Effects of Cladophora glomerata and Limnospira platensis on growth and photosynthetic pigments of safflower (Carthamus tinctorius L.)

BACKGROUND: Intensive use of synthetic fertilizers has raised significant concerns due to their adverse impacts on the environment, soil quality, and human health. This has increased interest in sustainable agricultural inputs that can improve crop performance while reducing dependence on fertilizers. Algae-based biostimulants are promising in this context because they contain nutrients and bioactive compounds that may improve plant growth, physiological activity, and yield. METHODS: This study evaluated the effects of Limnospira platensis and Cladophora glomerata on growth and yield components of safflower (Carthamus tinctorius L.) cv. Remzibey-05. Different concentrations of L. platensis (control, 0.25%, 0.50%, 0.75%, 1.00%, and 1.25%) and C. glomerata (control, 1%, and 2%) were applied either individually or in combination. Treatments were applied at three growth stages, including rosette, stem elongation and branching, and flowering. Agronomic, physiological, and yield-related traits, including plant height, root length, flower head diameter, fresh plant weight, root weight, flower head weight, number of flower heads, number of seeds per flower head, seed yield per plant, 1000-seed weight, chlorophyll a, chlorophyll b, and carotenoid contents, were recorded at harvest. RESULTS: All treatments significantly improved the recorded traits compared with the untreated control (p < 0.05). The greatest increase in plant height (45.3%) was recorded with the sole application of 1% L. platensis. The combined application of 1.25% L. platensis and 1% C. glomerata caused the highest increases in fresh plant weight and root weight (64.5% and 91.8%, respectively). The highest increase (72%) in Chlorophyll a content was recorded with the combined application of 1% L. platensis and 2% C. glomerata. Similarly, the combined application of 1.25% L. platensis and 1% C. glomerata increased seed yield per plant and 1000-seed weight by 210% and 116%, respectively, compared with the control. CONCLUSION: Combined application of L. platensis and C. glomerata significantly improved safflower growth, photosynthetic pigment accumulation, and yield-related traits under greenhouse conditions. The combined application of 1.25% L. platensis and 1% C. glomerata resulted in the highest seed yield per plant and 1000-seed weight. These results indicate that the combined use of algae-based biostimulants may represent a promising low-input approach for enhancing safflower productivity while reducing reliance on synthetic fertilizers. Field-based validation across contrasting environments is required to confirm their agronomic consistency and support their wider use in sustainable safflower production.