Involvement of Ethylene in Phytochrome-mediated Carotenoid Synthesis

Ethylene production was induced in sections of dark-grown Sorghum vulgare L. seedlings by treatment with light in the blue and far red regions of the light spectrum. The action spectrum closely resembled the previously reported spectra for high irradiance response; thus, light-induced ethylene production is probably a high irradiance response with phytochrome as the initial photoreceptor.Ethylene production in plant tissue may be regulated by light. Two modes of regulation are frequently encountered.In one, ethylene production is decreased by light exposure and is associated with low irradiance, short induction time, and the fully reversible phytochrome system. In the second, ethylene production is increased after light exposure and appears not to be mediated through the low irradiance, reversible phytochrome receptor.Ethylene production measured by Goeschl et al. (7) in etiolated pea seedlings decreased after exposure to red light. Far red irradiation immediately following the red light treatment reversed the effect of red light and gave ethylene production identical with that produced by far red alone. Red light has also been shown to reduce the rate of ethylene production in bean hooks (12) and rice coleoptiles (10).An increase in the rate of ethylene production following light exposure has been observed in lettuce seeds (2), cranberries (4), sorghum seedlings (5), rose tissue cultures (14), and oat seedlings (15). In each case, light approximately doubled the rate of ethylene production. However, the particular wavelengths of light that are active in inducing ethylene production by plant tissue are unknown. Earlier work (2) has shown that light-induced ethylene production in lettuce seeds was not caused by red or far red light. The purpose of these experiments was to determine the effectiveness of selected wavelengths of light for inducing ethylene production in plant tissue.MATERIALS AND METHODS Tissue sections from 4-day-old seedlings of Sorghum vulgare L. cv. E55 and E57 were used. The seedlings were grown in the dark on agar in 125-ml Erlenmeyer flasks at 28 + 1 C as previously described (5 measurements of ethylene production, 10-mm sections were cut just proximal to the first node from the seedling tissue under a green safelight (fluorescent lamp with acrylic and cellophane filters) (3) that produced no detectable effect on ethylene production even after extended, continuous exposure.After cutting, the sections were left on moist paper for 4 hr for dissipation of wound ethylene. The sections of tissue were then mixed, and a random selection of 10 sections for each sample was sealed with a rubber vaccine cap in a 20-ml vaccine bottle containing 2 ml of sterile 1.5% agar along one side.Irradiation treatments were done in an interference filter monochromator system modified for 1 500-w incandescent sources after Withrow (16) and utilizing Baird Atomic and Bausch and Lomb blocked interference filters with maximum half band width of ± 15 nm. The action spectrum was done in two sections (345-450 nm an...

Section: Resultssupporting

confidence: 66%

Light-induced Ethylene Production in Sorghum

Craker¹,

Abeles²,

Shropshire³

1973

“…It has recently been reported that light inhibits ethylene production in segments of green oat leaves but not in etiolated leaves (7). The experiments dealing with the effect of monochromatic light on plant tissues suggest an inhibitory effect of red light as compared to darkness on the rate of ethylene production (8,11,12,18). However, Janes et al (10) found no effect of red light on the rate of ethylene production in the intact lettuce seedlings.…”

Section: Discussionmentioning

confidence: 89%

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

Bassi¹,

Spencer²

1982

High CO2 concentration (0.5%) increased the rate of ethylene production, measured in a continuous flow system, in intact sunflower (Helianthus auwus L.) plants. However, the rate of ethylene production subsided to near control levels after approximately 24 hours. The effect of high CO2 could only be observed in light. Although high CO2 concentration had no effect on the rate of ethylene production in darkness, prolonged exposure (approximately 16 hours) of plants to high CO2 in the dark prevented the increase in ethylene production when the plants were exposed to light and high C02.The interactions between CO2 and ethylene are of interest both for their role in the basic understanding of ethylene action in plants and for their use in preservation of produce, flowers, and fruits, etc. Little work has been done to study the effect of CO2 on the rate of ethylene production in plants. Aharoni and Lieberman (2) have reported recently that CO2 stimulates the ethylene production of tobacco leaf discs senescing in the dark. In an earlier report by Imaseki et al. (9), it was shown that the removal of CO2 from the atmosphere surrounding sweet potato tuber sections infected by black rot fungus decreased the rate of ethylene production. CO2 has been reported either to inhibit (15,20) or to have no effect (4) on ethylene production in ripening fruit but the results are difficult to interpret because of the possible effects of ethylene on its own production in these tissues (13).In most of the above cases, the experiments were done with excised plant parts sealed in closed systems. 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 change in rate of ethylene production was evident within the first few minutes of the carbon dioxide treatment. All the experiments reported in that paper were done in continuous light.The present study was undertaken to further explore the rela-'Financial assistance from the Natural Sciences and Engineering Re- MATERIALS AND METHODS The seedlings of sunflower (Helianthus annus L.) were started in trays containing vermiculite, in a constantly lit controlled environment growth chamber. The temperature in the growth chamber was maintained at 27 ± 1°C and the RH at 75%. After 7 d, the seedlings were transplanted to individual pots containing sand:vermiculite:peat moss (1:1:1).A 2-week-old plant ...

“…Therefore, it is of interest to ask whether inhibition of ethylene production might be responsible for the red light-induced enhancement of phototropic curvature in the pea seedling. If a response induced by red light is indeed mediated by inhibition of ethylene production, it can be mimicked by placing the responsive plant or tissue under hypobaric conditions where diffusive escape of ethylene is greatly enhanced (8,9,11,12). Phototropic behavior of the etiolated pea seedling is not affected by hypobaric treatment (data not shown), suggesting that changes in endogenous ethylene are not involved in red light enhanced-phototropic curvature in clear distinction from the mechanism of red light enhancement of geotropism (9).…”

Section: Resultsmentioning

confidence: 96%

“…Yet the mechanism by which red light enhances phototropic curvature development in etiolated pea seedlings is distinct from that by which it promotes geotropism (9) and other photomorphogenic processes where ethylene plays a regulatory role (8,9,11,12). This conclusion is based on the facts that (a) the time course for the red light action on blue light-induced phototropism (Table I) does not parallel that on geotropism and ethylene production (9); (b) hypobaric treatment does not affect phototropism whereas it does other ethylene-related photomorphogenic responses including geotropism (8,9,11,12); (c) ethylene inhibits gravity-induced downward migration of auxin (5), but has no effect on photoinduced lateral auxin movement (Table III). In geotropism, ethylene was suggested to act on a process intervening between the perception of gravity and the lateral movement of auxin (13), and thus has no direct action on the lateral auxin transport system itself either for geotropism or phototropism.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Red Light Enhancement of the Phototropic Response of Etiolated Pea Stems

Kang¹,

Burg²

1974

Self Cite

In the subapical third internode of 7-day-old etiolated pea seedlings, the magnitude of phototropic curvature in response to continuous unilateral blue illumination is increased when seedlings are pre-exposed to brief red light. The effect of red light on blue light-induced phototropism becomes manifest maximally 4 or more hours after red illumination, and closely parallels the promotive action of red light on the elongation of the subapical cells. Ethylene inhibits phototropic curvature by an inhibitory action on cell elongation without affecting the lateral transport of auxin. Pretreatment of seedlings with gibberellic acid causes increased phototropic curvature, but experiments using "C-gibberellic acid indicate that gibberellic acid itself is not laterally transported under phototropic stimuli.