Thesis (Ph. D.)--University of Minnesota, 1938. / Includes tables. Vita. Published also as Technical bulletin 136, March 1939, of the Minnesota Agricultural experiment station, with title: Nutritive value and chemical composition of certain fresh-water plants of Minnesota. Consists of three parts, part one only (p. 3-34) represents the author's thesis. "Literature cited": p. 31-34, 42, 47.

Methods for the determination of boron are reviewed. A thorough investigation of the curcumin method was undertaken. Factors such as spectral absorption, boron volatilisation and the effects of pH, the stability of reagents and colour solutions, the drying of reaction products and the interference from certain elements, were investigated. A study of the efficiency of extracting boron from plant material using an ashing procedure is presented. The modified curcumin method for the determination of boron in plant material is described. The statistical accuracy and precision of the modified method is presented. The modified method was used to determine the boron content in citrus and pineapple leaf samples obtained from various parts of the Eastern Cape.

Grand fir (Abies grandis (Dougl.) Lindl.) and amabilis fir (A. amabilis (Dougl.) Forbes) were grown in sand cultures from seed for two growing seasons in a greenhouse. The effects of deficiencies of nitrogen, phosphorus, potassium, calcium, magnesium, and sulphur on the growth and development of the seedlings were studied. Four soil treatments were included to provide a comparison with natural media. These deficiencies caused a significant reduction of growth of both species, except in the low sulphur treatment; this was attributed to contamination. The treatments also affected the root/shoot and foliage/stem ratios, and produced a reduction in the total moisture content. The foliage was analysed for the total concentration of each of the six elements studied. In each case that of the deficient element was much reduced. The grand fir foliage concentrations were consistently higher than for amabilis fir and were influenced more greatly by the treatments. Each deficiency produced a different visual effect. These were documented photographically, chiefly in colour. The actual colours of symptoms were not specific, but the patterns generally were. Diagnostic keys to the deficiency symptoms were prepared. Magnesium and phosphorus symptoms were very distinctive, potassium and calcium were usually so, and nitrogen the least. An unreported type of calcium deficiency symptom, interpretable as a dieback phenomenon, was observed and described. Neither dry weight nor any other single criterion was able to express the net result of any treatment. A method to do this is proposed. It was found that the expression of the deficiency symptoms changed with time. In general it was observed that grand fir is more sensitive to deficiencies than amabilis fir. / Science, Faculty of / Botany, Department of / Graduate

In a vegetable nutrition experiment, fertilizers were applied in such a way as to make possible a study of the effects of three levels each of nitrogen, phosphorus, and potassium on the yield and food value of carrots. The levels of each nutrient applied were: nitrogen 50, 100, and 150 pounds; phosphoric acid 100, 200, and 300 pounds; and potash 50, 100, and 150 pounds per acre. The experiment was arranged in a 3 X 3 X 3 design with second order interactions confounded with blocks. Under the conditions of the experiment it was found that applications of nitrogen caused a very highly significant, positive, linear response for root yield; that applications of phosphorus had no primary effect on yield; and that applications of potassium caused a highly significant, positive, linear and quadratic response for root yield. Nitrogen applications caused a very highly significant, positive, linear trend for crude protein content, and a negative trend of similar significance for crude ash content. No effect was observed on dry weight, total available carbohydrate or total carotenoid contents. Phosphorus applications had no primary effect on those food value factors assayed. Potassium applications caused a significant, negative, linear trend for dry weight, and a highly significant, positive, linear trend and a significant, positive, quadratic trend for ash content. No primary effect was observed on total available carbohydrate, crude protein, or total carotenoid contents. Five significant interactions were found. These were: quadratic phosphorus X linear potassium, for total yield; linear nitrogen X linear phosphorus and linear phosphorus X quadratic potassium, for total available carbohydrates; quadratic phosphorus X quadratic potassium, for crude protein; and quadratic nitrogen X linear phosphorus for crude ash content. The experimental design adopted, and the statistical analysis used, proved satisfactory for the evaluation of primary and second order interaction effects. Significance of pairs of adjusted means for root yield, calculated as a part of the statistical analysis, has been summarized by means of the tri-cyclograph. / Land and Food Systems, Faculty of / Graduate

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Thesis (DScAgric)--University of Stellenbosch, 1958. / OBJECTIVE. High economic production has ever been the aim and aspiration of the agriculturist and no less that of the fruit farmer. In striving towards this aim the latter has for a long time been at a disadvantage with regard to control of his nutritional programme. Even on naturally fertile soil, the question continually arises as to what the correct fertilizer treatment should be to maintain high productivity and how such a decision can be arrived at. A satisfactory answer to these questions could have been obtained from fertilizer trials if it was not such a difficult matter, in view of the extensive and long-term nature of such trials with fruit trees, to establish a sufficient number for each fruit species on different soil types and under different climatic conditions. Efforts to find a new approach to the problem have turned attention to the plant itself and its chemical make-up as affording the best index of its nutritional requirements. Intensive work in this direction has resulted in the evolution of a new tool in agriculture, the technique of diagnostic leaf analysis or 1Toliar diagnosis" as originally proposed by Lagatu and Maume in France and Thomas in u.s.A. A review of the literature is presented indicating the prodigous amount of research which has been applied to studies of the relationship between plant response and nutrient supply in terms of plant composition. Agriculturists have been quick to recognize the potentialities of leaf analysis as a practical guide in nutritional problems and advisory services based on foliar analysis have already been established for certain crops overseas. The experimental basis for formulating such a scheme for deciduous fruit in the Western Cape Province is provided by the factual evidence presented in this thesis.THE TECHNIQUE. The technique of diagnostic leaf analysis comprises sampling of leaves, preparation of sample for analysis and the analysis itself followed by interpretation of the analytical results by comparison with previously determined nutritional standards. Numerous factors were found to influence the final composition of the leaf sample as determined by analysis, such that strict adherence to a standardized procedure through all phases of sampling and preparation of leaf samples for analysis is required to eliminate or reduce errors likely to cause misleading interpretations. Experimental data are presented suggesting how the leaf sample should be selected on a tree and how it should be handled, cleaned, dried, ground and stored to reduce sampling and other errors. The final procedure as adopted eliminates most of the potential sources of experimental error but two unavoidable sources of e~ror remain to be accounted for, that due to tree variation and seasonal effect. The variation in leaf composition from tree to tree was found to be very considerable, so that aampling from a large enough group of trees (6 to 10) to reduce the error involved is essential in order to obtain leaf data which correctly reflects the nutrient status of the portion of the orchard concerned. Secondly, on the grounds of marked consistency found in different fruit species as to seasonal and year to year variation in mineral nutrient concentration, correction factors have been formulated and are suggested as a means of overcoming these sources of error. THEORETICAL BASIS. A diagnosis of the nutrient status in terms of the analytical results as finally determined is obtained by comparison of the data with previously established leaf composition standards of reference and by correct interpretation of the deviations from these standards. The theoretical basis for setting up these index values is discussed. The criterion used is based on the concept of Optimum Values which aaequately integrates the known relationships between plant response and nutrient supply in terms of internal nutrient concentration. A modification of this concept is proposed to the effect that for maximum growth and yield there exists an optimum range of nutrient concentrations with upper and lower limits for each of the functional elements, and that within this range the interrelationship between the individual nutrient elements is also optimal. Since no local fertilize~ trials with deciduous fruit trees are available and only one for grapes, data from highly productive plants in commercial orchards and vineyards were used to determine the upper and lower limits of the "optimum range", on the following premise. If leaf analysis data are available from a sufficient number of high performance orchards in different localities representing a wide range of nutrient supply and environment, the highest and lowest values obtained may be considered to represent a close approximation of the limits of the range required for optimum performance. It is contended that index values obtained in this way must be of practical value in assessing the nutrient status of fruit trees. It is further postulated that the lower limits for the micro-nutrients and even for magnesium may be justifiably adjusted according to the concentration levels associated with symptom expression. INDEX VALUES. The necessary data for determining standards of leaf composition were obtained from leaf analysis surveys of orchards and vineyards and from a grape fertilizer experiment in the Western Cape Province. Visual symptoms of prevailing nutritional disorders are described (supplemented by photographic illustrations) and their relation to leaf composition indicated. Tentative index values have been determined on the basis indicated for each fruit species, apple, pear, peach, apricot, plum, prune and grapes. These nutritional levels comprise upper and lower limits for the nutrients N, P, K, Ca, Mg 1 Mn 1 Fe and Cu, as well as the upper limits for B and Na. DIAGNOSTIC INTERPRETATIONS. Assessment of the nutrient status in terms of these index values suggests that many orchards and vineyards in the Western Cape Province, particularly prune, apricot and grapes, are suffering from malnutrition in some form and are likely to show a marked response to nutritional treatment as suggested by foliar diagnosis. The use of diagnostic leaf analysis constitutes an important advance in dealing with orohard problems in that an immediate decision is possible regarding nutrient status and related aspects such as selection of suitable sites for fertilizer trials and adjustment of the fertilizer programme. / AFRIKAANSE OPSOMMING: geen opsomming

published_or_final_version / Botany / Master / Master of Science

The thesis is primarily concerned with the rate of uptake of nutrients by plant roots in relation to the ability of soil to supply nutrients to roots by diffusion and by mass flow. In Chapter One, some current concepts of the chemistry and availability of plant nutrients in soil are briefly discussed. Particular attention is paid to work that stresses the role of the dynamic processes of diffusion, and the mass flow of dissolved nutrients in the transpiration stream, in supplying nutrients to roots. In Chapter Two, diffusion coefficients of nutrients in soil are discussed. In Chapter Three, the mathematical description of nutrient flow to a root system in soil is discussed. An equation is developed which relates the mean nutrient inflow into a root system to the concentration of nutrients initially present in the soil solution, to the mean concentration of nutrients in the soil solution at the surface of the root system,to the mean rate of flow of water to the roots, to the diffusion coefficient of the nutrient in the soil, and to the age of the roots. The mean nutrient inflow into a root system is defined as the mean rate of flow of nutrients into unit length of root. In Chapter Four, an experiment is described in which all the terms in the above mentioned equation were measured apart from the mean root surface concentration of nutrients. In the experiment, the growth and nutrient uptake of leek plants growing outdoors in a moist, fertilised, silty loam soil was followed. The plants were grown in large pots containing an ample reservoir of soil water, so that watering was unnecessary during growth. The growing period was from early May to mid-July. The nutrient uptake rate was followed by harvesting, and analysing for nutrients, samples of ten plants taken at approximately ten day intervals. Root length was measured at each harvest after washing the roots free from the soil. The pots were weighed every few days to determine the water lost by transpiration. At intervals during the growing period soil samples were taken from the pots, and the soil solution was extracted and analysed. From separate experiments, diffusion coefficients for nutrients in the soil were calculated. The data from the experiments yielded all the terms in the above mentioned equation except mean root surface concentration which could be calculated. The nutrients considered were N, P, K, Ca, Na, Mg, S and Cl. It was found that mass flow supplied on average more of all nutrients to the roots than they absorbed apart from K and P, which were supplied mainly by diffusion. For those nutrients that were found to be supplied by mass flow in excess of uptake, calculations indicated that the resultant mean accumulations at the root surface did not give rise to a solution concentration at the root surface greater than 120% of the initial concentration in the soil. In contrast it was calculated that the root surface concentration of K was less than half its initial level in the soil. P had a concentration dependent diffusion coefficient which meant that the quantity of P diffusing to a root had to be calculated numerically using a computer. The results of such a calculation are given in Chapter Five. It was found that even if the roots acted a zero sink for phosphate, the theoretical mean inflow of phosphate was somewhat less than the observed mean inflow. In Chapter Seven an experimental investigation is described into the accumulation of sulphate at the surface of a root in conditions of high mass flow. Autoradiography using S³⁵ was the technique used. In accordance with theory, accumulations became large only when the soil was fairly dry. One of the difficulties in the mathematical analysis of nutrient flow to roots is the uncertainty about the inherent absorbing power of roots of different ages. In Section Three, experiments are described in which the uptake of short segments of leek root of different ages was measured. The leeks for these experiments were grown in solution culture and the mean inflow into the roots was measured by sampling and analysis as described for the pot experiment in soil. Some plants from solution were then selected and short segments of the roots of different ages were sealed into tubes containing two radioactively labelled nutrients, the rest of the root system being grown in unlabelled nutrient solution. P³², and either K⁴² or Sr⁸⁵, Sr⁸⁵ being taken as a label for Ca, were the labelled nutrients used. The plants were harvested after twenty four hours of exposure to labelled nutrients and the quantity of label absorbed was measured. There were no significant differences in the mean absorption of different aged roots, but different root segments varied very widely in their uptake in a way that could not be connected with their age. The possibility of such variation in absorbing power in roots in soil and its consequences in soil are discussed at the end of Chapter Eleven. In Chapter Twelve values for the mean inflow of nutrients into roots from a wide range of published experiments are tabulated. The rates are also given as specific absorption rates, this term meaning the rate of flow of nutrient into unit fresh weight of root. Similar values of mean inflow and specific absorption rate have been measured in widely different conditions, ranging from a few minutes uptake from solution to several weeks uptake from soil. Plant factors which affect mean nutrient inflows are discussed and possible future developments along the lines suggested by the experiment in Chapter Four are considered. In the final Chapter the evidence is stated on which is based current theory of nutrient flow to roots by mass flow and diffusion. In conclusion the insight the theory provides into the concept of nutrient availability in soil, into root competition for nutrients and into ideas about root system efficiency is considered.

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