Monday, November 5, 2007 - 4:15 PM
70-6

Physiological Responses to Plant Growth Regulators Related to Ethylene Metabolism in Maize Crops Grown Under Abiotic Stress.

Maria Otegui, Avda. San Martin 4453 (C1417DSE), Fac. of Agronomy UBA-CONICET, Buenos Aires, Argentina

Ethylene is one of the main five plant hormones. It is linked, among other aspects, to the response of plants to many biotic and abiotic stresses. Consequently, different synthetic plant growth regulators (PGRs) have been developed that affect ethylene-mediated processes, like ethephon and 1-MCP. The former promotes ethylene synthesis, and is used in extensive crops for reducing plant height. The latter blocks ethylene receptors, and is currently used in fruit storage for delaying over ripening. In this presentation I will analyze the physiological responses of maize (Zea mays, L.) crops subjected to different abiotic stresses (light, N or heat stress) and to the application of PGRs. Field experiments were conducted at the Pergamino station (33º 56’S) of the National Institute of Agricultural Technology (INTA) in Argentina. One set of experiments was performed during 2005-2006 and 2006-2007, and included single-cross hybrids of contrasting tolerance to high stand density (i.e. light stress) exposed to contrasting [stand density x N] levels and treated with 1-MCP. A second experiment was conducted during 2006-2007, and included a factorial combination of (i) two air temperature regimes (control with no heating or a heat stress of ca. 10 d duration immediately before anthesis) and (ii) application of two plant growth regulators (ethephon or 1-MCP). Measurements performed in experiments included: plant growth rate around flowering, flowering dynamics, leaf senescence dynamics during grain filling, SPAD, light interception, photosynthesis, grain yield and grain yield components (kernel number and kernel weight). Collectively, PGRs helped mitigate the negative effects of stress.

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