Abstract
The effects of planting depth on the development and growth of contractile root (s) and daughter corm or bulbs were investigated in gladiolus and oxalis.
1. In gladiolus, all contractile roots were markedly depressed in elongation and thickening, being 5mm in length and turning brown at their tips, at a planting depth of 0cm. At planting depths of 15 and 30cm, the contractile roots elongated a little but were very poor in thickening growth. At the standard depth of 5cm, however, they elongated, thickened and then contracted much favorably. In oxalis, the growth of the contractile root was more favored with increases in planting depth within the range 4 to 12cm and even at 0cm it reached about a half of that at 4 to 12cm. They contracted smoothly at all planting depths.
2. In both gladiolus and oxalis, daughter corm or bulbs, like contractile root (s), were always inferior in their growth at a planting depth of 0cm. In oxalis, the daughter bulbs corresponded well in their early growth with the contraction of the contractile root and their final weights were greater with greater planting depths within the range 4 to 12cm. In gladious, the growth of daughter corm was markedly inferior at a planting depth of 30cm, but at 15cm, it was excellent regardless of poor growth of contractile roots and superior, though a little, to that at 5cm, where the growth and contraction of contractile roots proceeded favorably.
3. The contribution rate of the contractile root (s) to the thickening growth of daughter corm or bulbs at the early days of contraction of the contractile root (s) was estimated at about 52% in oxalis regardless of planting depth. While, in gladiolus, it was below 1% except about 18% at a planting depth of 5cm.
