Emanation of water from underground plant parts

Abstract

A device was designed which used gypsum and electrical conductivity as a means of detecting and quantitizing the amount of water emanating from underground plant parts under natural conditions. Use of this device with the Common French Bean demonstrated that considerable amounts of moisture emanated from the underground part of the stem. The amount of water emanated was found to be influenced by environmental conditions, differences in soil type and degree of soil compaction. When plants were grown in an environment of approximately 100 per cent relative air humidity and at a temperature of 28 to 30°C, 115 to 125 µl of water emanated from an 11 mm length of stem in a 24-hour period, in contrast to 70 to 80 µl of water emanating from plants grown at 50 to 60 per cent relative air humidity and at a temperature of 18 to 20°C. Water emanation was more rapid in a compacted soil than loose soil and also appeared to be dependent on the amount of sand in a soil. Whereas 115 to 125 µl of water emanated in a silt loam soil, only 35 to 45 µl emanated in a loamy sand soil and less than 10 µl in washed sea sand during a 24-hour period. The sensitivity of the conductivity unit to changes in moisture and the utility of its design enables its employment under varied environmental conditions and offers a technique for plant pathologists to study the effect of both the below- and aboveground environments on moisture emanation from underground plant parts and the resultant effect on the associated microflora.