Thesis (M.S.)--University of Wisconsin-Madison, 1985. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S. in horticulture)--Washington State University, December 2006. / Includes bibliographical references.

Thesis (M.S. in Electrical Engineering)--Vanderbilt University, Dec. 2006. / Title from title screen. Includes bibliographical references.

Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

The effects of colchicine and IAA on roots of Vicia faba L. have been examined; changes were found mitotic index, polarity and differentiation. The following conclusions were reached: 1) IAA suppresses or delays some process(es) in the G2. S and probably also the G1 stages of interphase. IAA has no effect on mitosis, but because of its effects on interphase, causes a decrease in the MI. IAA does not appear to be a factor involved in spindle formation, and the time at which spindles reappear after colchicine treatment is not influenced by IAA. Colchicine blocks the anaphase separation of the chromatids. This is not due to a change in pH and it does not involve IAA. Because colchicine blocks the anaphase separation of the chromatids, restitution takes place and polyploid cells are seen in division one mitotic cycle later. The duration of metaphase is apparently increased after colchicine treatment. A result of colchicine induced metaphase delay is that the relative duration of metaphase is lengthened and a change occurs in the prophase: metaphase ratio in favour of metaphases, compared with the control values. This change in the prophase: metaphase ratio is reversed by IAA, many hours after treatment, to produce prophase: metaphase ratios similar to those of the control roots. IAA has this effect for at least two reasons; the relative duration of metaphase is shortened from the value found after treatment with colchicine, to a value similar to that of the controls and, the percentage of polyploid metaphases found after colchicine treatment is lowered by treatments with both IAA and colchicine. 4) Following colchicine treatment, changes occur in the MI; there is a significant increase 24 hours after treatment but after a further threa days the MI is less than 1. 5) Polarity of root growth is initially determined by the plane of cell division. In more basal regions of the root, it is determined by both the plane of cell division and that of cell expansion. Finally, it is determined by the plane of cell expansion along. 6) IAA induces lateral root primordia formation, but these fail to develop normally, however, unlike the primordia that appear in the apical 10 mm of roots treated with colchicine and which 'gram out as lateral roots. 7) The polarity of cell division is re-established in colchicine treated roots as soon as normal mitosis reappears. Thus, one aspect of root polarity returns to normal several days before cell elongation recommences. IAA does not affect the polarity of cell elongation or division in the concentration used. 8) The cessation of root growth after colchicine treatment is not due to the cessation of cell division, but to the altered polarity of cell division. 9) Differentiation of xylem vessel elements occurs closer to the apex in colchicine treated roots than in the controls. IAA does not prevent this differentiation. In roots treated only with IAA xylem elements are seen closer to the apex compared with the control roots. 10) All of the primordia that develop after colchicine or colchicine and IAA treatments do so, at least partly, from cells affected by the colchicine. This is also true of the new meristem which forms, after these treatments, in the root apex. The new apical meristem forms partly from the cells of the meristem which was present at the time of treatment and partly from the cells of the quiescent centre. 11) IAA does not induce polyploidy, nor does it induce polyploid cells present at the time of treatment to divide. 12) The response of roots to IAA treatment, with respect to MI, depends on the age of the root at the time of treatment.

1. The net annual primary productivity of L, hyperborea has been estimated from biomass increment croppings and biomass: age relationships, The values of 16.5 mt organic matter/ha/year at 3.lm and 8,Omt organic matter/ha/year at 9.1m indicate., the high productivity of this species, 2. Various other growth parameters such as maximum biomass, LAI, net assimilation rate, chlorophyll content and index, and photosynthetic rates have been compared with the data for other communities. 3. An 'in situ' technique, which seems to measure a value close to gross photosynthesis in L, hyperborea, has been used to estimate the photosynthetic capacity of tissues of L. hyperborea at various depths, under the forest canopy, and during the seasonal growth with the following conclusions:- a) Photosynthetic efficiency was found to increase with depth b) The forest canopy had a marked shading effect on the photosynthetic capacity of tissue sections, c) Photosynthesis measured during the season showed that growing lamina tissue was below the compensation point in February, that maximum photosynthesis was in May, and that photosynthesis decreased in the summer. d) The values for daily net photosynthesis compared favourably with estimates of net assimilation rate from biomass studies, 4, Laboratory investigations on photosynthesis gave the following saturation and compensation data:- The new lamina of shallow plants was found to have a higher photosynthetic efficiency than the old lamj.na of shallow plants at low irradiance. The old lamina was found to have a slightly higher photo synthetic efficiency at low irradiance than the lamina of deep growing plants. 5. Respiration rates were measured at various temperatures and the stenothermal nature of the lamina tissue was shown in the RT curve, Lamina tissue was found to have a low optimum temperature for respiration of 9.5°C, The respiration rate of deep-growing plants appeared to be lower than shallow plants. Mannitol was implicated as the primary respiratory substrate and was interconvertible with laminarin; the latter did not appear to be utilised as suggested by Yamaguchi et al. (1966). There appeared to be little heterotrophic uptake and utilisation of exogenously supplied glucose but differences in uptake rates found were found between tissues, that of the stipe and holdfast being greater than the lamina, 6. Young sporophytes maintained in culture showed that low irradiance resulted in a thinner lamina than that found in high light grown plants and light was implicated as an additional factor to wave action in the control of lamina morphology 'in situ'. Deep-growing plants which also had a thinner lamina than shallow plants, had an increased chlorophyll content on a weight basis but not on lamina area basis compared with shallow plants. The increased chlorophyll content was not accommodated by changes in the internal ultrastructure of the chloroplasts, 7. Evidence was presented for a translocation of C14 labelled assimilates from the old lamina to the new lamina and stipe and from the stipe to the lamina. The rate of movement varied from 1.5 to 9cm/h. The mass transfer varied from 0.1.mg mannitol/day from the lamina to the stipe and from 13mg mannitol/day from the stipe to the new lamina, and from 2 to 6mg mannitol/day from the old lamina to the new lamina. These amounts were considered to be capable of supporting observed growth rates of the new lamina from biometric data.

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The action of formaldehyde as a stimulant to plant growth revives the so-called law or hypothesis of Arndt (1)** that substances toxic to the living plant may, in very dilute concentrations, act as a stimulant. In general, between the toxic and stimulative concentrations there is the gradation of the former into the latter. This gradation may properly be called "toleration". (See plate 1.)

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