An Effect of Water Stress on Ethylene Production by Intact Cotton Petioles

Abstract

The concept that ethylene is an endogenous growth regulator has evolved in the past few years (16). This concept has been strengthened by recent findings that internal concentrations of endogenous ethylene in vegetative tissues reach physiologically active levels (3,12,13). These internal concentrations have been directly related to the corresponding production rates of excised tissues (13), although parallel data on production rates of intact plant tissues are not available. Using excised abscission zones from primary bean leaves, Jackson and Osborne (9) presented evidence that the timing of abscission of explant petioles can be related to the extent of ethylene production adjacent to the separation zone. They suggest that the ethylene production is coupled to a particular stage of senescence. Further, they proposed that in natural leaf abscission ethylene initiates the biochemical sequences leading to separation, but the mechanism is not clear. Beyer and Morgan (4) have recently shown that ethylene production by and internal levels in detached cotton cotyledons increases as auxin transport declines. Amounts of exogenous ethylene necessary to induce abscission and inhibit auxin transport were similar. They propose that the rise in ethylene production and decline in auxin transport capacity are causally related and that reduced auxin transport is one of the ethylene mediated actions which precede induction of hydrolytic enzymes in the separation layer. Their measurement of ethylene involved whole cotyledons and was not restricted to the petiole. McAfee and Morgan (13) found internal ethylene levels and production rates were several times higher in petioles than leaf blades. Since auxin must be translocated through the petiole to the abscission zone, this observation strengthens the proposed role of ethylene in auxin transport inhibition preceding cotton leaf abscission (4). Alternatively, high rates of ethylene production by petiole tissue near the abscission zone may directly trigger the biochemical changes preceding separation independent from the proposed effect on auxin supply to the abscission zone.Aside from abscission related to senescence, little attention has been directed to other problems of natural abscission, particularly those involving environmental stresses. Plant water deficits may induce both leaf and boll abscission from cotton under field conditions (5, 6, 18). In most instances, actual separation follows relief from the deficit and rehydration of the abscission zone. This communication describes the effect of a brief period of water deficit on ethylene production by intact cotton petioles. MATERIALS AND METHODSCotton plants (Gossypium hirsutum L. var TM-1) used in this study were grown in pots containing sand in a greenhouse and were between 75 and 90 days of age. Each pot contained two plants of equal size, each with 15 to 17 leaves on the main stem. The use of paired plants made possible the determination of leaf water potential on one plant, while ethylene production was measured on the ...

Does Water Deficit Stress Promote Ethylene Synthesis by Intact Plants?

“…The earliest, widely cited study reporting evidence that plant water deficits promote ethylene production was that of McMichael et al (25) in which two-piece glass chambers were employed to enclose a portion of mature leaf petioles. Ethylene levels in the chambers were assayed after 2 to 4 h collection periods for 36 h, and chambers were flushed after each assay.…”

“…The data indicate that detached leaves react differently to rapid drying than intact plants react to drying of the soil with regard to ethylene production. This result suggests the need for additional attention to ethylene as a complicating factor in experiments employing excised plant parts and the need to verify the relevance of shock stresses in model systems.interest because the ethylene could be responsible for senescence and abscission induced by water deficits (13,25,26).Although the promotion of ethylene synthesis by water deficits appears firmly established, there are a number of concerns. First, to have a convenient experimental system, water deficits have often been imposed rapidly by drying detached leaves or fruits (3-6, 16, 18, 24, 31).…”

“…interest because the ethylene could be responsible for senescence and abscission induced by water deficits (13,25,26).…”

Differential regulation of the tomato ETR gene family throughout plant development

“…During the next 6 days, imposition of water stress led to the detachment of the remaining cotyledon and varying levels of senescence in the first four primary leaves, as assessed visually by chlorophyll degradation. The stimulation of ethylene production in both leaves and petioles subjected to water deficit stress is well established (Apelbaum and Yang, 1983;Ben-Yehoshua and Aloni, 1974;Hoffman et al, 1983;McMichael et al, 1972). Thus, total RNA isolated from each leaf and its associated petiole was subjected to RNase protection analysis using LeETR RNA hybridization probes in order to establish the impact of stress-accelerated senescence on the accumulation of LeETR mRNA transcripts (Figure 4).…”

The Effects of Figaron and Water Deficit on Seed Yield of Two Soybean Cultivars

“…Several investigators have reported that any kind of water stress in soybean tends to accelerate abscission of reproductive organs resulting in decreased yield (Kato, 1964;Doss et al, 1974;Ashley and Ethridge, 1978;Korte et al, 1983). Water deficiency also changes the status of internal hormonal balance in the plant (Mcmichael et al, 1972;Guinn, 1976;Guinn and Brummett, 1988;Guinn et al, 1990). It enhances the rate of ethylene production (Guinn, 1976), increases abscisic acid (ABA) content in young cotton bolls and decreases the free indole-3-acetic acid (IAA) content (Guinn, 1982;Brummett, 1987 and1988).…”