Role of Ethylene in the Geotropic Response of Bermudagrass (Cynodon dactylon L. Pers.) Stolons

Abstract

We studied the relationship between ethylene and gravityinduced upward bending of bermudagrass (Cynodon dactylon L. Pers.) stolons. Ethylene production begins within 3 hours of the onset of gravistimulation, and increases thereafter until the 15th hour, after which it declines. There is a close positive relationship between ethylene production and upward bending during the first 12 hours of gravistimulation. Incubation of stolons with AgNO3 did not prevent ethylene evolution but delayed upward bending. In addition, ethylene production was 10-fold greater and peaked earlier in gravistimulated nodes incubated with 1-aminocyclopropane 1-carboxylic acid. The gravitational stimulation could be due to an increase in both 1-aminocyclopropane 1-carboxylic acid synthase and the ethylene forming enzyme. The results suggest that ethylene promotes the activity of indoleacetic acid.Bermudagrass (Cynodon dactylon L. Pers.) stolons normally grow horizontally when attached to the plant. However, their excision results in the reorientation of apical tissue growth from horizontal to vertical (12). Since the work of Neljubow on pea (discussed by Abeles [1]), it has been known that ethylene can alter the orientation ofstem growth from vertical to horizontal in pea and cotton (7) and conversely, from horizontal to vertical in strawberry clover (8) for 12 h in a vertical position to eliminate the effects ofwound ethylene (unpublished personal observations) and then were arranged horizontally on a framework, which consisted of a wooden base, above which two vertical wooden frames were tightly mounted. Sixteen holes were drilled into each frame, so that each flask could be placed horizontally and fit tightly. Curvature measurements of 32 stolons were made from photographs taken manually every 3 h during a 23 h time period.To minimize biological variability between stolons, values are given as the percentage of curvature with respect to the final curvature of each stolon: final curvature percentage (FCP) = observed curvature/final curvature X 100. This normalization allowed us to determine when differences in the rate of bending were significantly different. Ethylene MeasurementsGroups of 25 apical nodal segments of bermudagrass stolons were weighed, and then arranged in 7-mL, gas-tight vials containing washed vermiculite to provide moisture and support them in the proper orientation. Only the apical node of each stolon, including 5 mm of surrounding tissue, was used. The vials were kept upright and unsealed in humidified plastic boxes for 12 h at 20°C in the dark to allow dissipation of wound ethylene. Vials then were placed horizontally according to the treatment and subjected to gravistimulation for time periods of 3, 7,11,15,19, and 23 h. The flasks were sealed 3 h before assay for ethylene. All experiments were performed in darkness and at a room temperature of 28°C.A l-mL gas sample was withdrawn from each flask, and ethylene was assayed with a gas chromatograph equipped with a stainless steel column filled with Chromosor...

Comparative proteomic analysis provides new insights into the specialization of shoots and stolons in bermudagrass (Cynodon dactylon L.)

“…The ratio of red/far red light, can also finely regulate the differentiation of stolons and shoots through phytochrome-mediated photoassimilate partitioning [15, 16]. Phytohormones, including auxin, ethylene and gibberellin, synergistically adjust the morphology of bermudagrass by regulating the development and growth of stolons and shoots [13, 17]. These observations collectively imply that the plant architecture characteristics of bermudagrass could be modified by external factors.…”

Brassinolide interacts with auxin and ethylene in the root gravitropic response of maize (Zea mays)

“…Ethylene is also known to play an important role in the gravitropic response, in spite of the fact that there are opposing reports based on the relationship between the gravitropic response and ethylene production (Kaufman et al 1985, Harrison and Pickard 1986, Balatti and Willemoes 1989, Woltering 1991). It has been reported that ethylene is responsible for decreased starch levels in the columella cells, and thus, possibly results in inhibition of the gravitropic response of Arabidopsis roots (Guisinger and Kiss 1999).…”

Regulation of the Gravitorpic Response and Ethylene Biosynthesis in Gravistimulated Snapdragon Spikes by Calcium Chelators and Ethylene Inhibitors

“…However, the role of ethylene in gravitropism is still controversial, since inhibitors of ethylene synthesis or action were not always effective in inhibiting the gravitropic response of various systems (Wheeler and Salisbury, 1981;Clifford et al, 1983;Kaufman et al, 1985;Balatti and Willemoes, 1989;Woltering, 1991). Also, the role of the increased ethylene production obtained in various plant organs upon their reorientation from the vertical to the horizontal is still obscure (Wheeler et al, 1986;Harrison and Pickard, 1989;Woltering, 1991).…”