ADAPTATION OF ALLIUM CEPA L. TO CONDITIONS OF REDUCED LIGHT INTENSIT

Abstract

This study summarizes current scientific knowledge and presents experimental results on the effects of reduced light intensity on morphological, anatomical, and physiological traits of Allium cepa L.. Particular attention is given to the integrated response of plants at early ontogenetic stages under conditions of light deficiency. The experiment was conducted under controlled light regimes, and plant development was assessed dynamically over time. The results demonstrate that reduced light availability induces a restructuring of growth processes. Under extremely low light intensity, a significant stimulation of shoot elongation was observed, indicating the activation of adaptive mechanisms aimed at maximizing light capture. At the same time, biomass accumulation patterns were altered: although fresh biomass of the aboveground part remained relatively stable, a decrease in dry matter content was detected, reflecting limitations in photosynthetic productivity. Anatomical analysis revealed pronounced structural modifications of leaf tissues. In particular, a reduction in mesophyll thickness, including both palisade and spongy parenchyma, was observed, along with significant changes in stomatal characteristics, such as decreased density and size. These alterations indicate a functional adjustment of the photosynthetic apparatus and gas exchange system under limited light conditions. Physiological measurements confirmed a direct dependence of photosynthetic intensity on light level, consistent with the classical light-response curve of photosynthesis. In contrast, respiration rates remained relatively stable across treatments, suggesting a lower sensitivity of respiratory processes to variations in light intensity during early developmental stages. Overall, the obtained results are consistent with modern concepts of photomorphogenesis and plant adaptive responses to environmental stressors. The findings highlight the coordinated nature of morphological, anatomical, and physiological adjustments in response to light limitation. The practical significance of this study lies in substantiating approaches for optimizing the cultivation conditions of vegetable crops under reduced light availability, particularly in controlled environments and dense agroecosystems.