Ambuja Pillai

Studies on the Developmental Anatomy of Ranales II — Nodal Anatomy of Certain Members of Annonaceae, Magnoliaceae, Menispermaceae and Ranunculaceae

Summary Anatomy of mature nodes of Polyalthia, Annona, Artabotrys, Michelia, Cocculus, Delphinium, Nigella and Clematis has been described. Michelia shows a multilacunar multitrace node while all others show a trilacunar, three trace condition. The present study lends support to S innotts view that the three trace trilacunar node is primitive.

Shoot Apical Organization in Acacia nilotica (L.) Delile

Summary The vegetative apices have a tunica-corpus organization and no cytohistological zonation. The corpus is divided into a central mother cell zone (CMZ), peripheral zone (PZ) and pith meristem (PM) based on analysis of the cell net. The tunica is 2-layered, the clarity of the layers depending on the plastochronic stage. The CMZ shows a decrease in depth from the minimal to the maximal stage of the plastochron. The inflorescence and floret apices show a mantle-core organization. In the young reproductive apex the axial cells of the mantle are ligthly stained. The complete inflorescence apex is used up in the production of bracts and florets.

Seedling anatomy of some Asclepiadaceae

Two-day and eight-day old seedlings ofAsclepias curassavica, Calotropis procera andLeptadenia pyrotechnica were studied. The basipetally differentiating epicotylar vasculature and the root-hypocotyl-cotyledonary vasculature are ontogenetically separate units. The cotyledonary node is unilacunar two-trace and the foliar nodes, unilacunar one trace. The unilacunar two trace cotyledonary nodes in advanced families like Apocyanaceae and Asclepiadaceae seem phylogenetically significant.

Zonation in the shoot apex ofMatthiola incana R. Br.

Zonation in the shoot apex ofMatthiola incana was studied histochemically from the mature embryo to flowering. The plumular apex of the mature embryo shows a single-layered tunica covering a homogeneous mass of cells. The first evidence of zonation is seen in the shoot apex of the 2-day old seedling. Zonation is well established on the fourth day after seed wetting with a single-layered tunica covering a lightly stained central mother cell zone, a subjacent pith meristem and a densely stained peripheral zone. In the transitional apex zonation is less marked and there is increased stratification. At 6-weeks, the apex changes into the indeterminate inflorescence apex showing acropetally developing floral primordia. The axially located cells of the inflorescence apex are lightly stained. The histological and histochemical data indicate that zonation resembling that in the vegetative apex is retained to a lesser degree in the inflorescence apex as well.

Studies on the Developmental Anatomy of Ranales VIII Shoot Apical Organisation in Some Members of Menispermaceae and Ranunculaceae

Summary Shoot apical organisation in Clematis, Cocculus, Nigella and Ranunculus is reported. Apical organisation in Clematis and Cocculus fall under one type and in Nigella and Ranunculus under another. In the former the apex is a broad high dome without distinct cytohistological zonation while in the latter it is a low to high dome with cytohistological zonation. The apex shows a tunicacorpus organisation with a single layered tunica in Cocculus and Nigella and two layered in Clematis and Ranunculus. Nigella shows “axial tunica” cells at the summit of the dome. Cytohistologically, the corpus shows corpus mother cells, peripheral and pith mother cells zones. In Clematis nodal plates are noticed. The fluctuation in the number of tunica layers within species does not seem to be taxonomically significant.

Apical meristems inNymphaea stellata Willd

The shoot apex ofNymphaea stellata Willd. shows a tunica-corpus organization with a cytohistological zonation. The tunica is single-layered and the corpus exhibits three zones, the corpus mother cells zone, the flanking zone and the pith-rib meristem zone. The plastochron is divided into five stages based on the plastochron index—the minimal, early post-minimal, late post-minimal, pre-maximal and maximal. A cambium-like zone is developed proximal to the corpus mother cells zone in apices at the post-minimal stages, which contributes to the increase in height of the apex.The root apex shows a transversal meristem, which is in the form of a curved plate of cells. This cell plate gives rise to the central cylinder, cortex and epidermis proximally, and the columella and periheral region of the root cap distally.

Some aspects of the anatomy ofTecoma stans (L.) H. B. K.

Embryogeny, histogenesis, shoot and root apical meristems, seedling, nodal and floral anatomy and the anatomy of the mature root, stem and leaf ofTecoma stans were studied. During histogenesis the radicular apex is the first to become distinct in the heart-shaped embryo, the epicotyl apex becoming organised later. The radicle has three tiers of initials one each for the stele, cortex and the third for the rhizodermis and root cap. This continues unchanged in the root. The shoot apex shows four cytohistological zones with two to three tunica layers. The node has unilacunar three-trace condition. The floral anatomy is simple and the members of each whorl develop antero-posteriorly. In the hypocotyl of the seedling the xylem and phloem do not split, the xylem groups rotating through 180°. The mature stem, root and leaf show normal structures.