PLANT GROWTH REGULATORS AS INSTRUMENTS FOR ARCHITECTURAL OPTIMIZATION AND YIELD FORMATION IN OILSEED FLAX

Abstract

Plant growth regulators (PGRs) represent an important agronomic tool for improving crop productivity through the regulation of canopy architecture and physiological processes. In oilseed flax (Linum usitatissimum L.), yield formation largely depends on early canopy development and reproductive sink establishment; however, the relationships between canopy photosynthetic activity and yield structure remain insufficiently understood. This study aimed to assess the effects of different plant growth regulators on canopy architecture, yield structure components, and productivity of oilseed flax under field conditions.

Field experiments were conducted using biostimulant-based growth regulators applied at critical growth stages. Canopy development was evaluated by plant height and normalized difference vegetation index (NDVI), while yield structure was characterized by capsule number per plant, seed number per capsule, thousand-seed weight, and final yield. Data were analyzed using analysis of variance and correlation analysis.

Plant growth regulator application significantly enhanced canopy photosynthetic activity, particularly at the flowering stage, as reflected by increased NDVI values. However, yield improvement was primarily driven by changes in yield structure rather than canopy vigor alone. Capsule number per plant showed a strong positive correlation with seed yield, identifying it as the main yield-determining component. The biostimulant treatment resulted in the highest capsule number and yield by combining enhanced photosynthetic activity with efficient assimilate allocation to reproductive organs. Nitrogen- and micronutrient-based treatments predominantly increased source activity, whereas boron improved reproductive efficiency.

Overall, the results demonstrate that optimizing canopy architecture and source–sink relationships through plant growth regulators is an effective strategy for stabilizing oilseed flax yield under variable environmental conditions.