Effect of pre-conditioning water regimes during nursery production on seedling root system characteristics of Silene vulgaris

The influence of pre-conditioning water regimes during nursery production on seedling root characteristics was investigated in Silene vulgaris (Moench.) Garcke, a Mediterranean native wild herb, considered of interest for edible and medicinal uses and for phytoremediation of soils contaminated with heavy metals. Throughout the nursery period, seedlings growing in polystyrene trays were overhead watered twice a week (Monday and Thursday), using three irrigation treatments: WW (well-watered), irrigated at 75% of the water-holding capacity (WHC); MS (moderate-stressed), watered at 50% of the WHC; and HS (high-stressed) watered at 15% of the WHC. At the end of the nursery period, seedlings raised under MS treatment showed greater total root length (68 cm), specific root length (SRL) (2.52 cm mg(-1)), root branching degree (4.12 forks per cm root), root fresh weight (FW) 27 mg) and dry weight (DW) (4.3 mg), and root DW:volume ratio (0.021 g cm(-3)) than those raised under WW treatment. Under the HS treatment, seedlings had greater values for the SRL (3.44 cm mg(-1)) than those obtained under the MS treatment. However, these seedlings were too small and over-hardened, with reduced root systems development (31 cm root length, 9 mg FW and 1.6 mg DW) and, therefore, not qualified for marketing. The MS seedlings turned out to be the ones with the highest quality.