Growth and Flowering of Leucojum aestivum L. and L. autumnale L. Grown Outdoors

Abstract

The bulb structure, and the growth periodicity of plants grown outdoors were observed using Leucojum aestivum which comes into bloom in early spring and L. autumnale which blooms in August.
1. A bulb shows a sympodial branching system, each unit of which is composed of 6-8 or 9-10 foliage leaves in L. aestivum or L. autumnale, respectively, and a lingulate scale, and terminates in an inflorescence. The bases of foliage leaves, which encircle the axis and gradually enlarge, serve as a food storage organ.
2. When the spathe leaf is being initiated at the apex during the latter part of May, a lateral bud is formed in the axil of the uppermost leaf, which develops into the next sympodial unit.
3. In both species, leaf initiation continues from spring to autumn. Leaves and the primary inflorescence of L. aestivum emerge simultaneously from early to mid-February just before flowering. The leaves wither acropetally from the lower to upper ones and are completely dry by the end of May. In L. autumnale, leaves appear in September and October after flowering and die progressively from the lowest to the apical leaf between December and July. The foliar canopy consists of a few leaves which formed in the upper nodes of the sympodial unit with the flower bud and those which formed in the basal nodes of the next sympodial unit.
4. Initiation of flower bud started in mid-May in L. aestivum and at the end of May in L. autumnale. Inflorescence growth of L. autumnale progressed faster than did that of L. aestivum. Carpel primordia in the first floret of L. autumnale were observed in early June, and pollen tetrads in the latter part of July. The inflorescence bloomed in early August.
5. Carpel differentiation in the first floret of L. aestivum began during the latter part of June but ceased further development until the middle of October. Pollen tetrads were formed in the latter part of February and anthesis occurred in March. In both species, floral parts of the secondary or tertialy inflorescencee differentiated after a slight delay following the formation of florets in the primary inflorescence.