Bibliography: leaves 98-123. This thesis investigates the symptoms of leaf senescence in response to plant shoot water stress and demonstrates the effect of a non-hydraulic root signal in the senescence response of mature leaves of sunflower. The alleviation of the leaf soluble protein loss rate by excision of the root system in drying soil indicates that this signal originates in roots in dry soil and acts to promote protein loss.

Bibliography: p. 261-273. The general hypothesis tested in this study was that: 'partial drying of the root system of grapevines will result in reduced vegetative growth with beneficial effects for fruit yield, fruit composition and water-use efficiency'. Previously published work has suggested that partial drying of the root system may give rise to non-dydraulic root-derived signals capable of changing leaf development and transpiration.

Graduation date: 1992

A field lysimeter experiment was conducted on a sandy loam soil during the 1990 and 1991 growing seasons. The experiment tested the effects of different watertables on soybean yields, and on moisture distribution and nitrogen concentration of the soil profile. The watertable depths were 40, 60, 80, and 100 centimeters (cm). / Yields were measured in terms of number of beans per plant, number of pods per plant, number of beans per pod, and seed protein content at harvest. / Soil samples collected at depths of 30 and 70 cm from the soil surface were analyzed for moisture content and NO$ sb3 sp-$-N and NH$ sb4 sp+$-N concentrations. / The experimental results showed that controlled watertable management increased the yield and decreased soil NO$ sb3 sp-$-N levels. The best results from the watertables tested were found to be at 60 and 80 cm. This is suggested as the range of watertable depths that should be maintained for optimum soybean production.

A field lysimeter experiment was conducted during 1993 and 1994 using 4 water table depths (WTD) (0.3, 0.6, 0.8, and 1.0 m), 13 treatment levels of calcium (0, 1500, and 2500 kg/ha) and potassium (0, 160, and 400 kg/ha), to determine their effects on tomato quality and yield. Plant parameters measured included: yield (fruit/plant), fruit height, maximum and minimum equatorial width, degree of catfacing (scale of 1 to 5), and sunscald (scale of 0 to 2). / Water table treatment was usually highly significant for the parameters measured at harvest. Largest height, equatorial width and yield of tomato fruit occur with 0.6 to 0.8 m WTD. Fertilizer treatments were rarely significant by WTD, but if they were, they tended to be in the 0.3 or 1.0 m WTD. Maintaining a WTD of 0.6 to 0.8 m and fertilizing with 160 kg/ha of K can improve quality and total yield of tomatoes.

The objectives were to induce and study the effects of adverse climatic conditions on sugar maple. Two different snow removal treatments were applied over the winter period of 1990-91 and a tarpaulin treatment was applied over the summer period of 1991 to a sugar maple stand in the Morgan Arboretum. The complete snow removal and tarpaulin treated trees showed decreased leaf water potential and increased peroxidase activity over the growing season. Foliar Ca was reduced in the two different snow removal treatments early in the growing season while foliar N was reduced in the complete snow removal trees late in the growing season. Soil NO$ sb3 sp-,$ K$ sp+$ and Mn$ sp{2+}$ was elevated in the complete and partial snow removal, and tarpaulin treatments at various times throughout the growing season. The snow removal treatments affected both water and nutrient status as well as tree health.

Includes bibliographies. / vi, 176, 29 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis describes an irrigation experiment established on Vitis vinifera cv. Shiraz in a mature vineyard in the Australian Murray-Darling basin. It concentrates on the relationship between the timing of the water deficit and the depth of irrigation applied and the difference in berry weight between different irrigation treatments. The study includes a polynomial equation which describes the relation between growing degree days and ?p0?sBrix. A two phase linear model is used to describe the change in red-free glycosyl-glucose (G-G). / Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 1997

Bibliography: p. 261-273. / vi, 273 p. : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The general hypothesis tested in this study was that: 'partial drying of the root system of grapevines will result in reduced vegetative growth with beneficial effects for fruit yield, fruit composition and water-use efficiency'. Previously published work has suggested that partial drying of the root system may give rise to non-dydraulic root-derived signals capable of changing leaf development and transpiration. / Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 1998

Bibliography: leaves 200-225 / xxiii, 225 leaves, [39] leaves of plates : 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, 1984

Thesis (MSc (Horticulture))--University of Stellenbosch, 2007. / This study was undertaken to quantify some of the effects of daily fertigation on ecophysiological responses in citrus trees (Citrus spp.). Initial research was conducted to optimise and standardise the sampling procedure to quantify stem water potential (ψstem) in citrus trees. To reliably determine the plant water status of citrus trees, the following conditions are required to minimise unwanted variation in ψstem measurements. Bagging of leaves with black polyethylene envelopes covered with aluminium foil 3 to 4 hours prior to measuring ψstem allows the plant water status in those leaves to equilibrate with whole-tree plant water status, thereby providing a realistic measurement of the current water status. The use of aluminium foil to cover the bagged leaves, reduces unwanted heat stress by reflecting sunlight, and dramatically reduced variation in ψstem. The time of day at which ψstem measurements are made is important to ensure consistency in comparisons among treatments and interpretation of irrigation treatment effects. “Physiological midday” is the preferred time of day to measure ψstem, i.e. 1100 HR. Transpiring leaves with open stomata would be in sun-exposed positions on the east side of trees and should be used for making ψstem measurements. Under similar experimental conditions as those used here, only three leaves per replicate are required to detect a difference of 0.05 MPa in ψstem between treatment means. Plant water status categories were developed which may have useful practical applications, i.e. >-1.0 MPa = no water deficit; -1.0 to -1.2 MPa = low water deficit; -1.2 to -1.4 MPa = moderate water deficit; <-1.4 to -1.6 MPa = high water deficit; and <-1.6 MPa = severe water deficit. Attempts are being made to develop systems that improve crop management and enhance citrus fruit production through efficient and timeous application of water and mineral nutrients which has led to the use of daily drip fertigation or the open hydroponics system (OHS). However, the perceived benefits are not necessarily supported by facts. Fruit size and yield are apparently enhanced, but possible negative aspects of the system have not been quantified. Fruit produced on trees grown under daily drip fertigation generally have a lower total soluble solids concentration than on trees under micro-sprinkler irrigation. This is mainly due to a dilution effect that is caused by the greater availability of water and the uptake thereof. Sugar accumulation can be optimised by controlling the amount of water that the plant receives at different developmental stages. Therefore, it is essential to quantify the ecophysiological responses and benefits of OHS/daily fertigation, as well as the effects of this technology on fruit quality. ‘Nules Clementine’ mandarin (C. reticulata Blanco) trees in two commercial orchards in Simondium, Western Cape province, South Africa, received differential irrigation treatments. The treatments were applied at the end of stage I (± mid December) of fruit development. Stem water potential, fruit size and internal fruit quality were determined. Water-deficit stress enhanced sugar accumulation of ‘Nules Clementine’ mandarin by 0.3 to 0.6 °Brix under certain conditions. These conditions require that the difference in ψstem should be of a sufficient intensity of between 0.16 and 0.3 MPa, and this difference should be maintained for a sufficient duration of between 4 and 6 weeks. Furthermore, deficit irrigation should be applied relatively early in fruit development, namely during the sugar accumulation stage which starts within 4 weeks of the end of the fruit drop period and continues until harvest.