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.