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Institute of Life Long Learning, University of Delhi 
 
0 
                                                                                              
 
Lesson Prepared Under MHRD project “National Mission on 
Education Through ICT” 
Discipline: Botany 
Paper: Plant Anatomy 
National Coordinator: Prof. S.C. Bhatla 
Lesson: Trichomes and Stomata  
Lesson Developer: Dr Smriti Singh 
Department/College: Acharya Narender Dev College 
 
Lesson Reviewer: Dr Girish Mishra 
Department/College: Botany, University of Delhi 
Language Editor: Dr Sonal Bhatnagar 
Department/College: Hindu College 
 
 
Lesson Editor: Dr Rama Sisodia, Fellow in Botany ILLL
Page 2


 
 
 
Institute of Life Long Learning, University of Delhi 
 
0 
                                                                                              
 
Lesson Prepared Under MHRD project “National Mission on 
Education Through ICT” 
Discipline: Botany 
Paper: Plant Anatomy 
National Coordinator: Prof. S.C. Bhatla 
Lesson: Trichomes and Stomata  
Lesson Developer: Dr Smriti Singh 
Department/College: Acharya Narender Dev College 
 
Lesson Reviewer: Dr Girish Mishra 
Department/College: Botany, University of Delhi 
Language Editor: Dr Sonal Bhatnagar 
Department/College: Hindu College 
 
 
Lesson Editor: Dr Rama Sisodia, Fellow in Botany ILLL
Trichomes and Stomata 
Institute of Lifelong Learning, University of Delhi 1 
Table of Contents  
Chapter: Trichomes and Stomata 
? Trichomes 
? Types 
? Glandular trichomes 
? Non glandular trivhomes 
? Functions             
? Stomata 
? Types 
? Functions             
? Summary 
? Glossary    
? Exercise 
? References 
 
 
 
 
 
 
Page 3


 
 
 
Institute of Life Long Learning, University of Delhi 
 
0 
                                                                                              
 
Lesson Prepared Under MHRD project “National Mission on 
Education Through ICT” 
Discipline: Botany 
Paper: Plant Anatomy 
National Coordinator: Prof. S.C. Bhatla 
Lesson: Trichomes and Stomata  
Lesson Developer: Dr Smriti Singh 
Department/College: Acharya Narender Dev College 
 
Lesson Reviewer: Dr Girish Mishra 
Department/College: Botany, University of Delhi 
Language Editor: Dr Sonal Bhatnagar 
Department/College: Hindu College 
 
 
Lesson Editor: Dr Rama Sisodia, Fellow in Botany ILLL
Trichomes and Stomata 
Institute of Lifelong Learning, University of Delhi 1 
Table of Contents  
Chapter: Trichomes and Stomata 
? Trichomes 
? Types 
? Glandular trichomes 
? Non glandular trivhomes 
? Functions             
? Stomata 
? Types 
? Functions             
? Summary 
? Glossary    
? Exercise 
? References 
 
 
 
 
 
 
Trichomes and Stomata 
Institute of Life Long Learning, University of Delhi 
2 
 
Trichomes  
Trichomes are the unicellular or multicellular epidermal appendages that occur in various 
morphological forms like hairs, scales, warts, papillae etc. They can be persistent or 
ephemeral (fall off) e.g. Lantania verschaffeltii. They are found on almost all the above 
ground parts (shoot) of the plant body. All the trichomes on a plant body are collectively 
referred to as indumentums. 
Different types of trichomes 
Trichomes are of two types: glandular and non-glandular. Glandular trichomes secrete 
water, salt, mucilage, nectar, alkaloid, terpenes, resins etc. They are also known as 
secretory trichomes or glands. They can also be classified on the basis of number of cells 
(unicellular/multicellular) and layers (uniseriate/multiseriate). Multicellular or multiseriate 
trichomes are also known as shaggy e.g. Anabasis, Cleome. 
 
 Figure: Classification of trichomes 
 
Glandular 
 
Trichomes 
(unicellular/multicellular) 
 epidermal appendages 
Lipophilic 
Ocimum, 
Mentha 
Non-glandular 
Vesicular hair 
(non-flattened) 
Gossypium, Triticum 
Squamiform 
hair 
(flattened) 
Stellate 
Styrax,  
Platanus 
T-shaped 
Corokia, 
Olearia 
Scales 
(sessile) 
Croton, 
Bromeliaceae 
 
Peltate 
(Stalked) 
Oleo 
Dendroid 
Brassica,  
Iberis 
Hydrophilic 
Atriplex, 
Rumex 
Page 4


 
 
 
Institute of Life Long Learning, University of Delhi 
 
0 
                                                                                              
 
Lesson Prepared Under MHRD project “National Mission on 
Education Through ICT” 
Discipline: Botany 
Paper: Plant Anatomy 
National Coordinator: Prof. S.C. Bhatla 
Lesson: Trichomes and Stomata  
Lesson Developer: Dr Smriti Singh 
Department/College: Acharya Narender Dev College 
 
Lesson Reviewer: Dr Girish Mishra 
Department/College: Botany, University of Delhi 
Language Editor: Dr Sonal Bhatnagar 
Department/College: Hindu College 
 
 
Lesson Editor: Dr Rama Sisodia, Fellow in Botany ILLL
Trichomes and Stomata 
Institute of Lifelong Learning, University of Delhi 1 
Table of Contents  
Chapter: Trichomes and Stomata 
? Trichomes 
? Types 
? Glandular trichomes 
? Non glandular trivhomes 
? Functions             
? Stomata 
? Types 
? Functions             
? Summary 
? Glossary    
? Exercise 
? References 
 
 
 
 
 
 
Trichomes and Stomata 
Institute of Life Long Learning, University of Delhi 
2 
 
Trichomes  
Trichomes are the unicellular or multicellular epidermal appendages that occur in various 
morphological forms like hairs, scales, warts, papillae etc. They can be persistent or 
ephemeral (fall off) e.g. Lantania verschaffeltii. They are found on almost all the above 
ground parts (shoot) of the plant body. All the trichomes on a plant body are collectively 
referred to as indumentums. 
Different types of trichomes 
Trichomes are of two types: glandular and non-glandular. Glandular trichomes secrete 
water, salt, mucilage, nectar, alkaloid, terpenes, resins etc. They are also known as 
secretory trichomes or glands. They can also be classified on the basis of number of cells 
(unicellular/multicellular) and layers (uniseriate/multiseriate). Multicellular or multiseriate 
trichomes are also known as shaggy e.g. Anabasis, Cleome. 
 
 Figure: Classification of trichomes 
 
Glandular 
 
Trichomes 
(unicellular/multicellular) 
 epidermal appendages 
Lipophilic 
Ocimum, 
Mentha 
Non-glandular 
Vesicular hair 
(non-flattened) 
Gossypium, Triticum 
Squamiform 
hair 
(flattened) 
Stellate 
Styrax,  
Platanus 
T-shaped 
Corokia, 
Olearia 
Scales 
(sessile) 
Croton, 
Bromeliaceae 
 
Peltate 
(Stalked) 
Oleo 
Dendroid 
Brassica,  
Iberis 
Hydrophilic 
Atriplex, 
Rumex 
Trichomes and Stomata 
Institute of Life Long Learning, University of Delhi 
3 
 
 
Figure: Different types of trichomes 
Source: http://www.cas.miamioh.edu/~meicenrd/ANATOMY/Ch11_Secretory/trichomes.jpg 
 
Glandular trichomes  
These can be classified as hydrophilic and lipophilic, depending upon the nature of their 
secretions. In the former type, the secretion is in the form of an aqueous solution, whereas, 
the latter secrets resins, essential oils, waxes and lipids. Glandular trichomes consist of a 
secretory apical bulbous cell attached to non-secretory stalk and basal cells. In some 
species there are collecting cells which are modified epidermal cells. Similar to epidermal 
cells, trichomes also have cuticle covering and secreted substances accumulate beneath the 
Page 5


 
 
 
Institute of Life Long Learning, University of Delhi 
 
0 
                                                                                              
 
Lesson Prepared Under MHRD project “National Mission on 
Education Through ICT” 
Discipline: Botany 
Paper: Plant Anatomy 
National Coordinator: Prof. S.C. Bhatla 
Lesson: Trichomes and Stomata  
Lesson Developer: Dr Smriti Singh 
Department/College: Acharya Narender Dev College 
 
Lesson Reviewer: Dr Girish Mishra 
Department/College: Botany, University of Delhi 
Language Editor: Dr Sonal Bhatnagar 
Department/College: Hindu College 
 
 
Lesson Editor: Dr Rama Sisodia, Fellow in Botany ILLL
Trichomes and Stomata 
Institute of Lifelong Learning, University of Delhi 1 
Table of Contents  
Chapter: Trichomes and Stomata 
? Trichomes 
? Types 
? Glandular trichomes 
? Non glandular trivhomes 
? Functions             
? Stomata 
? Types 
? Functions             
? Summary 
? Glossary    
? Exercise 
? References 
 
 
 
 
 
 
Trichomes and Stomata 
Institute of Life Long Learning, University of Delhi 
2 
 
Trichomes  
Trichomes are the unicellular or multicellular epidermal appendages that occur in various 
morphological forms like hairs, scales, warts, papillae etc. They can be persistent or 
ephemeral (fall off) e.g. Lantania verschaffeltii. They are found on almost all the above 
ground parts (shoot) of the plant body. All the trichomes on a plant body are collectively 
referred to as indumentums. 
Different types of trichomes 
Trichomes are of two types: glandular and non-glandular. Glandular trichomes secrete 
water, salt, mucilage, nectar, alkaloid, terpenes, resins etc. They are also known as 
secretory trichomes or glands. They can also be classified on the basis of number of cells 
(unicellular/multicellular) and layers (uniseriate/multiseriate). Multicellular or multiseriate 
trichomes are also known as shaggy e.g. Anabasis, Cleome. 
 
 Figure: Classification of trichomes 
 
Glandular 
 
Trichomes 
(unicellular/multicellular) 
 epidermal appendages 
Lipophilic 
Ocimum, 
Mentha 
Non-glandular 
Vesicular hair 
(non-flattened) 
Gossypium, Triticum 
Squamiform 
hair 
(flattened) 
Stellate 
Styrax,  
Platanus 
T-shaped 
Corokia, 
Olearia 
Scales 
(sessile) 
Croton, 
Bromeliaceae 
 
Peltate 
(Stalked) 
Oleo 
Dendroid 
Brassica,  
Iberis 
Hydrophilic 
Atriplex, 
Rumex 
Trichomes and Stomata 
Institute of Life Long Learning, University of Delhi 
3 
 
 
Figure: Different types of trichomes 
Source: http://www.cas.miamioh.edu/~meicenrd/ANATOMY/Ch11_Secretory/trichomes.jpg 
 
Glandular trichomes  
These can be classified as hydrophilic and lipophilic, depending upon the nature of their 
secretions. In the former type, the secretion is in the form of an aqueous solution, whereas, 
the latter secrets resins, essential oils, waxes and lipids. Glandular trichomes consist of a 
secretory apical bulbous cell attached to non-secretory stalk and basal cells. In some 
species there are collecting cells which are modified epidermal cells. Similar to epidermal 
cells, trichomes also have cuticle covering and secreted substances accumulate beneath the 
Trichomes and Stomata 
Institute of Life Long Learning, University of Delhi 
4 
 
cuticle, which are secreted out subsequently either by rupture of cuticle or through pores in 
it. 
 
Hydrophilic type 
1) Salt secreting trichomes: These are very common in halophytes and marshy plants 
such as Tamarix, Avicenna and Atriplex. They secrete out the excess salt and help in 
maintaining the osmolarity. In Atriplex salt secreting structure consists of a stalk of two to 
three cells and a vesiculate head which has large vacuoles where the salt solution 
accumulates. Once they are full of salt, the trichome withers away and the stalk remains on 
the leaf surface as a salty deposit. 
 
 
 
 
 
 
 
 
 
 
Figure: Salt gland in Atriplex B- bladder, C- cuticle, Ch- chlorophyll, E- epidermal cells, M- 
mitochondria, P- plasmodesmata, v- vacuole 
 
Source:http://upload.wikimedia.org/wikipedia/de/thumb/0/00/Halophyt02_003.jpg/220px-
Halophyt02_003.jpg 
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FAQs on Lecture 9 - Trichomes and Stomata - Plant Anatomy - Biotechnology Engineering (BT)

1. What are trichomes and stomata in plant biology?
Ans. Trichomes are small hair-like structures that can be found on the surface of leaves, stems, and other plant parts. They serve various functions such as reducing water loss, protecting against herbivores, and providing shade. Stomata, on the other hand, are tiny pores found on the surface of plant leaves and stems. They regulate the exchange of gases, including oxygen and carbon dioxide, as well as water vapor.
2. How are trichomes and stomata important in biotechnology engineering?
Ans. Trichomes and stomata play significant roles in biotechnology engineering. Trichomes can be manipulated to enhance the production of medicinal compounds, such as cannabinoids in cannabis plants. By modifying the trichome density or size, biotechnologists can increase the yield of these valuable compounds. Stomata, on the other hand, are crucial for optimizing photosynthesis and water-use efficiency in crops, which can be improved through biotechnological approaches.
3. Can trichomes and stomata be engineered to improve crop traits?
Ans. Yes, trichomes and stomata can be engineered to improve crop traits. For example, by manipulating the density or type of trichomes, scientists can enhance resistance against pests and diseases. Similarly, controlling stomatal density or behavior can improve a plant's water-use efficiency, allowing it to better withstand drought conditions. Biotechnology offers tools for genetic modification and genome editing that can be employed to achieve these desired traits.
4. How do trichomes and stomata contribute to plant defense mechanisms?
Ans. Trichomes serve as physical barriers against herbivores, making it difficult for them to feed on plants. Some trichomes also produce toxic or irritating substances that deter herbivores. Stomata, on the other hand, can close in response to herbivore attack or pathogen invasion, reducing the entry points for these attackers. By triggering defense responses, trichomes and stomata contribute to the plant's overall defense mechanisms.
5. Are there any disadvantages to manipulating trichomes and stomata in plants?
Ans. While there are potential benefits to manipulating trichomes and stomata, there can also be disadvantages. Altering trichome density or size may inadvertently affect other plant traits or disrupt ecological interactions, such as pollination. Manipulating stomatal behavior could also have unintended consequences on a plant's overall physiology or susceptibility to certain stresses. Therefore, careful consideration and thorough research are necessary to minimize any potential negative impacts when engineering trichomes and stomata in plants.
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