Abstract
Comparative methods for measuring water potential in leaves and tubers of potatoes (Solarium tuberosum L., var. Russet Burbank) are described.
For leaves drier than -3 bars, the pressure chamber gave estimates of water potential which were zero to three bars drier than potentials measured using thermocouple psychrometers. Pressure chamber readings ranged ±2.5 bars from psychrometer value for leaves wetter than -3 bars; the psychrometer measurement usually was drier than the pressure chamber when leaves were sampled in the evening.
With tubers, water potential measurements usingin situ psychrometers and the pressure chamber agreed to within one bar,except in tubers drier than -7 bars, where there were discrepancies of± 2.5 bars. However, if the interval between psychrometer insertion and water potential measurement were longer than 24 hours, serious errors arose in the psychrometer measurements, apparently from suberization of tissues surrounding the psychrometers which prevented vapor equilibrium.
Pressure chamber measurements of tubers also were compared with tuber water potentials determined from the weight changes of tuber samples immersed in graded sucrose osmotica. For tubers wetter than -5 bars, the osmotica method gave drier estimates than the pressure chamber; for tubers drier than -5 bars the reverse occurred. Causes for these discrepancies are discussed.
Resumen
Se describen métodos comparativos para medir potenciales de agua en hojas y tubérculos de papa (Solanum tuberosum L., var. Russet Burbank).
Para hojas contenidos de humedad menores que -3 bars, la cámara de presión dió estimados de potenciales de agua que estuvieron entre cero y tres bars por debajo de los potenciales medidos usando psicómetros de termocupla. Las lecturas de la cámara de presión se desviaron± 2.5 bars de los valores del psicómetro para hojas más húmedas que -3 bars; las medidas del psicómetro dió contenidos de humedad más bajos que la cámara de presión cuando las muestras de hojas se tomaron al anochecer.
En tubérculos, las demidas del potencial de agua usando psicómetros en situ y la cámara de presión concordaron dentro del limite de 1 bar, excepto en tubérculos con humedad menor que -7 bars, donde hubieron discrepancias de ± 2.5 bars.
Sin embargo, si el intervalo entre la inserción del psicómetro y la medida del potencial de agua fue mayor de 24 horas, serios errores surgieron en las medidas del psicómetro, aparentemente debido a la suberización de tejidos alrededor del psicómetro, impidiendo así al equilibrio del vapor.
Las medidas de la cámara de presión para tubérculos también se cómpararon con potenciales de agua determinados por el cambio de peso de las muestras de tubérculos sumergidos en soluciones osmóticas de sucrosa. Para tubérculos con contenidos de humedad mayores que -5 bars, el mético dio estimados de humedad más bajos que la cámara de presión; lo opuesto ocurrió en tubérculos menos húmedos que -5 bars. Se discuten las causas de estas discrepancias.
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Contribution from the Department of Soil Science, University of Wisconsin. Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison, Wisconsin, 53706, and by USDA Hatch funds.
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Gandar, P.W., Tanner, C.B. Comparison of methods for measuring leaf and tuber water potentials in potatoes. American Potato Journal 52, 387–397 (1975). https://doi.org/10.1007/BF02852793
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DOI: https://doi.org/10.1007/BF02852793