- Author: Marie Jasieniuk
- Posted by: Gale Perez
Herbicides are the main means of controlling weeds. Recently, there has been increasing concern over the potential impacts of climate change, specifically, increasing temperatures and elevated carbon dioxide (CO2) concentrations, on the sensitivity of weeds to herbicides. A postdoctoral fellow in my lab, Maor Matzrafi, investigated the response of horseweed and lambsquarters to treatment with glyphosate under the higher temperatures and CO2 levels that are predicted to exist in northern California around 2050. Maor showed that the sensitivity of both weeds to glyphosate was reduced in response to increased temperature, elevated CO2 level, and the combination of both factors. He also found that glyphosate-treated plants lost apical dominance and initiated multiple lateral buds when grown under high temperature alone and the combination of both high temperature and elevated CO2 level. Maor's research shows that overreliance on glyphosate for weed control under the climatic conditions predicted for northern California in the future is likely to result in more weed control failures.
The picture below shows the translocation of glyphosate through a plant 48 hours after treatment (HAT), and the loss of apical dominance and initiation of lateral shoots one and two weeks after treatment (WAT) in lambsquarters.
of plant maturity, it could highly suggest that above weeds should have been treated at earlier maturity. Especially before they had ability to reform as lateral buds.
I'd interpret the four images represent to represent what would happen to one plant over time following the application. Day 1 is the day of treatment, the next one is 2 days later (48 hours after treatment), the third and four ones are 1 week and 2 weeks after treatment (WAT). The point of the red leaves at 48 HAT and then the "empty" boxes at 1 and 2 WAT is that the apical meristem died. The 4 WAT plant is bigger because it's had 14 more days to grow since the sub-lethal herbicide treatment.
When the apical meristem is absent, there is often a response where lateral buds are released because of a change in hormone levels (IAA vs cytokinin). Essentially, the apical meristem forces the axillary (or lateral) meristems to remain dormant but this suppressive effect is removed when the apical portion is killed/removed.
You can find information on some really classic plant physiology experiments that were used to help understand plant hormones and hormonal effects like this if you search "plant apical dominance" or similar terms.