Influence of paclobutrazol on water consumption and plant performance of Arbutus unedo seedlings

The purpose of this study was to examine the effect of paclobutrazol on the water consumption, plant water relations, gas exchange and development of strawberry tree seedlings (Arbutus unedo L.), to evaluate water resource management. Seedlings (8 cm in height) were subjected to a single drench of 60 or 100 mg of paclobutrazol and pot-grown in a greenhouse for 4 months. Untreated plants acted as control. Paclobutrazol reduced the development and improved the water status of the seedlings. At the end of the experimental period, it was seen that the two doses studied had reduced the plant dry weight, plant height and foliar development compared with the untreated plants. Paclobutrazol significantly reduced water consumption by 10% (60 mg) and 20% (100 mg) compared with the control. Plants treated with 100 mg showed the highest leaf water potential values at predawn. Paclobutrazol-treated plants presented turgor potential at values midday higher than control. This retardant stimulated a more efficient stomatal regulation, permitted an improved water status; however, it altered photosynthesis, reducing the plant growth. The lowered water consumption in paclobutrazol-treated plants was the result of a combination of mechanisms which reduced water loss through transpiration.