Rootstocks induce functional
differences that affect carbon isotope discrimination and water
relations in the apple scion
Erica Casagrande Biasuz; Lee A. Kalcsits
Department of Horticulture, Tree Fruit Research and Extension Center,
Washington State University, 1100 North Western Avenue, Wenatchee, WA
98801
This research was funded by the U.S. Department of Agriculture (USDA),
National Institute of Food and Agriculture—Specialty Crop Research
Initiative project “AppleRoot2Fruit: Accelerating the development,
evaluation, and adoption of new apple rootstocks” (2016-51181-25406).
Abstract
Composite trees combine optimal traits from both the rootstock and the
scion. Dwarfing rootstocks are commonly used to reduce shoot vigor and
improve fruit quality and productivity. Although growth habits of
different rootstocks have been clearly described, the underlying
physiological mechanisms regulating scion vigor are not well understood.
Plant water status and stem water potential are strongly influenced by
stem hydraulic resistance to water movement. In the scion, stomata
regulate transpiration rates and are essential to prevent hydraulic
failure. Lower stomatal conductance contributes to enriched leaf carbon
isotope composition (δ13C). Combined, the effects of
increased hydraulic resistance, limited stomatal control, and
subsequently, limited gas exchange can affect tree growth. These
differences may also correspond to differences in scion vigor. Here,
vegetative growth, gas exchange, stem water potential, and leaf
δ13C were compared to determine how rootstocks affect
scion water relations and whether these differences correspond to shoot
vigor. B.9 had the lowest shoot vigor compared to the more vigorous
rootstock, G.890. Similarly, photosynthetic rates were also lower.
Rootstock vigor was closely associated with leaf gas exchange and stem
water potential in the scion and were reflected in leaf
δ13C signatures. Dwarfing was strongly related to
hydraulic limitations induced by rootstock genotype and these changes
are distinguishable when measuring leaf and stem δ13C
composition.
Keywords. Malus domestica, shoot vigor, carbon assimilation, stem
water potential, dwarfing
Acknowledgments: We would like to acknowledge the support of Michelle
Reid, Katie Mullin, and Hector-Camargo-Alvarez for technical assistance
and the Washington State University Stable Isotope Laboratory for
isotope analysis and support.
Rootstock-induced functional differences in the scion and its effect on
carbon isotope discrimination and water relations in apple
Abstract
Composite trees combine optimal traits from both the rootstock and the
scion. Dwarfing rootstocks are commonly used to reduce shoot vigor and
improve fruit quality and productivity. Although growth habits of
different rootstocks have been clearly described, the underlying
physiological mechanisms regulating scion vigor are not well understood.
Plant water status and stem water potential are strongly influenced by
stem hydraulic resistance to water movement. In the scion, stomata
regulate transpiration rates and are essential to prevent hydraulic
failure. Lower stomatal conductance contributes to enriched leaf carbon
isotope composition (δ13C). Combined, the effects of
increased hydraulic resistance, limited stomatal control, and
subsequently, limited gas exchange can affect tree growth. These
differences may also correspond to differences in scion vigor. Here,
vegetative growth, gas exchange, stem water potential, and leaf
δ13C were compared to determine how rootstocks affect
scion water relations and whether these differences correspond to shoot
vigor. B.9 had the lowest shoot vigor compared to the more vigorous
rootstock, G.890. Similarly, photosynthetic rates were also lower.
Rootstock vigor was closely associated with leaf gas exchange and stem
water potential in the scion and were reflected in leaf
δ13C signatures. Dwarfing was strongly related to
hydraulic limitations induced by rootstock genotype and these changes
are distinguishable when measuring leaf and stem δ13C
composition.
Keywords: Malus domestica, rootstock, shoot vigor, carbon isotope,
water relation