ISHS Acta Horticulturae 664: IV International Symposium on Irrigation of Horticultural Crops
RESPONSE OF STEM DIAMETER TO WATER STRESS IN GREENHOUSE-GROWN VEGETABLE CROPS |
| Authors: | M. Gallardo, R.B. Thompson, L.C. Valdez, C. Pérez |
| Keywords: | linear variable displacement transducers, LVDT, irrigation scheduling, plant sensors, water deficit |
| Abstract:
The ability of stem diameter measurements to detect water stress in mature vegetable crops, grown in greenhouses, was evaluated in tomato and melon grown in soil. Water stress was applied by withholding irrigation, for 9 days in tomato, and for 10 days in melon. In both crops, there were well-irrigated control plants. The treatments were applied when the tomato crop was at late fruit filling stage, and the melon crop at fruit maturity. In tomato, parameters derived from continuous measurements of stem diameter (SD) were compared with discrete measurements of rates of net photosynthesis and stomatal conductance. In melon, the SD-derived indices were compared with midday measurements of leaf and stem water potentials. In both tomato and melon, withholding irrigation had a clear effect on the SD-derived indices. In un-watered plants compared to control plants, the daily maximum (MXSD) and daily minimum (MNSD) stem diameter values decreased, and the maximum daily contraction (MDC) increased. These differences were maintained until irrigation was resumed. Of the three SD indices, the trend in MNSD appeared to be the most sensitive indicator of plant water stress in both tomato and melon. MDC was the second most sensitive indicator. Measurements of net photosynthesis and stomatal conductance did not detect water stress in tomato. In melon, stem and leaf water potential detected plant water deficit as early as SD-derived indices; however, the relative magnitude of the response to water stress was much smaller than for the SD-derived indices. This study demonstrated in greenhouse-grown tomato and melon that indices derived from SD measurement are sensitive indicators of water stress, in mature fruit-bearing plants. | |
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