Progress 09/11/06 to 09/10/11
Outputs
Progress Report Objectives (from AD-416) 1. Determine if early-season irrigation and water stress are associated with changes in grape berry xylem connection to the vine. 2. Determine if late-season irrigation and water stress are associated with changes in grape berry volume. 3. Determine if berry water can flow back to the vine under conditions of water stress. Approach (from AD-416) Pot-grown grapevines with very distinct genetic backgrounds will be used for this study. Soil moisture will be altered independently of air humidity by using drip irrigation. We will attempt to modify the xylem connection between the berries and the rest of the vine by varying soil moisture deficit during bloom and early berry development. Irrigation treatments will include regulated deficit irrigation (RDI), partial rootzone drying (PRD), and abundant irrigation (no water stress). The vines will then be subjected to dry-down and rewatering cycles before and after veraison. Determine the influence of soil moisture on changes in berry volume and final berry volume. Individual clusters will be dipped in water beakers to assess the potential for direct absorption of water through the berry skin. Berry diameter will be monitored continuously using pressure transducers coupled to a data logger. Simultaneously, leaf water potential will be monitored non-destructively using a leaf psychrometer system. Meteorological conditions will be recorded with temperature and relative humidity sensors to calculate the air vapor pressure deficit during experiments. In premium wine production, fruit quality is considered to be far more important than crop yield, and small berry size is often deemed desirable, especially for red wine. There is a widespread belief in the wine industry that rain or irrigation close to harvest may increase berry size and cause a �dilution� of solutes (sugars, acids, anthocyanins, tannins, etc.) or even cracking (splitting) of berries. In Europe this belief is often written into law, and irrigation is prohibited or strictly regulated. Even in the New World, wineries may encourage growers to withhold irrigation water at this critical time to avoid any perceived adverse effects. In juice grapes, on the other hand, excessive water is often applied in an attempt to maximize berry size and increase yield. However, both withholding irrigation water and over-irrigating in the arid inland Pacific Northwest and other dry areas throughout the world is risky, because excessive water deficit or supply may not only have the opposite effect, namely reduced fruit quality, but may also compromise canopy efficiency and thus cold acclimation, bud fruitfulness (next-year productivity), and vine longevity. Moreover, it is unclear whether the suspected change in berry volume is due to water uptake by the roots and transport to the berries via the vascular system or due to direct absorption of water through the berry skin. This research focused on berry water uptake in relation to berry anatomy and final berry size. We used field- and pot-grown grapevines of diverse genetic backgrounds (Merlot and Concord) to study the effects of soil moisture independently from those of air humidity. Berry diameter was monitored during dry-down and rewatering cycles. In addition, root pressure was applied to force water up the vine in order to test whether excessive soil moisture would increase berry size. Ripening berries or whole clusters were immersed in water to determine changes in berry volume due to water uptake through the skin. We also used dye tracers and microscopy to study the direction of water flow to and from the berries at various stages of development. All of the data collected as part of this study confirm our new theory about grape berry water relations and fruit ripening, which contradicts the current textbook opinion that grape berries become hydraulically isolated from the shoot during ripening. We propose that instead of being ruptured, the berry xylem serves to recycle excess phloem water back to the shoot. This mechanism may be halted under conditions of root pressure, which may result in berry cracking in vulnerable cultivars. Similarly, water uptake through the berry skin during rainfall or overhead irrigation, but not water uptake by the roots, may lead to berry cracking, volume gain and solute loss, which is detrimental to fruit quality. Methods of project monitoring included meetings, e-mail, and phone calls.
Impacts
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Publications
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Progress 10/01/09 to 09/30/10
Outputs
Progress Report Objectives (from AD-416) 1. Determine if early-season irrigation and water stress are associated with changes in grape berry xylem connection to the vine. 2. Determine if late-season irrigation and water stress are associated with changes in grape berry volume. 3. Determine if berry water can flow back to the vine under conditions of water stress. Approach (from AD-416) Pot-grown grapevines with very distinct genetic backgrounds will be used for this study. Soil moisture will be altered independently of air humidity by using drip irrigation. We will attempt to modify the xylem connection between the berries and the rest of the vine by varying soil moisture deficit during bloom and early berry development. Irrigation treatments will include regulated deficit irrigation (RDI), partial rootzone drying (PRD), and abundant irrigation (no water stress). The vines will then be subjected to dry-down and rewatering cycles before and after veraison. Determine the influence of soil moisture on changes in berry volume and final berry volume. Individual clusters will be dipped in water beakers to assess the potential for direct absorption of water through the berry skin. Berry diameter will be monitored continuously using pressure transducers coupled to a data logger. Simultaneously, leaf water potential will be monitored non-destructively using a leaf psychrometer system. Meteorological conditions will be recorded with temperature and relative humidity sensors to calculate the air vapor pressure deficit during experiments. Documents Grant with Washington State University. Formerly 5358-21000-034-19G (12/2008). In premium wine production, fruit quality is considered to be far more important than crop yield, and small berry size is often deemed desirable, especially for red wine. There is a widespread belief in the wine industry that rain or irrigation close to harvest may increase berry size and cause a �dilution� of solutes (sugars, acids, anthocyanins, tannins, etc.) or even cracking (splitting) of berries. In Europe this belief is often written into the law, and irrigation is prohibited or strictly regulated. Even in the New World, wineries may encourage growers to withhold irrigation water at this critical time to avoid any perceived adverse effects. In juice grapes, on the other hand, excessive water is often applied in an attempt to maximize berry size and increase yield. However, both withholding irrigation water and over-irrigating in the arid inland Pacific Northwest and other dry areas throughout the world is risky, because excessive water deficit or supply may not only have the opposite effect, namely reduced fruit quality, but may also compromise canopy efficiency and thus cold acclimation, bud fruitfulness (next-year productivity), and vine longevity. Moreover, it is unclear whether the suspected change in berry volume is due to water uptake by the roots and transport to the berries via the vascular system or due to direct absorption of water through the berry skin. This research focused on berry water uptake in relation to berry anatomy and final berry size. We used field- and pot-grown grapevines of diverse genetic backgrounds (Merlot and Concord) to study the effects of soil moisture independently from those of air humidity. Berry diameter was monitored during dry-down and rewatering cycles. In addition, root pressure was applied to force water up the vine in order to test whether excessive soil moisture would increase berry size. Ripening berries or whole clusters were immersed in water to determine changes in berry volume due to water uptake through the skin. We also used dye tracers and microscopy to study the direction of water flow to and from the berries at various stages of development. All of the data collected as part of this study confirm our new theory about grape berry water relations and fruit ripening, which contradicts the current textbook opinion that grape berries become hydraulically isolated from the shoot during ripening. We propose that instead of being ruptured, the berry xylem serves to recycle excess phloem water back to the shoot. This mechanism may be halted under conditions of root pressure, which may result in berry cracking in vulnerable cultivars. Similarly, water uptake through the berry skin during rainfall or overhead irrigation, but not water uptake by the roots, may lead to berry cracking, volume gain and solute loss, which is detrimental to fruit quality. Methods of ADODR monitoring included meetings, e-mail, and phone calls.
Impacts
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Publications
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Progress 10/01/08 to 09/30/09
Outputs
Progress Report Objectives (from AD-416) 1. Determine if early-season irrigation and water stress are associated with changes in grape berry xylem connection to the vine. 2. Determine if late-season irrigation and water stress are associated with changes in grape berry volume. 3. Determine if berry water can flow back to the vine under conditions of water stress. Approach (from AD-416) Pot-grown grapevines with very distinct genetic backgrounds will be used for this study. Soil moisture will be altered independently of air humidity by using drip irrigation. We will attempt to modify the xylem connection between the berries and the rest of the vine by varying soil moisture deficit during bloom and early berry development. Irrigation treatments will include regulated deficit irrigation (RDI), partial rootzone drying (PRD), and abundant irrigation (no water stress). The vines will then be subjected to dry-down and rewatering cycles before and after veraison. Determine the influence of soil moisture on changes in berry volume and final berry volume. Individual clusters will be dipped in water beakers to assess the potential for direct absorption of water through the berry skin. Berry diameter will be monitored continuously using pressure transducers coupled to a data logger. Simultaneously, leaf water potential will be monitored non-destructively using a leaf psychrometer system. Meteorological conditions will be recorded with temperature and relative humidity sensors to calculate the air vapor pressure deficit during experiments. Documents Grant with Washington State University. Formerly 5358-21000-034-19G (12/2008). Significant Activities that Support Special Target Populations In premium wine production, fruit quality is considered to be far more important than crop yield, and small berry size is deemed desirable. There is a widespread belief in the wine industry that rain or irrigation close to harvest may increase berry size and cause a �dilution� of solutes (sugars, acids, anthocyanins, tannins, etc.) or even cracking (splitting) of berries. In Europe this belief is often written into the law, and irrigation is prohibited or strictly regulated. Even in the New World, wineries may encourage growers to withhold irrigation water at this critical time to avoid any perceived adverse effects. In juice grapes, on the other hand, excessive water is often applied in an attempt to maximize berry size. However, both withholding irrigation water and over-irrigating in the arid inland Pacific Northwest is risky, because excessive water deficit or supply may not only have the opposite effect, namely reduced fruit quality, but may also compromise canopy efficiency and thus cold acclimation, bud fruitfulness (next-year productivity), and vine longevity. Moreover, it is unclear whether the suspected change in berry volume is due to water uptake by the roots and transport to the berries via the vascular system or due to direct absorption of water through the berry skin. This research focuses on berry water uptake in relation to berry anatomy and final berry size. We use pot-grown grapevines of very different genetic makeup (Merlot and Concord) to study the effects of soil moisture independently from those of air humidity. Berry diameter is monitored continuously during dry-down and rewatering cycles. In addition, root pressure is applied to force water up the vine in order to test whether this simulation of excessive soil moisture will increase berry size. When the berries approach maturity, intact clusters are immersed in water to determine changes in berry volume due to water absorption through the skin. At harvest, fruit is assessed for basic quality attributes in relation to berry size. In addition, we use dye tracers and microscopy to study if water can flow back from the berries to the vine at various stages of berry growth and ripening. Methods of ADODR monitoring included meetings, e-mail, and phone calls.
Impacts
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Publications
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Progress 10/01/07 to 09/30/08
Outputs
Progress Report Objectives (from AD-416) 1. Determine if early-season irrigation and water stress are associated with changes in grape berry xylem connection to the vine. 2. Determine if late-season irrigation and water stress are associated with changes in grape berry volume. 3. Determine if berry water can flow back to the vine under conditions of water stress. Approach (from AD-416) Pot-grown grapevines with very distinct genetic backgrounds will be used for this study. Soil moisture will be altered independently of air humidity by using drip irrigation. We will attempt to modify the xylem connection between the berries and the rest of the vine by varying soil moisture deficit during bloom and early berry development. Irrigation treatments will include regulated deficit irrigation (RDI), partial rootzone drying (PRD), and abundant irrigation (no water stress). The vines will then be subjected to dry-down and rewatering cycles before and after veraison. Determine the influence of soil moisture on changes in berry volume and final berry volume. Individual clusters will be dipped in water beakers to assess the potential for direct absorption of water through the berry skin. Berry diameter will be monitored continuously using pressure transducers coupled to a data logger. Simultaneously, leaf water potential will be monitored non-destructively using a leaf psychrometer system. Meteorological conditions will be recorded with temperature and relative humidity sensors to calculate the air vapor pressure deficit during experiments. Documents Grant with Washington State University. Significant Activities that Support Special Target Populations Data collected confirmed our new theory about grape berry water relations and fruit ripening (Keller et al. 2006), which contradicts the current textbook opinion that grape berries become hydraulically isolated from the shoot during ripening. We propose that instead of being ruptured, the berry xylem serves to recycle excess phloem water back to the shoot. Our results showed that solutes accumulate in the berry apoplast during grape ripening. This is the likely reason results from experiments using xylem- mobile dye have been misinterpreted in the past. Regardless of cultivar, shriveling grape berries that went through veraison during a dry-down episode resumed expansion, while the green berries on the same cluster continued to shrink until the plants were rewatered. Rewatering led to rapid recovery of photosynthesis and greatly enhanced the size recovery of berries undergoing veraison. We conclude that the increase in berry size during water stress at veraison is due to an increase in phloem influx, as no xylem water would have been available at that time. Once berries approached maturity and sugar accumulation began to slow, this effect was greatly diminished, and water supply at this time only served to stop berry shrinkage. We were able to �push� xylem-mobile dye into ripening berries by applying pressure to the shoot base. Moreover, dye fed to attached berries moved back to the plant through the pedicel xylem of post- veraison berries only after pressure to the root system was released. These results confirm that the berry xylem remains functional in ripening grape berries and suggest that recycling of excess phloem water out of the berries may cease under conditions of root pressure. Pressurizing the root system during veraison increased the volume of green berries, but no increase in berry size could be detected in berries undergoing color change, even though some of the Concord berries cracked under the pressure when they reached over 11 Brix. Cracking of berries and subsequent leaching of sugars was also observed when berries were immersed in water. Using deionized instead of tap water led to an increase in the rate and extent of cracking, possibly because the greater osmotic gradient between berry pulp and deionized water increased water absorption through the skin. This suggests that berry cracking may be worse under rainy conditions than under overhead sprinkler irrigation. Methods of ADODR monitoring included meetings, e-mail, and phone calls.
Impacts
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Publications
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Progress 10/01/06 to 09/30/07
Outputs
Progress Report Objectives (from AD-416) 1. Determine if early-season irrigation and water stress are associated with changes in grape berry xylem connection to the vine. 2. Determine if late-season irrigation and water stress are associated with changes in grape berry volume. 3. Determine if berry water can flow back to the vine under conditions of water stress. Approach (from AD-416) Pot-grown grapevines with very distinct genetic backgrounds will be used for this study. Soil moisture will be altered independently of air humidity by using drip irrigation. We will attempt to modify the xylem connection between the berries and the rest of the vine by varying soil moisture deficit during bloom and early berry development. Irrigation treatments will include regulated deficit irrigation (RDI), partial rootzone drying (PRD), and abundant irrigation (no water stress). The vines will then be subjected to dry-down and rewatering cycles before and after veraison. Determine the influence of soil moisture on changes in berry volume and final berry volume. Individual clusters will be dipped in water beakers to assess the potential for direct absorption of water through the berry skin. Berry diameter will be monitored continuously using pressure transducers coupled to a data logger. Simultaneously, leaf water potential will be monitored non-destructively using a leaf psychrometer system. Meteorological conditions will be recorded with temperature and relative humidity sensors to calculate the air vapor pressure deficit during experiments. Documents Grant with Washington State University. Significant Activities that Support Special Target Populations This report serves to document research conducted under a grant agreement between ARS and Washington State University. Additional details of research can be found in the report for the parent project 5358-21000-034- 00D, Production Systems to Promote Yield and Quality of Grapes in the Pacific Northwest. Dr. Keller and collaborators conducted the following research towards the agreements objectives: We subjected pot-grown Vitis vinifera (cv. Merlot) and Vitis labruscana (cv. Concord) to water deficit during the lag phase of berry growth and used electronic transducers to monitor changes in berry diameter. In a second experiment, shoots with their bases immersed in a solution of the xylem-mobile dye basic fuchsin were pressurized using a pressure chamber to determine if the dye could be forced into post-veraison berries. In addition, excised berries were immersed in distilled water with or without the skin or pedicel sealed to test if water can be absorbed through the skin and if sugars can be lost from the berries through the pedicel. Finally, we built a device that enabled us to separately extract sap from the berry apoplast (xylem, cell walls and intercellular spaces) and the symplast (mainly cell vacuoles), which was then analyzed for its chemical composition. . We have shown that the xylem connection between grape berries and the shoot remains open during ripening. In the first year of this project we found that, given sufficient root pressure, the backflow of xylem water from the berries to the shoot could be stopped and even reversed. We also obtained unequivocal evidence for our hypothesis that phloem influx into grape berries suddenly increases at veraison (beginning of ripening), even in the face of severe water deficit stress. We also found that solutes imported via the phloem are accumulated in the berry cell walls along with their accumulation (storage) in the mesocarp cells. This finding confirms our hypothesis that solute accumulation in the berry apoplast is responsible for the decrease in driving force for xylem water movement into ripening grape berries. There were some striking differences in the behavior of Merlot and Concord berries, but it is premature to speculate about the implications of these disparities in apoplast solute contents. Another important finding is that while late-season (preharvest) irrigation does not seem to induce increases in berry size, it does prevent berry shrinkage due to water stress. Thus growers may use irrigation close to harvest as a tool to maintain yield without significantly altering berry constituents. On the other hand, we demonstrated that water can be absorbed through the berry skin, which may result in cracking (splitting) of berries and subsequent loss of sugar and other solutes, which would effectively �dilute� grape quality. These results open up interesting questions about the role of rainfall and/or overhead sprinkler irrigation in potential fluctuations in both berry size and quality. ADODR Statement: The ADODR met with the cooperating PI and project personnel at meetings during the year and discussed results through phone calls, e-mail, and in person.
Impacts
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