Fanourakis D, FZJ
At first, the tray (4 cm³ cells) is filled with substrate, the substrate is gently pressed, and then another layer of substrate is added on the top (Fig. 1). The seeds are placed in approximately 0.5 cm depth by using tweezers (Fig. 2). Afterwards, the substrate is watered gently (otherwise seeds may be washed out).
Fig. 1. Empty (left) and filled (right) tray with 4 cm³ cells.
Fig. 2. Planting of the seed in approximately 0.5 cm depth.
Definition of phenological stages
Stage 0: Two weeks (at about 20 oC) following sowing (the first true leaf is smaller than 5 mm; Fig. 3), the seedlings are selected based on uniformity in both length and leaf area.
Fig. 3. Seedlings ready for transplantation.
A small hole needs to be prepared in the pot (Fig. 4) that half of the shoot is covered by the substrate after transplanting (otherwise plants may bend). Each seedling is transplanted by a spoon (care needs to be taken not to hurt the roots).
Fig. 4. Seedling (abstracted by using a spoon) before and after transplantation.
Plants at different stages
Fig. 5. Canola plants at second-, third-, fourth-, and fifth-leaf stages.
Determining the leaf appearance
A growing leaf is counted as a leaf, when it reaches 10 cm (Fig. 5).
Leaf growth or emergence is estimated by using the Plastochton Index (PI) :
PI = n + [log(Ln) – log(λ)]/[log(Ln) log(Ln+1)]
n=leaf number; Ln=length of the youngest leaf ≥ λ (cm); λ =leaf larger than a trash-hold leaf length (10 cm for canola); Ln+1= length of the youngest leaf < λ (cm)
The length of the two youngest leaves (Ln & Ln+1) can be measured by using regular ruler, the required precision is ±1cm.
Fig. 6. Measurement of the leaf length of a leaf > 10 cm (left, 16 cm) and < 10 cm (right, 6cm) with a regular ruler.
 Erikson RO & Michelini FJ (1957) The Plastochron Index. Americal Journal of Botany 44, 297 – 305