This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Chlorosis in plants has been recognized as a devastating disease for over one-hundred and fifty years. It is easily recognized by a yellowing of the plant foilage and is associated with a reduced chlorophyll synthesis. Chlorosis is found so frequently on calcareous soils that its cause is attributed at least in part to this soil factor. It is therefore referred to as lime-induced chlorosis. This type of chlorosis has become a serious problem, especially in many of the fruit-growing regions of Europe and the Western United States where the soils are calcareous. In Utah the disease is more destructive than any other nutritional disease that affect horticultural crops. The exact cause of lime-induced chlorosis is not known, nor has a satisfactory control been developed as yet. Many conditions found in high-lime soils have been studied with regard to chlorosis, yet the problem is not so simple as it may appear. Green and chlorotic plants are frequently found growing in the same field, and yet a chemical analysis of the two soils fails to indicate a significant difference between them. It is common in chlorotic orchards to see trees where some of the major branches produce chlorotic foilage while the remainder of the tree is healthy and green. The severity of chlorosis varies from tree to tree as well as from season to season. It has been found that the heavier textured soils which are poorly drained are more conductive to chlorosis than are the lighter textured soils. If the soil moisture is held near field capacity, chlorosis is much more severe than if the soil is allowed to approach the wilting point before irrigation. Recent studies have also shown that the bicarbonate ion in solution cultures can induce chlorosis and retard the uptake of iron by plants. Since these factors--high moisture, soil aeration, and bicarbonate ion concentration--are all interrelated, it seems that their relationship to chlorosis should be investigated more thoroughly. Workers in the past have failed to show a consistent correlation between either the oxygen or the carbon dioxide can be measured at the soil-root interface. this is after all the only place in the soil that is of great importance as far as the living plant is concerned. Since the severity of chlorosis increases under poorly aerated conditions on calcareous soils, this hypothesis has been advanced: The respired carbon dioxide is given off at the plant root as carbonic acid which in a calcareous soil reacts with calcium and magnesium carbonate to give an increased bicarbonate ion concentration in the root environment. The resulting increased concentration of bicarbonate may reduce the effective oxygen at the root and thereby disturb the normal respiration and active-ion absorption of the roots or the increased concentration of bicarbonate may affect the roots absorption and plant metabolism in some other manner. The purpose of this investigation was to study the effect of the bicarbonate ion and different aeration mixtures on chlorosis. A preliminary study was made to relate the composition of the soil solution taken from the field with different conditions associated with chlorosis.

Throughout the years lime-induced chlorosis has contributed to untold economic losses. Although this disease has challenged the technical ingenuity of outstanding plant and soil scientists, the exact cause has never been determined; consequently, no preventative measures or permanent cures can, as yet, be recommended. This physiological malady, unchecked, continues its rampage in regions where the disease is prevalent.

The so-called "lime-induced" chlorosis has been recognized for many years as a problem where plants are grown on calcareous soils. The characteristics associated with lime-induced chlorosis are the same as those associated with iron deficiency chlorosis--interveinal yellowing of the leaves at the meristemic region combined with reduced vigor of the plant as a whole. Lime-induced chlorosis is unique in that the iron content of both chlorotic plant and the soil do not always show a deficiency in iron when chemically analyzed. This leads to the theory that iron is inactivated in both the soil and plant. Although no single factor has been found to adequately explain this physiological disease, many factors have been associated with it. Thorne, Wann, and Robinson (1950) observed that calcareous soils characterized by fine texture, high moisture content, poor aeration, and cool temperatures intensify the development of chlorosis in plants. In general increased chlorosis has also been noted under conditions of high pH. The pH and phosphorus effects appear to involve reduced iron solubility in the soil and within the plant while the exact effects of the bicarbonate ion on chlorosis have not been established.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

No description available.

This thesis is an investigation of photoperiodic injury (PI) in tomato plants and practices to alleviate the problem. PI is a physiological disorder characterized by chlorosis and necrosis of leaves when plants are grown under either long photoperiods or non-24 h light/ dark cycles. Solanum lycopersicum L. (tomato) is particularly susceptible to PI. Our group has shown a correlation between PI and altered circadian expression patterns for the nitrate assimilatory enzymes nitrate reductase (NR) and nitrite reductase (NiR) in tomato, resulting in accumulation of the toxic metabolite nitrite, particularly at specific times of day (TOD) when the NiR/NR activity ratio is low. We hypothesized that accumulation of nitrite and PI can be alleviated by altering nitrate nutrition at specific times of day and the use of an air temperature differential. The tomato cultivars ‘Micro Tom’ (PI-tolerant) and ‘Basket Vee’ (PI-susceptible) were grown under various photoperiod regimes to determine: (1) if a positive correlation exists between PI and nitrite accumulation as determined by visual assessment, and chlorophyll and nitrite quantification; (2) if 24 h light affects the diel pattern of nitrate uptake in a way that favours PI through measurements of nitrate depletion; and (3) if PI can be alleviated by altering nitrate nutrition at two specific TOD when tomato is susceptible to nitrite accumulation. A positive correlation was found between nitrite accumulation and PI. Nitrate uptake experiments showed that the nitrate uptake rate per se is not responsible for PI in tomato, but maintenance of circadian nitrate uptake patterns even in 24 h light in combination with a loss of the circadian patterns for NR and NiR activities could contribute to PI. Nitrite accumulation and PI was decreased by utilizing a nutrient solution containing 25% total nitrogen at two specific 4 h periods in the day when tomato is susceptible to nitrite accumulation. We call this new technique TOD fertigation. Time-of-day fertigation in combination with a 6 oC temperature differential further reduced nitrite accumulation and PI. These findings showed the response of greenhouse tomatoes to supplemental lighting and the potential for increasing the photoperiod threshold for PI. / The Mexican Council for Science and Technology (CONACYT); The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)

No description available.

Resumo: Seis cultivares de laranjeiras doces (Sanguínea, Olivelands, Vaccaro Blood, Folha Murcha, São Miguel e Finike) foram avaliadas no campo em quatro experimentos e cada experimento sobre um porta-enxerto (limoeiro 'Cravo', citrumeleiro 'Swingle', tangerineiras 'Sunki' e 'Cleópatra'). Durante a safra 2005/2006, foram avaliadas quanto às características que convencionalmente são atribuídas à qualidade dos frutos (massa, altura, diâmetro, rendimento de suco, teor de sólidos solúveis, acidez titulável e ratio). Na safra 2006/2007, foram quantificados os danos provocados pela Clorose Variegada dos Citros e, em ambas, quanto à produção de frutos e de sólidos solúveis por árvore. Na ocasião da colheita de cada cultivar, seus frutos mostraram-se semelhantes quanto às características químicas. As cultivares Olivelands e Finike destacaram-se em relação à produção de frutos, porém a 'Olivelands' se destacou também pela maior produção de sólidos solúveis por planta. Quanto a reação à CVC, houve diferenças entre as cultivares quanto à intensidade de doença e na produção de frutos de plantas sadias em comparação com as doentes, nos dois anos de avaliação. 'Olivelands' e 'Finike' apresentaram baixos índices de doença e pequena diferença na produção de frutos e sólidos entre suas plantas sadias e doentes, mostrando maior tolerância à infecção por Xilella fastidiosa. / Abstract: Six sweet orange cultivars (Sanguínea, Olivelands, Vaccaro Blood, Folha Murcha, San Miguel and Finike) were evaluated in four experiments. Each budded on a rootstock (Rangpur lime, 'Cleopatra' and 'Sunki' mandarins and 'Swingle' citrumelo). Over 2005/2006 season, the characteristics that are conventionally attributed to the fruits quality (weight, height, diameter, yield of juice, soluble solids, acidity and ratio) were evaluated. In the 2006/2007, the damage caused by Citrus Variegated Chlorosis, and in both, as the fruit and soluble solids yield per tree were quantified. At the each cultivar harvest, its fruits have shown similar chemical characteristics. 'Olivelands' and 'Finike' highlighted up to the fruit yield, but the 'Olivelands' stood out also by the increased production of soluble solids per tree. In reaction to Xilella fastidiosa infection, there were differences to the cultivars on the disease intensity and the fruit yield by healthy trees compared with patients in two years of evaluation. 'Olivelands' and 'Finike' showed low rates of disease and small difference in the fruit and soluble solids yield to their plants healthy and sick, showing greater tolerance to Xilella fastidiosa infection. / Orientador: Antonio Baldo Geraldo Martins / Coorientador: Eduardo Sanches Stuchi / Banca: Antonio de Goes / Banca: Francisco de Assis Alves Mourão Filho / Mestre