Physiological performance of glyphosate and imazamox mixtures on Amaranthus palmeri sensitive and resistant to glyphosate

Abstract

The herbicides glyphosate and imazamox inhibit the biosynthetic pathway of aromatic amino acids (AAA) and branched-chain amino acids (BCAA), respectively. Both herbicides share several physiological effects in the processes triggered in plants after herbicide application that kills the plant, and mixtures of both herbicides are being used. The aim of this study was to evaluate the physiological effects in the mixture of glyphosate and imazamox in glyphosate-sensitive (GS) and -resistant (GR) populations of the troublesome weed Amaranthus palmeri. The changes detected in the physiological parameters after herbicide mixtures application were similar and even less to the changes detected after individual treatments. This pattern was detected in shikimate, amino acid and carbohydrate content, and it was independent of the EPSPS copy number, as it was detected in both populations. In the case of the transcriptional pattern of the AAA pathway after glyphosate, interesting and contrary interactions with imazamox treatment were detected for both populations; enhancement of the effect in the GS population and alleviation in the GR population. At the transcriptional level, no cross regulation between AAA and BCAA inhibitors was confirmed. This study suggests that mixtures are equally or less toxic than herbicides alone, and would implicate careful considerations when applying the herbicide mixtures.

Physiological Approach to the Use of the Natural Compound Quinate in the Control of Sensitive and Resistant Papaver rhoeas

“…The DAHPS content was not affected by the herbicide in any of the populations ( Figure 5 A), which conforms to reports of the same effect in other ALS-inhibitors in Amaranthus palmeri leaves [ 45 ]. On the contrary, previous studies have shown induction of the secondary metabolism after treatment with ALS-inhibitors, which is related to an induction of the first enzyme of the shikimate pathway in pea roots [ 48 ].…”

“…On the contrary, previous studies have shown induction of the secondary metabolism after treatment with ALS-inhibitors, which is related to an induction of the first enzyme of the shikimate pathway in pea roots [ 48 ]. Similarly, the sulfonylurea application did not induce quinate accumulation or AAA accumulation, as reported after other ALS-inhibitors [ 7 , 45 ]. The lack of detection of these typical physiological effects on the secondary metabolism after ALS-inhibition suggests that the study did not continue long enough to induce them.…”

“…Accumulation of total soluble sugars in the sensitive plants treated with the ALS-inhibitor was detected ( Figure 4 A). This physiological effect can be considered as a typical marker of these herbicides as has been reported in other species, such as pea [ 5 ], Arabidopsis thaliana [ 44 ], and the weed Amaranthus palmeri [ 45 ]. This carbohydrate accumulation detected in the leaves after herbicide treatment has been previously attributed to growth arrest.…”

Hypoxic Treatment Decreases the Physiological Action of the Herbicide Imazamox on Pisum sativum Roots

“…Carbohydrates were accumulated in the roots as a consequence of ALS inhibition (Figure 4) as has been described before [8][9][10][11]14,32,33]. The accumulation in roots was due to a lack of use of available sugars because growth was arrested (Figure 3).…”

“…The effects on free amino acid profile were studied in the No-Hypoxia and Hypoxia-24h groups ( Figure 5) by monitoring five physiological parameters previously described to be affected by ALS inhibitors: free amino acid content, BCAA, aromatic, acidic, and amide amino acid contents [6,10,14,27]. As ALS -inhibitors cause a general increase in the content of free amino acids that could mask the specific changes in each absolute content [27,28], BCAA, aromatic, acidic and amide amino acids are shown as their relative content in terms of percentage of total amino acid content ( Figure 5).…”