摘要:

Glucose cultures ofChlorella vulgariswere grown in white light, in monochromatic light, and in darkness. Difference spectra showed that all wavelengths resulted in increased pigmentation over the dark controls.Cells irradiated with the 600 mμbeam showed a much higher absorption in the blue end of the spectrum with respect to the red end than is normally found in absorption spectra of white-light grownChlorellacells.Dry weight comparisons between monochromatic light and dark controls showed the controls to be somewhat higher. This demonstrated that the monochromatic irradiation produced pigment synthesis but no increase in growth. Dark growth experiments suggested that cultures incubated in darkness on glucose excreted an acidic product

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1966

数据来源: ASPB

摘要:

Chlorella vulgarisBeyerinck (Emerson's strain), fails to grow in the dark even when sugars are provided. This phenomenon was clearly demonstrated in the alga,C. vulgaris,for which the growth rate in darkness on a glucose medium remained constant for 2 days and then declined to approach zero. Pigment concentrations also declined in darkness. Changes in flow rate of 1% CO2-in-air from zero to 7 ml per minute caused a progressive increase in the dark growth rate over a 5-day period, but did not maintain growth in the dark. Rates above 7 ml per minute produced no changes in growth rates.White light intensities below the compensation point of the alga maintained heterotrophic growth. The saturation value for this response was 0.8μw/cm2. White light also initiated growth in nongrowing cultures transferred from darkness to light.The action spectrum for heterotrophic growth indicated a porphyrin as the active pigment. Light in the 425 mμregion was 4 times as effective as white light in stimulating heterotrophic growth. A secondary peak of growth stimulation occurred in the 575 mμregion.The respiration of glucose by the alga was stimulated by low intensities of white light. This response was not immediate, but was clearly present after the third day of incubation.Malonate and cyanide were inhibitory to growth ofC. vulgarison inorganic medium or glucose medium under 300 ft-c of white light. These data suggested that succinic dehydrogenase and cytochrome oxidase systems were present.Substances inhibitory to growth were excreted into the medium under dark-growth conditions, and 2 of these substances were indentified as formic and acetic acids.The evidence suggested that respiration of glucose cannot proceed for an extended period of time in darkness. The reason for this is postulated to be the lack of a cytochrome or a cytochrome precurs

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1966

数据来源: ASPB

摘要:

Acropetal and basipetal movement of indole-3-acetic acid through coleoptiles ofAvena sativaL. was studied. Sections 10-mm long were supplied with either apical or basal sources containing C14carboxyl-labeled indoleacetic acid (10−5m). Anaerobic conditions inhibit metabolically dependent movement (transport) thus reducing basipetal but not acropetal movement. Total inhibition of basipetal transport abolishes the polarity of auxin uptake and movement. The nonpolar movement that remains in anaerobic sections is free diffusion with an average diffusion coefficient of approximately 1×10−4mm2per second. During an 8-hour diffusion, at least the first millimeter of the section comes to equilibrium at approximately the same concentration as the donor.Acropetal movement is probably by diffusion and is accompanied by an aerobic immobilization of indoleacetic acid that increases more than proportionally to concentration. Anaerobic conditions totally prevent this immobilization and reduce acropetal uptake but not the amount of indoleacetic acid moving into the upper parts of the section; there is, therefore, no evidence for acropetal transport.Polarity of auxin movement in aerobic coleoptile sections is achieved by strict basipetal transport of auxin. The basipetal transport may intensify the polarity by recycling auxin that is moving acropet

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1966

数据来源: ASPB

摘要:

Filter paper, nonabsorbent cotton, and cotton wax were found to be progressively richer sources of germination-stimulatory activity effective in counteracting the self-inhibition ofPuccinia graminisvar. tritici Erikss. and E. Henn uredospores. The major stimulatory component of cotton wax was purified and partially characterized. It was catalytically effective in stimulating germination and oxygen consumption of uredospores and appeared to be as active as pelargonaldehyde. Unlike most of the previously reported chemical stimulants, however, it was not active across an air gap.Although the active compound was not identified, both the ultraviolet spectrum and the nonionic and solubility properties of the active fractions were consistent with the infrared spectrum which indicated a relatively long-chained.α.βunsaturated carbonyl compound such as a ketone or possibly an ester.The purification procedure involved deionization of ethanolic extracts from cotton or cotton wax on Dowex 50 (H+) and Dowex 1 (OH−) columns followed by chromatography on neutral alumina using ethylene dichloride as the developing and eluting solv

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1966

数据来源: ASPB

摘要:

The accumulation and incorporation of externally applied P32into ATP and the effect of 4,6-dinitro-o-sec-butylphenol (DNBP) on these processes was studied, using tomato (Lycopersicon esculentumMill.) leaf disks.P32was, in most part, actively accumulated into leaf disks with time and was incorporated into ATP and other organic phosphates. DNBP inhibited both P32accumulation and ATP generation. The amount of inhibition increased with time of incubation.It is concluded that P32accumulation is related to ATP generation. Even though DNBP greatly inhibits phosphorus accumulation, there is little or no effect on its retention.DNBP has the ability to uncouple oxidative phosphorylation. Therefore, it is assumed that its inhibitory effect on phosphate accumulation and generation of high-energy phosphorus esters is related to its inhibition of oxidative phosphorylation.A method is described which appears to be satisfactory to determine the relative amounts of ATP and ADP in leaf disks labeled with P32.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1966

数据来源: ASPB

摘要:

CO2depresses water influx into sunflower hypocotyl segments of low water potential; by contrast, it stimulates flux into segments of high water potential. When segments of high potential were placed in a series of mannitol concentrations and allowed to achieve steady rates of water uptake, influx into CO2-treated tissue in a solution of 3 atm equalled that into control tissue in water. Reasons are given for deducing that a change in internal osmotic concentration (πi) of the order of 40% would be necessary to account for this result on the basis ofπi. Direct measurements (by cryoscopy and by the minimum volume method) detected no difference in the steady state value forπias between CO2-treated and control tissue. It was therefore concluded that CO2had caused some reduction in turgor pressure.Water uptake into tissue treated with CO2for only the first 2 minutes of a 30-minute period was equal to that into tissue treated continuously with CO2, i.e. 3 times the control value. Ten seconds' CO2treatment produced a significant stimulation. When the cycles of treatment were repeated the samples receiving flashes of CO2maintained a rate of water uptake superior to that of the control, whereas influx into continuously treated tissue fell below the control value after 1 hour.CO2treatment applied in a moist air chamber stimulated subsequent water influx when the tissue was transferred to water. Fifteen seconds' treatment was sufficient to produce a marked effect. Even when a transition period of 30 minutes in the moist chamber was interposed between CO2treatment (5 minutes) and transfer to water, a stimulation was observed. The CO2effect could be achieved at zero degrees; 5 minutes' treatment in the moist chamber at zero degrees, followed by a 15-minute transition period at the same temperature, substantially increased subsequent water uptake at 2

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1966

数据来源: ASPB

摘要:

The effect of ethylene on the uptake, distribution and polar transport of C14from indole-3-acetic acid-2-C14and naphthalene acetic acid-1-C14in tissue sections was studied. Test species were cotton (Gossypium hirsutum, L.) and cowpea (Vigna sinensis, Endl.). Generally, incubation of tissue or intact plants with ethylene reduced the degree of polar auxin transport. Ethylene inhibited the movement of both auxins in stem tissue and IAA in petiole tissue of cotton. The effect of ethylene on auxin movement in cow-peas was more complex. Ethylene apparently inhibited transport in younger petiole and stem tissue, but stimulated the process to a small but significant degree in basal petiole segments.Ethylene, in some experiments, reduced C14(auxin) uptake. This reduction was consistently smaller than the inhibition of transport. Effects upon transport were observed when uptake was not different. Differences in uptake declined as the period of incubation with auxin was lengthened, but transport was inhibited for up to 23 hours.It is proposed that ethylene may, through its effect on transport, cause localized shortages and surpluses of auxin which in turn contribute to symptoms now associated with the response of sensitive species to ethylene.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1966

数据来源: ASPB

摘要:

The isolation, crystallization, and partial identification of potato factor II, a stimulator from the chemically neutral fraction of potato extract, is described. The compound was originally found to stimulate elongation of dwarf peas grown under red light, a gibberellin bioassay. It melts between 137°and 139°. In paper chromatography it migrates to RF0.62 in isopropyl alcohol: ammonium hydroxide: H2O (10:1:1, v/v). Based on infrared and NMR data, it does not contain a lactone ring and possibly possesses an amide radical and an OH−group, as well as many methylene radicals. Potato factor II may be similar to certain of the fatty acid derivatives previously reported to stimulate growth of excised sections, but it is unique in that it stimulates growth of intact plants. This effect points to the need for completely separating neutral from acid gibberellin-like substances when the latter are assayed on dwarf p

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1966

数据来源: ASPB

摘要:

The effect of phototropic stimulation ofZeacoleoptile tips on the distribution of both endogenous indoleacetic acid (IAA) and applied C14-labeled IAA was determined. The tips rested on bisected agar blocks. More IAA was found in the blocks under the shaded side of the coleoptile tips than those under the irradiated side. However, no significant difference was observed between the total amounts of IAA, endogenous or labeled, in the irradiated and shaded sides of the experimental system. In addition, less endogenous auxin was found in the shaded tissues than in their irradiated counterparts. It is suggested that phototropism following unilateral irradiation with first positive radiant densities might be a consequence of lateral inequalities in the ability of the irradiated and shaded tissues to transport auxin basipetally.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1966

数据来源: ASPB

摘要:

En enzyme system has been found in peas which converts mevalonic acid to isoprenoid compounds. Among the intermediates in such conversion are mevalonic acid-5-phosphate and pyrophosphate, isopentenyl pyrophosphate and dimethylallylpyrophosphate. Among the products formed by the system are the pyrophosphates of geraniol, farnesol, nerolidol and higher isoprenoid alcohols.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1966

数据来源: ASPB