Dendometria

Response of Stem Diameter to Water Stress in Greenhouse-Grown Vegetable Crops

M. Gallardo1, R.B. Thompson1, L.C. Valdés1 and C. PérezM.D. Fernández2

1 Dpto. De Producción Vegetal 2Cajamar, E.E. Las Palmerillas

Universidad de Almería Apdo. 250
04120, Almería, Spain 04080 Almería, Spain

Keywords: linear variable displacement transducers, LVDT, irrigation scheduling, plantsensorss, water deficit

Abstract

In this study we evaluate Tthe ability suitability of stem diameter measurements to detect water stress in mature vegetable crops, grown in under greenhouses, was evaluated in tomato and melon grown in soil in a plastic greenhouse conditions. These two species study was care amongst onducted in both, a tomato and a melon crops which are the most commonlygrown crops in the large greenhouse-based vegetable production industry located along representative of major crops in tthe Spanish Mediterranean coast. Tomato is generally grown from autumn to spring, and melon from a winter crop and melon is grown in sspring to -summer. Water stress was The water deficit was applied by withholding irrigation, for during a 9 days in tomato, and for 11 days inmelon. In both crops, there were well-irrigated control while control plants were well-irrigated (field capacity??). WWhen tThe he drying treatments were applied, when the tomato crop plants in both crops was at late were adults in the fruit filling stage, and the melon crop crop at stage (tomato) and fruit maturity. in melon??. In tomato, stem diameter (SD) -dderived parameters derived frombased oin continuous measurements of stem diameter (SD) SD were compared with discrete measurements of rates of net photosynthesis and stomatal conductance. In melon, the SD-derived indicesparameters were compared with midday measurements of leaf and stem water potentials. In both tomato and melon, withholding irrigation had a clear effect oin the the SD-derived indicesparameters. In un-wateredplants cCompared to control plants, tThe daily maximum (MXSD) and daily minimum (MNSD) stem diameter values decreased, and the maximum daily contraction (MDC) increased in in un-watered plants and the MDC increased compared to that of “well-watered” plants. These differences were maintained until the day when irrigation was resumed. The day a, when fter resuming irrigation, the three SD parameterswere very similar in the plants which had been subjected to water deficit and “un-watered” plants the control plants. Of thereached values very similar to that of the “well-watered” plants. T three SD indices, the trends in MNSD appeared to be the most sensitive indicator of plant water stress in both tomato and MXSD in melon. ; MDC was the second most sensitive indicator. which give a measurementof cumulative growth were the indices more severely affected by water deficit followed by MDC. Measurements of net photosynthesis and stomatal conductance did not were unable to detect water stress in tomato. Stem and leaf water potential were able to detected plant water deficit as early ier as the SD-derived indicesparameters; however, the relative magnitude of the response to water stress wasmuch smaller than for the SD-derived indices. s ratio between un-watered plants and controls plants appeared to be was considerablye higher lower that for the SD-derived indices. This study demonstrated concluded that in greenhouse-grown tomato and melon crops SD measurementsthat inindices derived from SD measurement are appear to be sensitive indicators of water stress, in mature fruit-bearingplants. allows stress detection being the growth related indices the most sensitive.

INTRODUCTION

The Mediterranean coast of Spain is the location of a large and expanding greenhouse-based vegetable production system. Being an In aarid region,s the adoption of improved irrigation scheduling practices will contribute to the more efficient use of scarce water resources, and also to...