Upon resupply of exogenous nitrogen to nitrogen-stressed plants, uptake rate of nitrogen is enhanced relative to nonstressed plants. Absorption of nitrogen presumably is dependent on availability of carbohydrates in the roots. A buildup in soluble carbohydrates thus should occur in roots of nitrogen-stressed plants, and upon resupply of exogenous nitrogen the increased uptake rate should be accompanied by a rapid decline in carbohydrates to prestress levels. To evaluate this relationship, three sets of tobacco plants growing in a complete hydroponic solution containing 1.0 mM NO3- were either continued in the complete solution for 21 d, transferred to a minus-nitrogen solution for 21 d, or transferred to a minus-nitrogen solution for 8-9 d and then returned to the 1.0 mM NO3- solution. These nitrogen treatments were imposed upon plants growing at photosynthetic photon flux densities of 700 and 350 micromoles m-2 s-1. Soluble carbohydrate levels in roots increased during onset of nitrogen stress to levels that were fourfold greater than in roots of non-stressed plants. Following resupply of external nitrogen, a rapid resumption of nitrogen uptake was accompanied by a decline in soluble carbohydrates in roots to levels characteristic of nonstressed plants. This pattern of soluble carbohydrate levels in roots during onset of and recovery from nitrogen stress occurred at both irradiance levels. The response of net photosynthetic rate to nitrogen stress could be expressed as a nonlinear function of concentration of reduced nitrogen in leaves. The net photosynthetic rate at a given concentration of reduced nitrogen, however, averaged 10% less at the lower than at the higher irradiance. The decline in net photosynthetic rate per unit of reduced nitrogen in leaves at the lower irradiance was accompanied by an increase in the nitrate fraction of total nitrogen in leaves from 20% at the higher irradiance to 38% at the lower irradiance.
14C-benzyladenine (BA) and 14C-indole-3-acetic acid (IAA) were used to study hormone transport to the tiller bud and hormone catabolism in excised oat stem segments. Acropetal BA transport was greatest from upright stem segments to tiller buds suppressed by apical dominance. IAA, abscisic acid (ABA), and C2H4 inhibited BA transport to the tiller bud. IAA transport to the tiller bud site was inhibited by BA, C2H4, or after gravistimulation, which affected BA transport to a lesser extent than IAA transport. Multiple peaks of radioactivity were observed in 14C-BA- or 14C-IAA-treated stem segments after 9 h of transport. IAA, ABA, and C2H4 promoted BA catabolism. Auxin, ABA, and C2H4 may inhibit tiller bud release by inhibiting cytokinin transport to the tiller bud and by promoting cytokinin catabolism. Gravistimulation may promote tiller release by inhibiting IAA transport to the tiller bud and allowing cytokinins to accumulate there preferentially.
Daily relative accumulation rate of soluble carbohydrates (RARS) and reduced nitrogen (RARN) in the shoot, as estimates of source strength, were compared with daily relative growth rates (RGR) of the shoot, as an estimate of sink demand, during floral transformation in apical meristems of tobacco (Nicotiana tabacum 'NC 2326') grown at day/night temperatures of 18/14, 22/18, 26/22, 30/26, and 34/30 C. Source strength was assumed to exceed sink demand for either carbohydrates or nitrogen when the ratio of RARS/RGR or RARN/RGR was greater than unity, and sink demand was assumed to exceed source strength when the ratio was less than unity. Time of floral initiation, which was delayed up to 21 days with increases in temperature over the experimental range, was associated with intervals in which source strength of either carbohydrate or nitrogen exceeded sink demand, while sink demand for the other exceeded source strength. Floral initiation was not observed during intervals in which source strengths of both carbohydrates and nitrogen were greater than or less than sink demand. These results indicate that floral initiation is responsive to an imbalance in the relative availabilities of carbohydrate and nitrogen.
The growth rate of excised soybean (Glycine max [L.] Merrill) embryos grown in liquid culture increased linearly as photoperiod was increased from 0 to 20 h at an irradiance of 9 W m-2 measured between wavelengths of 700-850 nm from clear incandescent lamps. When irradiance levels were varied between 0.1 and 1.7 W m-2, the maximum growth rates of embryos occurred at ca. 0.5 W m-2 at both 10- and 16-h photoperiods. When the light source was changed from clear incandescent lamps, with a red (600-700 nm) to far-red (700-770 nm) ratio of ca. 1.07, to a BCJ incandescent lamp (Corning Glass dark red, transparent envelope and a red to far-red ratio of ca. 0.19), the growth rate of embryos slowed. These results are consistent with a high irradiance response for growth of soybean embryos.
The study tested the hypothesis that resupplying nitrogen after a period of nitrogen stress leads to restoration of the balance between root and shoot growth and normal functional activity. Nonnodulated soybean plants were grown hydroponically for 14 days with 1.0 mM NO3- in a complete nutrient solution. One set of plants was continued on the complete nutrient solution for 25 days; a second set was given 0.0 mM NO3- for 25 days; and the third set was given 0.0 mM NO3- for 10 days followed by transfer to the complete solution with 1.0 mM NO3- for 15 days. In continuously nitrogen-stressed plants, emergence and expansion of main-stem and branch leaves were severely inhibited as low nitrogen content limited further growth. This was followed by a shift in partitioning of dry matter from the leaves to the roots, resulting in an initial stimulation of root growth and a decreased shoot:root ratio. Reduced nitrogen also was redistributed from the leaves into the stem and roots. When nitrogen stress was relieved, leaf initiation and expansion were renewed. With the restoration of the balance between root and shoot function, the shoot:root ratio and distribution of reduced nitrogen within the plant organs returned to levels similar to those of nonstressed plants.
Elongation of main stem internodes and petioles of soybeans, Glycine max 'Ransom,' was examined in response to various photoperiod/temperature combinations and to end-of-day (EOD) light quality. Photoperiod treatments consisted of 10, 14, and 16 h in combination with day/night temperatures of 18/14, 22/18, 26/22, 30/26, and 34/30 C. The EOD treatments consisted of exposing plants to illumination from either incandescent (high far-red component, FR) or fluorescent (high red component, R) lamps during the final 0.5 h of a 10-h photoperiod. Internode elongation was not significantly promoted by the photoperiod treatments, and, in fact, under the two highest temperature regimes, internode elongation was suppressed under the longer photoperiods. Petiole elongation, however, was enhanced under the longer photoperiods at all temperatures. In the EOD light study, internode and petiole elongation was significantly greater on plants exposed to 0.5 h EOD from incandescent lamps than from fluorescent. Under the incandescent EOD treatment, plants increased dry matter production by 41% and exhibited greater partitioning of assimilates in stem and root portions than under fluorescent EOD.
Shoot inversion promotes a significant increase in ethylene production in the inverted part of the Pharbitis nil main shoot. The latent period for shoot inversion-induced ethylene production is ca. 2.75 h. Our results indicate that the shoot-inversion ethylene response is not persistent and can be terminated and rapidly reinitiated by appropriate alteration of the orientation of the main shoot regardless of prolonged previous exposures of the shoot to various orientations. The time course of the production of ACC (1-aminocyclopropane-1-carboxylic acid), the immediate precursor of ethylene, follows a pattern similar to that of ethylene during the various alterations of shoot orientation. Excised stem segments and intact stems are capable of induction, inhibition, and reinduction of ethylene evolution. Ethylene production reported here for shoot inversion does not result from segmenting (wounding) of the tissue.
This study reports on the effects of nitrogen stress and restoration of nitrogen availability after a period of stress on expansion and photosynthetic rate of soybean leaves of differing maturity. We hypothesized that nitrogen resupply would lead to additional accumulation of reduced nitrogen in the leaves and, ultimately, resumption of leaf initiation and expansion and photosynthetic activity. In continuously nitrogen-stressed plants, expansion of middle trifoliolates of main-stem trifoliates and leaf area at full expansion were severely restricted. Leaves showing the greatest effects were initiated after removal of nitrogen. When the reduced nitrogen concentration in mature leaves of continuously stressed plants fell below 9 mg dm-2, the photosynthetic rate per unit leaf decreased rapidly, reaching a minimum of ca. 6-8 mg dm-2 h-1. The older mature leaves tended to abscise at this point, while the youngest leaves remained on the plant and continued to photosynthesize slowly. When nitrogen was resupplied, leaf expansion and final leaf area increased. Leaf initiation was also stimulated as reduced nitrogen levels rose in the leaves. Photosynthetic rates of the oldest and youngest pair of mature leaves returned to values comparable to those of similar-aged leaves of nonstressed soybean plants.
Thesis (Ph. D.)--University of Chicago, 1915. "Reprinted from the Botanical gazette, vol. LX, no. 6, 1915." "Contributions from the Hull botanical laboratory 210." "Literature cited": p. 470-471.
Typescript. "Reprinted from The Botanical Gazette, Vol. xxiv, No. 4, October 1897." Thesis (M.S.)--University of Wisconsin--Madison, 1896. Includes bibliographical references.
"Reprinted ... from the Botanical gazette, Vol. LXXXIX, no. I, March 1930." Presented as Thesis (Ph. D.)--University of Wisconsin--Madison, 1927. Includes bibliographical references (p. 38-39).
When D-fructose was used as a carbon source for Hansenula anomala instead of D-glucose, an apparent inhibition of glycolysis in early stages of yeast growth was observed. There was an increase in the unidentified nonvolatile acid, previously reported in this yeast, which is thought to be produced through a hexose-monophosphate shunt. In later stages of growth, products of the glycolytic pathway increased. The results indicate a possible interaction between the two pathways. Acid production in H. anomala may be influenced by the permeability of the cell membrane to substrates and inhibitors used in this study, by the intracellular transport of sugars and their effect on permeability of intracellular membranes, and by the interaction of glucose and fructose.
A controlled-environment study was conducted with clones of a naturally occurring aspen-poplar hybrid (Populus grandidentata x P. alba Michx.) to determine the independent effects of five soil water potentials and three clones on net photosynthesis, leaf relative turgidity, and the growth parameters of weight, stem height, and leaf area. Net photosynthesis per plant, leaf relative turgidity, fresh and dry weight, stem height, and leaf area increased with soil water potentials from -15 bars to -1/3 bar. At higher soil water potentials all variables decreased. There were significant differences among clones in fresh and dry weight, leaf area, and net photosynthesis per unit weight and leaf area.
"Reprinted for private circulation from the Botanical gazette, vol. 122, no. 3, March 1961"--P. 155. Thesis (Ph. D.)--Catholic University of America, Washington, D.C., 1961? Includes bibliographical references (p. 173-174).
"A Private Edition Distributed by the University of Chicago Libraries." "Reprinted from the Botanical gazette, vol. LXI, no. 6." Thesis (Ph. D.)--University of Chicago, 1916.
Experiments were conducted on transpiration capacity of excised dormant buds of trembling aspen (Populus tremuloides Michx.), white birch (Betula papyrifera Marsh.), red pine (Pinus resinosa Ait.), white pine (P. strobus L.), and jack pine (P. banksiana Lamb.). The bases of the buds were fixed in Petri dishes containing parawax and paraffin oil. Bud transpiration was determined gravimetrically under a range of temperatures and relative humidities. Bud transpiration of all species was responsive to changes in vapor-pressure gradients from the bud surface to the surrounding atmosphere. Large species differences were found in bud transpiration. Water loss among the pines was in the following order: white pine > red pine > jack pine. Vegetative buds of Populus tremuloides transpired faster than flower buds. Bud transpiration did not correlate well with bud size or surface development.
T.-p., typewritten. Thesis (S.M.)--University of Chicago (Dept. of Botany). "Contributions from the Hull Botanical Laboratory 302." "Reprinted for private circulation from the Botanical Gazette, vol. LXXV, no. 1., March, 1923." "Literature cited": p. 57-59.
The variation pattern of the Opuntia lindheimeri group is affected by natural hybridization in various ways: hybrid swarms, segregating introgressive populations, geographical races of introgressive origin, and clonal microspecies. Clonal microspecies are uniform populations with distinctive character combinations of hybrid origin which have developed by vegetative reproduction and occupy local areas. They are interspersed among the segregating populations and introduce a complicating factor into the overall variation pattern. Four hybrid clonal microspecies are described as representative examples. The total number in the species is probably in the hundreds. Although there have been few previous attempts to delineate clonal microspecies, this population unit is probably developed more or less widely in plant groups which have the combination of natural hybridization and vigorous vegetative reproduction. A brief review of other cases shows that hybrid clonal microspecies are prominent features of the variation pattern in the Iris hexagona group of the Mississippi delta, the Solanum tuberosum group sensu lato of the Andean region, the Opuntia fulgida group of the Sonoran desert, and the Populus tremuloides group in Michigan and Idaho.
The pattern of tissue organization in roots of cultured immature maize embryos was studied using morphometric methods. After five periods of in vitro culture, ranging from 0 h up to 48 h, cell dimensions were measured in various regions of the root using an image analyzer. Cell elongation was scored directly; because mitotic figures were rarely observed, cell division activity was derived indirectly from planes of new cell walls and the decrease in cell lengths. The tissues, distinguished as protoderm, outer ground meristem, pro-endodermis, pericycle, procambium, and pith, displayed different patterns of development. Proceeding from the root tip to the base, various regions were defined. After 24 h of culture new transverse cell walls were observed in most tissues. In the stele they occurred just behind the root tip. In the ground meristem-protoderm complex they were found at some distance from the tip. After 42 h of in vitro culture new cells were observed from the region bordering the quiescent center up to the basal zone. After that, the cells of the ground meristem, procambium, and pith in the basal region of the root showed evidence of cell elongation rather than cell division. Cells of the protoderm, pro-endodermis, and pericycle did not elongate. Periclinal divisions occurred in the ground meristem and pith, mainly in the regions just behind the root tip. Toward the root base, cell width increased. In the procambium periclinal divisions were found along the entire length of the embryo root. Therefore the ultimate number of cell layers in the various tissues was not realized at the same distance from the tip. The influence of the in vitro conditions was evident. Under these conditions the length of the meristematic zone increased more than under in vivo conditions. Culture also caused a complex arrangement of the procambium, including an increased number of metaxylem files.
Thesis--Univ. of Chicago, 1947. "Contributions from the Hull Botanical Laboratory, 580." "Reprinted from the Botanical gazette, vol. 108, no. 3, March, 1947." "Literature cited": p. 393.
cover-title. At head of title: Reprinted from the Botanical gazette, vol. XXIX, no. 1, January 1900. Inaug.-diss.--University of Michigan. Thesis (Sc. D.)--University of Michigan, 1897. Bibliography: p. 60-63.
"A Private Edition Distributed by the University of Chicago Libraries." "Reprinted from the Botanical Gazette, Vol. LXIII, No. 3." Thesis (Ph. D.)--University of Chicago, 1915. "Literature cited": p. 187-189.
"A Private edition distributed by the University of Chicago Libraries." "Reprinted from the Botanical Gazette, Vol. LXIII, No. 5, May 1917." Thesis (Ph. D.)--University of Chicago, 1912. "Literature cited": p. 371-372.
"Private edition, distributed by the University of Chicago Libraries, Chicago, Illinois." "Reprinted from the Botanical gazette, Vol. LXVII, No. 5, May 1919." Thesis (Ph. D.)--University of Chicago, 1918. "Literature cited": p. 436. Also available as electronic reproduction. Master and use copy. Digital Master created according to Benchmark for Faithful Digital Reproductions of Monographs and Serials. Version 1. Digital Library Federation, December 2002 digitized
