Programmed Cell Death During Cavity Formation In The Leaf Of Typha Angustifolia Linn

Aerenchyma is the term given to plant tissues containing enlarged gas spaces exceeding those commonly found as intracellular spaces. It is formed in the root and shoot of wetland species. Aerenchyma are various in shape, and the structure is complex but the function unitary. The classical viewpoint consider that it is the channel for gas transport. Aerenchyma exists not only in root, stem and leaf but the pericarp also found. Two mechanisms of aerenchyma formation have been described:schizogenous aerenchyma and lysigenous aerenchyma. Schizogenous, in which development results form the cell separation; lysigenous aerenchyma is the other type which formation involves cell death. As an aquatic plant, and one of major limitation is gas transport, aerenchyma formation in the leaves and roots of Typha angustifolia Linn can solute this problem.The study about shape and structure of mature aerenchyma in the leaf of T. angustifolia has been reported, but the relationship between aerenchyma and programmed cell death has not been seen. The morphological characteristics and development of cavity in the leaf of T. angustifolia. was studied by plant anatomy. DNA gel electrophoresis and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) focus on DNA cleavage. DAPI staining shows the changes of nucleus shape. Transmission electron microsope indicates ultrastructural changes in death cells. All the methods reveal programmed cell death play a role in the aerenchyma formation in the leaf of T. angustifolia.The development of cavity in the leaf of T. angustifolia start from solid phase, cells deformation result to gaps appear between cells, and then afer cells degradation the cavity formation. Obvious PCD characteristics during the development of cavity in the leaf of T. angustifolia. Gel electrophoresis indicates that DNA cleavage is random and does not result in bands that represent multiples of internucleosomal units. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) positive also indicates that DNA cleavage event. DAPI can clearly show that all periods of nuclei changes in shape. Initial nucleus is regular roundness, then chromatin condensed, nucleus deformity finally disappear in the cell. Ultrastructural analysis of cells reveals missshapen, densely stained nuclei with condensed chromatin, disrupted vacuoles, and condensed cytoplasm, finally cell well has been hydrolysed. All these events have shown that the cavity formation in the leaf of T. angustifolia result from programmed cell death.