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Type: Theses
Title: The role of calcium in the cell wall of grape berries
Author: Hocking, Bradleigh James
Issue Date: 2015
School/Discipline: School of Agriculture, Food and Wine
Abstract: Calcium has defined roles in plant signalling, water relations and cell wall interactions. Calcium nutrition impacts fruit quality by facilitating developmental and stress response signalling, stabilising membranes, and modifying cell wall properties through cross-linking of de-esterified pectins. The importance of calcium in fruit development and ripening is reviewed, experimental work probing the relationship between calcium nutrition and fruit development in grape berries is undertaken. Relationships between calcium uptake and pectin modification were investigated in a survey of red, white, and table grape varieties collected from two sites varying in calcium levels. Grapes harvested at the Barossa site showed higher calcium concentrations within apoplastic fluid, skin and mesocarp tissues than those from Waite. Chenin Blanc had higher apoplastic calcium content than other varieties. Fluorescent immuno-labelling revealed de-esterified pectin localisation in the middle lamella of all varieties with punctillate staining patterns observed in Grenache and Thompson Seedless. A negative correlation between apoplastic pH and apoplastic calcium concentration was observed. Shiraz was the only variety to demonstrate any significant difference between sites in apoplastic pH and apoplastic calcium activity. Effects of low and high calcium supply in grapevines were investigated. Low calcium grown Shiraz showed early berry softening and onset of berry weight loss. High calcium grown Shiraz showed delayed and asynchronous fruit development. Berry hydration assays indicated that early onset of berry weight loss in low calcium grown berries was a result of higher post-veraison berry transpiration. High calcium grown berries demonstrated lower berry water uptake rate pre-veraison, and lower berry transpiration rates throughout development. Whole vine physiology was assessed in Chenin Blanc; high calcium grown vines demonstrated reduced transpiration and net assimilation rates compared to basal and low calcium grown vines. An image analysis macro was developed for quantification of cell vitality (with fluorescein diacetate; FDA) and pectin de-esterification (with propidium iodide; PI) staining patterns. Chenin Blanc maintained higher PI staining in skin tissue than Shiraz throughout development; higher magnification imaging revealed this staining to be localised to the epidermis and peripheral vasculature of Chenin Blanc berries. Transmission electron microscopy demonstrated cuticle localisation of de-esterified pectin in Chenin Blanc and Shiraz berries, particularly of low calcium grown berries; low levels of calcium-pectin crosslinkages and high rates of berry transpiration result in increased movement of de-esterified pectin from the epidermis into the cuticle. Shiraz cuticle de-esterified pectin levels increased throughout development, indicating pectin solubilisation. Chenin Blanc showed strong de-esterified pectin labelling in epidermal and hypodermal cell walls, consistent with patterns visualised using PI staining. Low calcium grown Chenin Blanc berries showed a higher Botrytis infection rate than basal or high calcium grown berries. Differences in calcium accumulation and pectin modification contribute to varietal diversity in ripening physiology. Berries supplied with low calcium are early softening and susceptible to shrivel and Botrytis infection, whereas high calcium supply results in changes in vine physiology, including delayed and asynchronous berry development.
Advisor: Gilliham, Matthew
Burton, Rachel Anita
Tyerman, Stephen Donald
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2015.
Keywords: grapevine physiology
cell walls
grape berries
fruit quality
image analysis
Provenance: This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at:
Copyright material removed from digital thesis. See print copy in University of Adelaide Library for full text.
Appears in Collections:Research Theses

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