Plant Tissue Systems
Session 4: Plant Tissue Systems
Total Session Time: 60 minutes
Prerequisites
Learning Tasks
By the end of this session students are expected to be able to:
Resources Needed:
SESSION OVERVIEW
|Step |Time |Activity/ |Content |
| | |Method | |
|1 |05 minutes |Presentation |Introduction, Learning Tasks|
|2 |45 minutes |Presentation |Tissue Systems and their |
| | |Small group |Categorization |
| | |discussion | |
|3 |05 minutes |Presentation |Key Points |
|4 |05 minutes |Presentation |Evaluation |
SESSION CONTENTS
STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)
READ or ASK students to read the learning objectives and clarify
ASK students if they have any questions before continuing.
STEP 2: Tissue Systems and Their Categorization (45 minutes)
|Activity: Small Group Discussion (15 minutes) |
| |
|Ask students to work in groups on the following question: |
|How do you categorize tissues system? |
| |
|ALLOW few students to respond |
| |
|WRITE their responses on the flip chart/board |
| |
|CLARIFY and SUMMARISE by using the content below |
irrespective of its position in the plant body
o Dermal (Epidermal) tissue system,
o vascular tissue system and
o Fundamental (Ground) tissue system
o Epidermal Tissue System:
epidermis
o Are unicellular or multicellular appendages originating from the
epidermal cells
o Trichomes may be branched or unbranched
o Excessive loss of water due to the presence of cuticle
o Epidermis protects the underlying tissues
o Stomata are involved in transpiration and gaseous exchange
o Trichomes help dispersal of seeds and fruits
o Root hairs absorb water and mineral salts from the soil
o Consists of xylem and phloem
o Elements of xylem and phloem are always organized in groups called
vascular bundles
o In dicot stems, the vascular bundle consists of cambial tissue in
between xylem and phloem (i.e. Open vascular bundle)
o In monocot stem, cambium is absent in the vascular bundle (i.e. closed
vascular bundle)
o In roots, xylem and phloem are arranged in an alternate manner on
different radii, this is called radial arrangement
o In stems and leaves, xylem and phloem are arranged at the same radius
and form a vascular bundle together (i.e. Conjoint vascular bundle)
o Conjoint vascular bundles may be;
o Concentric vascular bundle
o Either phloem or xylem surrounds the other completely
o It is amphicribral if the phloem completely surrounds the xylem
o It is amphivasal if the xylem completely surrounds the phloem
o Form the main body of the plants (bulk of plant)
o Includes all the tissues except epidermis and vascular bundles
o In monocot stem, ground tissue system is a continuous mass of
parenchymatous tissue in which vascular bundles are found scattered
i.e. ground tissue is not differentiated into cortex, endodermis,
pericyclic and pith.
o In the leaves, ground tissue is made of chlorenchyma tissues forming
the mesophyll
o These cells are arranged in a single layer without intercellular spaces
o Cells in the pith generally store starch, fatty substances, tannins,
phenols, calcium oxalate crystals, etc.
o Cells or organizations of cells that produce a variety of secretions
o Secreted substance may remain deposited within secretory cell itself or
may be excreted (released from the cell)
o The substance maybe excreted to the surface of the plant or into
intercellular cavities or canals
o Some of the secretions are waste products e.g. resins, rubber, tannins
and various crystals
o Other secretions are useful in plants e.g. enzymes and hormones.
o Secretory structures may be single cells or group of cells (glands)
o Oil cells occur in ginger, pepper, mace, cardamoms, cinnamon and cassia
o The latex cells (produce latex) are found e.g. in Cannabis sativa
STEP 3: Key Points (5 minutes)
irrespective of its position in the plant body
vascular tissue system and fundamental (Ground) tissue system
systems
STEP 4: Evaluation (5 minutes)
References
Trease, G. E., Evans, W. C., & Evans, D. (2009). Trease and Evans
pharmacognosy. London: Saunders.
Joanne Barnes et al (2002), Herbal medicines 3rd Edition: Pharmaceutical
Press
Wallis, T. E. (2005). Textbook of pharmacognosy. New Delhi: CBS.
Robbers, J. E., Speedie, M. K., Tyler, V. E., & Tyler, V. E. (1996).
Pharmacognosy and pharmacobiotechnology. Baltimore: Williams &
Wilkins.
Heinrich, M., Kinghorn, A. D., Maizels, D., Gibbons, S., & Phillipson, J.
Churchill Livingstone/Elsevier.
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