A Cuvette Design for Measurement of Ethylene Production and Carbon Dioxide Exchange by Intact Shoots under Controlled Environmental Conditions

Abstract

A cuvette is described for simultaneous measurement of ethylene production and CO2 fixation by intact shoots under controOed enviromental conditions. This design overcomes potential problems associated with closed systems conventionaUly used for studies on ethylene production, allowing accurate determination of rates of ethylene production in plants exposed to different environmental conditions. There has been considerable interest in recent years in studying the roles of ethylene in different stages of plant growth and development (1). Many plant responses can be elicited by very low concentrations of ethylene. Much progress has been made in development of techniques for ethylene analysis; it is now possible to determine a fraction of a nanoliter of ethylene with gas chromatography. Even smaller amounts of ethylene in air can be determined by collection of the ethylene on an adsorbent before gas chromatographic analysis (5,6).However, little work has been done to improve the experimental techniques for studies of ethylene evolution from plants. Most studies are done using closed systems (e.g. 7, 8, 11, 15 12,13,15). The tissue produces ethylene continuously and is exposed to constantly changing ethylene concentrations. Also, hydrocarbon contaminants are present in room air and in most commercially available gases, including compressed air and CO2. Thus, even in the few studies done using continuous flow systems, there has been inadequate control over hydrocarbons. We have recently reported (6) an efficient method for removing hydrocarbons from an air stream through the use of metal catalysts at high temperatures. In addition to the problem associated with contamination of the air stream, a cuvette recently described (5) does not provide for selective sealing of the shoot, adequate air circulation, and temperature control.To our knowledge, no hydrocarbon-free cuvette has been de- ' We wish to thank the National Research Council of Canada for Grant A-1451 to MSS in aid of this research.signed for accurate measurement of ethylene production from intact plant shoots. The cuvettes used for CO2 exchange studies invariably rely on rubber and plastics and hence are of little use for ethylene studies. Even in CO2 exchange studies, the variation in ethylene concentration could lead to erroneous conclusions. In this paper, we describe a cuvette that allows simultaneous measurement of CO2 exchange and ethylene production by intact shoots of plants under controlled environments.The cuvette (Fig. 1) We have tried "O" rings ofdifferent materials such as Neoprene, Viton, and natural rubber, but they were all found to contaminate the air stream with ethylene. For example, when a natural rubber gasket was used to seal the cuvette, it produced 4.74 nl/h ethylene when exposed to a balanced spectrum of light. The level of ethylene declined to 0.96 nl/h I h after the lights were switched off. Ethylene production completely subsided after 24 h, only to resume again when the lights were turned back on. Silicone rubber di...

Effect of Carbon Dioxide and Light on Ethylene Production in Intact Sunflower Plants

“…Numerous possible sources of error inherent in such techniques have already been pointed out (3,6). Further, with such systems it is not feasible to study the exact relationship between CO2 concentration and the rate of ethylene production on a temporal basis since the tissue is sealed for a considerable duration before sufficient amount of ethylene can accumulate to permit accurate analysis.Techniques have been developed in our laboratory that allow measurement of rate of ethylene production by the intact shoots of plants in a continuous flow system (3,6). Using these techniques, we have recently reported that an increase in the concentration of CO2 in the atmosphere surrounding the sunflower plants increased the rate of ethylene production (5).…”

“…The ethylene measurements were made by enclosing the plant in a specially designed glass cuvette (3), in a continuous flow system using hydrocarbon free air (6). The environmental parameters and the techniques used for purification of air, CO2 treatment and ethylene measurement were the same as described in our earlier papers (3,5,6). The air mixtures containing different concentrations of CO2 were also passed through the purification system before entering the cuvette.…”

Effects of Carbon Dioxide on Ethylene Production and Action in Intact Sunflower Plants

“…For each experiment, one 16-day-old plant (6-leaf stage) was sealed around the stem in a specially designed glass cuvette described earlier (3). After sealing the plant in the cuvette, the system was allowed to equilibrate overnight in an air stream to avoid any problems related to abnormal ethylene production from mechanical stimulation during sealing.…”

Ethylene Production by Attached Leaves or Intact Shoots of Tobacco Cultivars Differing in Their Speed of Yellowing during Curing

“…Although some workers propose that a rise in ethylene production triggers senescence in leaves (4,13,17,18) taut by clamping it between two bars of Plexiglas, and tightened with wing nuts. The space provided between the basal end of the leaf and center edge of the bag was carefully sealed with waterbased cellulose filler, Polyfilla (5), thus avoiding wounding of the leaf. In experiments using the glass cylinder the open end was likewise covered with 1-cm thick Teflon designed to fit in place with a Teflon 0 ring, and all spaces were sealed with Polyfilla.…”

“…uous flow system for detection of ethylene was developed in this laboratory (5,12), and it has been used with both intact shoots and excised segments of leaves or seedlings (7). It was found that intact shoots of sunflower, soybean and tomato seedlings in a flow-through open system produce less ethylene than the corresponding excised leaf segments in a closed system (7).…”