CONSEQUENCES OF WATER-STRESS APPLIED AT DIFFERENT GROWTH-STAGES IN THE PRODUCTION OF PEPPER PLANTS

The effects of water stress occurring at various periods during the growth cycle of peppers was studied in greenhouse-grown plants under stable climatic conditions (table II). The method used to provoke water stress was the Robelin method, which consists of applying an identical dryness coefficient (ratio of plant transpiration during drying-out phase to maximum transpiration of the same well-irrigated plants) for a certain time period and during a certain vegetative phase. This method was applied to 4 phenological stages: vegetative growth, early flowering, early fruit setting, and fruit formation (table I, fig 1). A theoretical analysis of the dryness coefficient shows that climatic conditions (temperature, wind speed and leaf surface a elements affecting the intensity of the water stress provoked when this coefficient is applied for short time periods (h, d). Under the present experimental conditions (stable climatic conditions, dryness coefficient applied every 10 d) and using direct measurements of plant water status, the authors note that water stress is of comparable intensity during Phenological stages with high leaf surfaces (flowering, early fruit setting, and fruit formation stages) and that, on the other hand, water stress intensity is markedly reduced when leaf surface is low (fig 2). These observations are the basis for certain suggestions aiming at a better adaptation of the Robelin method to research objectives. An evaluation of the sensitivity of phenological stages submitted to identical water stress was obtained by comparing (fig 3, table IV) 4 yield components analyzed on a plant scale (bulk and dry weight, fruit size and number) to those of a well-irrigated plant (table III). The sensitivity is greater at the early fruit setting stage than at the flowering or fruit formation stages. These observations could have an effect on methods for care and irrigation of peppers.