Natural biostimulants from kiwi and peach pollen extracts improve in vitro growth and rooting along with metabolic partitioning in cherry rootstocks

Plant-derived pollen extracts are rich sources of growth regulators, nutrients, and vitamins, making them promising biostimulants for plant tissue culture. This study evaluated kiwi and peach water pollen extracts (WPEs) at different concentrations (50–600 mg L −1 ) as natural alternatives to synthetic indole-3-butyric acid (IBA; 0, 0.5, 1, 2, and 4 mg L −1 ) for the in vitro propagation of CAB-6P and Gisela 6 cherry rootstocks. Low concentrations of kiwi WPE (50–100 mg L −1 ) promoted shoot growth, with maximum shoot height observed in Gisela 6 (24.50 mm) at 50 mg L −1 and in CAB-6P (20.00 mm) at 100 mg L −1 . Peach WPE was more effective in rooting, with 200 mg L −1 producing the highest rooting in Gisela 6 (7.57 roots; 70%) and 600 mg L −1 giving maximum root length (52.50 mm) and rooting percentage (50%) in CAB-6P. In CAB-6P, kiwi WPE enhanced photosynthetic pigments, while peach WPE increased chlorophyll, porphyrins, and root carbohydrates. In Gisela 6, kiwi WPE reduced proline accumulation and promoted shoot growth, whereas peach WPE improved rooting and carbohydrate content. Multivariate analyses (Pearson correlation, Principal Component, and Hierarchical cluster) revealed strong correlations among physiological and biochemical traits, indicating coordinated responses to treatments. This study provides the first evidence that kiwi and peach WPEs can act as effective, low-cost, and eco-friendly alternatives to synthetic phytohormones, supporting efficient micropropagation of elite cherry rootstocks.