The response of various plant tissues to different conditions of culture was compared. The tissues used were cambium-containing discs from carrot roots, undifferentiated carrot callus, bacteria-free sunflower tumorous (crown-gall) tissue, and segments of sunflower stems. The culture conditions compared, in combination, were agar versus liquid medium, shaken versus non-shaken liquid medium, and continuous light versus continuous dark. The response of the tissues to White's basal nutrient medium with added coconut milk (15 %) and indoleacetic acid (0.1 mg/l) and Hildebrandt's improved sunflower medium was also compared under these different culture conditions. Agitation of the liquid medium was accomplished through the use of a newly designed shaker, which consists basically of a horizontally oscillating bank of shelves. The tissues rested on the bottom of culture flasks (medicine bottles) on these shelves and were alternately exposed to medium and air as the liquid medium washed back and forth. Any horizontally oscillating platform could replace this shaker and almost any type and size of culture flask could be used. Probably any type of plant tissue could be cultured under these shaking conditions. It is not necessary that the tissues adhere to the walls of the culture vessels as in other agitation methods so far used in plant tissue culture. Growth (weight increase) of all tissues in shaken liquid medium (in both light and dark) was markedly superior (two to six times greater average weight in 42 days) to that of tissues on agar and in non-shaken liquid medium. The superiority of growth in shaken liquid medium is probably due to several factors; nutrients and gasses are supplied to the entire surface of the tissues, there is no drying and hardening of the tissue surfaces, resulting in a greatly increased surface area, harmful excretions can not collect at the tissue surface, and diffusion of nutrients is not hindered by adsorptive effects of agar particles. To compare the growth of these cultures with those of other workers using agitation methods is difficult due to the different sources of plant material, different sizes of tissues cultured, and different periods of culture used. In general the stimulatory results of shaking obtained appear to be at least as good as those obtained by Caplin and Steward with the much more elaborate and limited 'auxophyton '. There was no sign of eventual growth stoppage as obtained by White, using roller tubes. Light consistently stimulated tissues grown in liquid medium, particularly those in shaken liquid medium. The effect was especially marked on carrot callus and tumorous sunflower tissues grown in Hildebrandt's medium. It is suggested that light may play a role in the synthesis of growth factors supplied by coconut milk. Light had no significant effect on the growth of tissues on agar medium, indicating that the primary limiting factor in the growth of such tissues may be the rate of diffusion of nutrients from the agar. Carrot tissues showed better overall growth in the enriched White's medium while the sunflower tumorous tissue grew better in Hildebrandt's medium. The effect on carrot was probably primarily through indoleacetic acid and coconut milk. The response of sunflower tissue is difficult to evaluate at present. All carrot tissues developed chlorophyll throughout all of the experiments if cultured in light, while tumorous sunflower tissue remained white until placed in Hildebrandt's medium, when it turned light green. The significance of these differences is not known. One experiment showed that carrot discs derived from different carrots grew at significantly different average rates, indicating that discs to be compared should be derived from the same root. The plane in which the discs were cut did not seem to influence subsequent growth. 'Intra root' variation in disc growth necessitates replication. / Science, Faculty of / Botany, Department of / Graduate

Cultured tissues derived from the coffee plant, Coffea arabica L., were grown in vitro in the form of both callus and suspension cultures. The suspension cultures grew rapidly and appeared healthy. Microscopic examination showed that the cells characteristically grew in long filamentous chains. Suspension cultures were examined for the presence of three components - free amino acids, caffeine and chlorogenic acid. By examining these components the species specificity could be determined. The free amino acids of the coffee bean are thought to be one of the major precursors of coffee aroma on roasting. The coffee suspension cultures were shown to contain a similar pattern of free amino acids although the total content was much higher in the cultures than in the intact green coffee bean. Aspartic acid, glutamic acid, phenylalanine, alanine, valine, threonine, serine, and glycine were the predominant amino acids present in the coffee suspension culture. Threonine, serine, glycine, alanine and phenylalanine were the major free amino acids in the green coffee bean. The free amino acid content in the suspension culture exhibited an initial rise, decreased during active growth, then increased rapidly to the maximum level during the decline of the culture. Roasted coffee bean extracts were investigated to ascertain whether one solvent could in preference extract some of the major precursors of coffee aroma. Methanol was found to extract material from green coffee beans which on roasting produced coffee aroma. Caffeine was detected in the cell suspension cultures. However, problems with the analytical methods gave rise to questionable results. The suspension cultures, at maximum caffeine yield, contained 0.03% caffeine (dry weight) whereas the green coffee bean contained considerably more caffeine (1.15%, dry weight). The caffeine content of the tissues increased during the lag phase, decreased during the rapid phase and then increased again in the stationary phase and ultimately production levelled off during the deline phase of growth. The cell cultures produced chlorogenic acid in low concentrations at the maximum 0.14% dry weight in contrast to the green coffee bean which contains 6.5% dry weight. The production or accumulation of chlorogenic acid followed a similar pattern to that of the cell caffeine production over the growth curve. Caffeic acid was also detected. The cell suspension cultures of Coffea arabica L. were shown to be species specific in their biochemical capabilities. / Land and Food Systems, Faculty of / Graduate

No description available.

No description available.

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

The shoot apex of rice, Oryza sativa CV Balilla was studied with a view to obtaining information about the meristematic activity of the different regions. The vegetative state only was studied and the rice was grown for 4-5 days at 30°C or 35°C under 4cm water in darkness, intermittent white light or continuous white, red, far-red or blue light. The part of the shoot apex studied was that above the level of the youngest leaf primordium and it was divided into six regions which took into account the tunica and corpus and regions of leaf initiation. The mitotic index was found every 2hrs. throughout 24hrs. in plants growing in continuous darkness, in a 12hr. day with white light of 10,000 lux and in continuous white light of 2,400 lux. The mitotic index varied little and no pronounced synchrony was evident under any of these conditions. The mitotic index of the flank and corpus regions was higher than that of the summit and sub-summit regions. The meristematic activity of the regions was investigated further using colchicine to accumulate metaphases. Colchicine blocks mitosis at metaphase, but does not affect the rate of entry of the cells into mitosis. The gradient of the increase in metaphases over 3-4 hours was used to calculate the cell-doubling time in each region and the effects of different environments on this were found. Cells of the summit region were found to divide at least 7 times more slowly than cells of the flanks and corpus and intermediate rates occurred in tie sub-summit regions. In 10,000 lux white light and at 30°C, the cell-doubling time for flanks and corpus averaged 13 hours which is shorter than any reported for equivalent regions in other plants. Cell-doubling times for the summit were over [illegible] hrs. In experiments where the intensity of white light varied during the growth of the seedlings a different relationship between the regions was found. The cells of the flanks and corpus divided more slowly and only about twice as fast as in the summit. The effect on cell-doubling times of excision on the shoot was studied and the immediate result was to speed up cell cycles in the leaf primordium and corpus. Excision has often been used to facilitate entry of a chemical into the shoot apex and it may have given a misleading picture of the situation in undisturbed shoot apices. Nuclear DNA synthesis in the regions was studied using tritiated-thymidine. In 1,000 lux continuous white light the flanks and corpus showed a gradual increase in labelling throughout the feeding which lasted for 72hrs. while the sub-summit and summit regions showed a negligible or low level of labelling in the same period of time. The level of DNA synthesis taking place in the regions thus paralleled that of meristematic activity found by using colchicine. The supply of tritiated thymidine to plants grown in continuous white light at 10,000 lux produced a non-linear low labelling pattern which could not be easily explained. Many attempts were made to overcome this lack of success involving excision, and surgery of various kinds, use of (6-³H) thymidine as well as (methyl-³H) thymidine and experimentation with red, far-red and blue light. However, none of those succeeded and so a pulse-labelling experiment was not attempted. The effect of an acute dose of X-rays was studied by finding the mitotic index immediately afterwards, andfrac12;hr. afterwards and 24hrs. afterwards and by studying the level of metaphases after colchicine in control and irradiated plants. A dose of 1, 2, 4 and 8 k.rad had a differential effect on the regions which is interpreted as a reflection of their different levels of meristematic activity. No stimulation of division of the summit was found which is the reverse of what has been found in the quiescent centre of roots after acute X-irradiation, although this region in often equated to the summit of the shoot. A study of cell pattern throughout a plastochron suggested on the basis that evidence of cell division and cell size are related, that meristematic activity in the tunica is highest in the flanks and that, as the activity progresses round the circumference of the apex in the formation of the leaf primordium, which sheaths the stem, cell division also takes place for a short distance toward the summit. In this way, preparation for formation of a leaf primordium occurs sometimes before it appears as a bump. The summit is considered to be carried forward passively and not to contribute a significant number of cells to the rest of the meristem. This interpretation supports the view that the summit is not the site of apical initials in higher plants as considered by the orthodox view. A study of the effect on cell kinetics of red and far-red light by using accumulation of metaphases with colchicine revealed a change in response to far-red light with the age of the seedling. Forty hrs. red and far-red light given to dark-grown 3andfrac12; day-old seedlings caused increased meristematic activity to take place in all regions but 16hrs. far-red light reduced activity and 16hrs. red light was stimulating. Forty hrs. far-red light after 2andfrac12; days dark gave high rates similar to 4andfrac12; day-old plants given 16hrs. far-red. Comparison of these rates on the basis of the age of the seedling at the end of the treatment revealed that plants which are 5 days old had similar rates after 16 or 40hrs. far-red, but plants which were 4 days old had higher rates after 40hrs. far-red than after 16hrs. far-red. Variation of response to far-red with age of the seedling has been found before and the link between phytochrome and leaf initiation is discussed. All regions of the apex, including the summit respond to light by a speeding-up of mitotic cycles but the summit is still at least seven times slower than the flanks and corpus. Finally, consideration is given to the significance of the results in rice and the mandeacute;ristandegrave;me d'attente controversy. Cell divisions in the summit may vary in importance in different apices but in the absence of the possibility of proving presence or absence of apical initials the controversy is put aside. The shift of growth balance in apices of plants subjected to different conditions is brought out and the importance of the summit to growth of the shoot apical meristem and the nature of its influence is discussed.

Typescript (photocopy)

Inaug.-Diss.--Basel. / Includes bibliographical references.

Thesis (Doctoral)--Kaiser Wilhelms Universität, Strasbourg, 1889. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.