Decapitated Pea Seedlings Research Articles

The release of the cotyledonary shoot ofpisum sativum from inhibition in relation to changes in the levels of endogenous auxins, cytokinins, and gibberellins

Both axillary buds belonging to the cotyledons (cotyledonary buds) start to grow on decapitated pea seedlings, but one of them (the dominant shoot) prevails in growth over the other (the inhibited shoot). If the dominant' cotyledonary shoot is removed, the inhibited shoot is released from inhibition and starts to grow. This release from inhibition of the inhibited cotyledonary shoot is accompanied within two hours from the removal of the dominant cotyledonary shoot by a marked increase in the level of endogenous cytokinin-like substances and by a decrease in the level of endogenous IAA. By contrast, a significant increase in IAA level and a decreasing trend in the level of cytokinin-like substances occur in the originally inhibited cotyledonary shoot between hour 4 and hour 48 after the release from inhibition of the inhibited cotyledonary shoot. The level of gibberellin-like substances in the cotyledonary shoot released from inhibition steadily increases from the beginning of the release.

Translocation of14C-abscisic acid from roots into the aboveground part of pea (pisum sativum L.) seedlings

The translocation of14C-ABA from roots into other parts of the plant was followed in intact and decapitated pea seedlings. In intact plants ABA from roots was translocated above all into the apical part of epicotyl. In decapitated plants the regulative ability of intact apex can be partly simulated by exogenous IAA. The growth of lateral buds occurring after decapitation was associated with an intensive flow of14C-ABA from roots into released lateral buds as late as 72 h after decapitation,i.e. in the stage of intensive elongation growth of buds.

The role of gibberellins and cytokinins in the growth correlative effect of cotyledons in flax and pea

It is wellknown that following the amputation, or darkening of one cotyledon in decapitated flax seedlings, the opposite remaining, or illuminated, cotyledon exerts a stimulatory effect on the growth of its axillary bud. For the induction of this stimulating effect a 21–72 h continuous darkening of the cotyledon is sufficient. Endogenous gibberellins take part in the stimulation effect of the illuminated cotyledon, since their level in the illuminated cotyledon increases as early as 12–48 h following the darkening of the opposite cotyledon. The apical part of the cotyledon has a higher growth stimulatory effect on the growth of the cotyledonary axillary bud than the basal half. This again is associated with endogenous gibberellins the level of which is higher in the apical half of the cotyledon than in the basal one. Upon removal of the root and hypocotyl base in decapitated flax seedlings deprived of one cotyledon, the remaining cotyledon loses its stimulatory influence, so that the bud of the amputated cotyledon grows more vigorously (Dostál 1955). In this growth correlative phenomenon the root may be substituted by cytokinin BA applied in the form of a 0.1–1.0 per cent paste onto the remaining cotyledon, for again in this case the bud of the preserved cotyledon grows more vigorously. Following the decapitation of the axillary of the amputated cotyledon in decapitated pea seedlings with an intact root and deprived of one cotyledon, the axillary of the remaining cotyledon grows more intensively than the serial of the removed one. If the plants operated on in the same way are deprived of the root, the serial of the removed cotyledon gains a correlative growth predominance. If the plants deprived of root are cultivated at the same time in a solution of BA (10–20 mg 1−1), the correlative predominance is acquired by the axillary of the remaining cotyledon. In growth correlations between cotyledons and their axillary buds in pea seedlings the root may thus be substituted by exogenous cytokinin, as well.

The Role of Endogenous Abscisic Acid in the Correlation Between the Cotyledon and Its Axillary Bud in PeaPisum sativum L

On cutting off one cotyledon from decapitated pea seedlings cultivated in the dark, the apical dominance is restored, as is well-known, by the growth of the bud of the removed cotyledon. As early as 12 h following cotyledon amputation(i.e. at the time when buds of both cotyledons-remaining and removed-are not yet differentiated in size), a decrease in the level of endogenous abscisic acid can be demonstrated in the bud of the removed cotyledon.

Effect of short-term geo-stimulation on the distribution of32P in decapitated pea seedlings

Three-leaf pea (Pisum sativum L. cv. ‘Alaska’) seedlings were oriented horizontally and32P was applied to leaf-2 for 6 h period, at the end of which the distribution of isotopes in the seedlings was determined. It was found that (i) isotope accumulation in the apices of the vertical and horizontal seedlings remained almost the same; (ii) on decapitation almost all the isotopes in the apex diverted to the roots in the vertical seedlings; (iii) among the horizontal seedlings32P was retained in the hanging treated leaf and the rest moved to the roots via shoots; (iv) the dry weight of the hanging treated leaf was slightly greater than the above-axis one; (v) the position of buds on the axis had no effect on the initial32P accumulation in them, however, a trend of greater isotope accumulation was noted in the above-axis basal buds; (vi) geo.stimulation had no effect on the total dry weight of the seedlings; and (vii) in geo-stimulated seedlings decrease in the dry weights of shoots and its concomittant increase in roots was primarily the result of the movement of substances.

Effect of Prolonged Geo‐stimulation and Presence of 32P on the Elongation of Lateral Shoots of Decapitated Pea Seedlings

AbstractThe effects of prolonged geo‐stimulation and presence of 32P on 3‐leaf decapitated pea (Pisum sativum L. cv. Alaska) seedlings were studied with regard to lateral bud elongation as well as accumulation and recovery of isotope.Prolonged geo‐stimulation favoured the dominance of basally located, upwardly directed buds and suppressed the elongation of subapical bud — a gravimorphic response similar to the one shown by intact geo‐stimulated branches of woody plants. Basal bud 2 was an exception as it dominated both in the above‐ and below‐axis position.Accumulation of 32P in buds was the result of their own growth, whereas in the other parts of the seedlings accumulation of isotope was not necessarily related to growth.Geo‐stimulation affected 32P recovery in redistribution experiments, whereas it had no effect in distribution experiments. In the former, the decrease in the isotope level in the seedling suggests a loss of 32P.Prolonged presence of 32P in the seedlings had a deleterious effect on bud elongation.

Transport of 14C-kinetin in intact and decapitated pea seedlings (Pisum sativum L.)

Summary In intact, decapitated and/or indoleacetic acid (IAA)-treated (0.007 and 0.5%) pea seedlings the translocation of 14C-kinetin applied to roots was investigated. During the whole experiment the plants were kept in darkness. In intact plants 14C-activity accumulated in apical buds. In decapitated and IAA-treated seedlings the accumulation of activity occurred in the IAA-treated part of the stump. In decapitated seedlings (without IAA) the removal of the apical bud resulted in growth of lateral buds. However, the initiation of growth in these buds did not induce an increased translocation of labelled kinetin to lateral buds. In lateral buds of decapitated seedlings a significantly higher activity was observed as late as 96 hours after the decapitation.

Cotylar Dominance in Pea and Flax Seedlings with Regard to Growth Regulators

The growth of axillary buds (cotylars) was followed on decapitated pea seedlings with intact and reduced cotyledons. It was found that the production of dry matter of cotylars per 1 g of dry matter of cotyledons increased with the reduction of the mass of cotyledons. BA and GA promoted while IAA and TIBA reduced this production. BA applied on a naturally inhibited cotylar of decapitated pea seedlings induced a correlative reversal: the inhibited cotylar became a dominating one and vice versa. If the original size difference between cotylars was 12 mm, the correlative reversal was observed in 75 % of cases. If flax seedlings were deprived of one cotyledon, primary root and hypocotyl base the hypocotyl stump on the side of the remaining cotyledon bended due to an intensive growth. The application of IAA paste on the stump of the removed cotyledon established very often a growth (i. e. bending) balance between the effects of cotyledons and IAA paste: No bending of the hypocotyl stump occurred. This phenomenon was most frequent after the application of 0.12 % IAA paste.

Effect of auxin on the elongation of lateral buds and 32P accumulation in 2-leaf decapitated pea seedlings

The effect of short and long term auxin treatments on the elongation of axillary buds and32P accumulation were studied in 2-leaf decapitated Alaska pea sailings. It was found that (1) auxin delayed the elongation of the lateral buds, (2) none of the auxin concentration applied completely inhibited the elongation of axillary buds, (3) auxin had no retarding effect on the growing buds, (4) strong polarization of 32P occurred in the parts above the treated leaf, when auxin was applied for a short period just after decapitation, (5) long term auxin treatments did not induce any such polarization of 32P to the parts above the treated leaf, (6) the root acted as an alternate accumulating organ for 32P when the apex was removed and the buds were inhibited, and (7) in decapitated plants the growing buds polarized 32P.

Gibberellin-cytokinin interaction in the correlation between the cotyledon and its axillary bud in pea (Pisum sativum L.)

If one cotyledon is removed from decapitated pea seedlings and the remaining one is treated with the cytokinin BA, then a complete correlation reversal occurs in numerous cases: instead of the bud belonging to the removed cotyledon, the bud belonging to the remaining cotyledon starts to grow. However, if GA is applied to the remaining cotyledon together with BA, then the number of these correlation reversals sharply drops. This in respect to cytokinin morphogenetically (correlatively) contradictory effect could play a significant role in apical dominance in plants.

Effect of Abscisic Acid and Other Plant Hormones on Growth of Apical and Lateral Buds of Seedlings

AbstractThe effect of abscisic acid (AbA) on the growth of lateral and apical buds was studied in seedlings of Pisum sativum and some other species. The hormone was applied in three different ways: 1) directly to the lateral bud on the second node of decapitated pea seedlings as 5 μI droplets in an ethanolic solution; 2) to the cut surface of decapitated seedlings: 3) to the apical bud of intact plants.AbA directly applied in amounts of 5 to 0.1 μg to the lateral bud of the second node of decapitated seedlings had a strong inhibitory effect on the bud. Application to the cut surface of seedlings decapitated about 5 mm above the second node resulted in slight inhibition of the lateral bud on the second node and in growth promotion of the bud on the first node. When AbA at 10 to 0.1 μg was applied to the apical bud of intact seedlings, the growth of this bud was inhibited but the lateral buds grew out.It is concluded that the release of the lateral buds from apícal dominance is the result of the inhibitory effect of AbA on growth of the apical bud and of low transport of AbA. This conclusion is supported by application of GA3 and IAA, individually and each combined with AbA.

Bacteriophages of Agrobacterium tunefaciens. 3. Effect of attenuation of virulence on lysogeny and phage production.

Two avirulent clones of Agrobacterium tumefaciens which appeared spontaneously during culture are indistinguishable from the parental strains from which they were derived with respect to either sensitivity to the bacteriophages tested or the production of phages during growth. One attenuated clone, isolated after treatment of the virulent B6 strain with proflavin is able to induce limited proliferations in infected tissues that do not progress into visible tumors. These proliferations do not respond to exogenous auxin. Tumors appearing in decapitated pea seedlings inoculated with the attenuated clone after infection by virulent bacteria are larger than those of seedlings inoculated only with virulent bacteria. When introduced into tissues before virulent bacteria, attenuated bacteria inhibit tumor formation. Like the parental strain, the attenuated clone is lysogenic for phages inducible by ultraviolet irradiation and also by conditions within host tissues.

On the interaction of growth retardants with IAA and kinetin

In the pea test a highly positive response to the treatment with IAA reversed to a negative one or became 5 to 6 times weaker when CCC was applied together with IAA. In cultivating pea seedlings, following their decapitation, for two days in a 0.25 per cent CCC solution and then in water, growth of their cotyledonous axillaries (cotylaries) were inhibited. This inhibitive action of CCC could be made ineffective when the seedlings, following two-days’ cultivation in the CCC solution, were grown further in kinetin solutions (0.37–3 mg per 1). Cotylaries of decapitated pea seedlings, when grown in kinetin solutions were inhibited. With kinetin solutions of 6–12 mg/l a strong inhibition also occured in the growth of roots at the apical parts of which spherical swellings were developing. The CCC supplied to the roots of intact etiolated pea seedlings is translocated acropetally into the stem at a rate of about 5 cm per hour. Decapitation of the plant causes retardation of this transport, yet a coat of 0.00001–1% IAA or kinetin paste produces acceleration of the stream. Existence of an antagonism between CCC and IAA, demonstrated earlier, was found holding true also for B-9 (N, N-dimethyl-aminesuccinamic acid) and IAA, as the inhibitive action of B-9, 0.06% solution on the growth of lettuce hypocotyls was reduced to a highly significant degree when the plants were supplied with B-9 together with IAA at a concentration of 10 mg/l.

The Role of 3-Methyleneoxindole in Auxin Action

A product of the enzymatic oxidation of indole-3-acetic acid, 3-methyleneoxindole, is at least 10-fold more effective than indole-3-acetic acid as a plant auxin as estimated by stimulation of elongation of excised pea and mung bean stem segments and by the stimulation of protein synthesis in the subapical regions of decapitated pea seedlings. An obligatory role for 3-methyleneoxindole in such auxin-stimulated responses is suggested by the following additional observations. 1. Chlorogenic acid, which blocks the enzymatic oxidation of indole-3-acetic acid to 3-methyleneoxindole in peas, antagonizes the stimulatory effect of indole-3-acetic acid on elongation and protein synthesis but does not interfere with the same stimulatory effects of 3-methyleneoxindole, the product of the blocked reaction. 2. 3-Methyleneoxindole reacts directly with sulfhydryl compounds; as expected, its growth-promoting activity is blocked by reduced, but not by oxidized, glutathione. Reduced glutathione also blocks the action of indole-3-acetic acid, which does not react directly with sulfhydryl compounds. 3. A synthetic auxin, 1-naphthaleneacetic acid, cannot be oxidized to 3-methyleneoxindole; however, it has another relationship to 3-methyleneoxindole metabolism as an inhibitor of the enzymatic reduction of 3-methyleneoxindole to 3-methyloxindole, an inert substance. Small amounts of 1-naphthaleneacetic acid, inactive alone, cause a considerable reduction in the amount of 3-methyleneoxindole required for optimal stimulation of growth. It is therefore suggested that 1-naphthaleneacetic acid might act by maintaining endogenous supplies of 3-methyleneoxindole at elevated intracellular levels through inhibition of 3-methyleneoxindole reductase. It is proposed that the stimulatory effects of 3-methyleneoxindole might result from its previously demonstrated ability to render a growth rate-limiting regulatory protein insensitive to its negative effector in a bacterial model system. The necessary specificity of action, both in terms of comparison to ordinary sulfhydryl reagents which do not have auxin activity and from the point of view of interaction with its cellular targets, may reside in its oxindolic structure and in the fact that it is a specific substrate for inactivating enzymes of plants, 3-methyleneoxindole reductases.

Crown gall: effect of temperature on tumorigenesis in pea seedlings

The development of crown gall tumors on decapitated pea seedlings grown in vitro is evaluated in terms of the mean weight of excised tumors. Reproducible quantitative results are obtained when mean weights of tumors are adjusted for the growth of lateral shoots. The regression line for tumor weight on the length of lateral shoots suggests that the growth of tumors and shoots is competitive. Optimal tumor formation occurs when seedlings are inoculated either immediately or within a few hours after decapitation of the seedlings. Wound healing after decapitation is not accompanied by the appearance of cells in stages of active division. Dividing cells are not observed in tissues below decapitation sites unless seedlings are inoculated with the crown gall bacterium. In darkness, large tumors develop within 2 weeks on inoculated seedlings kept at 24 °C. However, although normal growth continues, tumor formation is almost completely inhibited at 15 °C. When inoculated seedlings are held at 24 °C and 15 °C for alternate periods of varying duration, the adjusted tumor weight decreases as the duration of the period at the lower temperature increases. However, tumor size is not determined simply by the time interval during which plants are exposed to the inhibiting temperature, but also by the order of exposure to the two temperatures.

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.

Effect of the amputation of the cotyledon and of the application of growth regulators on the transport of32P in decapitated pea seedlings

When the epicotyl and one cotyledon is cut off from pea seedlings, only the axillary of the amputated cotyledon is known to grow. When32P is applied to the roots of such plants, then a higher radioactivity appears in the axillary of the amputated cotyledon already 24 hrs. after amputation of one cotyledon, although this axillary is of the same size at this time as that of the remaining cotyledon. This fact indicates a more extensive material transport to the axillary bud of the amputated cotyledon already during the first day after amputation The effect of individual regulators on the32P transport was investigated in an experiment where pea seedlings cultivated in the dark were decapitated and a 0.5% paste, containing the regulatory compounds was placed either on the cutting surface in the apical part of the epicotyl stump or in its central part. After a week the plant roots were supplied with32P and its transport to the upper part of the epicotyl stump was followed. This transport increased about 10-fold in the case of a paste, containing indolyl acetic acid, when the paste was spread on the apical cutting surface of the stump. However, the transport was inhibited when the paste was applied in the central part of the stump. These results indicate that only the transport of32P towards the paste with indolyl acetic acid is accelerated, whereas it is decelerated above this paste. A paste, containing triodobenzoic acid inhibited32P transport only when applied to the apical cutting surface of the epicotyl stump and not when spread over the middle part. In this case32P transport was more rapid above the paste than towards the paste. The situation was similar in the case of gibberellin and kinetin.

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