Effects of Soil Drought on Competitiveness of the Invasive Weed Aegilops tauschii

Aegilops tauschii Coss., an invasive weed, has a detrimental impact on the winter wheat cultivation areas of China. Understanding how drought influences competitive ability of A. tauschii can help identify traits related to its invasiveness and guide management. Slight, moderate, and severe soil drought stress conditions were established using potted weighing and water control methods. Concurrently, the de Wit replacement experiment was conducted to assess changes in morphological structure, biomass allocation, and physiological characteristics under varying intensities of soil drought stress. Based on observations of alterations in plant height, total leaf area, and total biomass, two-factor variance analysis revealed that soil drought inhibited the growth and development of both A. tauschii and Triticum aestivum L. (‘Xinmai 32’). Furthermore, one-factor variance analysis revealed that A. tauschii and wheat responded to soil drought stress by increasing superoxide dismutase (SOD) activity and proline content. However, as drought severity escalated, chlorophyll content in A. tauschii and wheat declined significantly, while relative electrical conductivity (REC) and thiobarbituric acid (TBA) content increased markedly. The results of the fuzzy membership function indicated that A. tauschii exhibited greater drought tolerance compared to the tested wheat variety. Lastly, considering adjustments in the corrected index of relative competition intensity (CRCI), it was observed that soil drought amplified the competitive inhibition of A. tauschii on wheat. In short, A. tauschii was more tolerant of the soil drought stress than wheat through the favorable adjustment of morphology, biomass allocation pattern and physiological features, and soil drought intensified its competitive inhibition on wheat.