Abstract
We investigated how root-zone calcium (Ca) concentration influences shoot development, tissue Ca accumulation, and antioxidant-related secondary metabolism in in vitro potato ( Solanum tuberosum L. cv. Russet Burbank) plantlets. Micropropagated shoots were cultured on Murashige and Skoog medium modified with a gradient of Ca levels (6.8–3000 µM calcium chloride) under controlled environmental conditions. Morphological features, Ca content in plant tissue, total phenolic content, and antioxidant capacity [Trolox equivalent antioxidant capacity (TEAC) and ferric-reducing antioxidant power (FRAP) assays] were evaluated after 4 weeks. Results showed a strong Ca-dependent shift in plant growth and metabolic profiles. Low Ca induced shoot tip necrosis, loss of apical dominance, and increased axillary branching, whereas Ca concentrations ≥ 1360 µM supported normal shoot architecture and sustained growth. The content of Ca in plant tissues increased proportionally with higher Ca levels, increasing 12.7-fold from 153.63 to 1950.44 mg·L –1 . In contrast, phenolic levels and TEAC antioxidant capacity showed an inverse trend, decreasing from 928.44 to 515.27 µg gallic acid equivalents·g –1 dry weight (DW) and from 84.26 to 43.88 mg·g –1 Trolox DW, respectively, with increasing Ca levels. In contrast, FRAP activity increased from 100.95 to 427.20 mg·g –1 Trolox DW at higher Ca levels. Regression analyses revealed negative correlations between tissue Ca and both phenolics and TEAC, and a positive correlation between tissue Ca and FRAP. These findings demonstrate that Ca regulates growth and defense metabolism in potato plants. Low Ca appears to trigger phenolic-based defense pathways, whereas Ca applied at adequate levels supports optimal structural development but alters antioxidant composition. Our results suggest that Ca acts as a key regulatory factor in morphogenesis and secondary metabolism, and unlocks possibilities for optimizing nutrient strategies in controlled environments and micropropagation systems.