by Chan Wai-yi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 142-154). / Abstract --- p.i / Acknowledgements --- p.iii / List of Tables --- p.iv / List of Figures --- p.vi / List of Plates --- p.vii / List of Appendices --- p.viii / Chapter CHAPTER 1 --- INTRODUCTION / Chapter 1.1 --- Urban environment and urban trees in Hong Kong --- p.1 / Chapter 1.2 --- Conceptual framework of the study --- p.3 / Chapter 1.3 --- Objectives of the study --- p.12 / Chapter 1.4 --- Scope and significance of the study --- p.12 / Chapter 1.5 --- Organization of the thesis --- p.14 / Chapter CHAPTER 2 --- STUDY AREA / Chapter 2.1 --- Location --- p.15 / Chapter 2.2 --- Climate --- p.19 / Chapter 2.3 --- Planter --- p.21 / Chapter 2.4 --- Soils --- p.22 / Chapter 2.5 --- Management --- p.23 / Chapter 2.5.1 --- Authority --- p.23 / Chapter 2.5.2 --- Management intensity --- p.26 / Chapter CHAPTER 3 --- INVENTORY OF PLANTER GREENERY / Chapter 3.1 --- Introduction --- p.30 / Chapter 3.2 --- Methodology --- p.33 / Chapter 3.2.1 --- Sampling --- p.33 / Chapter 3.3 --- Results --- p.36 / Chapter 3.3.1 --- Species composition --- p.36 / Chapter 3.3.2 --- Tree structure and size (physiognomy) --- p.40 / Chapter 3.3.3 --- Growth performance --- p.44 / Chapter 3.3.4 --- Tree growth problems --- p.45 / Chapter 3.3.5 --- Shrub and ground cover --- p.47 / Chapter 3.4 --- Discussion --- p.48 / Chapter 3.4.1 --- Inventory of planter greenery in the study areas --- p.48 / Chapter 3.4.2 --- Growth performance and problems --- p.57 / Chapter 3.5 --- Conclusion --- p.62 / Chapter CHAPTER 4 --- SELECTED PROPERTIES OF PLANTER SOILS / Chapter 4.1 --- Introduction --- p.65 / Chapter 4.2 --- Methodology --- p.67 / Chapter 4.2.1 --- Sampling --- p.67 / Chapter 4.2.2 --- Soil texture --- p.68 / Chapter 4.2.3 --- Soil reaction --- p.68 / Chapter 4.2.4 --- Organic carbon --- p.69 / Chapter 4.2.5 --- Total Kjeldahl nitrogen (TKN) --- p.69 / Chapter 4.2.6 --- Mineral nitrogen (ammonium and nitrate nitrogen) --- p.70 / Chapter 4.2.7 --- Total phosphorus --- p.70 / Chapter 4.2.8 --- Available phosphorus --- p.70 / Chapter 4.2.9 --- "Exchangeable K, Na，Ca and Mg" --- p.71 / Chapter 4.2.10 --- Carbon : nitrogen ratio --- p.71 / Chapter 4.3 --- Statistical analysis --- p.71 / Chapter 4.4 --- Results --- p.72 / Chapter 4.4.1 --- Soil texture --- p.72 / Chapter 4.4.2 --- Soil pH --- p.72 / Chapter 4.4.3 --- Organic matter --- p.73 / Chapter 4.4.4 --- Total Kjeldahl nitrogen --- p.74 / Chapter 4.4.5 --- Ammonium nitrogen and nitrate nitrogen --- p.75 / Chapter 4.4.6 --- Total phosphorus and available phosphorus --- p.76 / Chapter 4.4.7 --- Exchangeable cations --- p.78 / Chapter 4.5 --- Discussion --- p.80 / Chapter 4.5.1 --- Comparison with other studies --- p.80 / Chapter 4.5.2 --- "Are the planter soils optimal in pH, phosphorus and exchangeable cations?" --- p.84 / Chapter 4.5.3 --- "Deficiencies of SOM, TKN and mineral N" --- p.88 / Chapter 4.6 --- Conclusion --- p.91 / Chapter CHAPTER 5 --- NITROGEN AND PHOSPHORUS MINERALIZATION / Chapter 5.1 --- Introduction --- p.93 / Chapter 5.2 --- Methodology --- p.96 / Chapter 5.2.1 --- In situ incubation --- p.96 / Chapter 5.2.2 --- "Determination of N mineralization, leaching and uptake" --- p.98 / Chapter 5.2.3 --- "Determination of P mineralization, leaching and uptake" --- p.100 / Chapter 5.2.4 --- Statistical analysis --- p.101 / Chapter 5.3 --- Results --- p.102 / Chapter 5.3.1 --- Temporal changes of ammonification and nitrification --- p.102 / Chapter 5.3.2 --- Temporal changes of P mineralization --- p.103 / Chapter 5.3.3 --- "Net ammonification, NH4 leaching and uptake" --- p.104 / Chapter 5.3.4 --- "Net nitrification, N03 leaching and uptake" --- p.105 / Chapter 5.3.5 --- "Net N mineralization, leaching and uptake" --- p.106 / Chapter 5.3.6 --- "Net P mineralization, leaching and uptake" --- p.107 / Chapter 5.4 --- Discussion --- p.108 / Chapter 5.4.1 --- Comparison with other studies --- p.108 / Chapter 5.4.2 --- N mineralization in the planter soils --- p.112 / Chapter 5.4.3 --- P mineralization in the planter soils --- p.116 / Chapter 5.4.4 --- Leaching loss of mineral N and P in the planter soils --- p.118 / Chapter 5.4.5 --- Uptake of N and P in the planter soils --- p.121 / Chapter 5.5 --- Conclusion --- p.124 / Chapter CHAPTER 6 --- CONCLUSION / Chapter 6.1 --- Summary of findings --- p.127 / Chapter 6.2 --- Implications of the study --- p.131 / Chapter 6.2.1 --- Site-specific management programme --- p.131 / Chapter 6.2.2 --- Application of results --- p.134 / Chapter 6.3 --- Limitations of the study --- p.137 / Chapter 6.4 --- Suggestions for future study --- p.139 / REFERENCES --- p.142 / APPENDICES --- p.155

Vegetational responses to changes in exposures within a constant slope range were studied on the Shallow Upland Range Sites and Granitic Hills Range Site in the Chihuahuan semidesert grasslands in Central Arizona. Sixteen exposures with slopes between 11 and 17 degrees were chosen for subsample sites. Environmental, complete soil descriptions, and vegetational composition data were taken. All data were analyzed using analyses of variance, ordination programs, and regression analyses to determine climate, soils, and vegetational relationships among exposures. The resulting data indicated that the geological lithologic unit on which the soils formed was the most important factor affecting apparent vegetational type. In this study, the data obtained from the complete soil profile descriptions contributed little information to the understanding of vegetational responses. Soil surface characteristics and surface soil horizon properties influenced soil moisture relationships. The conservation of soil moisture appeared to be more important to plant communities than did the total moisture holding capacity of the soil continuum. Monthly precipitation reliability and soil surface reflectances were environmental factors affecting plant communities occurring on different exposures. Fall/spring, winter/spring, and spring soil temperature interactions were the most important environmental factors affecting vegetation on different sloping exposures. All exposures within each of the four sample locations had vegetational components that were similar to the vegetational components of other exposures but all exposures were found to have different plant communities. Each exposure within a given slope range is a phase and/or subphase of currently used range site descriptions. A range site that is based on a potential natural community at one type location cannot be extrapolated across broad geographical expanses to define vegetative potentials for other areas having similar vegetative aspects. Range site descriptions must be site specific for one geographical rangeland that has had the same historical uses.

The potential growth-regulating compound 4-chloroglutaranilic acid (CGA) was tested in whole-plant bioassay systems which utilized sunflower seedlings (Helianthus annuus, L.). Test systems included the growth of plants in soil , solid inert (Vermiculite) substrate, and hydroponic (Seed-Pak) pouches.

No description available.

"September 2001" Includes bibliographical references (leaves 206-230)

"September 2001" / Includes bibliographical references (leaves 206-230) / xviii, 230 leaves : ill., plates ; 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 Agronomy and Farming Systems, 2002

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.

Common root rot is a major disease of commercially grown snap bean (Phaseolus vulgaris L.) on the irrigated sandy soils of central Wisconsin. The objective of this study was to determine the relationships between soil properties and suppressiveness to common root rot of snap bean (causal agent Aphanomyces euteiches) in soils. The soils had been annually amended for three years in a field trial on a Plainfield sandy loam in Hancock, WI. Soils were amended each year from 1998 to 2001 with three rates of fresh paper-mill residuals (0, 22 or 33 dry Mg ha�����) or composted paper-mill residuals (0, 38 or 76 dry Mg ha�����). Soil was removed from each treatment in April (one year after last amendment) and brought to the laboratory. This was repeated with a field soil sample taken in September, 2001. The soils from the two samplings were incubated at room temperature and periodically assayed (days 9, 44, 84, 106, 137, 225 and 270 for April sampling) (days 13, 88 and 174 for September sampling) for suppressiveness of snap bean root rot (0 to 4 where 0=healthy and 4=dead plant). The same days, incubated soils were characterized for ��-glucosidase, arylsulfatase and fluorescein diacetate activities; microbial biomass C (by chloroform fumigation); water stable aggregation (WSA) and total C. In the first incubation, there were large differences between field amendment treatments in terms of snap bean root rot incidence. The disease was suppressed by both fresh and composted amendments, but compost was most suppressive at high compost rates with disease incidence <40% which are considered healthy plants that can reach full yield potential. In the second incubation, disease severity difference among treatments were similar to the first incubation. This would indicate the suppression was induced prior to initiation of this experiment. Disease severity of bean plants grown in unamended field soil was high but in amended soils tended to decrease in intensity over time. Root rot severity was negatively related to ��-glucosidase, and microbial biomass at the beginning and the end of the first incubation period, respectively. FDA hydrolysis was not correlated with disease severity and WSA moderately correlated with disease. The best indicator of disease severity was arylsulfatase which was significantly and negatively correlated with disease severity in 4 of 5 sampling periods. / Graduation date: 2003

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 31-39). Also available on the World Wide Web.

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