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Nutrient availability and pH level affect germination traits and seedling development of Conyza canadensis.

ABSTRACT: Reducing pesticide application in agricultural land is a major challenge for the twenty-first century. Responses of weed seed's germination and seedling's early development to chemical soil conditions around the seed may be a promising way to aid weed control in a no-till system. Thus, the objective of this work was to test, under controlled conditions, whether different chemical conditions affect the germination and development of horseweed [Conyza canadensis (L.) Cronquist]. We used, as treatment, solutions containing different nutrients (P, K, Ca, and Mg), separately and in combination, and at two pH levels (4.8 and 6.5). Phosphorus alone inhibited horseweed seed germination at ~ 7 times while had ~ 4 times reduction in final germination percentage and germination speed index for both pH tested. Other nutrients tested had a no-effect in germination speed index compared to the control treatment. Potassium alone or associated with other ions (P, Ca, and Mg) at pH 4.8 had a synergistic effect on seedling development (root and shoot length). In the same way, K associated with Mg was synergistic to the root length at pH 6.5. Seeds in the control treatment (distilled water) presented a high germination speed index at pH 6.5, while at low pH this parameter was higher when in association with KMg, PMg and Ca. The findings demonstrate that seed germination traits and seedling development of horseweed depend on nutrient kind exposure and pH conditions in the seed environment. This work suggests that adequate topsoil management (i.e., pH and nutrient availability) may aid to reduce weed germination, because, it consists of an important factor of weed occurrence in agricultural areas.

SUBMITTER: Follmer CM

PROVIDER: S-EPMC8329304 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Herbicide resistance is a challenge for modern agriculture further complicated by cases of resistance to multiple herbicides. Conyza bonariensis and Conyza canadensis are invasive weeds of field crops, orchards, and non-cropped areas in many parts of the world. In California, USA, Conyza populations resistant to the herbicides glyphosate and paraquat have recently been described. Although the mechanism conferring resistance to glyphosate and paraquat in these species was not elucidated, reduced translocation of these herbicides was observed under experimental conditions in both species. Glyphosate and paraquat resistance associated with reduced translocation are hypothesized to be a result of sequestration of herbicides into the vacuole, with the possible involvement of over-expression of genes encoding tonoplast transporters of ABC-transporter families in cases of glyphosate resistance or cationic amino acid transporters (CAT) in cases of paraquat resistance. However, gene expression in response to herbicide treatment has not been studied in glyphosate and paraquat resistant populations. In the current study, we evaluated the transcript levels of genes possibly involved in resistance using real-time PCR. First, we evaluated eight candidate reference genes following herbicide treatment and selected three genes that exhibited stable expression profiles; ACTIN, HEAT-SHOCK-PROTEIN-70, and CYCLOPHILIN. The reference genes identified here can be used for further studies related to plant-herbicide interactions. We used these reference genes to assay the transcript levels of EPSPS, ABC transporters, and CAT in response to herbicide treatment in susceptible and resistant Conyza spp. lines. No transcription changes were observed in EPSPS or CAT genes after glyphosate or paraquat treatment, suggesting that these genes are not involved in the resistance mechanism. Transcription of the two ABC transporter genes increased following glyphosate treatment in all Conyza spp. lines. Transcription of ABC transporters also increased after paraquat treatment in all three lines of C. bonariensis. However, in C. canadensis, paraquat treatment increased transcription of only one ABC transporter gene in the susceptible line. The increase in transcription of ABC transporters after herbicide treatment is likely a stress response based on similar response observed across all Conyza lines regardless of resistance or sensitivity to glyphosate or paraquat, thus these genes do not appear to be directly involved in the mechanism of resistance in Conyza spp.

Project description:Worldwide drylands are threatened by changes in resource availability associated with global environmental change. Functional traits may help predict which species will be most responsive to these alterations in nutrient and water availability. Current functional trait work focuses on tissue construction and nutrient concentrations, but plant performance in low resource environments also may be strongly influenced by traits related to nutrient budgets and allocation. Our overall objective was to compare trait responses in a suite of serpentine and nonserpentine congener pairs from the California chaparral, a biodiverse region facing nutrient deposition and future changes in precipitation. In a common garden greenhouse environment, we grew small plants of Arctostaphylos manzanita, A. viscida, Ceanothus cuneatus, C. jepsonii, Quercus berberidifolia, and Q. durata in contrasting soil nutrient and moisture treatments. We measured a suite of traits representing physiological, growth, and mineral nutrient responses to these treatments. Overall, plant growth rate and leaf-level phosphorus use efficiency were greatest in the low water, high nutrient treatment, and lowest in the high water, low nutrient treatment. Variation in growth rate and plasticity among species and treatments was primarily associated with differences in mineral nutrition-based traits as opposed to differences in biomass allocation or specific leaf area. Namely, faster growing species and species with greater plasticity allocated more nitrogen and phosphorous to leaves and demonstrated greater photosynthetic phosphorus use efficiency. Overall, nonserpentine species had greater plasticity and biomass response to resource addition than serpentine species, and congener pairs responded to these resource additions more similarly to each other than species across congener pairs. This study extends our general understanding of how functional traits may influence species responses to environmental change and highlights the need to integrate mineral nutrition-based traits, including allocation of nutrient pools and nutrient use efficiency into this larger trait framework. Ultimately, this insight can help identify, in part, why coexisting species may vary in sensitivity to anthropogenic driven changes in soil resource availability.

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Nutrient availability and pH level affect germination traits and seedling development of Conyza canadensis.

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