Pharmacognosy I Lecture 4 (Anatomy) PDF

Pharmacognosy I Lecture 4 ‫اﶈﺎﴐة اﻟﺮاﺑﻌﺔ‬ Ahmed Elbermawi, PhD Lecturer of Pharmacognosy Type of stomata ? A B C D Describe ? Type of Vascular bundle ? A B  Anatomy...

Pharmacognosy I Lecture 4 ‫اﶈﺎﴐة اﻟﺮاﺑﻌﺔ‬ Ahmed Elbermawi, PhD Lecturer of Pharmacognosy Type of stomata ? A B C D Describe ? Type of Vascular bundle ? A B  Anatomy of primary plant organs Leaves  The plant main photosynthetic system. Stems  A support system for the plant body.  A transport system that carries nutrients.  A defense system that protects the plant against predators and diseases. Roots  Absorb water and dissolved nutrients.  Anchor plants in the ground.  Protect the plant from harmful soil bacteria and fungi. primary and secondary growth in plants. Primary growth increases the length of the plant, occurring at the tips of roots and shoots due to the activity of apical meristems, while secondary growth increases the thickness or girth of the plant due to the activity of lateral meristems (vascular cambium and cork cambium).  Anatomy of the root A root consists of a central vascular cylinder (stele) surrounded by ground tissue (cortex), and the epidermis (piliferous layer, epiblema). Why are root hairs important for plant survival? Answer: Root hairs increase the surface area for absorption, allowing the plant to take in more water and nutrients from the soil, which is essential for growth and development. The root cap protects the Apical meristem of the root during growth. 1- Piliferous layer: One layered, cells are thin with no cuticle or stomata, their outer walls have many root hairs. 2- Cortex: It consists of several layers of parenchyma cells, or some of them are sclerenchymatous as in monocot. After the piliferous layer is ruptured, the cells of the outermost layer or few layers of the cortex become suberized and replace the piliferous layer in the function of protection. This hypodermal layer called exodermis. What is the main function of the Casparian The innermost layer of the cortex strip in roots? develops into an endodermis, which is The Casparian strip regulates the flow of water characterized by the presence of the and dissolved minerals into the vascular tissue casparian strips. by forcing substances to pass through the Casparian strips are deposits of suberin plasma membrane of the endodermal cells. and lignin on the radial walls only (in dicots), or on radial and inner tangential Pericycle is the plant structure responsible for walls (in monocots). the initial formation of lateral roots. Vascular cylinder (Stele) It is surrounded by the pericycle. The pericycle consists of one layer of thin-walled parenchyma cells, rarely more than one layer. The vascular tissues are phloem and xylem on alternating radii. Xylem: is differentiated into proto- and meta- xylem Proto-xylem has narrow vessels and locates opposite to the pericycle, the meta-xylem vessels are wider and directed towards the center. Anatomy of the root Dicot root Monocot root Comparison between Dicot root and monocot root Anatomy of the stem  1- Dicotyledons Stem 1- Epidermis single row of cells generally bears stomata and hairs and covered with cuticle. 2- Cortex (ground tissue): narrow, it may be differentiated into a- Hypodermis: collenchyma in nature devoid of contents. b- Ground parenchyma: o Outer region: usually contain chloroplasts ‫صغير‬ ‫وهو‬ (chlorenchyma). o Middle region: may show sclerenchyma or secretory structures (oil cells, glands or laticeferous ducts) or idioplasts of ca-ox crystals. c- Endodermis: The innermost layer of cortex of dicot stems contains starch grains and is called starch sheath. ♣ Cambium arranged in a single ring around central region called pith or medulla. ♣ M.R. are a number of parenchymatous strands between V.B. from pith to the cortex. ♣ Ground tissues: composed of cortex, pith, and medullary rays.  2- Monocot Stem ♣ Showed a large number of closed V.B. scattered irregularly through the ground tissues. ♣ They are smaller and more crowded near the periphery of the stem than in the center, where they are larger and less in number. ♣ Pith, M.R., cortex, endodermis and pericycle are indistinguishable. ♣ Hypodermis: mostly sclerenchymatous.  Dicot stem Monocot stem  V.B Open  V.B Closed  V.B. arranged in a single ring around  V.B. large number and scattered a central region called pith. irregularly through the ground  Cortex, Pith, Pericycle, Endodermis tissue. are well-marked.  Cortex, Pith, Pericycle, Endodermis  Hypodermis almost collenchyma. are indistinguishable.  Hypodermis almost sclerenchyma. Anatomy of the leaves  The distribution of tissues in leaves is quite different from that of roots and stems. It is also different in both midrib and lamina regions. In T.S, tissues are arranged from upper to lower surfaces as follows: o The epidermis o The ground tissue o The vascular tissue The epidermis Is found as a single layer on both the upper and lower surfaces. Trichomes and stomata are present on either sides or one of them, stomata are more frequent on the lower epidermis. The ground tissue It is known as mesophyll which is usually specialized as a photosynthetic tissue. In Dicots, it is divided into palisade and spongy parenchyma. a. Palisade tissue consists of one or more layers of elongated cells below the epidermis and perpendicular to it. - The palisade cells contain abundant chloroplasts and have narrow intercellular spaces between them. - Palisade may be present on one surface only (dorsiventral leaves) or on both surfaces (isobilateral leaves). a. Spongy tissue consists of irregular shaped cells, have large intercellular spaces. The cells contain less chloroplasts than the palisade cells, so they are less specialized as photosynthetic tissue. In monocots, the mesophyll cells are all alike i.e., not differentiated into palisade and spongy cells. The Vascular tissue:  In the center, there is the main vascular bundle. The type of the V.B. of the leaf is the same as that in the corresponding stem.  The vascular tissues is formed of xylem and phloem arranged in strands; the xylem is located above the phloem.  The protoxylem is directed towards the upper epidermis. In Dicot o The large bundles is surrounded by several layers of parenchyma (sheath). o Supporting tissues are of collenchyma cells located below the upper and lower epidermis opposite to the bundles. In monocots: o The bundle sheath may be parenchyma or sclerenchyma or thick walled parenchyma. o Supporting tissues are usually fibers (above and below the bundles). Comparison between Dicot leaf and monocot leaf differentiated undifferentiated Dicot leaf Monocot leaf ‫ﻟﻼﻃﻼع ﻓﻘﻂ‬ ‫ﻟﻼﻃﻼع ﻓﻘﻂ‬ Choose * Sclereids are considered as one of the following tissues: 1- Conducting 2- Secretory 3- Dermal 4- Ground * The main function of parenchyma is: 1- Support 2- Protection 3- Conduction 4- Storage * Tracheids differ from fibers by having: 1- Bordered pits 2- Half bordered 3- Simple pits 4- No pits * Hypodermis layer in cortex in Dicot. Stems is: 1- Collenchyma 2- Parenchyma 3- Aerenchyma 4- Sclerenchyma * The main function of the dermal tissue is: 1. Protection 2- Support 3- Secretion 4- Conduction * Dermal tissue is presented in plants as: 1. Pith 2- Cortex 3- Epidermis 4- Phloem * Hairs is called glandular when they have: 1- Branched stalk 2- Secretory head 3- unicellular stalk 4- Bicellular stalk * Supporting tissue in Dicot. Stems is: 1. Sclerenchyma 2- Aerenchyma 3- Parenchyma 4- Collenchyma * Dicot. Roots differ from Monocot. Roots by having: 1. Wide pith 2- Numerous V.B. 3- Collateral V.B. 4- V.B. from 2-8