The histology of Belladonna, Catharanthus, Datura, and Withania refers to the microscopic structure of their tissues. Each of these plants is used medicinally, and studying their histology helps to understand their pharmacognostic characteristics. Here’s an overview of the histology for each plant:


1. Belladonna (Atropa belladonna)

  • Family: Solanaceae
  • Tissues:
    • Root:
      • Shows secondary growth. The outer layer is composed of the periderm, replacing the epidermis. The cortex consists of parenchymatous cells with starch grains. The central region has a vascular bundle, including phloem and xylem arranged in a ring, surrounded by cambium.
    • Stem:
      • The epidermis is covered with a cuticle and often has unicellular or multicellular trichomes (hairs). The cortex is parenchymatous with some collenchyma layers for mechanical strength. Secondary growth is visible, with xylem and phloem arranged in vascular bundles. The medullary rays are parenchymatous.
    • Leaf:
      • The epidermis is single-layered and has a thick cuticle. The palisade layer beneath is composed of chlorenchyma. Spongy parenchyma is present in the mesophyll. There are numerous stomata, which are anisocytic (irregularly shaped subsidiary cells).
    • Fruit:
      • The fruit is a berry with an outer epicarp, mesocarp filled with parenchyma cells, and seeds contained within.

2. Catharanthus (Catharanthus roseus)

  • Family: Apocynaceae
  • Tissues:
    • Root:
      • The root has a thick periderm, secondary growth, and xylem vessels arranged in radial bundles. The cortex is parenchymatous, with starch grains and calcium oxalate crystals. The secondary xylem forms a dense wood with abundant lignification.
    • Stem:
      • The epidermis is a single layer of cells with trichomes. The cortex contains collenchyma and parenchyma, with intercellular spaces. Vascular bundles are arranged in a ring, with phloem on the outside and xylem towards the inside. The medullary region contains parenchymatous cells.
    • Leaf:
      • The leaves are dorsiventral, with a distinct palisade and spongy mesophyll layer. The epidermis is cutinized with both upper and lower stomata. Calcium oxalate crystals can be found in the mesophyll region.

3. Datura (Datura stramonium)

  • Family: Solanaceae
  • Tissues:
    • Root:
      • Similar to other Solanaceae members, the root exhibits secondary growth, with a well-developed xylem and phloem. The cortex is made of parenchymatous cells, and starch grains and calcium oxalate crystals are common.
    • Stem:
      • The stem is herbaceous with secondary growth. The epidermis is covered by a thick cuticle and contains trichomes. The vascular bundles are arranged in a ring, with cambium activity leading to secondary thickening. Parenchymatous cells are found in the cortex and pith.
    • Leaf:
      • Leaves are dorsiventral with a distinct cuticular layer. The mesophyll consists of palisade and spongy parenchyma. Stomata are present on both surfaces but more numerous on the lower side (hypostomatic). Trichomes are also present.

4. Withania (Withania somnifera)

  • Family: Solanaceae
  • Tissues:
    • Root:
      • The roots show secondary growth. The cortex is parenchymatous with numerous starch grains and calcium oxalate crystals. Xylem is lignified and forms a solid core in older roots. Phloem is present in a ring outside the xylem.
    • Stem:
      • The stem has a cutinized epidermis with glandular and non-glandular trichomes. The cortex contains parenchymatous cells and some sclerenchyma. Vascular bundles are arranged in a ring with secondary growth, and medullary rays are well developed.
    • Leaf:
      • Leaves are dorsiventral. The upper epidermis is thick with a cuticle. There is a single layer of palisade cells beneath the upper epidermis, while the spongy parenchyma occupies the lower region. Stomata are more frequent on the lower epidermis.

Summary:

  • All four plants exhibit secondary growth in their roots and stems.
  • Parenchymatous cortex, presence of trichomes, and stomata distribution are common histological features.
  • Calcium oxalate crystals and starch grains are frequently observed in the root and stem tissues.

Each plant's histological features are closely related to their family characteristics, with similarities in tissue structure, particularly in Solanaceae members like Belladonna, Datura, and Withania.