*3.5. Arsenic Speciation in Root*

Arsenic speciation in root was significantly affected by 'As concentration × rootstock' interaction (Table 5). In As− treatment, Asinorganic in root accounted from 40.1% ("Shintoza") to 60.1% ("Proteo"); however, in the As+ solution, this variable significantly decreased in the intraspecific rootstocks, namely "Proteo", "Dinero", and "Magnus" (−14.57%, on average), while it increased in the interspecific hybrids "RS841", "Shintoza", and 'Strong Tosa' (+34.93%, on average) (Table 5). In As− treatment, AsIIIroot widely differed among rootstocks, ranging from 0.01 to 1.94 mg kg−<sup>1</sup> DW in "RS841" and "Proteo", respectively. In the As+ treatment it showed the highest rise in 'Strong Tosa' (+577.24 mg kg−<sup>1</sup> DW; i.e., +3207 fold than control) and "Shintoza" (+287.39 mg kg−<sup>1</sup> DW; i.e., +3193 fold), and the least one in "RS841" (+82.25 mg kg−<sup>1</sup> DW; i.e., +8225 fold) (Table 5). In As<sup>−</sup> treatment, AsVroot showed the highest value in "Proteo" (5.17 mg kg−<sup>1</sup> DW) and the least one in "Dinero" and "RS841" (2.88 mg kg−<sup>1</sup> DW, on average) (Table 5). When plants were grown in the As+ solution, such variable showed the highest increase in "Magnus" (by 345.94 mg kg−<sup>1</sup> DW; i.e., +80 fold than control), followed by "Proteo" and "Dinero" (by 255.88 mg kg−<sup>1</sup> DW, on average; i.e., +64 fold), and the least one in 'Strong Tosa' (by 41.85 mg kg−<sup>1</sup> DW; i.e., +14 fold) (Table 5).

**Table 5.** Inorganic As (percentage of total), As(III), and As(V) (mg kg−<sup>1</sup> DW) in root of melon plant as affected by As concentration in the nutrient solution and rootstock. Different letters within main factors indicate significance at Fisher's LSD test (*p* = 0.05).

