Uma abordagem neurofisiológica da acetilcolina em plantas de milho hidratadas e sob condições de estresse hídrico / A neurophysiological approach to acetylcholine in maize plants hydrated and under water stress conditions

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

18/04/2012

RESUMO

The occurrence of action potential and neurotransmitters, the major components of animal nervous system, in plants, bacteria and fungi, shows the universality of signaling principles and information transmission in the way of chemical and electrical signals in all organisms. These study topics, along with plant intelligence and vesicular-based auxin transport, constitute the major research lines of the newly created Plant Neurobiology. Among the neurotransmitters found in plants, the acetylcholine plays a role in phytochromecontrolled growth and development and in membrane ion permeability. In this context, it was suggested that acetylcholine can play an important role in the regulation of stomatal movements, having stimulatory effect in the stomatal opening. In addition it can play a role in root-to-shoot signaling process. Therefore, it was proposed to identify the presence of this neurotransmitter in maize plants hydrated and under water stress, with the aim of correlating the presence of acetylcholine with the stomatal responses of such plants. Moreover, another aim of the study was to evaluate physiological parameters like water potential, stomatal conductance, transpiration rate and net photosynthetic rate and their possible relationship with the acetylcholine in three leaves of hydrated and stressed plants. Therefore, an experiment was set up in randomized block design in 2x3 factorial. The factors were: water, in the levels of hydration and stress, and leaves age in the levels leaf 4 (older), leaf 5 (intermediary age) and leaf 7 (younger). The plants were divided in 20 blocks, and each one has had one hydrated plant and one stressed plant and the physiological analysis was made in three leaves. The plants were placed in B.O.D. growth chamber under controlled conditions of light and temperature. After the physiological analysis, the leaves were used to extraction and determination of acetylcholine. The dried and purified extracts were subjected to pyrolysis and gas chromatography and the substances identified by mass spectrometry. The acetylcholine was not detected in plants, although earlier studies have had demonstrated its occurrence in maize leaves and seeds. Hypotheses were elaborated to explain such fact. Regarding the physiological variables, water stress reduced the plants transpiration rate in 59%, stomatal conductance in 65% and net photosynthesis in 59%. Stomatal conductance, transpiration and photosynthesis were strongly related. On the other hand, the water potential showed weak correlation with that variable. As for the age factor, leaves 7 had higher photosynthetic rates, conductance and transpiration than the leaves 4 and 5.

ASSUNTO(S)

milho neurofisiologia vegetal neurotransmissores neurotransmitters plant neurophysiology stomata water balance balanço hídrico corn cromatografia gasosa estômatos gas cromatography

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