Root dynamics in response to abiotic and biotic stressors in Vitis
Open Access
- Author:
- Bauerle, Taryn Lynette
- Graduate Program:
- Horticulture
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 12, 2007
- Committee Members:
- David Eissenstat, Committee Chair/Co-Chair
Kathleen Marie Brown, Committee Member
Roger Tai Koide, Committee Member
John Charles Schultz, Committee Member - Keywords:
- minirhizotrons
root survivorship
root production
hydraulic redistribution
herbivory - Abstract:
- Root system potential growth rate was examined in response to soil moisture heterogeneity. Root dynamics were studied using genetically identical grapevine shoot systems (Vitis vinifera cv Merlot) on genetically distinct root systems that promote high and low shoot vigor under three different levels of water stress severity. We utilized minirhizotrons to examine a more vigorous rootstock (1103P) and a less vigorous rootstock (101-14 Mgt) in an Oakville, CA vineyard with high soil clay content. Our results demonstrated that compared to a lower vigor root system, a grape root system of higher vigor exhibit greater morphological plasticity in response to heterogeneous moisture supply but similar tolerance as indicated by root survivorship in dry soil. The lower-vigor vines also developed more root biomass over several years, especially under conditions of no irrigation. Similar root lifespans in wet and dry soil suggested the possibility that hydraulic redistribution was a source of water transfer from areas of high soil moisture to those of low soil moisture through the plant during periods of low evaporative demand. We hypothesized that hydraulic redistribution prevented an appreciable reduction in root water potential and contributed to the prolonged root survivorship in dry soil. With thermocouple psychrometers, we measured water potentials of roots of the same plant with its roots system split into an irrigated pot and an unirrigated pot. We found reduced root survivorship was directly associated with plants in which hydraulic redistribution was reduced by 24 h light. Electrolyte leakage in dry roots was twice that compared to those in wet soil of the same plant. Our study demonstrated that besides a number of ecological advantages to protecting tissues against desiccation, internal hydraulic redistribution of water is a mechanism allowing extended root survivorship in dry soils. Plants with fast growth rates are hypothesized to be more tolerant of herbivory than slower growing plants. Our data on root systems that differ in potential growth rate supported the hypothesis proposed for leaves, that phylloxera insect infestation was proportional to number of growing tips. Lifespans of uninfested roots were similar for both root systems; however, the infested roots of the faster-growing root system were shorter than that of the slow-grower. The fast-growing rootstock had an older age structure due to the mortality of young root tips. We did not find a trade-off between potential growth rate and relative rate of root infestation in these cultivars, but our study indicates that a fast-growing root system may more readily shed infested roots.