Plant responses to environmental changes are associated with electrical excitability and signaling; automatic and continuous measurements of electrical potential differences (DeltaEP) between plant tissues can be effectively used to study information transport mechanisms and physiological responses that result from external stimuli on plants. The generation and conduction of electrochemical impulses within plant different tissues and organs, resulting from abiotic and biotic changes in environmental conditions is reported. In this work, electrical potential differences are monitored continuously using Ag/AgCl microelectrodes, inserted 5 mm deep into sapwood at two positions in the trunks of several Avocado trees. Electrodes are referenced to a non polarisable Ag/AgCl microelectrode installed 20 cm deep in the soil. Systematic patterns of DeltaEP during absolute darkness, day-night cycles and different conditions of soil water availability are discussed as alternative tools to assess early plant stress conditions.
A review on agricultural effects of restricted soil drainage conditions is presented, related to soil physical, chemical and biological properties, soil water availability to crops and its effects on crop development and yield, soil salinization hazards, and the differences on drainage design main objectives in soils under tropical and semi-arid water regime conditions. The extent and relative importance of restricted drainage conditions in Agriculture, due to poor irrigation management is discussed, and comprehensive studies for efficient drainage design and operation required are outlined, as related to data gathering, revision and analysis about geology, soil science, topography, wells, underground water dynamics under field conditions, the amount, intensity and frequency of precipitations, superficial flow over the area to be drained, climatic characteristics, irrigation management and the phenology of crop productive development stages. These studies enable determining areas affected by drainage restrictions, as well as defining the optimal drainage net design and performance, in order to sustain soil conditions suitable to crops development.
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