<p> Almond water use was investigated at the leaf, plant and canopy level under a range of irrigation conditions in commercial orchards in California. Understanding plant response to water stress, specifically the behavior of plant transpiration and water use during periods of water stress, has important implications for irrigation scheduling in agriculture but also for water resources management and policy making. </p><p> Leaf gas exchange measurements of stomatal conductance and photosynthetic rate were performed at midday on shaded and on sunlit leaves, with midday stem water potential used to assess plant water stress. An essentially linear decline in both photosynthetic rate (from 25 to 5 &mu;mol m^-2 s^-1) and stomatal conductance (from 400 to 50 mmol m^-2 s^-1) as stem water potential declined over the range of -0.5 to -3 MPa was observed in sunlit leaves. These data indicated a strong sensitivity of leaf-level physiological processes to water stress. However, evapotranspiration at the canopy level, measured using Eddy Covariance, did not show a reduction relative to atmospheric demand during periods of water stress. The apparent disconnect observed between leaf conductance, responsive to water stress and canopy evapotranspiration, insensitive to water stress, is the central problem investigated in this study.</p><p> When the transpiration data was analyzed in the framework of a "Big Leaf" model, decoupled conditions (i.e. a limited stomatal control of transpiration) were shown to prevail at the experimental site, contrary to previous findings reported in the literature for tall crops such as almond orchards. Low coupling implies only a moderate sensitivity of transpiration to stomatal closure. Measured coupling increased substantially with wind speed but showed a wide range of values at the low wind speeds (&lt;1m s^-1) that were observed at the site. At any wind speed however, higher canopy resistance resulted in higher coupling. The high leaf area index observed in the orchard may have been responsible for causing decoupled conditions, because when leaf area decreased as a result of harvesting operations, canopy transpiration appeared to become more sensitive to water stress. </p><p> Cumulative daily sap velocity was used as an estimate of plant transpiration. At the plant level, contrasting behaviors were observed in plant transpiration in the presence of water stress, depending on the duration and intensity of the stress. During long soil dry-down periods encompassing several weeks, plant transpiration relative to the evaporative demand of the atmosphere showed a statistically significant decline associated with a decrease in stem water potential and in stomatal closure. However, when the cycle of water stress was short (days), reductions in stem water potential seemed to be associated with an increase in cumulative sapflow velocity. The analysis of these results led to the development of a simple model that describes the theoretical interactions between three dependent variables, namely stem water potential, stomatal conductance and transpiration. The model output suggested that in wet soil, an increase in transpiration may be caused by increasing evaporative demand even if stem water potential and stomatal conductance decrease.</p>

<p> Nitrate (NO₃^-) leaching from fertilized land can be detrimental to aquatic ecosystems and human health. Although NO₃^- leaching potential is generally found to be low in turfgrass, certain conditions can occur that result in increased leaching loss of nitrogen. Kentucky bluegrass (<i>Poa pratensis</i> L.) is the most widely used cool-season turfgrass species in the temperate and subarctic climate zones in the United States. Due to its popularity, many new cultivars are bred and released each year. Despite the ample amount of information characterizing the agronomic features of Kentucky bluegrass genotypes, little is available documenting their physiological characteristics related to nitrogen use efficiency and how these might affect the NO₃^- leaching potential of the genotypes. Such information would be of great value for both scientists and customers.</p><p> In this comprehensive study, a screening procedure was developed using nutrient solution culture to evaluate differences in NO₃^- uptake among sixty Kentucky bluegrass genotypes. Two cultivars were selected from the sixty to represent genotypes having high vs. low capacity for NO₃^- uptake. These two cultivars were then used to examine the relationship between NO₃^- uptake efficiency and competitiveness for soil nitrogen. Finally, these two cultivars were compared to determine if NO₃^- uptake efficiency affected NO₃^- leaching potential.</p><p> There were significant differences in NO₃^- uptake at both high (1 mM) and low (0.05 mM) N concentrations among sixty Kentucky bluegrass genotypes, with a strong correlation between uptake rates at high and low N concentrations. Julia and Midnight were selected as representing cultivars with efficient and inefficient nitrate uptake, respectively. In nutrient solution culture, Julia exhibited 56% higher NO₃^- uptake rates than Midnight. In a root competition study, in which the root systems of the two cultivars occupied the same soil volume, Julia was more competitive for nitrogen acquisition (absorbed 20 to 71% more NO₃^- ) than Midnight. However, the higher NO₃^- uptake capacity and better competitiveness for soil N in Julia did not result in lower NO₃^- leaching potential. These results suggest that differences in root morphology and architecture may play a more important role than uptake capacity in determining nitrate leaching potential among Kentucky bluegrass genotypes.</p>

<p> The objective of this study was to determine the effects of propagation media containing composted material on the rooting of hardwood and softwood blueberry cuttings. The physical properties were measured at the end of the experiment. The media used were pine bark fines, composted pine bark with ammoniated nitrogen added, hardwood bark and composted chicken manure, pine bark and cotton gin waste, and control (peat moss and perlite, 1:1). All treatments resulted in a low number of rooted hardwood cuttings compared to the control. The total number of roots per cutting and alive cuttings hardwood cuttings was increased by pine bark and ammoniated nitrogen compared to the remaining treatments. The control treatment resulted in the highest number of roots per softwood cutting. None of the treatments increased the number of roots of softwood cuttings and the number of alive cuttings was increased by all treatments compared to the control.</p><p></p>

Low stone rows and alignments were reported as early as 1904 on the coastal platform of eastern Palliser Bay. In all subsequent references it was assumed that the features were horticultural and, on the grounds of their appearance, of considereable age. Methodical investigation of these claims within the context of a three year archaeological programme (1969-1972) including analysis of prehistoric settlements, economy, and physical anthropology, was regarded as a worthwhile project, since orthodox opinion at the time favoured a later introduction of Polynesian horticulture some centuries after initial settlement of New Zealand about the 9th century AD. Extensive field surveys showed that at least 93ha of the coastal platform between Whatarangi and Cape Palliser had been subject to stone clearance according to several simple principles, such as equal access to the best soils, maintenance of a rectilinear system, and the clear separation of individual plots with boundary markers and paths. In addition, excavations conducted within the major complexes revealed artiificial deepening of the prehistoric topsoil, frequent incorporation of wood charcoal, rare addition of beach gravel, and inclusion of domestic refuse where the walls were adjacent to coastal villages. Both radio-carbon dates and artefacts found in association with the stone structures indicate early establishment of horticulture on this coast by the 12th century AD with an apparent peak of activity and complexity of garden system before the beginning of the 15th century, followed by decline and virtual abandonment. Climatic conditions prevailing in Palliser Bay today preclude cultivation of all Polynesian cultigens except the kumara (Ipomoea batatas) and gourd (Lagenaria siceraria). It is now accepted that mean annual temperature at the time of settlement was 1� - 2�C higher. Even so, growing season length and rainfall would probably not have been adequate for crops such as taro or yam. Within New Zealand, the kumara gardens of Palliser Bay find close parallels on both sides of Cook Strait, and on the eastern coast of the Wairarapa. Similar principles of garden layout applied in the larger Auckland wall complexes, and in 18th century gardens north of Hawkes Bay. From a survey of tropical Polynesian garden structures it appears that an extensive repertoire of horticultural techniques was introduced by the first settlers to temperate New Zealand and despite the loss of variety in cultigens it persisted until the 18th century as a viable means of subsistence.

Thesis (M.S. - Plant Sciences)--University of Arizona, 1984. / Includes bibliographical references (leaves 47-51).

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains ix, 184 p. : col. ill. Vita. Includes abstract. Includes bibliographical references (p. 155-156).

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Robert E. Lyons, Dept. of Plant & Soil Sciences. Includes bibliographical references.

Thesis (M.S.)--Ohio State University, 1987. / Includes bibliographical references (leaves 98-99). Available online via OhioLINK's ETD Center

Texte remanié de: Th. Ph. D.--Warwick university, 1995. / Bibliogr. p. 66-71.

Thesis (MScAgric)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Fruit size can be a problem in 'Clementine' mandarin and 'Valencia' orange in the Western Cape region of South Africa. Small fruit is not only unacceptable to the consumer but is also more difficult and expensive to harvest. Means of alleviating this problem is to manage the crop load. Hand thinning trials were conducted to evaluate the effect of timing and severity thereof in enhancing fruit size. The benefits of enhancing large fruit size was obtained by a heavy-thinning (60% fruitlet removed) treatment, but the actual benefits were offset by a reduction of total yield. Yield was reduced up to 30% when heavy thinning treatments were applied. No effect on early or late treatments were obtained since the trial was conducted rather late (4 to 6 weeks after the physiological fruit drop period) to obtain the desirable results. However, better packouts are expected with thinning treatments since blemished fruit are also removed. The effect of multiple 2,4-dichlorophenoxy propionic acid (dichlorprop) sprays were also evaluated on 'Nules Clemetine' mandarin. Comparing multiple sprays with a single spray, it was observed that more than one spray was no better in improving fruit size. The use of multiple dichlorprop sprays resulted in no additional yield reduction, while internal fruit quality was also not affected. The best results were obtained with dichlorprop at 50 mg. L-1 • The use of dichlorprop with different surfactants was evaluated in both 'Clementine' mandarin and 'Valencia' orange. The fruit size was increased from 50 mg. L-1 up to 100 mg. L-1 • Yield was usually not affected but, where reductions were experienced, yield of large fruit (>55 mm) was not significantly affected. In the 'Valencia' orange trials, during the first year, dichlorprop was sprayed relatively late (fruit diameter: 19 mm). No fruit size, yield and internal fruit quality effects were observed. The following year, when early and late sprays (fruit diameter at spray time = 8 and 12 mm, respectively) were evaluated, it was observed that late sprays had no effect on fruit size, whereas fruit size (48 fruit per carton) was significantly increased by early sprays. This implies that the dichlorprop effect on fruit size is during the early stages of fruit development, just after or during the late stage of the physiological fruit drop period. Yield was drastically reduced by up to 35%, which affected the actual kilograms of large fruit adversely in some treatments. Juice percentage was inconsistent and tended to be reduced by dichlorprop application. Dichlorprop tended to increase TSS slightly in year one and significantly so in year two, but did not affect the TSS:TA ratio. The use of Orchex mineral oils as surfactant at 150 mL. 100 L-1 was effective and seemingly allowed lower rates of dichlorprop to be used. Therefore, surfactants seemed to show potential in enhancing dichlorprop efficiency to reduce the application cost. The dichlorprop-sprayed fruit was used to measure carotenoid content of the rind during the later stage of fruit development. Observations indicate that dichlorprop-sprayed fruit at 50 mg. L-1 obtained better carotenoid content in both 'Clementines' mandarin and 'Valencia' orange. Also, fruit exposed to light had higher carotenoid levels as compared to fruit shaded with brown paper bags. However, dichlorprop-sprayed fruit at 100 mg. L-1 , even though exposed to light did not show significant differences with unsprayed in both shaded and exposed conditions. Therefore, no consistent effect of dichlorprop was established on total carotenoid content of the rind. / AFRIKAANSE OPSOMMING: Vruggrootte van 'Clementine' mandaryn en 'Valencia' lemoene kan 'n probleem wees in die Wes Kaap area van Suid Afrika. Klein vrugte is nie net onaanvaarbaar vir die verbruiker nie, maar is ook moeilik om te oes. Vrugdrag manipulasie is een manier om hierdie probleem te beheer. Hand uitdunningsproewe is uitgevoer om die effek van tyd en graad van uitdunning op vruggrootte te bepaal. Strawwe vruguitdunning (60% van vruggies verwyder) het groter vrugte tot gevolg gehad maar het gelei tot 'n verlaagde opbrengs. Opbrengs is tot soveel as 30% verlaag met die strawwe vruguitdunning. Vroeë en laat behandelings het egter geen effek gehad nie, aangesien die proewe te laat uitgevoer is (4 tot 6 weke na die fisiologiese vrugvalperiode) om die gewenste effek te verkry. Beter uitpak word verwag na uitdunning, aangesien vrugte met letsels ook verwyder word. Die effek van veelvuldige 2,4-dichlorofenoksie-propioonsuur (dichlorprop) spuite IS ook geëvalueer op 'Nules Clementine' mandaryn. Daar is geen verskil gevind tussen enkel en veelvuldige spuite in terme van vruggrootteverbetering nie. Die gebruik van veelvuldige dichlorprop spuite het nie tot 'n verlaging in opbrengs gelei nie, en interne vrugkwaliteit is ook nie beïnvloed me. Die beste resultate is verkry met die 50 mg. L-1 dichlorprop behandeling. Die gebruik van dichlorprop saam met verskillende benatters is op beide 'Clementine' mandaryn en 'Valencia' lemoene geëvalueer. Vruggrootte het toegeneem vanaf 50 mg. L-1 tot 100 mg. L-1 • Opbrengs was net in sekere gevalle verlaag en dan sonder 'n betekenisvolle verskil in groot-vrug produksie (>55 mm: Clementines). Tydens die eerste jaar van die 'Valencia' lemoen proef is die dichlorprop relatief laat gespuit (vrug deursneë: 19 mm). Daar was geen effek op vruggrootte, opbrengs en interne vrugkwaliteit nie. Tydens evaluasie van vroeë en laat bespuitings die volgende jaar is waargeneem dat laat bespuitings geen effek op vruggrootte gehad het nie, terwyl vruggrootte (48 vrugte per karton) betekenisvol verhoog is deur die vroeë bespuitings (Vruggrootte voor bespuiting = 8 en 12 mm, onderskeidelik). Dit impliseer dat dichlorprop se effek op vruggrootte gedurende die vroeë stadiums van vrugontwikkeling is, net na of gedurende die laat stadiums van die fisiologiese vrugvalperiode. Opbrengs is drasties verlaag deur dichlorprop, tot soveel as 35% wat die kilogram groot vrugte negatief beïnvloed het in sommige behandelings. Sappersentasie was nie konsekwent affekteer nie, maar is verlaag deur die dichlorprop bespuitings. Dichlorprop het die TSS effens verhoog in beide jare, maar het geen effek gehad op die TSS:TA verhouding nie. Die gebruik van Orchex minerale olie as benatter was effektief by 150 mL. 100 L-1 , en laat klaarblyklik die gebruik van dichlorprop by laer konsentrasies toe. Dus, kom dit voor dat benatters die potensiaal het om die effektiwiteit van dichlorprop te verbeter wat lei tot 'n verlaging in toedieningskoste. Die dichlorprop gespuite vrugte is gebruik om karotenoïed-inhoud van die skil te meet tydens die laat stadiums van vrugontwikkeling. Vrugte gespuit met dichlorprop teen 'n konsentrasie van 50 mg. L-1 het 'n beter karotenoïed-inhoud in beide 'Clementine' mandaryn en 'Valencia' lemoene tot gevolg gehad. Vrugte blootgestel aan lig het ook 'n hoër karatenoïedkonsentrasie gehad as vrugte wat met bruin papiersakke bedek was. Dichlorprop bespuite vrugte teen 100 mg. L-I, alhoewel blootgestel aan lig, het geen betekenisvolle verskil gehad in vergelyking met onbespuite vrugte nie. Dus is daar geen konsekwente effek van dichlorprop op karotenoïde inhoud van die skiI waargeneem nie.