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

Abstract

Quinate (1,3,4,5-tetrahydroxycyclohexanecarboxylate) is a compound synthesized in plants through a side-branch of the shikimate biosynthesis pathway, which is accumulated after glyphosate and acetolactate synthase inhibiting herbicides (ALS-inhibitors) and has phytotoxic potential. The objective of this study was to evaluate the phytotoxicity of quinate on several weed species. Among the species evaluated, Cynodon dactylon, Bromus diandrus, Lolium rigidum, Sinapis alba, and Papaver rhoeas, P. rhoeas was the most sensitive, and its growth was controlled with quinate concentrations above 100 mM at the phenological stage of 6-8 true leaves. A physiological study, including the shikimate pathway and the physiological markers of ALS-inhibitors (carbohydrates and amino acids), was performed in the sensitive and resistant plants treated with sulfonylureas or quinate. The typical physiological effects of ALS-inhibitors were detected in the sensitive population (free amino acid and carbohydrate accumulation) and not detected in the resistant population. The mode of action of quinate appeared to be related to general perturbations in their carbon/nitrogen metabolism rather than to specific changes in the shikimate pathway. These results suggest the possibility of using quinate in the weed control management of P. rhoeas.

Keywords: corn poppy; free amino acids; physiological effects; quinate; shikimate pathway; sulfonylureas.

Figure 1

Dose-response of the shoot fresh biomass in Papaver rhoeas plants 18 days following quinate application, as a percentage of the control plants. Quinate was applied when plants showed four true leaves (black) or when plants had 6–8 true leaves (white). Log-logistic dose-response curves.

Figure 2

Fresh weight per plant (A), dry weight per plant (B), and chlorophyll content (C) in the sensitive (left) and resistant (right) P. rhoeas populations. Plants were untreated (Control, C) or treated with quinate (Q) or sulfonylurea herbicide (H) (Mean ± SE; n = 4–10). Different letters in each population indicate significant differences between treatments (p-value ≤ 0.05, Tukey).

Figure 3

Amino acid profile. First column: Total free amino acids (A), branched-chain amino acid (BCAA) (B), acidic (Glu+Asp) (C), and amide (Gln+Asn) (D) contents in the untreated plants of the sensitive (CS) and resistant (CR) populations of P. rhoeas. The symbol (*) indicates significant differences between the control plants of each population (p-value ≤ 0.05, t-student). Second and third columns: amino acid profile of sensitive and resistant plants, respectively. Contents are expressed as % of the respective control. Plants were untreated (Control, C) or sampled three days after quinate (Q) or sulfonylurea herbicide (H) treatments (Mean ± SE; n = 4–5). Different letters in each population indicate significant differences between treatments (p-value ≤ 0.05, Tukey).

Figure 4

Total soluble sugars (A) and starch content (B) in the sensitive (left) and resistant (right) P. rhoeas populations. Plants were untreated (Control, C) or sampled three days after quinate (Q) or sulfonylurea herbicide (H) treatments (Mean ± SE; n = 4). Different letters in each population indicate significant differences between treatments (p-value ≤ 0.05, Tukey).

Figure 5

The pattern of the shikimate pathway. Plants were untreated (Control, C) or sampled three days after quinate (Q) or sulfonylurea herbicide (H) treatments. 3-deoxy-darabino-heptulosonate-7-phosphate-synthase (DAHPS) protein content (A). Band intensity on blots is presented as the relative ratio of the respective control (mean ± SE; n = 3). Control is arbitrarily presented as 100%. A representative blot is shown. Quinate (B), shikimate contents (C), and aromatic amino acid (AAA) content (D) are expressed as a percentage of the respective control (Mean ± SE; n = 4). Different letters in each population indicate significant differences between treatments (p-value ≤ 0.05, Tukey).