Influence of temperature (a,b), salt (c,d) and osmotic (e,f) stresses on the fresh biomass accumulation in the transgenic grapevine callus cell lines overexpressing the VaCML21v2 and VaCML21v4 splice variants. The average growth rates were assessed after 30 days of cultivation in the dark under the control (24 °C), cold stress (+16 °C), heat stress (+37 °C), salt stress (NaCl 50 and 100 mM), and high-mannitol (200 and 300 mM) conditions. v2-1, v2-2, v2-3—VaCML21v2-transformed calli; v4-1, v4-2, v4-3—VaCML21v4-transformed calli. KA-0—control cell culture transformed with the “empty” vector. The data are presented as the mean ± SE (two independent experiments with ten replicates each). Means followed by the same letter were not different using one-way analysis of variance (ANOVA), followed by the Tukey HSD multiple comparison test. A value of p ≤ 0.05 was considered as significant.