Endogenous auxins in apical buds ofChenopodium rubrum L. after application of (2-chloroethyl) trimethylammonium chloride (CCC)

Apical buds ofChenopodium rubrum from plants treated with CCC contain more endogenous auxins than buds from control plants, the level of these compounds increasing with the application of rising concentrations of the retardant. An especially marked increase was observed in the level of substance “X” which on chromatographic separation runs in the zone of tryptamine or its derivative. Since it has been shown in previous experiments that the inhibitory effect of CCC on flowering ofChenopodium rubrum may be reversed by indole-3-acetic acid (IAA) it is believed that the increase in auxins after application of CCC does not concern biologically active substances immediately available to the plant. It seems more likely that inactive precursors are involved which cannot be converted to the active substance in the presence of CCC, possibly due to blocking of the pertinent enzyme. If we assume that the wheat coleoptile used in the auxin bioassay in our experiments contains the pertinent enzyme it might convert the inactive precursors to active substances and, therefore, exhibit a growth stimulation even though the substances concerned would not necessarily be active in the buds from which they were extracted.     

Changes in the level of endogenous cytokinins in apical buds ofChenopodium rubrum L.

CCC (2-chloroethyl)trimethylammonium chloride applied to plants ofChenopodium rubrum during floral induction led to an increase in the level of endogenous cytokinins in the apical buds. Application of gibberellic acid or indole-3-acetic acid at concentrations reversing the effect of CCC reduced the level of cytokinins. After simultaneous treatment with both CCC and one of the growth substances this reduction was less pronounced. From the comparison bf the present results, as well as of those published in previous papers it follows that in apical buds ofChenopodium rubrum there exists a mutual interaction between gibberellins and cytokinins. Under certain conditions both these groups of hormones may substitute for each other in flowering. IAA seems to affect flowering by regulating the level of both gibberellins and cytokinins.     

Effect of (2-chloroethyl) trimethylammonium chloride (CCC) and gibberellic acid (GA3) on the flowering ofChenopodium rubrum L.

U rostliny krátkého dne Chenopodium rubrum L. se dá kvetení indukovat íty?mi 16hodinovými cykly tmy ji? 5 dní po vyklí?ení. Aplikace CCC v koncentraci 2.10^-3mvpr?běhu indukce kvetení zadr?uje a toté? piatí pro GA₃ i tehdy, je-li podáván ve velmi nízkých koncentracích (0,1 a? 0,01 mg/l). Av?ak sou?asná aplikace obou těchto látek v uvedených koncentracích vede k úplné reversi inhibice. Po p?enesení rostlin z média, obsahujícího CCC, na ?istý ?ivný roztok, inhibi?ní ú?inek CCC rychle zmizí a p?echází v slabou stimulaci. Na?e výsledky ukazují, ?e giberelin se zú?astňuje proces? kvetení i u rostliny krátkého dne.     

Changes in the content of endogenous auxins in apical buds ofchenopodium rubrum L. Induced with respect to the endogenous rhythm in capacity to flower

The content of endogenous auxins was examined in apical buds ofChenopodium rubrum plants induced by a photoperiodic cycle of 16h darkness and 8h light followed by a dark period of various duration so as to correspond with either maximal or minimal flowering response in the endogenous rhythm in capacity to flower initiated by the photoperiodic treatment. Apical buds of potentially generative plants contained less auxins than apical buds of plants which remained in the vegetative state. Apical buds from plants treated with kinetin (1. 10^-3 M) and therefore remaining in the vegetative state showed an auxin level comparable to that of untreated plants exhibiting minimal flowering response irrespective of the duration of the second dark period. Plants cultivated on a sucrose solution (0.6 M) during the second dark period became generative even at the normal minimum of flowering. The auxin content of the apical buds was low, similarly as in untreated plants induced for a period leading to maximal flowering response. On the other hand, apical buds from plants grown on sucrose solution during a dark period leading to the manifestation of maximal flowering response showed a relatively high auxin content comparable to that found in untreated plants which had obtained a more extended induction by three photoperiodic cycles. The results are discussed with respect to the possible role of endogenous auxins in the regulation of the changes in growth correlations occurring in the shoot apex during photoperiodic induction and in the expression of the competence to flower.     

Changes in endogenous level of auxins and cytokinins in axillary buds ofpisutn sativum L. in relation to apical dominance

Decapitation of the stem in one-week-old pea seedlings below the first node causes a rapid outgrowth of the two cotyledonary buds. One of them soon becomes dominant, while the other one is inhibited, but can be released from inhibition by cutting off the dominant bud. The level of endogenous auxins and cytokinins was determined in dominant and inhibited buds, as well as in released buds at different time intervals after deinhibition. It was found that the inhibited buds contained very little acidic, ether soluble auxins, a high level of tryptophan and also a high level of cytokinins, in comparison with dominant buds. When the inhibited buda were released from inhibition, their auxin content rose, while that of tryptophan and cytokinins decreased, reaching the level found in dominant buds within six days. Specific changes in content of two undetermined auxin-like substances were found in released buds during de-inhibition. These results are discussed in relation to the current views on the regulation of apical dominance.     

Inhibition of flowering ofChenopodium rubrum L. after the action of actinomycin D

Floral differentiation ofChenopodium rubrum is more AD-sensitive than growth of the vegetative organs. With a suitable combination of the manner of application and the concentration of AD used, selective inhibition of flowering can be attained without any effect on growth. The inhibition of flowering was greatest if AD acted during the first two days of photoperiodic induction. With later application its effect on flowering was weaker. RNA synthesized in the first days of photoperiodic induction to a considerable extent ensured its further course.     

Promotive effect of abscisic acid in flowering ofChenopodium rubrum as the result of decreasing apical dominance

Abscisic acid (ABA) was applied in a concentration of 1. 10^?3 M and 1. 10^?4 M to the quantitative SD plantChenopodium rubrum under various light regimes. ABA did not influence flowering in plants under continuous illumination, enhanced flowering in plants subjected to long days and inhibited it in plants induced by short days. It was concluded that ABA can not substitute for inductive treatment but its action may be additive to initial stages of reproductive morphogenesis (enhanced growth rate and branching of the apical meristem) as evoked by long days.     

The effect of IAA application on endogenous rhythm of flowering inChenopodium rubrum L.

The study deals with the effect of indol-3-ylacetic acid (IAA) on endogenous rhythm of flowering inChenopodium rubrum L. ecotype 374. Phase setting of the rhythm and length of its period were not affected, its amplitude decreased or changed insignificantly depending on the time and the site of IAA application. The intervals of significant inhibitory effect of IAA applied to apical buds terminated later than after IAA application to photoreceptive organs. The inhibitory effect did not correlate with the level of IAA uptake. Results obtained support the hypothesis that both photoreceptive organs and apical buds are the sites of inhibitory effect of applied IAA.     

Time-dependent reversal of the inhibitory effect of 5-fluorode-oxyuridine on flowering ofChenopodium rubrum L. by thymidine

Flower initiation induced by three inductive photoperiods inChenopodium rubrum L. was fully inhibited by treating the shoot apex with a 5 μl drop of 1×10^?5 m 5-fluorodeoxyuridine (FDU). This inhibition may be reversed by thymidine applied simultaneously with or after FDU treatment at any time during photoperiodic induction. One day after the end of induction the inhibition caused by FDU is irreparable even by increasing thymidine concentrations. It is concluded that photoperiodic floral induction may take place inChenopodium even if DNA synthesis is suppressed.     

Effect of different sugars on flowering ofChenopodium rubrum L. in dependence on the conditions of germination and initial growth

Flowering ofChenopodium rubrum seedlings fed different sugars at a concentration of 0.6 and 0.4 M, reap, during a single inductive cycle was stimulated or inhibited in dependence on the conditions of germination and initial growth. Plants allowed to germinate at alternating temperatures of 28 °C and 5 °C showed a slower initial growth and their development was stimulated by some sugars as compared to controls induced in the absence of sugars. Plants germinated at alternating temperatures of 32 °C and 5 °C exhibited a rapid initial growth and flowering was inhibited after induction in the presence of sugars. On the other hand, development proceeded more rapidly in control plants induced in the absence of sugars after germination at the higher temperature than after germination at the lower one. The differences between the two variants quoted above could be observed also after induction by two 16 h dark cycles. Glucose and sucrose were most effective in stimulating flowering under appropriate conditions of germination. Fructose was less effective and the action of maltose was very weak. Xylose, ribose and galactose were innocuous, while arabinose, glucoso-6-phosphate and mannitol were toxic to the plants. The sugars inhibited root growth in all cases and led to an increase in starch accumulation in the underground and overground plant organs. At a concentration of 0.6 M they mostly inhibited the length of the cotyledons and, especially, of the first leaf; at a concentration of 0.4 M growth of the overground organs was stimulated. The results are discussed with respect to the possible ohanges in photoperiodic sensitivity brought about by the rate of initial growth.     

The interaction of endogenous gibberellins in correlation with cotyledons and axillary buds in the pea (Pisum sativum L.)

After the decapitation and amputation of one cotyledon in germinating pea seedlings, the axillary bud of the amputated cotyledon always grows and the growth of the axillary bud of the remaining cotyledon is inhibited. Before morphological differences appear between the axillary bud of the amputated and preserved cotyledon, a higher endogenous gibberellin content can be demonstrated chromatographically in the axillary bud of the amputated cotyledon. This indicates that the increased growth of the axillary bud of the amputated cotyledon is in connection with an earlier increase in the activation of endogenous gibberellins.     

The effect of penicillin on the levels of endogenous gibberellins and cytokinins in mungbean (Vigna radiata L.) seedlings

The levels of gibberellin and cytokinin like substances are increased in mungbean (Vigna radiata L. Wilczek) seedlings by penicillin treatment. The possible role of penicillin in regulating the hormone levels in plant tissues is suggested.     

The effect of (2-chloroethyl)trimethylammonium chloride (CCC) and gibberellic acid on the growth and development of wheat cultivated under red or blue light

The effect of CCC and GA₃ on the growth and development of spring wheat (Triticum aestivum L.) cultivated under predominantly red (500–700 nm) or blue (400–500 nm) light was investigated. Red light enhanced the development of wheat during the exponential phase of growth. This effect presumably implicated the promotion of gibberellin synthesis under red light. The strong inhibitory action of CCC under red light (the inhibition was lower under blue light) might be interpreted in a similar way. The growth became more intensive under blue light after caring and was accompanied by increased susceptibility to giberellic acid treatment.     

The effect of carbon and nitrogen sources on auxins and gibberellin-like substances synthesis by bacteria isolated from the roots of pine seedlings (Pinus silvestris L)

It was found that in the presence of sodium succinate synthesis of auxins and gibberellin-like substances by microflora in the rhizosphere of pine seedlings was higher than in the presence of the other carbon sources. The smallest amounts of these substances were found in media with sodium pyruvate. The highest C-content (C:N = 60:1) was not optimal for the synthesis of plant growth regulators. Ammonia ions inhibited the production of gibberellin-like substances. The effect of different nitrogen sources and C:N ratio on the synthesis of auxins was different depending on bacterial strain used.     

The effect of light on the endogenous levels of cytokinins and gibberellins in seeds of sitka spruce (Picea sitchensis Carriere)

Abstract Maximum germination of Sitka spruce seed was obtained at 22°C under continuous fluorescent light or following a single 10 min exposure to red light (RL) given after 48 h of dark imbibition. The levels of endogenous cytokinins and gibberellins were examined in seeds which were exposed to different light regimes. Cytokinin levels in Sitka spruce seeds increased approximately 1.7–fold during exposure to continuous white light, during dark stratification, or within 1 h or a 30 min exposure to RL. A single peak of activity could be eluted from the LH^?20 Sephadex column which appeared in the same volume as authentic zeatin riboside. Gibber-ellin activity in Sitka spruce seeds increased rapidly during exposure to 30 min of RL and then declined during subsequent dark incubation. Similarly, under continuous white light, gibberellin activity was at least twice as high as in the dark. Two gibberellm-like substances were found in Sitka spruce seeds which appeared to be similar to GA₇ and GA₉ on the basis of their chromato-graphic properties. The zone of gibberellin activity directly associated with photo-excitation of Sitka spruce seeds contains conjugate gibberellins, possibly glucosyl esters, which when hydrolysed with β-glucosidase form two products which are similar to the free gibberellins which were detected. The light response in Sitka spruce seed is compared to a similar response in Scots pine (Pinus sylvestris L.) seeds.     

The effect of temperature,auxins, antiauxins and some other chemicals on the endogenous rhythm affecting photoperiodic response of Biloxi soybean (Glycine Max. L.;Merr.)

Ohne ZusammenfassungWith 2 Figures in the Text     

The antagonism of (2-Chlorethyl) trimethylammonium chloride and indole 3-acetic acid in epicotyl and axillary buds growth in the pea seedlings

The 0·03–0·06% indole-3-acetic acid (IAA) in lanoline paste smeared on the cut surface of decapitated epicotyl of the pea seedling inhibited the growth of the axillary buds of the cotyledons. 0·03–0·06% solution of (2-Chlorethyl) trimethylammonium chloride (CCC) considerably weakened the inhibitory effect of IAA when applied simultaneously to the roots. In a similar way CCC diminishes even the growth inhibition of intact pea epicotyls caused by 0·06% IAA lanoline paste. 0·03% solution of CCC administered to the roots of the decapitated pea seedlings significantly increased growth of the axillary buds. This effect may play a role in the demonstrated antagonism between the low concentration of CCC and IAA.     

The effect of auxins (IAA and 4-Cl-IAA) on the redox activity and medium pH of Zea mays L. root segments

Indole-3-acetic acid (IAA) and 4-chloroindole-3-acetic acid (4-Cl-IAA) were tested at different concentrations and times for their capacity to change the redox activity and medium pH of maize root segments. The dose-response surfaces (dose-response curves as a function of time) plotted for redox activity and changes in medium pH (expressed as ΔpH) had a similar shape for both auxins, but differed significantly at the optimal concentrations. With 4-Cl-IAA, the maximal values of redox activity and medium pH changes were observed at 10⁻¹⁰ M, which was a 100-fold lower concentration than with IAA. Correlations were observed between redox activity and medium pH changes at the optimal concentrations of both IAA and 4-Cl-IAA. The results are discussed herein, taking into account both the concentration of the auxins and the effects produced by them.