Bibliography: leaves 207-222 / xvi, 222 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1987

Growth, productivity and fruit quality of grapevines are closely linked to soil water availability. Withholding of water for any length of time results in slowed growth. If drought continues yield may be lost. Vines can be manipulated to stimulate early defence mechanisms by decreasing soil water availability. By using an irrigation technique, which allows for separate zones with different soil moisture status, it is possible to stimulate response mechanisms of the root system which are normally related to water stress. The difficulty of separating 'wet' and 'dry' zones was initially overcome by using split-root plants with root systems divided between two containers. Such experiments on split-root model plants resulted in the development of an irrigation technique termed partial rootzone drying (PRD). Results from irrigation experiments using PRD have shown that changes in stomatal conductance and shoot growth are some of the major components affected (Dry et al., 1996). The idea of using irrigation as a tool to manipulate stress responses in this way had its origin in the concept that root- derived abscisic acid (ABA) was important in determining stomatal conductance (Loveys, 1984). Later experiments on split-root plants have demonstrated that many effects of water stress can be explained in terms of transport of chemical signals from roots to shoots without changes in plant water status (Gowing et al., 1990). The necessary chemical signals are provided by the dry roots, and the wet roots prevent the development of deleterious water deficits. The general hypothesis tested during this study was that partial drying of the root system gives rise to a change in the supply of root-derived chemical signals which determine changes in grapevine physiology, thereby affecting fruit quality. Experiments were conducted on split-root vines (Vitis vinifera L. cvs. Cabernet Sauvignon and Chardonnay) grown in pots of different sizes, on field-grown vines which had either their root system divided by a plastic membrane (Vitis vinifera L. cv. Cabernet Sauvignon on own roots or grafted on Ramsey rootstocks) or conventional vines with a non-divided root system (Vitis vinifera L. cv. Cabernet Sauvignon, Shiraz and Riesling) with a commercial PRD irrigation design. The irrigation treatments were vines receiving water on both sides (control) and PRD-treated vines, which only received water on one side at any time. The frequency of alternation of 'wet' and 'dry' sides was determined according to soil moisture and other influences such as rainfall and temperature. In most of the experiments the irrigation was alternated from one side to the other every 10 to 15 days. Chemical signals from roots: the role of ABA and cytokinins Studies on chemical signals have concentrated on ABA and cytokinins (CK). An improved stable isotope dilution protocol, which enables analysis of ABA and CK from the same tissue sample, was developed. Analysis of cytokinins focused on zeatin (Z), zeatin riboside (ZR), zeatin glucoside (ZG) and iso pentenyl adenine (iP). Roots are relatively inaccessible, particularly in field situations. To enable easier access to roots of field-grown vines, split-root vines were planted in a trench which was refilled with a sandy soil. This created a homogenous soil substrate and did not restrict root growth while still allowing access to roots under field conditions. Analyses of root samples of field-grown vines have shown that cytokinins and ABA may originate in roots and their concentrations can be substantially altered during an irrigation cycle. Alternating soil water conditions showed that [ABA] in roots on the 'dry' side was significantly higher compared with the 'wet' side. Due to a reduction in CK on the 'dry' side of PRD-treated vines, the ratio between ABA and CK was substantially changed during an irrigation cycle. The ABA levels in root tissue and in petiole xylem sap were negatively related to stomatal conductance. This further suggests that ABA, mostly synthesized on the 'dry' side of the root system, might be responsible for a decline in stomatal conductance. Furthermore, a higher pH of petiole xylem sap was observed in PRD-treated vines which may also contribute to the regulation of stomatal conductance. Studies on stomatal patchiness showed that non-uniform stomatal aperture occurred in field-grown vines under natural environmental conditions and was more abundant under PRD conditions. The degree of stomatal opening, determined by using a water infiltration technique, correlated with measurement of stomatal conductance. Exogenous application of a synthetic cytokinin (benzyl adenine) can override the possible ABA-mediated stomatal closure resulting from PRD treatment, providing further evidence for the in vivo role of these growth regulators in the control of stomatal conductance. The effect of benzyl adenine was transient, however, requiring repeated applications to sustain the reversal. In addition, CKs may also be important in influencing grapevine growth. Following several weeks of repeated spray applications with benzyl adenine, it was found that the development of lateral shoots in PRD-treated vines was enhanced compared to PRD-treated vines sprayed with water only. This supports the idea that the reduction in lateral shoot development seen in PRD-treated vines is due to a reduced production of CKs (Dry et al., 2000a). By measuring shoot growth rate it was found that one common feature of PRD-treated vines, which were not sprayed with CK, was a reduction of lateral shoot growth. It can therefore be speculated that the reduction in lateral growth is related to a reduced delivery of cytokinins from the roots. Zeatin and zeatin riboside concentration in shoot tips and prompt buds/young lateral shoots were reduced by the PRD treatment providing further evidence in support of this hypothesis. Water movement from 'wet' to 'dry' roots Roots, being a primary sensor of soil drying, play an important role in long- and short-term responses to PRD. Using stable isotopes of water and heat-pulse sap flow sensors water movement was traced from wet to dry roots in response to PRD. The redistribution of water from roots grown in a soil of high water potential to roots growing in a soil of low water potential may be of significance with regard to the movement of chemical signals and the control of water balance of roots. Measurements of the relative water content (RWC) have shown a slower decline of RWC of the 'dry' roots of PRD vines relative to roots of vines which received no water, despite similar water content in soil surrounding those roots. The redistribution of water may help to sustain the response to PRD for longer periods possibly releasing chemical signals and to support the activity of fine roots in drying soil. Field vines, irrigated with PRD over several growing seasons, altered their root distribution relative to the control vines. PRD caused a greater concentration of fine roots to grow in deeper soil layers and this may contribute to a better water stress avoidance. The effect on root growth may be augmented by the water movement and by the large difference in ABA to cytokinin ratio, which are also known to alter root growth. PRD makes more efficient use of available water In experiments where both control and PRD-treated vines received the same amount of water many differences between the vines were demonstrated. Under conditions where water supply was adequate for both treatments, the stomatal conductance and growth of the PRD-treated vines was restricted as has been observed in many previous experiments. As total water input was reduced, however, the stomatal conductance of PRD-treated vines became greater than control vines, suggesting that the latter were experiencing a degree of water stress, whereas the PRD-treated vines were not. This may have been due to the greater depth of water penetration in the case of the PRD-treated vines, where water was applied to a smaller soil surface area. This distinction between PRD-treated and control vines, at very low water application rates, was also reflected in pruning weights and crop yields which were actually greater in PRD-treated vines. It was concluded that at low water application rates, the PRD-treated vines were more tolerant of water stress and made more efficient use of available water. Reduction in vigor opens the canopy. The initial aim of the research which led to the development of PRD was to achieve better control of undesirable, excessive shoot and foliage growth which, from a viticultural point of view, has many disadvantages. Grapevine shoot growth rate responds very sensitively to drying soil conditions. The irrigation strategy used in the PRD experiments maintained a reduction of both main shoot and lateral shoot growth. In response to PRD a decrease in shoot growth rate and leaf area was observed. Much of the reduction in canopy biomass was due to a reduced leaf area associated with lateral shoots, thus influencing the canopy structure. This was one major factor improving the light penetration inside the canopy. Control of vegetative vigour results in a better exposure of the bunch zone to light and, as a consequence, in improved grape quality. It is likely that changes in canopy density, as a result of PRD, is causing changes in fruit quality components. Anthocyanin pigments such as derivatives of delphinidin, cyanidin, petunidin and peonidin were more abundant in berries from PRD vines; by comparison the concentration of the major anthocyanin, malvidin, was reduced. When leaves were deliberately removed from more vigorous control vines, which improved bunch exposure, the differences in fruit composition were much reduced. This further supports the idea that a more open canopy, in response to PRD, improves fruit quality by affecting the canopy structure. Fruit quality consequently determines the quality, style and value of the finished wine. Wines from this study have been produced and data on wine quality from commercial wineries are also available. Sensory evaluations have demonstrated that high wine quality from PRD-treated vineyards can be achieved without any yield-depressing effects. This study has provided evidence to support the original hypothesis. The major findings were: a) Chemical signals, altered under PRD and mostly originating from roots, play an important role in the root to shoot communication in grapevines. b) The movement of water from 'wet' to 'dry' soil layers may help to sustain chemical signals as a response of grapevines to PRD and to support the activity of fine roots in drying soil. c) A reduction in vegetative growth, in particular of lateral shoots, was sustained using PRD and affected the canopy structure which in turn, due to a better light penetration into the canopy, improved the fruit quality. d) The reduction in irrigation water applied did not have a detrimental effect on grape yield and thus the efficiency of water use was improved. e) Application of relatively low irrigation rates showed that PRD-treated vines were more tolerant of water stress and made more efficient use of available water. / Thesis (Ph.D.)--Department of Horticulture, Viticulture and Oenology, 2000.

The increasing demand worldwide for Australian wine has driven the recent expansion in vineyard plantings which in turn, has increased the requirement for irrigation water in grape growing regions. Large areas of Australia's national vineyard are already irrigated with relatively poor quality water and many districts have a limited supply of water available for irrigation. Therefore, improving the efficiency of vineyard irrigation is essential for the long term sustainability of the Australian wine industry. Reducing the volume of irrigation applied to vineyards can improve water use efficiency (WUE) and reduce vine vigour. However, it can be difficult to accurately apply the required degree of water stress and this may result in a yield reduction. An irrigation technique known as partial rootzone drying (PRD) involves applying a continuous water deficit to alternate sides of the root system while ensuring the other half is well watered. This has been found to increase WUE, reduce vine vigour, improve fruit quality but not affect vine yield. Where the soil volume available for root growth is limited, so too is the resultant vine growth and yield, as access to water and nutrients is restricted. Shallow soil profiles present a major limitation to root development and grapevine vigour. In shallow soils, mounding topsoil from the vineyard mid row to form raised beds in the vine row has been found to improve vine growth and productivity. Soil mounds tend to have a higher moisture holding capacity than flat soil but the greater surface area of the mound can increase surface evaporation. Applying mulch to the mound surface has been shown to reduce evaporative soil moisture loss and conserve irrigation water. The general hypothesis tested in this experiment was that: 'Combining soil mounding, straw mulch and partial rootzone drying (PRD) irrigation will improve grapevine growth and production and reduce levels of sodium and chloride in the vine.' The experiment was established on Vitis vinifera cv. Shiraz in a mature vineyard at Padthaway, South Australia, where the soil profile consisted of a shallow loam over clay and limestone. Soils of the experimental site were classified as moderately saline because their electrical conductivity (ECse) was greater than 4 dS/m. Three main factors, irrigation method (standard or PRD), soil mounding (flat or mounded) and surface cover (bare or straw mulch) were combined into a 2X2X2 factorial experiment such that the randomised block experiment comprised three replicates of eight treatments. The irrigation treatments were control (the application of water to both sides of the vines) and PRD (the application of water to one side of the vines only at any time). In the PRD treatment the frequency of alternating the 'wet' and 'dry' sides was determined according to soil moisture measurements and was typically every 5-7 days. It was very difficult to accurately schedule the irrigation at this site to avoid applying a moisture deficit to the PRD treatment. The shallow soil profile dried very quickly following irrigation and there were problems with the accuracy of the soil moisture sensing equipment for the duration of the experiment. As a result, PRD vines experienced repeated, excessive soil moisture deficits such that vine growth and production were significantly reduced each season. Shoot length was measured weekly during the growing season, while photosynthetically- active radiation (PAR), leaf area and canopy volume were measured at full canopy. Shoot number and pruning weight were measured during dormancy. All measures of vegetative growth (with the exception of PAR) were reduced in response to PRD. The decrease in lateral shoot growth for PRD resulted in greater bunch exposure and PAR. As a direct result of the severe soil moisture deficits experienced by the PRD treatment, all components of yield were significantly reduced compared to the control treatment each season. In particular, bunch weight and berry weight were significantly lower in the PRD treatment compared to the control, which suggests a period(s) of severe soil moisture deficit was experienced. Despite the yield loss sustained by the PRD treatment, WUE was improved compared to the control treatment in the first two years of this experiment. Berry anthocyanin levels were higher for the PRD treatment than the control but this may be due to the reduction in berry size. Weekly volumetric soil moisture monitoring showed that mounded soil was wetter than flat soil each year at similar horizons. In addition, the larger soil volume of the mounded treatment enhanced vine root development. Vegetative growth was greater in the mounded treatment than the flat treatment. Mounded vines grew more shoots than non-mounded vines, although there was no effect of mounding treatment on shoot length. The difference in shoot number was significant only in year 2, possibly due to the time required for vine roots to establish in the mounds. Pruning weight and mean shoot weight were higher for the mounded treatment each year and mounded vines grew more shoots than non-mounded vines in years 1 and 2. The increase in shoot weight of mounded vines, relative to non-mounded, was most likely due to the increase in lateral shoot growth which is supported by the lower PAR values of the mounded treatment compared to the flat treatment. Each year soil mounding resulted in higher vine yields than in flat soil beds as a direct result of the increased vine capacity of mounded vines. The mounded treatment had more shoots per vine than the non-mounded treatment and thus more bunches per vine. In addition, bunch weights were higher in the mounded treatment each year, due mainly to improved fruit set and more berries per bunch. Despite the mounded treatment resulting in a denser canopy than the non-mounded treatment this did not affect fruit composition in years 1 and 2. WUE was higher for the mound treatment in years 2 and 3 only, due to the volume of irrigation water applied being reduced, yet mounded vines continued to produce higher yields than non-mounded vines. In year 3, berries from vines grown in mounded soil had significantly higher pH than berries from vines grown in flat soil beds. Mounding treatment did not consistently affect berry anthocyanin or phenolic levels. Soil moisture levels were higher in the mulch treatment than the bare treatment in all seasons. In contrast to the mounding treatment, wetter soil did not consistently lead to improved vine growth or yield. Mulched vines developed fewer roots than non-mulched vines which is likely to have limited vine access to water and nutrients. As a result, shoot growth was similar for both treatments each season. The only significant difference between treatments for pruning weight was found in year 3 and was due entirely to shoot weight. The mulched treatment had lower PAR than the bare treatment in year 3, probably the result of increased lateral shoot growth and thus increased shoot weight, although this was not significant. PAR was significantly higher for the mulch treatment, compared to the bare treatment, in year 1 only but this was not supported by significant increases in vegetative growth. The mulch treatment resulted in higher vine yield than the non-mulch treatment in years 1 and 3. This difference was significant in year 3 only when both bunch number and bunch weight were significantly higher for mulched vines. In year 1 only bunch weight was significantly higher for mulched vines. Differences between treatments occurred in year 2 for fruit composition, specifically juice TA and anthocyanin levels. The mulch treatment had significantly higher TA and a significantly lower anthocyanin concentration in berries than the non-mulch treatment in year 2. There was no evidence of increased shading in the mulched treatment relative to the bare treatment that year but the difference in anthocyanin concentration may be explained by the significantly smaller berries of the bare treatment. Analysis of samples taken regularly from the soil profile and vine rootzone showed that there was no treatment effect on soil salinity but that soil ECse increased with soil depth and time each year. Petiole samples were collected at flowering, veraison and pre-harvest and levels were deemed toxic by pre-harvest each year. The PRD treatment received approximately 60% of the salt applied to the control treatment. This did not reduce ECse but did result in lower measures of sodium and chloride in petioles and juice at harvest. Vines grown in soil mounds had access to a greater volume of soil water than the non-mounded vines. The mounded treatment had higher levels of pre-harvest petiole chloride in years 1 and 3 but this was significant only in year 3. There was no consistent trend in levels of sodium and chloride in the juice from either mound treatment, although in year 3 berry extract chloride levels were found to be significantly higher in the mounded treatment than the flat treatment. Similarly, a consistent trend in sodium and chloride levels of petioles and juice was not evident for the mulch treatment. Although, in year 3 petioles of vines grown in bare soil were found to contain significantly more petiole chloride than those which had straw mulch applied. The hypothesis that combining soil mounding, straw mulch and partial rootzone drying (PRD) irrigation will improve grapevine growth and production and reduce levels of sodium and chloride in the vine is rejected as there was not a consistent, cumulative effect of the three factors in this experiment. / Thesis (M.Ag.Sc.)--School of Agriculture and Wine, 2005.

Hydraulic conductance of roots of the grapevine cultivar, Chardonnay, varies diurnally, peaking at 1400 h. The diurnal amplitude of hydraulic conductance between 600 and 1400 h was not altered when potted grapevines were water-stressed by withholding water for 8 days. However, the diurnal change was greatly reduced for water-stressed Grenache. If the diurnal change in root hydraulic conductance is a result of changes in aquaporin gene expression or activity, it suggests that aquaporins respond differently in water-stressed Chardonnay and Grenache roots. Both Chardonnay and Grenache demonstrated a reduction in hydraulic conductance in response to water stress, with Grenache exhibiting a larger reduction. Suberisation of the roots increased in response to water stress, with complete suberisation of the endodermis occurring closer to the root tip of Grenache compared to the more drought sensitive Chardonnay. The drought sensitive rootstock, 101-14 (V. riparia × V. rupestris) demonstrated a similar reduction in hydraulic conductance to Chardonnay, while drought tolerant 1103 Paulsen (V. berlandieri × V. rupestris) had a non-significant reduction when water-stressed compared to the large reduction observed for drought tolerant Grenache. Therefore, in this study the degree of reduction in hydraulic conductance did not relate to the drought tolerance of the four varieties examined. The impact of partial drying (watering only half the root system) on hydraulic conductance also differed between Chardonnay and Grenache. There was no change in the conductance of the whole root system of Chardonnay due to an increase in conductance of the roots in the wet half which compensated for the reduction on the dry side. In contrast, Grenache did suffer a reduction measured over the whole root system due to a much larger reduction on the dry side compared to Chardonnay. There was an increase in hydraulic conductance on the wet side but this could not compensate for the large reduction on the dry side. Two aquaporins (VvPIP1;1 and VvPIP2;2) were cloned from the roots of grapevine cultivar Chardonnay. The genes were expressed in Xenopus oocytes to determine their osmotic permeability. As has been shown in a number of plant species, VvPIP1;1 was only slightly permeable to water, whereas VvPIP2;2 did transport water. However, when VvPIP1;1 was injected into the oocytes with VvPIP2;2, there was a substantial increase in the osmotic permeability. There was no significant variation in the diurnal expression of VvPIP2;2, whereas VvPIP1;1 showed a peak in expression at 1000 h prior to the peak in hydraulic conductance and peaked again at 1800 h. VvPIP2;2 did not vary in transcript level in response to water stress or rewatering in Chardonnay or Grenache roots. The level of VvPIP1;1 doubled in water stressed Chardonnay roots and declined again when the vines were rewatered 24 h previously. This response to water stress did not occur in Grenache roots. The roots used were from the apical 5 cm. Similar roots were used to measure the water permeability of the cortical cell membranes using the cell pressure probe. Changes in cell membrane permeability in response to water stress corresponded to changes in VvPIP1;1 expression. An experiment to determine if shoot topping had an effect on root hydraulic conductance revealed a significant 50% decline. This response was also observed in soybean (Glycine max L.) and maize (Zea mays L.). A range of experiments have been performed to determine the reason for the decline. Possibilities included a response to final leaf area and reduced transpirational demand; loss of a carbohydrate sink; or hormonal signals such as abscisic acid, auxin and ethylene. At this stage the nature of the positive or negative signal that causes the change in root hydraulic conductance remains elusive. However, the signal did cause a reduction in the transcript level of VvPIP1;1, indicating the involvement of aquaporins in the response. The root hydraulic conductance of grapevines is variable and dependent on factors such as time of day, water-stress, transpiration rate and unknown signals from the shoot. A proportion of this variability is due to changes in aquaporin number or activity. There are also genotypic differences which may be beneficial for future breeding efforts to improve water use efficiency of grapevines. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1311202

Hydraulic conductance of roots of the grapevine cultivar, Chardonnay, varies diurnally, peaking at 1400 h. The diurnal amplitude of hydraulic conductance between 600 and 1400 h was not altered when potted grapevines were water-stressed by withholding water for 8 days. However, the diurnal change was greatly reduced for water-stressed Grenache. If the diurnal change in root hydraulic conductance is a result of changes in aquaporin gene expression or activity, it suggests that aquaporins respond differently in water-stressed Chardonnay and Grenache roots. Both Chardonnay and Grenache demonstrated a reduction in hydraulic conductance in response to water stress, with Grenache exhibiting a larger reduction. Suberisation of the roots increased in response to water stress, with complete suberisation of the endodermis occurring closer to the root tip of Grenache compared to the more drought sensitive Chardonnay. The drought sensitive rootstock, 101-14 (V. riparia × V. rupestris) demonstrated a similar reduction in hydraulic conductance to Chardonnay, while drought tolerant 1103 Paulsen (V. berlandieri × V. rupestris) had a non-significant reduction when water-stressed compared to the large reduction observed for drought tolerant Grenache. Therefore, in this study the degree of reduction in hydraulic conductance did not relate to the drought tolerance of the four varieties examined. The impact of partial drying (watering only half the root system) on hydraulic conductance also differed between Chardonnay and Grenache. There was no change in the conductance of the whole root system of Chardonnay due to an increase in conductance of the roots in the wet half which compensated for the reduction on the dry side. In contrast, Grenache did suffer a reduction measured over the whole root system due to a much larger reduction on the dry side compared to Chardonnay. There was an increase in hydraulic conductance on the wet side but this could not compensate for the large reduction on the dry side. Two aquaporins (VvPIP1;1 and VvPIP2;2) were cloned from the roots of grapevine cultivar Chardonnay. The genes were expressed in Xenopus oocytes to determine their osmotic permeability. As has been shown in a number of plant species, VvPIP1;1 was only slightly permeable to water, whereas VvPIP2;2 did transport water. However, when VvPIP1;1 was injected into the oocytes with VvPIP2;2, there was a substantial increase in the osmotic permeability. There was no significant variation in the diurnal expression of VvPIP2;2, whereas VvPIP1;1 showed a peak in expression at 1000 h prior to the peak in hydraulic conductance and peaked again at 1800 h. VvPIP2;2 did not vary in transcript level in response to water stress or rewatering in Chardonnay or Grenache roots. The level of VvPIP1;1 doubled in water stressed Chardonnay roots and declined again when the vines were rewatered 24 h previously. This response to water stress did not occur in Grenache roots. The roots used were from the apical 5 cm. Similar roots were used to measure the water permeability of the cortical cell membranes using the cell pressure probe. Changes in cell membrane permeability in response to water stress corresponded to changes in VvPIP1;1 expression. An experiment to determine if shoot topping had an effect on root hydraulic conductance revealed a significant 50% decline. This response was also observed in soybean (Glycine max L.) and maize (Zea mays L.). A range of experiments have been performed to determine the reason for the decline. Possibilities included a response to final leaf area and reduced transpirational demand; loss of a carbohydrate sink; or hormonal signals such as abscisic acid, auxin and ethylene. At this stage the nature of the positive or negative signal that causes the change in root hydraulic conductance remains elusive. However, the signal did cause a reduction in the transcript level of VvPIP1;1, indicating the involvement of aquaporins in the response. The root hydraulic conductance of grapevines is variable and dependent on factors such as time of day, water-stress, transpiration rate and unknown signals from the shoot. A proportion of this variability is due to changes in aquaporin number or activity. There are also genotypic differences which may be beneficial for future breeding efforts to improve water use efficiency of grapevines. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1311202

Master of Science in Dentistry / This work was digitised and made available on open access by the University of Sydney, Faculty of Dentistry and Sydney eScholarship . It may only be used for the purposes of research and study. Where possible, the Faculty will try to notify the author of this work. If you have any inquiries or issues regarding this work being made available please contact the Sydney eScholarship Repository Coordinator - ses@library.usyd.edu.au

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 6 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2004. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2001. / Härtill 5 uppsatser.