Supporting regulatory approval of plant protection products through efficient testing of aquatic plant species

Blog by Hanna Armbruster, ibacon Group Leader, Aquatic Ecotoxicology

ibacon has considerable expertise in carrying out studies on higher aquatic plant species. We have an experienced team of study directors and technicians and our laboratories house the very latest, state-of-the-art equipment. We carry out analytical dose verification in water and sediment and our tests can be performed static, semi-static or in pulsed designs. Tailor-made designs are also welcome. High quality cultures for each plant species result in excellent plant material for testing.

We are proud to report high levels of customer satisfaction with our experienced team – not just for the advice they give, but also for the plant material and consistent results.

At ibacon we use three species of aquatic plants for different regulatory aspects: Lemna gibba, Myriophyllum spicatum and Glyceria maxima.

Lemna gibba, or Duckweed as it is more commonly known, is used for testing of herbicides and plant growth regulators or where a plant protection product shows herbicidal effects on terrestrial plant species.

ibacon has performed more than 600 GLP studies on Lemna gibba according to OECD 221.  Pulse designs are also performed from time to time as well as recovery studies. Because Lemna gibba is a monocot species, testing of an additional dicot species such as Myriophyllum spicatum is also required for Auxin inhibitors or herbicides effecting dicot species, or when effects on dicot species in terrestrial plant species were observed.

We have performed tests with Myriophyllum spicatum for many years and also taken part in ring tests for the development of the guidelines. Testing is usually performed according to OECD 239 with plant rooting in sediment, and exposure to the chemical through the spiking of  water or sediment in static, semi-static or pulsed-dose scenarios.

This test design is closer to reality as Myriophyllum grows with roots in the sediment, however, we can also carry out OECD 238 testing with floating plants without sediment in a sterile system. This is an advantage for some questions – such as the testing of substances easily degraded by microorganisms or with frequent water exchange.

Our culture of Myriophyllum is sterile which is very useful for growth suppression of algae and bacteria. It enables excellent plant growth and homogenous conditions among the different test groups and replicates.

Glyceria maxima is a test species suitable in situations where partitioning of the test substance to sediment is a concern and leads to exposure via root uptake and an activity on monocotyledonous species in terrestrial plant tests is shown. While the OECD guideline is still under development, two ring tests were performed in recent years with the contribution of ibacon. A third ring test will be conducted soon.

ibacon has vast experience with testing of Glyceria maxima and performed tests even before the ring test was initiated. We managed to grow the plants out of seeds and free of parasites and established a culture of rhizome propagated, healthy plants. Growth conditions are an important point and ibacon’s height-adjustable illumination guarantees the best light conditions for all plant heights.