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New Mexico State University (2002)

Ethylene and drought tolerance in selected legumes

Berumen-Padilla, Salvador

Titre : Ethylene and drought tolerance in selected legumes

Auteur : Berumen-Padilla, Salvador

Université de soutenance : New Mexico State University

Grade : Doctor of Philosophy (PhD) 2002

Two legumes, Medicago sativa (cvs parents 9-FC-99, ZIA-81, and progenies MDB, 5-S-54), and Cassia corymbosa were studied to evaluate the effect of drought on ethylene production and its importance in drought tolerance. Alfalfa, sown in 19-L pots was subjected to irrigation (irrigating at 70% of available moisture) and non-irrigation (withholding water) under greenhouse conditions. Cassia corymbosa , planted in pots, was supplied with 100%, 75%, 50%, 25%, and 0% of daily water use under lath house conditions. Alfalfa produced ethylene as a stress response. When wounded, ethylene production increased about 4-fold. Also, when alfalfa samples were dehydrated, two peaks in ethylene production were observed that coincided at 10-20% and 70% of water loss. Only ZIA-81 produced higher levels of ethylene under irrigated conditions. A reduction of ethylene production in drought-stressed plants was attributed to rapid dehydration. When water content decreased, ACC increased. Both progenies produced higher levels of ACC under drought conditions. Growth rates decreased one day before the peak of ethylene was present for all cultivars and when osmotic potential became more negative and when leaf water potential was about -0.4 MPa. Wounding leaf samples of Cassia corymbosa increased ethylene production 3-fold. Time course of ethylene production of excised leaves showed a peak of ethylene production, being earlier for highest dehydration temperature. The peak occurred at 15 to 35% of fresh weight loss. When plants were subjected to different irrigation levels, drought-stressed plants produced no more ethylene than non-drought stressed plants. Low ethylene production was observed when dehydration was rapid. A peak in ethylene production between day 8 and 12, was related to senescence and abscission even though the level of the peak was no higher then the levels produced under non-drought stressed conditions. This response was associated with higher sensitivity to ethylene under drought conditions. Cassia corymbosa placed under limited light conditions (in greenhouse and growth chamber) were stressed. Different photoperiods were evaluated (24, 18 and 14-h), at a light intensity of 250 μmol m -2 s-1 . Growth was not affected by different photoperiods. However, 24-h photoperiod reduced chlorosis and senescence. Photoperiod was important in compensating for low light intensity and quality under growth chamber conditions. Light intensity and low light quality induced a stress in Cassia corymbosa but ethylene, ACC and MACC were not changed as a light-stress response.

Mots clés : Agronomy, Cassia corymbosa, Legumes, Ethylene, Drought, Biological sciences Medicago sativa


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