The influence of water stress on growth, ecophysiology and ornamental quality of potted Primula vulgaris ‘Heidy’ plants. New insights to increase water use efficiency in plant production.

Efficient irrigation practices are required to reduce the amount of water used. In this study, the effects of different irrigation regimes on changes in growth, ecophysiology and ornamental traits of potted Primula vulgaris ‘Heidy’ plants were investigated. Three experiments were carried out. In the first, the plants were either fully irrigated (100% of container capacity) or not. In the second, plants were watered to full irrigation (control), to 50% of the control (moderate water stress), to 25% of the control (severe water stress), or not irrigated and followed by a rehydration phase. Both experiments were conducted under controlled growth conditions. The third experiment was performed under common nursery conditions in an unheated and shaded greenhouse where plants were either irrigated with common irrigation practices (control), or with 66% of the control amount (moderate water stress), or with 33% of the control (severe water stress). In general, the percentage of senescent plants, the growth index, the number of leaves, and the aerial fresh and the dry weight were not affected by moderate water stress treatments. As expected, increasing water stress resulted in a general decrease in all studied gas exchange parameters. However, stressed plants were more efficient in using water than control plants, suggesting that stomata closed to cope with drought conditions without damaging photosynthesis events. The number of fully opened flowers during the growing season was highest in both control and moderately water stressed plants. In conclusion, moderate water stress could be imposed in Primula vulgaris ‘Heidy’ pot production to reduce the water consumption, still maintaining plant ecophysiological performances and ornamental quality.