Transcription profiling by array of the root transcriptome from Arabidopsis thaliana plants grown on different growing substrates (hydroponics and soil)

In order to decipher the molecular alterations caused by the growing medium, we harvested the roots of plants grown in hydroponics and on soil for 6 weeks under 10-hour short days. The temperature was 20°C (day and night), the relative humidity was 70 %, and the light was provided by cool-white fluorescent tubes at 100 μE.m–2.s–1 during the first 10 days, 60 μE.m–2.s–1 later. The soil was composed of a mixture of peat compost and sand (3:1 v/v), which was watered daily with tap water. Plants were transferred to 1-liter containers (six plants/container) 18 days after sowing. Plants grown in hydroponics were sown on agar-containing (6.7 g.l–1; Kalys, France) seed-holders placed on 2-liter black containers and accessories (<a href="http://www.araponics.com" target="_blank">http://www.araponics.com</a>). The hydroponic solution, changed every two weeks, was prepared as described in Tocquin et al. (2003). During the first three weeks of growth, the number of plants per 2-liter tank was 35 and 18 afterwards. Harvesting was performed 8 hours after the beginning of the light period (16h30), and the roots from 35 to 45 individuals were pooled. Three independent biological replicates were performed for plants grown on both media.

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