You may want to try adding Roundup to your seedlings

See:

There is a Figure 4 in the full paper that pictures a control plant and then 9 plants that were subjected to increasing concentrations 1.8, 3.6, 7.2 18, 36, 72, 180, 360, and 720 (g AE per hectare). At 72 and above growth inhibition was observed (dosages are different for different plant species).They used commercial Roundup Original which has a concentration of 480 (g L-1) or stated in AE units (360 g AE L-1). A hectare is a unit of surface area equal to 10,000 square meters. An AE is an “acid equivalent”.

It appears that they had to calibrate their sprayer with a dye in order to report concentrations of g AE per hectare.

A second method that appears to be more useful for hybridizers with individual plants is to use a micro syringe to apply droplets to the leaves. For example, seedlings at the 4 leaf stage received 20 micro liters (one droplet of 5 micro liter on each of the four leaves. The concentrations tried were 0.15, 0.18, 0.25, 0.031, 0.39, 0.52, 1.25, 2.5, 5.0, 7.5,10.0, 15.0, and 20.0 g AE per liter.

Most of their data are reported using the hectare measurements; which are not of any practical use to me. For the micro syringe 4 leaf stage experiment mentioned above, about 1.0 g AE per liter concentration gave the maximun growth value (142 % dry weight above control).


An interesting sidelight: In the discussion they give references to 6 papers that discuss using low doses of glyphosate to enhance sucrose accumulation in sugarcane.