Photosynthetic Responses and Dry Matter Accumulation of Xanthium strumarium Under Water Deficit Conditions

Abstract

Water deficit is a major abiotic stress limiting weed growth dynamics and crop–weed interactions in rainfed and irrigated agroecosystems. Xanthium strumarium is a highly adaptable invasive weed species capable of surviving under diverse environmental constraints. The present study evaluated the photosynthetic responses and dry matter accumulation of X. strumarium under varying water deficit conditions. Plants were subjected to different levels of soil moisture stress under controlled experimental conditions, and physiological parameters such as chlorophyll content, net photosynthetic rate, stomatal conductance, and transpiration rate were measured. In addition, biomass accumulation, leaf area development, and total dry matter production were assessed to determine growth performance under stress. The results revealed that increasing water deficit significantly reduced photosynthetic efficiency, primarily due to stomatal closure and decreased chlorophyll content. A corresponding decline in transpiration rate and CO₂ assimilation was observed under severe stress conditions. Despite these limitations, X. strumarium demonstrated a notable capacity to maintain physiological activity under moderate stress levels, indicating adaptive drought tolerance mechanisms. Dry matter accumulation was progressively reduced with increasing water deficit, however, root-to-shoot ratio increased, suggesting resource allocation adjustments to enhance water uptake efficiency. The findings indicate that X. strumarium possesses physiological plasticity that enables survival under moisture-limited environments, contributing to its invasive success. This study provides valuable insights into the ecophysiological behavior of X. strumarium under drought stress and supports improved understanding of weed adaptation strategies in water-limited agroecosystems. The results may assist in developing integrated weed management approaches under changing climatic conditions.