Ethylene evolution and ammonium accumulation by tomato plants under water and salinity stresses. Part II

Abstract

Foliar wilting, epinasty, abscission, chlorosis, and necrosis are common symptoms in plants affected by water and salinity stresses. Ethylene evolution and ammonium accumulation frequently accompany the expression of the symptoms of stresses from various origins. These symptoms and physiological phenomena have been associated with other environmental stresses, such as ammonium toxicity. Intact and excised tomato plants (Lycopersicon esculentum Mill. ‘Heinz 1350’ and neglecta‐1) were subjected to stresses of waterlogging, water‐deficit, or saline conditions (NaCl or CaCl₂). In soil culture in the greenhouse, tomato plants subjected to waterlogging developed epinasty and chlorosis and had increased ethylene evolution and ammonium accumulation. The application of aminooxyacetic acid (AOA) ameliorated the symptoms and reduced ethylene evolution and ammonium accumulation. Tomato subjected to drought developed chlorosis and had enhanced ammonium accumulation, but no increased ethylene evolution was observed. The chlorotic and necrotic symptoms were observed for plants receiving NaCl or CaCl₂. Application of ammonium nutrition or water stress aggravated the development of toxic symptoms. Ammonium accumulation and ethylene evolution were enhanced with intact plants or excised seedlings under these stresses. Application of AOA through stems of excised seedlings suppressed the enhancement. ‘Heinz 1350’ receiving CaCl₂ accumulated more Ca⁺⁺ and had higher ethylene evolution than those receiving NaCl or the neglecta‐1 receiving CaCl₂. Neglecta‐1 accumulated more Na⁺ with the NaCl treatment and had higher ethylene evolution than ‘Heinz 1350’. The results indicate that environmental stresses stimulate ammonium accumulation and initiate ethylene evolution, which may function in development of stress induced symptoms.

Notes

Present address: Department of Soil Science, North Carolina State University, Raleigh, NC 27695–7619.