Effect of leaf water extracts of four Asteraceae alien invasive plants on germination performance of Lactuca sativa L. under acid deposition

Abstract

Allelopathy of alien invasive plants (AIP) on plant germination performance is essential for their successful invasion. However, the allelopathy of AIP may be reformed or even strengthened under acid deposition. AIP in Asteraceae covers the uppermost number of AIP species at the family level presently in China. It is necessary to estimate the allelopathy of multiple Asteraceae AIP under acid deposition to address the mechanism driving their successful invasion, especially under acid deposition. However, research in this area is very restricted presently. This study purposes to estimate the allelopathy of four Asteraceae AIP, i.e., Conyza canadensis L. Cronq., Erigeron annuus (L.) Pers., Aster subulatus Michx., and Bidens pilosa L., on germination performance of the cultivated Asteraceae plant species Lactuca sativa L. which is sensitive to allelochemicals under acid deposition with different levels of acidity. Of the four Asteraceae AIP, C. canadensis, E. annuus, and B. pilosa create noticeable allelopathy on germination performance of L. sativa. The allelopathy of the four Asteraceae AIP decreases in the following order: E. annuus, C. canadensis, B. pilosa, and A. subulatus. Acid deposition with a low level of acidity reduces the allelopathy of C. canadensis, E. annuus, and B. pilosa. Inversely, acid deposition with a high level of acidity elevates the allelopathy of B. pilosa. The progressively growing level of acid deposition with high acidity may facilitate the invasion process of B. pilosa via the improved level of allelopathy.

Aqueous Extracts of Three Herbs Allelopathically Inhibit Lettuce Germination but Promote Seedling Growth at Low Concentrations

“…Moreover, the mean lettuce seed germination time increased in response to the aqueous A. frigida extracts but decreased in response to those of A. splendens and S. chamaejasme (Figure 1c). and has high germination rates and rapid growth [34,43,44]. The aims of this study were to (1) clarify whether aqueous shoot extracts of donor plants have hormesis effects, (2) compare the allelopathic effects among the donor plants, (3) determine whether donor plant soaking time affects allelopathy, and (4) screen suitable recipient plant germination characteristics of lettuce to evaluate allelopathic potential.…”

“…Therefore, lettuce growth fitness may be substantially attenuated in response to allelopathy mediated by the foregoing herbs. The allelochemicals may poison weak seeds, impede nutrient absorption, and hinder seedling growth and development [44]. On the contrary, the donor aqueous extracts had positive influences on lettuce shoot length and biomass as well as leaf dimensions.…”

“…Each receptor type may respond differently to donor extracts [49,50]. L. sativa is sensitive to allelopathic effects and is a model recipient plant in allelopathy bioassay studies [34,43,44]. However, L. sativa is not ecologically related to donor grassland plant species.…”

“…In the present study, we analyzed the influences of leachates secreted by three degraded grassland plant shoots on lettuce (Lactuca sativa) seed germination and seedling development. We selected L. sativa as the recipient plant, as it is sensitive to allelopathy and has high germination rates and rapid growth [34,43,44]. The aims of this study were to (1) clarify whether aqueous shoot extracts of donor plants have hormesis effects, (2) compare the allelopathic effects among the donor plants, (3) determine whether donor plant soaking time affects allelopathy, and (4) screen suitable germination characteristics of lettuce to evaluate allelopathic potential.…”

Global Trends of Acidity in Rainfall and Its Impact on Plants and Soil

“…Invasion by alien plant species causes a significant effect on the ecosystem. An experiment performed by Cheng et al (2021) using four Asteraceae alien invasive plants (AIP), i.e., Conyza canadensis, Erigeron annuus, Aster subulatus, and Bidens pilosa, on germination of Lactuca sativa revealed that SAR of high acidity (pH 4.5) increases the process of invasion and allelopathy on the germination and root length of L. sativa.…”