Excision Effects on Leaf Water Potential of Five Herbaceous Species
1976
Baughn, J. W. | Tanner, C. B.
Dewpoint hygrometers were used to compare the in situ water potential of a leaf with the potential of a tissue piece excised from the same leaf and measured either by a hygrometer or psychrometer. Excised tissue potential was found to average 1.0 to 3.0 bars lower (drier), depending on species and water potential range, than the in situ potential for potato (Solanum tuberosum L.), sunflower (Helianthus annuus L.), pepper (Capsicum annuum L.), and soybean (Glycine max L.). With oat (Avena sativa L.) the potential increased after the tissue was excised. Internal tissue changes following excision contributed significantly to the potential changes in oat and soybean. Internal changes could not be separated from tissue drying for the other three species. Loss of tissue water during sample preparation and confinement in sample holder was superimposed on the internal shifts; drying losses appeared greatest for the psychrometer, on the average. All our data were obtained on glasshouse-grown plants, so there is no immediate extrapolation of our data to field-grown plants, nor to other species. It is clear, however, that water potential methods requiring excised tissue are liable to incur significant errors from the excision, especially in the wet range where such errors can be relatively large.
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