-deficient or ABA-over-expressing mutants. Exogenous application of GA can overcome the growth inhibiting effects of mature leaves, but not the signal produced by the expanding axillary buds. Inhibition of photosynthesis blocks the production or transport of the growth inhibitor from the mature leaves, but has little effect on the signal produced by the growing axillary buds. We have gone further to demonstrate that two days following removal of the aerial portion of the plant there is an increase in histone H1 phosphorylation by P13suc1-precipitable proteins. The presence of expanding axillary buds prevents the increase in histone