Chapter 2 50 2.4.2 Plant growth conditions 2.4.2.1 Root growth Solanum lycopersicum (cv Moneymaker) (Obtained from Intratuin B.V.) seeds were washed with 70% ethanol for 1 min and then washed for 20 minutes with ½ Glorix bleach. We continued to wash with MQ until no scent of bleach remained. Fifty seeds were sown on 12.5 cm square petri dishes containing MS medium (Murashige and Skoog medium (Duchefa Biochmie),) 1 g L-1 MES hydrate (Sigma-Aldrich), 0.8% agar w/v; pH =5.8, and germinated for 5 days. The seedlings were measured for current root length (starting length), and then 5 seedlings per plate were transferred to the 24 cm square agar plates with MS media. Seedlings were grown vertically under white light + far-red (WL+FR) or white light (WL) for one week, and then imaged with a plate scanner. 2.4.2.2 Seedling growth Tomato seeds (S. lycopersicum cv. Moneymaker and M82 (Obtained from Tomato Genetics Resource Center)) were sown in Agra® vermiculite or wetted tissue paper in a box for 1 week for germination, then transplanted to medium sized (8 cm * 8 cm) pot with Primasta® soil. The pots were all sprayed with entonem (Koppert®) for biological pest control. Seedlings were grown in a phytotron (long day, 22ᵒC, 65% humidity) for a week. One week after transplanting, tomato plants were treated in low R:FR condition for 3, 7 or 10 days. With 6 biological replicates per experiment, each phenotyping experiment was repeated at least 3 times. 2.4.3 Phenotyping 2.4.3.1 Root measurements In order to quantify root system architecture, image analysis was used. Petri dishes with seedlings were scanned with the Epson Perfection V800 Photo scanner using WinRhizo software (Regent Instruments Inc.) We adopted SmartRoot plugin (Lobet et al., 2011) embedded in Image J FUJI (Schindelin et al., 2012) to identify main root, lateral root and measure the length. 2.4.3.2 Plant architecture measurement After the light treatment, we took out plants at 11am to measure the whole stem length, hypocotyl length, internode lengths and the leaves’ petiole lengths, and the diameter of the first internode at the midpoint. For all the leaves, we dissected all the leaflets from the stem and
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