Endogenous and exogenous ethylene induces needle abscission and cellulase activity in post-harvest balsam fir (Abies balsamea L.) |
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Authors: | Mason T MacDonald Rajasekaran R Lada Martine Dorais Steeve Pepin |
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Institution: | (1) Christmas Tree Research Center, Department of Environmental Sciences, Nova Scotia Agricultural College, Bible Hill, NS, B2N 5E3, Canada;(2) Agriculture and Agri-Food Canada, Universit? Laval, Quebec, QC, G1V 0A6, Canada;(3) Horticultural Research Center, Universit? Laval, Quebec, QC, G1V 0A6, Canada; |
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Abstract: | Post-harvest needle loss is a major problem for balsam fir and other Christmas tree species. Recent evidence has implicated
ethylene as a signal responsible for post-harvest needle abscission, but enzymological changes remain unknown. The objective
of this study was to identify and quantify cellulase activity associated with endogenous and exogenous ethylene-induced abscission.
An experiment was designed with three treatments (control, endogenous ethylene, or exogenous ethylene) with five replicates.
Key response variables include needle retention duration, xylem pressure potential, ethylene evolution rate, and cellulase
activity. Two complimentary methods were used to assess cellulase activity: a cellulose plate digestion and zymography. The
results confirm ethylene as a signal for post-harvest abscission and identify ethylene-induced cellulase. Ethylene evolution
was typically between 15 and 16 μL g−1 h−1, but there was no difference among the three treatments. However, exogenous ethylene significantly decreased needle retention
by 60% and resulted in a sixfold decrease in xylem pressure potential. In addition, cellulase activity increased by 8- and
12-fold in endogenous and exogenous ethylene-induced abscission, respectively, compared to the control. Identification of
ethylene-induced cellulase activity has increased our understanding of the post-harvest needle abscission process and confirms
ethylene’s role as a signal molecule. |
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Keywords: | |
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