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University of São Paulo USP (2014)

Variação da pressão de turgor de plantas de milho em condições de déficit hídrico

Riboldi, Lucas Baiochi

Titre : Variação da pressão de turgor de plantas de milho em condições de déficit hídrico

Turgor pressure variation among maize plants under water deficit condition

Auteur : Riboldi, Lucas Baiochi

Université de soutenance : University of São Paulo USP - Escola Superior de Agricultura Luiz de Queiroz

Grade : Maîtrise 2014

Résumé
Maize is a relatively tolerant plant water stress, especially in their early stages of growth. Plants subjected to water deficit have reduced growth by decreased photosynthetic rate and the availability of water in their tissues. The monitoring of water potential is important as an indicator of water stress, but the few methods for determining it .are not amenable to automation and for being destructive nature ; the results are not always consistent with the actual conditions. With the new leaf patch clamp pressure probe developed by Zimmermann et al (2008) for the determination of leaf turgor, one can assess the water status of the plant and in some cases up to indicate the ideal time for irrigation. It is highly sensitive, versatile, non-destructive, easy to handle, with immediate results and available online. Thus the aim of this study was to determine if the maize plants subjected to drought cycles, had the ability to recover from water deficit, in addition to testing the effectiveness of this new method for monitoring stress. Plants were grown in pots in a greenhouse, where the leaf status was monitored through the leaf water potential, stomata conductance, leaf turgor pressure and photosynthesis. Plant growth (height, leaf area and dry mass) was continuously evaluated. Measures initiated one and half month after sowing and plants were monitored for about 30 days, by using the variable Pp (resulting pressure) given by de probe. Two treatments were imposed, one where the plant was kept irrigated and another where irrigation was suspended were established. As the days passed, the plants showed the first visual signs of stress, such as curling leaves. During this period we observed a fluctuation in the values of Pp throughout the day signaling loss of turgor, but with a recovery at night. There were significant differences between treatments for stomata conductance, water potential, photosynthesis and Pp over the days. After each irrigation, noticed a rapid recovery in all parameters analyzed. Thus, we concluded that maize plants were able to recover quickly from the water deficit, with a full recovery in just one day for all cycles analyzed. The turgor probe was able to display and monitor the water status of the plant, but in the last ten days of deficit it was not signaling an evident turgor loss as demonstrated by other indicators, as leaf curling, low leaf water potential, CO2 assimilation and stomata conductance. So, more studies are required to explain the probe response under these circumstances.

Mots clés : Zea mays Déficit hídrico Sonda magnética de turgor Zea mays Magnetic turgor probe Water deficit

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