Biological World

  Introduction to Pteridophytes Pteridophytes or ferns are a group of vascular plants with well-developed roots, stems, and leaves, or more usually, fronds, which reproduce via spores and have neither seeds nor flowers. True ferns are the largest group of pteridophytes, although the term is sometimes used to cover all the members of the clade . Accounting for around 10,600 species, they occur in a variety of habitats, particularly in warmer areas, and many have ornamental or agricultural uses such as the maile, a Hawaiian form used in decorations. The pteridophytes depend on a constant supply of water for the maturation of the spores. Most of them require shade for germination, initial development, and rooting. Though atmospheric humidity is advantageous, too much of it becomes detrimental for their growth. Their reproductive habits and the physiochemical nature of life, sap, or juices make them peculiarly vulnerable to drought or desiccation. They take years to produce young plant...

Mitochondria are organelles involved in respiration and energy production in eukaryotes. The shape, number, size and even ultra structure of mitochondria vary between cells, tissues and organisms. Progress in the field of 3D imaging of ultra structural refinement by cryo electron tomography, largely using cryo scanning electron microscopy and focused ion beam/SEM procedures, has greatly enhanced our understanding of cellular complexity. Mitochondria are large organelles (0.5-5.0 μm) in most mammalian cells and show a highly complex ultrastructural architecture. They are surrounded by two membranes, the outer mitochondrial membrane (OMM) and the inner mitochondrial membrane (IMM), which are separated by the intermembrane space (IMS) and the mitochondrial matrix, respectively. Mitochondria have morphological substructures adapted to the requirements of cellular metabolism that arise from invaginations of the IMM into the matrix space. The rigid and smooth part of the IMM is termed the in...