The PlantScreen™ may be programmed to deliver both water and nutrients to the plants throughout growth and/or measurement cycles. Watering and nutrient delivery may be combined with automated weighing of plants in pots so that specific watering regimes may be programmed in software. These regimes may be used to impose drought stress or water logging of varying degrees of severity, imposed rapidly or gradually.
When plants, such as Arabidopsis seedlings, are screened in trays, up to five plants may be watered and weighed individually and at the same time. Special pots and trays are provided with the PlantScreen™ to facilitate this process. For larger plants the conveyor system may be modified easily and rapidly to accommodate single pots. Larger pots are watered and weighed one at a time. Water may be supplied by gravity from a tank, or the PlantScreen™ may be configured to deliver both water and nutrients from a nutrient supply system. An option also exists for nutrient analysis. The nutrient supply system may be used to deliver specific nutrient mixtures to groups of plants so that responses to nutrient deficiencies may be monitored. The system may also be used in investigations of ecotoxicology, by providing plants with accurately defined levels of heavy metals, organic contaminants, herbicides etc.
Warering and Weighing (W&W) stations may be used for weighing and watering of individual pots, or for multiple pots in trays, depending on the system used. Several stations may be located on the same conveyor line, as required. Water or nutrient solutions may be added to pots in aliquots ranging from 2 mL to 500 mL. Liquid application is gentle, without spillage or splashing of soil, and is adjustable for the different pot sizes.
Homogenous watering for equal root growth is ensured by irrigation from multiple sides.
Irrigation is controlled via feedback based on the initial and required weight of the pot, the amount of water added being determined via a programmable protocol. The W&W system includes relative and absolute watering modes that allow the user to supply water in a fixed volume or to reach a percentage of initial pot weight. If the soil is very dry, and the difference between the actual and set value is too large, watering can be applied in cycles with pauses.
The W&W system conducts automatic calibration of the zero point before measurements, and recalibration is done using a special holder with a known mass. The recalibration process is automatic. The user is only required to load the holder and choose the calibration process in the supervising program. After the calibration process, new constants are saved and are ready to be used. All components of the W&W station have at least IP 66 protection. The station has protection against splashing water, soil and dust. The W&W station for large pots has a maximum load capacity of 10Kg with an accuracy of +/5 g, a repeatability error of 0.01% and a total error of +/- 0.017%. The W&W station for small pots in trays weighs and waters 5 pots simultaneously. It has a maximum load capacity of 500g with an accuracy of +/0.2 g, a repeatability error of 0.01% and a total error of +/- 0.017%.