Seedlings Of Chenopodium Rubrum Research Articles

Application of sonication-assisted Agrobacterium-mediated transformation in Chenopodium rubrum L

Chenopodium rubrum belongs to the plant species in which standard Agrobacterium-mediated transformation procedures remain inefficient. We demonstrate that the employment of sonication-assisted Agrobacterium-mediated transformation (SAAT) effectively enhanced transient expression of GUS gene coding for b-glucuronidase in Chenopodium rubrum. Further the results indicated that the age of seedlings is one of the limiting factors affecting the potency of Agrobacterium tumefaciens infection. Histochemical detection of b-glucuronidase activity revealed that two-days-old seedlings were much more susceptible to infection than ten-days-old ones. According to our results SAAT technology could provide an efficient tool for obtaining stable transformants when applied to two-days-old seedlings of Chenopodium rubrum.

Diurnal Fluctuations in Ethylene Formation in Chenopodium rubrum.

Ethylene formation was studied in 5- to 6-d-old Chenopodium rubrum seedlings under the following light regimes: continuous light (CL), continuous darkness (CD), and alternating light/darkness (12 h of each). No significant regular oscillations in ethylene formation were found in either the CL or CD groups. In the light/dark regime, pronounced diurnal fluctuations in ethylene formation were observed. Activity of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase was transiently increased on transfer from light to dark and vice versa. In CL, ACC oxidase activity did not change significantly, whereas in CD, it decreased continuously after the initial increase. The in vivo levels of ACC and N-malonyl-ACC (MACC) were constant for the first few hours of darkness, then decreased dramatically, but increased again in the light. In constant darkness, the level of ACC displayed endogenous rhythm, with minimum values at h 12 and 44, and a maximum value at h 32 to 36. The level of MACC in both shoots and roots decreased in the CD group until h 12, and then remained constant until h 30 before decreasing continuously. We conclude that the photoperiodic regime affects both ACC and MACC levels, as well as the conversion of ACC to ethylene. Correlation of the described changes in ethylene formation to photoperiodic flower induction is discussed.

Ethylene Production in Seedlings of Chenopodium rubrum, as Influenced by Seedlings Age, Light, and CO2 Concentration1)

Summary Ethylene formation in intact seedlings of a short-day plant Chenopodium rubrum was followed in the course of the first 26 d of growth. The highest values of ethylene evolution were found in the youngest (2 1/2-d-old) plants. Ethylene evolution then decreased up to the 4th d as expressed both on dry weight and on one plant basis. Later, ethylene evolution expressed on dry weight basis decreased till the 26th d, while that expressed on one plant basis increased from the 5th d onward, the rate of increase gradually leveling off. The peaks of flowering coincided with periods of low ethylene production, as expressed on dry weight. Light inhibited ethylene production in C. rubrum seedlings. A higher CO, level did not cancel such inhibition. A lower CO 2 level decreased ethylene production in darkness. ACC markedly increased ethylene evolution and this ACC-induced ethylene production is inhibited by light more strongly than that in the absence of ACC. The relationship between the levels of auxin and ethylene and the capacity for flowering is discussed.

DIURNAL MODULATION OF PHOTOTROPIC RESPONSE BY TEMPERATURE AND LIGHT IN Chenopodium rubrum L. AS RELATED TO STEM EXTENSION RATE ANDARGININE DECARBOXYLASE ACTIVITY*

Abstract— Seedlings of Chenopodium rubrum were grown under 12: 12 h light‐dark cycles with the light period at 32.5°C and darkness at 10°C (“normal” conditions) or with light at 10°C and darkness at 32.5CC (“inverse” conditions). When grown under unilateral white light with the photo‐thermoperiodic conditions described above, inverse seedlings did not show phototropic curvature while normal seedlings did. Regardless of temperature regime used, plants irradiated with unilateral blue light (456 nm) at 10°C failed to curve on subsequent incubation at 32.5°C. If the phototropic stimulus was given at 32.5°C followed again by 32.5°C in darkness, phototropic curvature was observed. The results with monochromatic blue light thus explain the lack of phototropic response of “inverse” seedlings with the unilateral light period given at 10°C. “Inverse “seedlings showed a sharp rhythm in their capacity to respond to phototropic stimulation at 32.5°C. The greatest capacity to respond came when the stem extension rate was actually zero. The differential growth accompanying phototropic curvature thus seems to be different from the growth responsible for uniform stem elongation. The curvature may result from differential turgor changes as in the case of sun tracking of leaves. “Inverse seedlings” showed clear signs of stress and displayed a rhythm in arginine decarboxylase, an enzyme thought to be stress‐related, with maxima during the low temperature light periods. It is concluded that the phototropic perception transduction chain is modified by the inverse conditions somewhere before the final growth‐turgor steps, since they exhibit geotropic sensitivity.

Photoperiod and light quality effects on rate of dark respiration and on photosynthetic capacity in developing seedlings of Chenopodium rubrum

Development and acclimation of energy transduction were studied in seedlings of Chenopodium rubrum L. ecotype selection 184 (50° 10′ N; 105° 35′ W) in response to photomorphogenic and photoperiodic treatments. Dark respiration and photosynthetic capacity [nmol O2 (pair of cotyledons)−1 h−1] were measured with an oxygen electrode. Changes in chloroplast ultrastructure were analyzed concomitantly. After germination, seedlings were grown at constant temperature either in darkness or in continuous light (white, red, far‐red and blue) or were subjected to diurnal cycles of light/dark or changes in light quality. Dark respiration was low in far‐red light treated seedlings. In red light treated seedlings dark respiration was high and the mean value did not depend on fluence rate or photoperiod. Blue light stimulated transitorily and modulated dark respiration in photoperiodic cycles. Photosynthetic capacity was reduced by far‐red light and increased by red light. In response to blue light photosynthetic capacity increased, with indications of a requirement for continuous energy input. Phytochrome and a separate blue light receptor seemed to be involved. In continuous red light a clear cut circadian rhythm of dark respiration was observed. Blue light had a specific effect on chloroplast structure.

Ribulose bisphosphate carboxylase capacity and chlorophyll content in developing seedlings of Chenopodium rubrum L. growing under light of different qualities and fluence rates

In order to evaluate the aclimation of Chenopodium seedlings to different quantum fluence rates of R and BL, kinetics of Rubisco capacity, Chl content and chloroplast structure were studied. Under monochromatic light photoreceptors are stimulated selectively and their influence on biosynthetis capacities during chloroplast development can be studied.R irradiations saturate Rubisco capacity even at the lowest quantum fluence rates applied, whereas Chl a+b synthesis depends strongly upon fluence rate of R. Under BL irradiations, both Rubisco capacity and Chl content are fluence rate dependent. R irradiations favour Chl b synthesis relative to Chl a, whereas under BL Chl a content is high relative to Chl b. Under R irradiation Pfr is the main photoreceptor involved in regulation of Rubisco capacity whereas under BL a specific BL absorbing photoreceptor may control the response. From the fluence rate dependency under BL irradiations it is concluded that the blue region of the day light spectrum may be the sensor for monitoring fluence rate and causing the characteristic changes in shade and high/low WL adaptation with respect to Rubisco levels in Chenopodium.

Effects of various alcohols on the induction of flowering in Chenopodium rubrum L.

Summary Seedlings of Chenopodium rubrum were treated with several alcohols during the 13 h dark period that induces flowering. The primary alcohols (C2-C5) inhibited the induction strongly. Secondary (C3, C4) and tertiary (C4) alcohols had no significant effect. Alcohol dehydrogenase in C. rubrum seedling extracts was acting on the primary alcohols only, its kinetic properties being comparable to those of the yeast enzyme (E.C. 1.1.1.1.). The profiles for ethanol sensitivity and for alcohol dehydrogenase activity in the seedlings were not identical, although both showed a slight increase at the end of the dark period. It was concluded that the inhibition of flowering is not by interference with a membrane system but via metabolic effects on the primary inductive process. On the basis of their relative turnover velocities with alcohol dehydrogenase, n-butanol and n-pentanol are the most effective inhibitors of the compounds tested.

Multiple circadian rhythms regulate photoperiodic flowering responses in Chenopodium rubrum

In constant conditions that follow daily temperature cycles, a circadian rhythm of cell division (20-h period) was apparent at the shoot apex of seedlings of Chenopodium rubrum. There was also rhythmicity in capacity to flower (21- to 24-h period) when the seedlings were exposed at various ages to a 12-h dark period. Neither oscillation was evident in seedlings raised under constant conditions. Rhythmical changes in flowering (20- to 24-h period) were also found upon treatment of seedlings for 6 h at different times with solutions of glucose (0.4 M), gibberellic acid (10−6 M), or ethanol (0.1%). This latter rhythm was apparent in constant conditions in the light long after export of floral stimulus from the cotyledons. It is argued that rhythmicity at the shoot apex, possibly in cell division, confers a 20- to 24-h periodicity on the flowering responses of C. rubrum.By contrast, exposure of seedlings or adult plants to a dark period of varied duration revealed a rhythm in capacity to flower but with a considerably longer period (about 30 h). This rhythm was present whether or not seedlings had been raised in fluctuating temperatures. The oscillation was also distinctive in that it originated in the leaf. Exposure of only one leaf on an adult plant to different durations of darkness induced the 30-h rhythm of flowering. Therefore, more than one rhythm, a leaf and an apex rhythm, may control flowering in C. rubrum.

Non-photosynthetic light requirement for the development of flowers in Chenopodium rubrum, a short-day plant

Seedlings of Chenopodium rubrum do not develop flowers in continuous darkness even with high concentrations of sucrose in the medium. Irradiation of plants with 5 min of red and (or) far-red wavelengths on the 6th to 8th days of darkness leads to a high degree of flowering. This non-photosynthetic light effect on flowering can be duplicated by a gibberellic acid (GA3) and kinetic application. The lack of flowering in continuous darkness appears to be due to a low apical activity. Red and far-red irradiation (via the formation of a critical level of PFR) and the plant growth hormones may have promoted flowering of C. rubrum by stimulating apical activity. Thus, light may be required after induction of flowering, not only to provide photosynthetic energy substrates but also to create a favorable balance of growth hormones that are required to maintain optimal apical activity essential for flower development.

Endogenous rhythmic activity of nitrate reductase in a selection of Chenopodium rubrum

Oscillations of nitrate reductase (NR) activity occurred after transfer of seedlings of Chenopodium rubrum L., ecotype 60°47′ N 137°32′ W, from an alternating temperature and light intensity germination program to constant temperature and light conditions; there were peaks of activity at 18, 30, and 45 h. The presence of half-strength Hoagland's nutrient solution during the germination period increased the range of the oscillations but did not affect the period. Changes in levels of nitrate and nitrite within the seedlings were consistent with the periodicity of NR activity during the light period after germination. Enzyme activity decreased if seedlings were placed in darkness, but the phasing of the oscillations was not altered by the transition from light to darkness. In addition, oscillations of NR activity with a period length of about 18 h occurred during continuous light after dark periods. This secondary rhythmicity is apparently superimposed upon the pattern of fluctuations previously established.On the basis of the rhythmicity that is characterized by these findings, and also in the light of other previously observed effects of altered environmental conditions on the activity of NR, hypotheses are presented to account for the endogenous oscillations of NR activity in Chenopodium rubrum. It is suggested that such rhythmic behavior of NR may occur in higher plants in general.

Endogenous rhythmicity and energy transduction VII. Phytochrome-modulated rhythms in pyridine nucleotide levels in seedlings of Chenopodium rubrum

It has been shown that the pool size of pyridine nucleotides display an endogenous rhythm with a period length of 9–12 h in continuous darkness. Phytochrome modulates the amplitude of the oscillation in NADP, NADPH and NAD during the first hours of darkness. It is concluded that phytochrome modulates electron flow under conditions where overall energy transduction displays a circadian rhythm.

Endogenous rhythmicity and energy transductionv. rhythmicity in adenine nucleotides and energy charge in seedlings of Chenopodium rubrum∗∗

Abstract The energy metabolism of Chenopodium rubrum seedlings is analyzed with respect to endogenous rhythmic changes in adenine nucleotides. It is demonstrated that the pool sizes of ATP, ADP and AMP display endogenous rhythms. Following Atkinson's hypothesis of adenylate control of metabolism and determining the “energy charge”; of the seedlings, a circadian rhythm is observed which is shifted by 180° in relation to the circadian rhythm in betacyanin turnover. The energy charge concept is discussed in view of a working hypothesis which assumes that circadian rhythms evolved as an adaptation of living organisms to diurnal cycles of energy supply from the environment.

Irreversible Flower Initiation of Chenopodium rubrum Seedlings and Excised Stem Tips

It was concluded that the first week of culture of excised stem tips might be concerned with other than flowering processes, and that only after 1 week's growth can flowering be manipulated by exposure to short or long days. A period of 14 short days, after the first week's growth, appears to be threshold for the flowering of excised stem tip cultures, and a period of no longer than 24 days led to 100% cultures in flower. Excised stem tips from 3- to 4-day-old seedlings normally do not flower if they are exposed to long-day conditions. However, stem tips, excised from seedlings given 6 short days, flowered even though they were exposed to long days only; tips from seedlings exposed to fewer than 6 short days did not flower when exposed to long days. Similarly, excised stem tips from seedlings, exposed to either 7 short days or to 7 long days, revealed the effect of the seedling induction on exposure to short days: the tips from the long-day seedlings flowered much later than those from the short-day seedlings. Seedlings exposed to various periods of long days, prior to exposure to short days, all flowered after 10-11 short days. These and other results were difficult to explain entirely on the basis of a postulated relationship between amount of leaf and amount of production of the flower stimulus.

The Effect of Defoliation, and Hypocotyl and Root Removal, on the Development and Flowering of Chenopodium rubrum L.

Seedlings of Chenopodium rubrum flowered earliest when they had intact cotyledons, and incremental cotyledon pruning delayed flowering. Seedlings with roots removed prior to photoperiodic induction regenerated roots quickly and, although this treatment delayed flowering slightly, the pattern of flowering of such seedlings with incremental cotyledon pruning was similar to that of seedlings with root and cotyledon pruning. Seedlings with hypocotyls and roots removed prior to photoperiodic induction took longest to flower compared with the other two types of seedlings, and time to flower was not linearly correlated with amount of cotyledon pruning. Presence of cotyledons on seedlings without hypocotyls and roots, that is, on excised stem tips, appeared to inhibit epicotyl development in culture. Gibberellic acid (GA3) overcame this inhibition, and earliest flowering was associated with 10-7M GA3. However, GA3 (10-8-10-6M) did not affect the flowering of cultured excised stem tips devoid of cotyledons.

Timing in Chenopodium rubrum of export of the floral stimulus from the cotyledons and its action at the shoot apex

When the cotyledons of 6-day-old seedlings of Chenopodium rubrum were removed at various intervals after exposure to a single 13.5-h dark period, defoliation during the first 6 h after darkness prevented flowering. If the cotyledons remained on the plant for a further 5 or more hours flowering gradually increased. Within 20 h after the end of the dark period, the cotyledons had completed their essential role and subsequent defoliation had no influence on flowering. A cotyledon area of about 30 mm2 was required for maximal floral induction.It can be concluded that a transmissible factor—often termed floral stimulus—was produced in the cotyledons following a short-day exposure. It is also apparent that flowering in Chenopodium rubrum depends on the generation of a floral stimulus in short days, rather than on control by a transmissible inhibitor of flowering produced under long days.After arrival of the floral stimulus at the apex there was a doubling from 2% to 4% in the percentage of cells undergoing mitosis. This increased value of the mitotic index was maintained during floral development and probably reflected an increased rate of cell division. There were rapid and sometimes rhythmic fluctuations in the percentage of dividing cells.

Conditioning circadian rhythmic control of betacyanin content in Chenopodium rubrum by temperature and light intensity cycles during germination

Evidence is presented that a circadian rhythm in betacyanin accumulation in Chenopodium rubrum seedlings (ecotype 50°10′ N, 105°35′ W, selection 184) was initiated or synchronized by the cyclic temperature and light conditions that were imposed during germination. This rhythm was probably free-running in the constant light conditions that preceded the imposition of darkness. Rhythmic fluctuations in the time course of betacyanin content during darkness, which are probably due to betacyanin turnover, showed correlations with the alternating germination conditions, thus indicating that the rhythm is not initiated or rephased by the transition from light of 600 or 3000 ft-c to darkness. Light following darkness increased the respective level of betacyanin accumulation but did not alter the phasing of the rhythm as compared with darkness. The metabolic activity of the seedlings in the light, following darkness, depends on the specific phase of the endogenous rhythm at the time of the dark: light transition.

Betacyanin accumulation, chlorophyll content, and flower initiation in Chenopodium rubrum as related to endogenous rhythmicity and phytochrome action

In Chenopodium rubrum seedlings (ecotypes 50°10′ N and 49°58′ N) betacyanin synthesis is light dependent (completely dark-grown seedlings contain no betacyanin) and is under phytochrome control via both the low energy and the high-energy (HER) reactions of photomorphogenesis. In continuous light, accumulation of betacyanin is linear with time. However, when a single dark period interrupts continuous light, the amount of both betacyanin and chlorophyll synthesized during a given period of time after the dark interruption shows a rhythm reflecting differences in the rate of, and (or) the capacity for, pigment accumulation that are dependent on the duration of the dark period. The rhythm in chlorophyll content was higher in frequency than circadian, with a period of about 15 h, while rhythmicity in the rate of synthesis of betacyanin was circadian. These results suggest that there is endogenous rhythmicity in the metabolic state of the system in darkness. The imposition of light after darkness apparently stabilizes the specific physiological status attained at that respective time of darkness and thus determines the metabolic activity of the seedlings.When glucose was supplied throughout darkness interrupting continuous light, the phasing of the rhythm of betacyanin synthesis was positively correlated with the rhythm of flower initiation, but this was not so when phenylalanine was supplied during darkness. In contrast, when glucose was supplied for a varied length of time in continuous light, there was rhythmicity in the rate of betacyanin accumulation, with a periodicity of about 15 h, that was dependent on the duration of the glucose application.When seedlings were supplied with 10−6 M gibberellic acid during darkness there was a rhythm in the amount of hypocotyl elongation that depended on the length of a single dark period interrupting continuous light. Other evidence has suggested that there is a rhythm in the stability of the cellular membranes; this rhythm was assayed (non-physiologically) by the time of onset of betacyanin leakage from seedlings into an extraction medium and was apparent only after application of 10−10 M gibberellic acid. The rhythms in hypocotyl elongation and in membrane stability that were revealed after the application of gibberellic acid suggest that there may be a rhythm in the rate of differentiation and (or) development of the system.It is postulated that endogenous rhythmicity is due to the spatial separation of energy production and use in different cell particulates, with phytochrome acting as a membrane operator.

Development and Histochemistry of the Endothecium in the Anthers of In vitro Grown Chenopodium rubrum L.

Seedlings of Chenopodium rubrum were grown on a fully defined medium and induced to flower by exposure to cycles of 8 hr light/16 hr darkness. The development of the anthers was studied using histochemical techniques. Particular attention was paid to the delayed development of the endothecium or fibrous layer and to the chemistry of the endothecial bars of thickening. These bars were found to consist mainly of α-cellulose as defined by insolubility in 17.5% NaOH. In contrast, most of the wall material in the other tissues of the another was low in oriented α-cellulose and consisted of pectic substances (0.5% ammonium oxalate soluble), hemicelluloses (4% NaOH soluble) and non-cellulosic polysaccharides (17.5% NaOH soluble); callose (defined as positive to lacmoid) was also detected as a transient material. Lignin was not detected in the endothecial bars of thickening. The concept of programmed control of tapetal and sporogenous tissues invoked in a paper by Heslop-Harrison (1964) has been extended to sugge...

Inhibition of Flowering of Chenopodium rubrum by Prolonged Far-Red Radiation

1. Chenopodium rubrum seedlings were used in a spectrographic analysis of flower inhibition by prolonged irradiation in the region of 700-800 mμ (farred). The seedlings were photoinductive as early as 2 days after emergence, and five 16-hour nights alternated with 8-hour days were sufficient to induce flowering. Several minutes of radiation in the region of 640 mμ (red) given near the middle of the 16-hour night completely inhibited flowering. When the red was followed immediately by several minutes of farred irradiation, flowering was repromoted. Prolonged irradiation with far-red, however, inhibited flowering, and the degree of inhibition varied with wavelength across the far-red region of the spectrum. 2. Comparison of far-red action-spectrum with phytochrome-absorption curves showed that the inhibitory action on flowering coincides with the weak overlapping of the phytochrome Pr (absorption maximum 660 mμ) absorption curve into the far-red region of the spectrum. A low level of phytochrome Pfr (absorption maximum 730 mμ) is maintained in the presence of continuous far-red radiation and is the effective inhibitor of flowering under prolonged far-red irradiation. 3. Molar absorbencies (ε) of the Pr and Pfr forms of phytochrome can be obtained from the results. Values of (εPr) and (εPfr) at various wavelengths in the region of 693-795 mμ are listed in table 6. They are compared in table 7 with values obtained from published results on control of flowering of Pharbitis nil (11). 4. Phytochrome in Chenopodium rubrum and Pharbitis nil under continued irradiation in the region of 730-790 mμ reaches a photochemical steady state with 1-2% Pfr present. Maintenance of this level for about 60 minutes is adequate to inhibit flowering. The rate of inhibition is independent of greater percentage transformation to Pfr under photochemical steady state.