Differential accumulation of tocochromanols in photosynthetic and non-photosynthetic tissues of strawberry plants subjected to reiterated water deficit

Tocochromanols are a group of lipid-soluble antioxidants that include tocopherols, tocotrienols and plastochromanol-8. Here, we examined a putative differential accumulation of tocochromanols in photosynthetic and non-photosynthetic tissues (including leaves and whole fruits) of strawberry (Fragaria x ananassa cv. Albion) plants and evaluated their endogenous variations in response to a reiterated water deficit during a vegetative (non-productive) and a fruiting (productive) period. In addition, we evaluated the concentration of tocochromanols in achenes (true fruits) and flesh of strawberries (whole fruits) at the white and full-red stages both under optimal and stress conditions. Results showed that leaves mainly accumulated alpha-tocopherol, with plastochromanol-8 and gamma-tocopherol being present at low amounts. In contrast, whole fruits did not accumulate plastochromanol-8, gamma-tocopherol being the major tocochromanol in the achenes (true fruit) and alpha-tocopherol in the flesh. While alpha-tocopherol content in leaves increased up to seven-fold after 12 weeks of stress during the fruiting period, it kept unaltered during the vegetative period. Neither plastochromanol-8 nor gamma-tocopherol contents increased in leaves of stressed plants. During the fruiting period, gamma-tocopherol content increased in whole fruits of stressed plants (most of it being accumulated in the achenes). Among the compounds examined, the flesh of strawberries accumulated alpha-tocopherol only, both at the white and full-red stages. It is concluded that (i) alpha-tocopherol is the major tocochromanol in leaves, while gamma-tocopherol is the major tocochromanol in achenes (ii) reiterated water deficit promotes the accumulation of alpha-tocopherol in leaves and gamma-tocopherol in fruits, (iii) alpha-tocopherol not only accumulates in photosynthetic tissues (leaves and whole fruits at green stages), but also in non-photosynthetic tissues (flesh of whole fruits at the white and full-red stages), and (iv) achenes (true fruits) of strawberry plants are an extraordinary rich source of tocopherols.