The Shoot Apex (Vegetative or Generative) of Heliconia bihai and H. latispatha in Relation to Growth
The shoot apex from plants of Heliconia bihai (L.) L. and H. latispatha Benth. growing under natural inductive conditions, and two shade-loving (60% and 0%) at different growth stages (one to six or eight expanded leaves) was studied. Observations were made using a light microscope, in 15-μm-thick sections. The analysis included changes in 1) size and shape of the meristem, 2) shape, ubication of new leaves, spathes, and flowers in the apex, and 3) relation between these characteristics, the condition of the apex (vegetative, transitional, and generative), and the plant growth stages. The anatomical structures of the shoot apex (meristem, leaves, and flowers primordias) are illustrated by photomicrographs. The meristem change in size and shape with grow up expanded leaf number. The condition of the apex was related to the total leaf number. The total leaf number was five or six in H. bihai under 60% and 0 % shade levels and 8 in H. latispatha at both shade levels. The apex reaches the generative stage when the plant has a minimum expanded leaf number of four (at 60 % shade) and five (0 %) in H. bihai and five in both shade conditions in H. latispatha. After this, the inflorescence started progressively to raise above the rest of rhizome.