Ethylene Stimulation Research Articles

Exogenous Polyamines Stimulate Ethylene Synthesis by Soybean Leaf Tissues

Exogenous supply of spermine (Spm) markedly stimulated ethylene evolution from intact soybean leaves of leaf discs, strongly increased the level of free 1-aminocyclopropane-1-carboxylic acid (ACC), and slightly stimulated ethylene forming-enzyme (EFE) activity Spm treatment also resulted in leaf epinasty and accelerated leaf senescence Ethylene stimulation was depressed, but not abolished, by light, and was suppressed by inhibitors of ACC synthase and EFE activity Spermidine had a less pronounced stimulatory effect on ethylene production whereas the diamines putrescine and diaminopropane were without effect These results contrast with other reports indicating that di- and polyamines inhibit ethylene biosynthesis in plants, and extend our previous results on detached tobacco leaves exogenously treated with polyamines

Prevention of salt-induced epinasty by ?-aminooxyacetic acid and cobalt

Ethylene production in leaf petiole and laminae tissues was stimulated in tomato (Lycopersicon esculentum Mill. cv. UCT5) plants exposed to salinity-stress. At the highest salinity level (250 mM NaCl), rates of ethylene production more than doubled over those observed in non-stressed plants. Correspondingly, petiolar epinasty increased with increasing levels of stress impositions. Both responses were suppressed when either 1 mM α-aminooxyacetic acid (AOA), or 100 μM Co2+ was simultaneously applied. Co2+, but not AOA, had a pronounced effect on ethylene production resulting from the application of a saturating dose (2 mM) of 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene. This result suggests that ethylene production is dependent upon the activity of ethylene forming enzyme (EFE). The magnitude of ethylene stimulation in leaf petioles was related to the salinity level imposed and to the induction of petiole epinasty. In the absence of stress impositions, epinastic responsiveness to ethylene or its precursor, ACC, might provide a simple, indirect criteria to adjudge salt-sensitivity among plants.

The Ultrastructural and Biochemical Changes Associated With Dormancy Breaking in Ricinodendron rautanenii Schinz. Seeds Following Ethylene Treatment

Summary Imbibition initiated digestion of both lipid and protein reserves in the manketti nut, although the embryo remained dormant. Dormancy was overcome by treatment with ethylene or ethrel whereupon the testa burst and the radicle emerged. Ultrastructural studies on the embryonic axis revealed that ethylene stimulation brought about changes in the nucleus and the pattern of protein digestion. The levels of proteins, lipids, sugars and starch were also monitored biochemically and it appeared that lipid was channelled into carbohydrates to support embryonic growth. Protein digestion took place at a slower rate than lipid digestion. The mobilization of reserves was more rapid in the embryonic axis than in the endosperm and cotyledons and all were accelerated by ethylene and ethrel treatments.

Cell specificity in auxin- and ethylene-induced ?supergrowth? in Riella helicophylla

In gemmalings of Riella helicophylla, auxin and ethylene stimulate elongation growth, especially of pillar cells. When the two hormones are supplied simultaneously, the effects are additive, i.e. the result is 'supergrowth'. In the cells of the meristem, elongation is enhanced by auxin, but not by ethylene when given alone. However, these cells also respond with 'supergrowth' to a combined treatment with auxin and ethylene. The antiauxin p-chlorophenoxyisobutyric acid suppresses both the ethylene stimulation of cell growth and the additive 'supergrowth'. The results support the concept that auxin pre-conditions the cells to the ethylene-dependent growth event. We suggest that the response elicited by the specific cell types could be related to differences in their level of endogenous auxin.

A review of the role of ethylene in biochemical control of ripening in tomato fruit

The possible ways in which ethylene controls cell wall degradation and colour change are compared with the control of the respiratory rate of ripening tomato fruit. It would appear that the biosynthesis of ethylene is intimately involved with the former change but control of the latter change is much more complex and could be less ethylene dependent than previously thought. Increases in the respiratory rate may either involve extra-mitochondrial decarboxylation and the cyanide-insensitive part of the electron transport chain or direct stimulation of dark respiration and the cyanide-sensitive electron transport. Although ethylene cannot be shown to influence the individual biochemical steps which would lead to increased respiration there appears to be ethylene stimulation of overall gas exchange. Existing data on the two separate systems of ethylene metabolism seem to rule out the OX (CO2 formation) pathway as the source of the “climacteric” carbon dioxide. Either the OX or the TI (tissue incorporation) systems of ethylene metabolism are candidates for the “switch on” of transcription and translation of genes involved in cell-wall hydrolysis. Considerable opportunities exist for clarification of the role of bioregulators in gas exchange in ripening tomato fruit.

A model for the mechanism of stimulation of latex flow in Hevea brasiliensis by ethylene

A model is proposed for ethylene stimulation of latex flow from tapping cuts of Hevea brasiliensis, based on the predicted effects of ethylene on the plasticity and structure of cell walls of the latex vessels. Evidence for the model comes from the effects of ethylene on etiolated shoots of Pisum sativum.

The relationship between ethylene and the synthesis of RNA and protein in ripening apples

The stimulation by ethylene of the respiration of whole fruits and peel discs prepared from them is followed using Worcester Pearmain and Cox's Orange Pippin apples. RNA and protein synthesis in relation to ethylene stimulation is investigated in terms of incorporation of 14C-uridine and 14C-valine into RNA and protein fractions in the discs of peel. Application of ethylene (40–60 ppm) to the preclimacteric fruit induces increased ethylene production in the fruit; uridine incorporation into RNA rises to a peak followed by a peak in valine incorporation into protein, while a malate decarboxylating system develops in the ripening fruit.

Kinetics of Abscission in the Bean Petiole Explant

The progress of bean petiole abscission has been followed using quantitative measurements of the mechanical force required to break explants at the separation zone. It is found that the shortest time for a measurable effect of ethylene (1 ppm) in stimulating the development of frangibility is about 1 hr. Removal of the ethylene is followed by a return to the endogenous rate of weakening, the slower rate being established in 1 hr. Application of the inhibitor cycloheximide leads to a cessation of abscission development within one-half hr. As in the stimulations of certain plant processes with auxins, gibberellins, and cytokinins. ethylene stimulation of abscission requires the continuous presence of the regulator.

Abscission: The Role of RNA Synthesis

Ethylene stimulated the incorporation of (32)P into RNA in the abscission zone of bean explants (Phaseolus vulgaris L. var. Red Kidney). The enhancement was observed in all fractions separated by methylated albumin kieselguhr column chromatography, although the magnitude of the increase was not the same for each fraction. Differential extraction of the nucleic acids indicated that the ethylene stimulation was confined to the fraction extracted with sodium lauryl sulfate, with the increase mainly in Fraction III (Ribosomal RNA) and Fraction IV (Messenger RNA). Actinomycin D, which blocks ethylene-stimulated abscission, inhibited (32)P incorporation into all column fractions. 5-Fluorouracil, which blocked 50% of the ethylene-enhanced (32)P incorporation, did not inhibit ethylene-enhanced abscission. The results indicate that ethylene may regulate abscission through control of specific RNA's.