Apical dominance in the rhizome of Agropyron repens: the influence of nitrogen and humidity on the translocation of 14C-labelled assimilates

1979 ◽  
Vol 57 (11) ◽  
pp. 1229-1235 ◽  
Author(s):  
F. A. Qureshi ◽  
G. I. McIntyre
Keyword(s):  
Protein Synthesis ◽  
Apical Dominance ◽  
Nitrogen Supply ◽  
Limiting Factor ◽  
High Humidity ◽  
Bud Size ◽  
Apical Node ◽  
Bud Growth ◽  
Stimulation Of ◽  
Agropyron Repens

When the buds on the rhizome of Agropyron repens were released from apical dominance either by increasing the nitrogen supply or by raising the humidity around the rhizome, their uptake of 14C-labelled assimilates from the parent shoot was significantly increased. While this effect was produced by each treatment when applied separately, the uptake of 14C by the buds was more than twice as great when both treatments were combined. The 14C level in the rhizome was also increased, this effect being greater and more consistent in response to the change in humidity than to the increased nitrogen supply. In the controls, uptake of the labelled assimilates was greatest by the bud at the apical node and decreased basipetally along the rhizome. This pattern was not correlated with bud size and probably resulted from a basipetal gradient of declining metabolic activity. Increasing the humidity around the rhizome altered this pattern, preferentially promoting the uptake of the label by the bud at the subapical node. To account for the stimulation of bud growth by high humidity when nitrogen was apparently the limiting factor, it is postulated that the increase in water potential of the bud may accelerate protein synthesis, thereby enhancing the bud's capacity to compete for the limiting nitrogen supply.

Influence of Nitrogen and Humidity on Rhizome Bud Growth and Glyphosate Translocation in Quackgrass (Agropyron repens)

Weed Science ◽  
1982 ◽  
Vol 30 (6) ◽  
pp. 655-660 ◽  
Author(s):  
Gordon I. McIntyre ◽  
Andrew I. Hsiao
Keyword(s):  
Apical Dominance ◽  
Growth Response ◽  
Dry Weight ◽  
Nitrogen Supply ◽  
Weight Basis ◽  
High Humidity ◽  
Apical Node ◽  
Bud Growth ◽  
Rhizome Bud ◽  
Agropyron Repens

When buds on the rhizome of quackgrass [Agropyron repens(L.) Beauv.] were released from apical dominance either by increasing the nitrogen supply to the parent shoot (from 5.25 to 210 ppm) or by raising the humidity around the rhizome (from 55 to 100%), the growth response of the buds was closely correlated with their uptake of foliar-applied14C-labeled glyphosate [N-(phosphonomethyl] glycine]. The14C level in the buds, expressed on a dry-weight basis, was greatest in the youngest, most rapidly growing bud at the apical node and decreased in successively older buds along the rhizome. A similar gradient was shown by the14C content of the associated rhizome nodes. The high-humidity treatment also increased the total amount of14C that was translocated into the rhizome, whereas increasing the nitrogen supply, while promoting14C uptake by the buds, markedly reduced the amount in the rhizome nodes and in other parts of the plant. This nitrogen-induced reduction in translocation was associated with a reduction of about 30% in uptake of the herbicide by the treated leaves.

Studies on the growth and development of Agropyron repens: interacting effects of humidity, calcium, and nitrogen on growth of the rhizome apex and lateral buds

1987 ◽  
Vol 65 (7) ◽  
pp. 1427-1432 ◽  
Author(s):  
Gordon I. McIntyre
Keyword(s):  
Apical Dominance ◽  
Water Status ◽  
Dry Weight ◽  
Apical Growth ◽  
High Humidity ◽  
N Supply ◽  
Lateral Buds ◽  
Low Humidity ◽  
Bud Growth ◽  
Agropyron Repens

A previous investigation of apical dominance in the rhizome of Agropyron repens showed that keeping the rhizome in a high humidity promoted the outgrowth of the lateral buds but strongly inhibited the growth of the rhizome apex. A study of these related responses demonstrated that the inhibition of apical growth was not prevented by excision of the lateral buds and was also induced when only the apex of the rhizome received the high humidity treatment. The necrotic lesions that developed in the arrested apices and the reduction of apical inhibition produced by various Ca treatments indicated that the inhibition of apical growth was caused by Ca deficiency. When the rhizome apex was exposed to low humidity, a localized high-humidity treatment of the lateral buds did not release the buds from apical dominance in low-N rhizomes but strongly promoted bud growth at a higher N level. When growth of the buds was induced at low humidity by increasing the N supply, the increase in bud weight was preceded by an increase in the water content of the bud when expressed on a dry weight basis. These results agree with those of previous investigations and suggest that the interacting effects of N and humidity on the water status of the buds may play a significant role in the mechanism of apical dominance.

Apical dominance in the rhizome of Agropyron repens: the influence of humidity and light on the regenerative growth of isolated rhizomes

1981 ◽  
Vol 59 (4) ◽  
pp. 549-555 ◽  
Author(s):  
Gordon I. McIntyre
Keyword(s):  
Relative Humidity ◽  
Water Potential ◽  
Apical Dominance ◽  
Shoot Growth ◽  
Causal Factors ◽  
Regenerative Growth ◽  
N Concentration ◽  
Apical Node ◽  
Bud Growth ◽  
Agropyron Repens

The influence of humidity and light on the regenerative growth of isolated five-node segments from rhizomes of Agropyron repens was investigated under controlled conditions. When the rhizomes were incubated in the dark at 20 ± 1 °C shoot growth at the apical node was significantly reduced by each 0.5% reduction in relative humidity between 100 and 98.5% and at 98.0% growth at all nodes was completely inhibited. The restriction of these effects to the apical end of the rhizome (nodes 1 and 2) was attributed to their interaction with the basipetal gradient of decreasing N concentration previously identified as one of the causal factors in the polarity of bud activity. Bud inhibition at a relative humidity of 98% was eliminated by supplying water through the basal end of the rhizome. This treatment also released the buds from the inhibition induced by the exposure of the rhizomes to light. Since the uptake of water by the rhizomes was also greater in the light than in the dark it was postulated that the light-induced inhibition of bud growth was due to a reduction in rhizome water potential mediated by an increase in the rate of transpiration.

Environmental control of apical dominance in Phaseolus vulgaris

1973 ◽  
Vol 51 (2) ◽  
pp. 293-299 ◽  
Author(s):  
Gordon I. McIntyre
Keyword(s):  
Water Stress ◽  
Phaseolus Vulgaris ◽  
Light Intensity ◽  
Nitrogen Content ◽  
Apical Dominance ◽  
Growth Response ◽  
Environmental Control ◽  
Nitrogen Supply ◽  
Soluble Nitrogen ◽  
Bud Growth

When seedlings of Phaseolus vulgaris were grown under controlled conditions at a light intensity of 3200 ft-c, 60% relative humidity, and at nitrogen levels of 5.25, 52.5, and 210 ppm, growth of the buds at the cotyledonary node, which served as a measure of apical dominance, showed a positive correlation with the nitrogen supply and with the soluble nitrogen content of the hypocotyl. Increasing the nitrogen supply to 420 ppm caused a proportionate increase in soluble nitrogen content but no additional bud growth response. That the growth response was limited by water supply was shown by growing plants at 420 ppm nitrogen and relative humidities of 30, 60, and 90%. Each reduction in water stress, as measured by leaf relative turgidity, caused a highly significant increase in growth of the cotyledonary buds. Under high nitrogen, low water stress conditions, bud growth was markedly inhibited by reduction of the light intensity from 3200 to 700 ft-c.These results support the concept of nutrient competition as a major factor in the mechanism of apical dominance and also suggest that conflicting reports on the effect of externally applied growth-regulating substances on lateral bud inhibition may be due partly to environmentally induced differences in nutritional status of the experimental plants.

Studies on bud development in the rhizome of Agropyron repens. II. The effect of the nitrogen supply

1972 ◽  
Vol 50 (3) ◽  
pp. 393-401 ◽  
Author(s):  
Gordon I. McIntyre
Keyword(s):  
Dry Weight ◽  
Nitrogen Supply ◽  
Parent Plant ◽  
Bud Development ◽  
Apical Buds ◽  
Rooting Medium ◽  
Correlative Inhibition ◽  
Bud Growth ◽  
Low Nitrogen ◽  
Agropyron Repens

Bud growth on isolated rhizomes of Agropyron repens showed a basipetal gradient of decreasing activity and was strongly inhibited at the basal nodes. This evident polarity was correlated with a gradient of decreasing nitrogen content at successively older nodes and with an apparent translocation of nitrogen from the basal to the apical nodes. Isolating the buds from one another reduced growth of the apical buds and prolonged the growth of buds at the basal nodes so that the polarity of bud growth, although still apparent, was much reduced.Supplying nitrogen as NH4NO3 through the cut end of rhizomes still attached to the parent plant caused apical buds to develop as shoots instead of rhizomes. Increasing the nitrogen supply to the rooting medium extended this response to buds at older nodes, restricting rhizome production to basal buds whose growth was inhibited in low nitrogen rhizomes.Buds developing as shoots had a considerably higher total nitrogen and moisture content and a lower dry weight than buds developing as rhizomes.The results emphasized the importance of the nitrogen supply not only in determining the polarity of bud growth and the degree of correlative inhibition, but also as a morphogenetic factor controlling bud development.

Apical dominance in the rhizome of Agropyron repens: the influence of water stress on bud activity

1976 ◽  
Vol 54 (23) ◽  
pp. 2747-2754 ◽  
Author(s):  
Gordon I. McIntyre
Keyword(s):  
Water Stress ◽  
Water Content ◽  
Apical Dominance ◽  
High Humidity ◽  
Apparent Increase ◽  
N Level ◽  
Lateral Buds ◽  
Influence Of Water ◽  
N Requirement ◽  
Agropyron Repens

Experiments conducted under both field and growth-chamber conditions showed that buds on the rhizome of Agropyron repens L. Beauv. could be released from inhibition by a localized reduction of water stress, e.g. by enclosing the rhizomes in moist vermiculite. This response was obtained even at low N levels, a fact which may be due partly to the relatively low N requirement of buds developing as rhizomes as compared with those developing as shoots. The induced growth of the lateral buds was correlated with a reduction or complete inhibition of apical growth of the parent rhizome or with its transition from rhizome to shoot development. Continuous root removal reduced the bud response to high humidity in N-deficient plants but had relatively little effect at a higher N level. In water-stressed rhizomes the apparent increase of bud inhibition with distance from the apex, a characteristic feature of apical dominance, was correlated with the water content of the rhizome, which was greatest at the apex and decreased basipetally. It is postulated that this gradient of decreasing rhizome water content may be causally related to the increasing inhibition of bud activity.

Apical dominance in the rhizome of Agropyron repens. The relation of amino acid composition to bud activity

1977 ◽  
Vol 55 (14) ◽  
pp. 2001-2010 ◽  
Author(s):  
S. N. Nigam ◽  
Gordon I. McIntyre
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Content ◽  
Limiting Factor ◽  
N Supply ◽  
Lateral Buds ◽  
Bud Growth ◽  
High Concentrations ◽  
Rhizome Buds ◽  
Agropyron Repens

The polarity of bud growth in isolated, decapitated rhizomes of Agropyron repens L. Beauv. was correlated with the amino acid content of the buds and rhizome nodes and with the external N supply. In rhizomes from low-N plants grown under controlled conditions, the levels of asparagine and glutamine decreased markedly from the apical to the basal nodes and this gradient was closely correlated with a basipetal reduction in the growth of the rhizome buds. All other amino acids included in the analysis also showed a basipetal gradient of decreasing concentration but they were present in much lower concentrations than the amides and their correlation with bud growth was less precise. In high-N rhizomes collected in the field, the amino acid gradient was considerably reduced and the relatively uniform distribution of amide-N along the rhizome was correlated with a similar uniformity in growth of the rhizome buds.Increasing the N supply to intact plants released the lateral buds from inhibition. A significant growth response occurred within 48 h and was associated with a 30% increase in the amide-N content of the rhizome. Sprouting of buds on isolated nodes resulted, within 48 h, in a 42% reduction in the amide concentration in the node, as compared with nodes from which the bud had been removed and in which considerable amide accumulation occurred. Significant reductions in proline, serine, and alanine were also recorded.It was concluded that, under N-deficient, low water stress conditions, the inhibition and polarity of bud growth is mainly determined by the N supply, whereas, the relatively high concentrations of amino acids found in the fully inhibited buds of field rhizomes suggested, in accordance with previous results, that water rather than N was more likely to be the limiting factor under field conditions.

scholarly journals Genetics of Apical Dominance in Plantain (Musa spp., AAB Group) and Improvement of Suckering Behavior

1994 ◽  
Vol 119 (5) ◽  
pp. 1050-1053 ◽  
Author(s):  
Rodomiro Ortiz ◽  
Dirk R. Vuylsteke
Keyword(s):  
Apical Dominance ◽  
Recurrent Selection ◽  
Recessive Gene ◽  
Limiting Factor ◽  
Incomplete Penetrance ◽  
Vegetative Development ◽  
Ratoon Crop ◽  
Terminal Bud ◽  
Lateral Bud ◽  
Bud Growth

Apical dominance, i.e., the inhibition of lateral bud growth due to growth substances released by the terminal bud, has been considered as a limiting factor for the perennial productivity of plantains (Musa spp., AAB group). Segregation ratios in F1 and F2 plantain-banana hybrids suggest that inheritance of apical dominance is controlled by a major recessive gene, ad. The dominant Ad allele improved the suckering of plantain-banana hybrids, as measured by the height of the tallest sucker at flowering and harvest. At harvest, the ratoon crop of the diploid and tetraploid hybrids had completed 70% to 100% of its vegetative development, whereas the ratoon of the plantain parents, due to high apical dominance, was only at 50% of total pseudostem growth. Sucker growth rates are generally the result of gibberellic acid (GA3) levels, and it is suggested that the Ad gene regulates GA3 production. However, the Ad gene has incomplete penetrance, genetic specificity, and variable expressivity. Increased frequency of the Ad gene and a commensurate improvement in the suckering behavior of the diploid populations may be achieved by phenotypic recurrent selection.

EFFECT OF ACTINOMYCIN D ON TSH-INDUCED STIMULATION OF THYROIDAL PROTEIN SYNTHESIS IN THE RAT

1974 ◽  
Vol 77 (1) ◽  
pp. 64-70 ◽  
Author(s):  
Gustav Wägar
Keyword(s):  
Protein Synthesis ◽  
Actinomycin D ◽  
The Other ◽  
Leucine Incorporation ◽  
Short Term ◽  
Other Hand ◽  
Thyroid Glands ◽  
Translational Level ◽  
Stimulation Of

ABSTRACT Whether the short-term regulation of thyroidal protein synthesis by TSH occurs at the transcriptional or the translational level was tested by measuring the effect of actinomycin D (act D) on the TSH-induced stimulation of L-14C-leucine incorporation into the thyroidal proteins of rats. TSH was injected 6 h before the rats were killed. The thyroid glands were then removed and incubated in vitro in the presence of L-14C-leucine for 2 h. The pronounced stimulation of leucine incorporation in the TSH-treated animals was depressed as compared with controls but still significant even when the animals had been pre-treated with 100 μg act D 24 and 7 h before sacrifice. On the other hand, act D strongly decreased incorporation of 3H-uridine into RNA. Short-term regulation of thyroidal protein synthesis by TSH appears to be partly but not wholly dependent on neosynthesis of RNA. Hence regulation may partly occur at the translation level of protein synthesis.

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