Dissertation
APPLE ROOTSTOCKS AFFECT SCION VIGOR THROUGH THEIR EFFECT ON SCION WATER RELATIONS
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000003361
Handle:
https://hdl.handle.net/2376/122787
Abstract
Dwarfing rootstocks are used to reduce shoot vigor and improve fruit quality and productivity. Although growth habits of different rootstocks have been clearly described, the underlying mechanisms contributing to dwarfing are not well understood. Plant water status and stem water potential are strongly influenced by water movement from the roots to leaves through the vascular system. Stomata regulate transpiration and are essential to protect the hydraulic system under water limitations and can also influence biomass isotope composition. Carbon (δ13C) and oxygen isotope composition (δ18O) are established proxy measures of water-use efficiency in plants. Combined, rootstocks may affect water movement and stomatal control, and subsequently, limit gas exchange affecting tree growth and biomass as well as tissue isotope composition. To evaluate this hypothesis, `Honeycrisp` apples were grafted on different rootstock and analyzed in the field and greenhouse. Vegetative growth, gas exchange, stem water potential, and leaf isotope composition were measured to understand how rootstocks affect scion water relations and whether these differences correspond to shoot vigor. These experiments showed a positive relationship between shoot growth and photosynthetic rate and stomatal conductance and a negative correlation with stem water potential. Experiments conducted in the greenhouse demonstrated that the rootstock effect on physiological traits in the leaf was consistent whether trees were grafted with a scion or not. Moreover, previous research has suggested that rootstocks may affect anatomical traits in the vascular system. Thus, another study was conducted to associate vegetative growth and water relations and to changes in anatomical traits in the stem and leaves. Scanning Electron Microscopy images were obtained for woody trunk, vegetative stem growth, and leaves. Measured parameters included ray parenchyma cells and xylem vessel diameter, and leaf traits. Dwarfing rootstocks affected xylem vessel density and leaf anatomy of the scion and has implications in water movement in the scion. The effects of rootstock on water relations were also observed for non-grafted plants. Consistently through independent experiments, the effect of dwarfing rootstocks corresponded to water limitations induced by rootstock genotype in apple that had strong downstream effects on physiology, anatomy, and overall growth.
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Details
- Title
- APPLE ROOTSTOCKS AFFECT SCION VIGOR THROUGH THEIR EFFECT ON SCION WATER RELATIONS
- Creators
- Erica Casagrande Biasuz
- Contributors
- Lee Kalcsits (Advisor)Markus Keller (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Horticulture, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 148
- Identifiers
- 99900652205401842
- Language
- English
- Resource Type
- Dissertation