Proper sowing depth is required for successful emergence of
tomato seedlings from soil.
We investigated effects of the sowing depth on tomato seed germination
and hypocotyl elongation, both of which are important for tomato
seedling production. We observed that the seedling emergence from soil
was significantly reduced by 38% and 50% at the sowing depth of
4 and 5 cm compared to 2 and 3 cm,
respectively (Figure 1A, B). We analyzed effects of the sowing depth on
the seed germination. Germination rates of seeds sown at
4 and 5 cm deep soil reduced by
22% and 33% compared to that at 2 and 3 cm deep soil (Figure 1C),
suggesting that reduction of seed germination in deep soil is one of
factors influencing the seedling emergence from soil. We further
analyzed hypocotyl elongation defects of tomato seedlings sown at 4 cm
deep soil. Hypocotyls elongated to various directions due to large
resistance, some of which may not be able to reach the surface of soil
(Figure 1D). Taken together, these data indicated that both seed
germination and hypocotyl elongation are significantly affected by the
sowing depth, which results in dramatical reduction of seedling
emergence from soil and the ultimate yield of plants.