Thesis
The relationship between shoot number and vigor in grapevines: physiological causes and practical implications
Washington State University
Master of Science (MS), Washington State University
2011
Handle:
https://hdl.handle.net/2376/101911
Abstract
One of the first lessons a viticulturist is taught is that high quality grapes are dependent on the ideal balance between grapevine shoot and fruit growth. As most of the vegetative growth occurs before fruit set, i.e. before the berries become strong sinks, it seems that competition between berry and shoot growth cannot be the reason for the reduction of vigor. A hydraulic limitation was believed to be the cause of the differences in vigor of vines with varying shoot numbers. The hydraulic limitation hypothesis was tested by pruning field-grown Merlot vines to a large range of bud numbers and exposing the vines to repeated water stress and irrigation. The resulting differences in vigor were assessed by measuring shoot length and final pruning weight, gas exchange, water potential, and the resistance to water flow through the vine at key stages of development. The study was conducted with field-grown, own-rooted grapevines. 100 vines were pruned in winter leaving between 5 and 200 buds per vine, and the clusters thinned to one cluster per shoot at bloom. It was found that the inverse relationship between shoot number and vigor was not caused by a hydraulic limitation as the vines' resistance to water flow was higher in vines with fewer shoots (i.e., more vigorous), and lower in vines with more shoots. Despite there being a greater resistance to water flow through vines with fewer shoots, the vulnerability of vines to water stress, increased with increasing shoot number, possibly due to having a larger crop yield and a stronger sink demand. The increased transpiration of vines with more shoots may have caused the decreased hydraulic resistance as more water was needed to sustain a larger leaf canopy. At harvest, mean cluster weight decreased with increasing shoot number per vine, while yield increased with increasing shoot numbers as they had more and smaller clusters. Soluble solids and titratable acidity both decreased as the number of shoots per vine increased, while the number of shoots had little effect on the pH and color of the berry juice.
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Details
- Title
- The relationship between shoot number and vigor in grapevines
- Creators
- Laura Susan Deyermond
- Contributors
- Markus Keller (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Horticulture, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525052701842
- Language
- English
- Resource Type
- Thesis