1. The experiments were carried out to see the influence of the partial pressure of oxygen in the soil aeration on the sprouting, growth of the root and top, especially on the growth of the new roots of mulberry seedling. The seedlings were cultured in sand, which was aerated by the gas mixture of various concentrations of oxygen and nitrogen in the ratios: 0, 1, 2, 3, 5, 10 or 20 parts to 100.
2. In each lot the water capacities and porocity was considered the same, the difference between each lot was considered to be brougnt about by the difference of the partial pressure of oxygen.
3. The sprouting was retarded a little in the 0% lot. After the expand of leaf, the growth-rate of leaf and shoot was parallel to the oxygen-pressure in the range from 1-20%, and below 3%, the growth did not advance beyond a certain limit. It was found the oxygenpressure above 5% was neccesary to allow the seedlings grow normal.
4. The root grew to some extent when the aerating gas contained oxygen above 2% but oxygen above 5% was neccesary for the root to develop normally.
5. Comparing the data in various fruit trees, such as the apple, the pear, the peach or the persimon with those mentioned above, it may he concluded that the mulberry seed-ling can grow in lower oxygen pressure than fruit trees.
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