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Localized Effects of Branch Defoliations on Weight Gain of Female Inflorescences in Betula pubescens
Juha Tuomi, Timo Vuorisalo, Pekka Niemelä, Sinikka Nisula and Veijo Jormalainen
Vol. 51, No. 3 (Mar., 1988), pp. 327-330
Stable URL: http://www.jstor.org/stable/3565314
Page Count: 4
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Separate branches of white birch were defoliated in early summer before leaves had fully expanded. Four branches within each experimental tree were treated as follows: complete defoliation (CD), partial defoliation (PD), defoliation of generative short shoots with female catkins (GD), and control with no treatment. The treatments did not affect final catkin length, but final catkin weight was reduced in all of them. Defoliation of generative short shoots and complete defoliation of branches influenced catkin weight more (GD 13%, CD 14%) than partial defoliation (7%). Unexpectedly, the weight gain of female catkins did not negatively correlate with the severity of defoliation (5 to 95%) among PD branches. Our results thus support only a limited autonomy of short shoots and branches in white birch. The weight gain of female catkins is mainly supported by resources that are transported from other parts of trees into generative short shoots. Consequently, short shoots and branches are semi-autonomous units which are integrated parts of larger functional units involving entire birch trees or their shoot-root sub-systems.
Oikos © 1988 Nordic Society Oikos