Some Effects of Ethylene on the Metabolism of Plants

Although essentially all plant parts and especially thin sections derived from them have been observed to leach solute upon immersion in water (17), fruits have attracted particular attention because of the concept that an increased permeability of the tonoplast may accompany or be a prerequisite of fruit ripening (3,19,27). Previously it was shown (9) that exposure to water causes sections of apple tissue to lose solute and water, decrease in their ability to produce ethylene, and undergo an extensive browning reaction. The changes in water content, ethylene production, and polypenolase activity were prevented by inclusion of a high concentration of various organic or inorganic materials in the soaking media, and the present communication demonstrates that solute leakage also is restricted by this condition. In fact, leakage probably is the indirect cause of many of these effects, and it occurs to a significant extent and in a closely similar manner not only in several fruits, but also in other plant tissues. Materials and MethodsBananas (var. Gros Michel) were donated by the Banana Supply Co. of Miami, who obtained the fruit from southern Ecuador, and apples (post climacteric), potatoes and pears were purchased in local markets. Peas (var. Alaska) were dark grown in moist vermiculite at 230 for 8 days, at which time 10 cm subapical sections were cut under dim red illumination (> 580 ,).Assay of reducing sugar was by the NelsonSomogyi method (23) methanol, had to be clarified with neutral lead acetate and deleaded with dibasic sodium phosphate before they could be analyzed for sugar content. Respiration rates were determined with contant pressure respirometers (35), except that a \Varburg manometer was used for pea sections and a Grubb-Parsons Infra Red Gas Analyzer for whole fruits and for rapid measurements with apple slices. Ethylene was assayed by means of gas chromatography as previously described (8).In a typical experiment, 1-cm diameter plugs were cut from a fruit or potato with a cork borer and sliced with a razor to yield disks approximately 1 mm thick. These were blotted twice on absorbent towel, and equivalent lots were weighed and floated for 60 minutes on 25 ml of solution contained in a petri dish. The tissue was then blotted and reweighed, and the reducing sugar content of the solution assayed. The total reducing sugar content of the untreated tissue was determined on a duplicate samiiple of sections. ResultsExperiments with McIntoshl Apples. In figure 1 the 2 major curves illustrate the rates at which reducing sugar is lost from apple slices suspended respectively in water and concentrated glycerol solution.

Section: Discussionmentioning

confidence: 99%

Relationship of Solute Leakage to Solution Tonicity in Fruits and Other Plant Tissues

Burg

Burg²,

Marks³

1964

“…Epinastic movement of petioles is the result of greater expansion of adaxial cells as compared to abaxial cells in specific regions of the petiole (10,17). In the tomato, both auxin and ethylene will induce petiole epinasty (9,11,13), with auxin action being dependent upon induction ' (23,24). The primary physiological lesion in this mutant is a marked insensitivity to exogenous auxin with respect to ethylene synthesis and hypocotyl elongation (12,25 Stem sections with attached petioles were excised from the third, fourth, and fifth nodes above the cotyledonary node 6 weeks after sowing.…”

mentioning

confidence: 99%

Auxin and Ethylene Regulation of Petiole Epinasty in Two Developmental Mutants of Tomato, diageotropica and Epinastic

Ursin¹,

Bradford²

1989

The epinastic growth responses of petioles to auxin and ethylene were quantified in two developmental mutants of tomato (Lycoperskon esculentum Mill.). In the wild type parent line, cultivar VFN8, the epinastic response of excised petiole sections was approximately log-linear between 0.1 and 100 micromolar indole-3-acetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) concentrations, with a greater response to 2,4-D at any concentration. When ethylene synthesis was inhibited by aminoethoxyvinylglycine (AVG), epinasty was no longer induced by auxin, but could be restored by the addition of ethylene gas. In the auxin-insensitive mutant, diageotropica (dgt), no epinastic response to IAA was observed at IAA concentrations that effectively induced epinasty in VFN8. In the absence of added IAA, epinastic growth of dgt petioles in 1.3 microliters per liter exogenous ethylene gas was more than double that of VFN8 petioles. IAA had little additional effect in dgt, but promoted epinasty in VFN8. These results confirm that tomato petiole cells respond directly to ethylene and make it unlikely that the differential growth responsible for epinasty results from lateral auxin redistribution. The second mutant, Epinastic (Epi), exhibits constitutively epinasty, cortical swelling, and root branching symptomatic of possible aitemation in auxin or ethylene regulation of growth. Only minor quantitative differences were observed between the epinastic responses to auxin and ethylene of VFN8 and Epi. However, in contrast to VFN8, when ethylene synthesis or action was inhibited in Epi, auxin still induced 40 to 50% of the epinastic response observed in the absence of inhibitors. This indicates that the target cells for epinastic growth in Epi are qualitatively different from those of VFN8, having gained the ability to grow differentially in response to auxin alone. The dgt and Epi mutants provide useful systems in which to study the genetic determination of target cell specificity for hormone action.

“…and 1000 p.p.m. causes the simple soluble substances of plants to increase at the expense of the higher soluble and insoluble forms (13,14,15,16). Ethylene, 1 p.p.m.…”

Section: Discussionmentioning

confidence: 99%

Morphological and Physiological Responses of Carnation and Tomato to Organic Phosphorus Insecticides and Inorganic Soil Phosphorus

Hall¹

1951

During the last few years considerable attention has been focused upon the use of the organic phosphorus compounds hexaethyl tetraphosphate and tetraethyl pyrophosphate as the active components of certain commercial insecticides. These substances are known to be toxic not only to insects but to other organisms in general as well. As the names of hexaethyl tetraphosphate and tetraethyl pyrophosphate are generally abbreviated HETP and TEPP, respectively, they will be referred to as such in this paper. HALL and JACOBSEN (11) concluded that HETP does not possess a definite structure by demonstrating that it is essentially a mixture of esters containing ethyl metaphosphate, triethyl orthophosphate, and tetraethyl pyrophosphate. These workers believe that the biological potency of the so-called HETP is actually due to the TEPP that it contains, although in a later publication, HALL (10) implied that HETP contains other toxic principles in addition to TEPP.These compounds become of interest to the plant scientist through the formative effects that they elicit in particular sensitive species and this paper reports some of the fundamental effects that these compounds, or their degradation products, have on plant metabolism. The formative effects produced in plants by these compounds so strikingly resemble, in most cases, those of the hormone-type phytocides that a number of workers have attributed the symptoms to 2,4-D contamination of either the insecticides or spray equipment. Carefully controlled experiments have demonstrated, however, that these characteristic symptoms can be initiated consistently by HETP and TEPP in carnation, tomato, and sunflower. This has been the case generally when slightly higher concentrations than recommended for insect control were employed. Other reports (24,26, 27,34) have appeared confirming this result for the same and other species. SMITH et al. (26, 27) have noted that tomatoes, roses, chrysanthemums and carnations are susceptible to HETP and TEPP and they cite many grower reports of formative effects appearing in greenhouse ornamentals treated with these compounds. ZIMMERMAN and HARTZELL (34) have noted that epinasty was produced in more than 20 species when exposed to HETP and TEPP. The report of MCILRATH (24), as well as many Texas grower reports of 2,4-D-