Studies on the Growth and Flowering of Bulbous Plants of Amaryllidaceae

1. Growth and Flowering of Lycoris Plants Grown in the Field

Abstract

The bulb structure, and the growth periodicity in mid-Japan in matured bulbs of six species of Lycoris were observed.
1. A bulb shows a sympodial branching system, each unit of which is composed of a membranous scale, a number of foliage leaf bases and a ungulate scale in 1/2 alternate arrangement from the base upwards, and terminates in an inflorescence. The number of foliage leaves developed from a nuit of the sympodium, whose bases encircle the axis differed between species, ranging from about 5 in L. radiata to 10 in L. squamigera.
2. At the time of flower initiation, lateral growing points are formed in the axil of the upper two or three leaves. When they carry on growth, the uppermost one grows into the next unit of the sympodium and the lower ones develop to be daughter bulbs. The new unit of the sympodial branch first forms a membranous scale on the same side as the inflorescence.
3. At lifting time, a large bulb is made up of three units or a threeyear-old entity. However the outer half of the leaf bases on a outermost unit have disappeared or became brown and papery.
4. The periodic growth during a year was observed from the middle of March. At this time, each of the species remained in vegetative growth. During the middle and end of April the apical growing point became broader and flatter than before, followed by the formation of two spathes a week later. We deemed this phase as the first sign of floral induction. Difference in the time of the spath formation among species was less than two weeks.
5. Initial of the first floret appears from the end of Aril to the middle of May, in which L. incarnata, L. sanguinea and L. squamigera initiated it somewhat earlier than L. albiflora, L. aurea and L. radiata. The inflorescence growth of the former three species progressed faster than the latter three species. Their first florets formed the pollen tetrad in the early of July and came into bloom in the middle or end of August. While, the latter species attained the pollen tetrad stage in the middle of August and bloomed one month later than the former ones.
6. In all the species, a plastclon of leaf formation on the developing bulb unit was short in the early stage of the development and gradually lengthened towards the termination of leaf formation in the latter part of September. The newly formed leaves, excluding a few upper ones, emerged above grouned together with a few leaves which had been formed in the upper nodes of the preceding unit of sympodium and had been resting until this time.
7. The leaves of L. albiflora, L. aurea and L. radiata emerged in the early of October and entered a period of senescence in the early of May and those of L. incarnata, L. sanguinea and L. squamigera began to February of the next year and withered one month later species.