appendix_a.md

Protocol for image acquisition

Materials and Equipment:

• Plants under study
• Black mat background (42 cm x 60 cm was used)
• Contrast paper sticker of known size (79 x 79 mm was used)
• Laboratory table with sufficient lighting
• Any digital camera, including in-built in mobile phones (12 - 16 MP smartphone cameras were used)
• Tripod (optional)

Procedure:

Write the plant group name on the paper sticker (just not to confuse photos) Place plants and paper sticker on black mat background as shown in the example below:

Important:

To achieve correct object recognition:

1. the seedlings should be aligned along the seeds and consistently oriented;
2. neighboring plants must not cross each other;
3. the paper sticker should be placed above the sprouts.

To achieve most accurate measurements:

1. all roots should be thoroughly split from each other to ensure their maximum visibility for the camera, as in the example below:

2. plants should be aligned along the seeds as in the example below:

Optimize exposure to exclude excessively bright spots and take an image (automatic adjustment is recommended). Visually ensure that the image has sufficient sharpness.