What is the Difference Between Animal and Plant Hormones

The main difference between animal and plant hormones is that animal hormones are complex organic substances, whereas plant hormones are simple organic substances. Furthermore, animal hormones diffuse through the blood, while plant hormones diffuse through xylem and phloem. Also, specific endocrine glands are there in the animal body to produce particular hormones while no specific organs are responsible for the production of plant hormones. 

Animal and plant hormones are two types of signaling molecules. Generally, they play a key role in the growth and development of animals and plants. 

Key Areas Covered 

1. What are Animal Hormones
     – Definition, Structure, Importance
2. What are Plant Hormones
     – Definition, Structure, Importance
3. What are the Similarities Between Animal and Plant Hormones
     – Outline of Common Features
4. What is the Difference Between Animal and Plant Hormones
     – Comparison of Key Differences

Key Terms 

Animal Hormones, Blood, Phloem, Plant Hormones, Signaling Molecules, Xylem

What are Animal Hormones 

Animal hormones are the signaling molecules produced by the endocrine glands of multicellular animals. Generally, they diffuse through the bloodstream to a distant target organ to regulate physiology or behavior of the animal. Moreover, animal hormones can be either a protein, peptides, amines, steroids, etc.

Furthermore, hormones play a key role in the communication between organs and tissues regulating physiological activities, including digestion, metabolism, respiration, excretion, growth and development, movement, reproduction, etc. They also regulate behavioral activities, including mood, stress, sleep, etc.

Figure 1: Types of Animal Hormones

The target organ of a particular hormone contains specific receptors to bind with the hormone. Generally, this binding activates a signal transduction pathway to exert a particular physiological or behavioral activity. Therefore, only a small concentration of hormones can produce the effect. However, after exerting their activity, hormones are broken down by various methods.  

What are Plant Hormones 

Plant hormones are the signaling molecules produced by plants in extremely low concentrations. Any plant cell is capable of producing plant hormones. Also, these hormones diffuse through xylem and phloem to the target organ. Moreover, they regulate all aspects of functions in plants including reproduction, embryogenesis, determination of the size of organs, pathogen defense, stress tolerance, etc. 

Figure 2: Plant Hormones

Moreover, some examples of plant hormones are: 

• Abscisic acid – An important plant growth inhibitor,
• Auxin – Responsible for cell enlargement, bud formation, as well as root initiation
• Brassinosteroids – A steroid hormone, regulating cell elongation and division, gravitropism, resistance to stress, and xylem differentiation
• Cytokinins  – Responsible for cell division and shoot formation 
• Ethylene – A gas hormone, affecting cell growth and cell shape 
• Gibberellins – Regulating multiple aspects of development 
• Jasmonates – A steroid-based hormone important in plant response to the attack from herbivores and necrotrophic pathogens  
• Salicylic acid – Important in the defense against biotrophic pathogens 
• Strigolactones – Promoting the growth of symbiotic arbuscular mycorrhizal (AM) fungi.  

Similarities Between Animal and Plant Hormones 

• Animal and plant hormones are two types of signaling molecules which play a key role in the growth and development of animals and plants. 
• Moreover, they regulate physiological activities and homeostasis. 
• Generally, various types of hormones occur in both animals and plants. 
• However, they act in very low concentrations. 

Difference Between Animal and Plant Hormones 

Definition 

Animal hormones refer to the organic substances secreted by the endocrine glands of animals to regulate physiological activities and homeostasis while plant hormones refer to any various hormones produced by plants to regulate germination, growth, metabolism, and other physiological activities in plants. Thus, this is the fundamental difference between animal and plant hormones.

Examples 

Generally, some examples of animal hormones are insulin, thyroxine, serotonin, estrogen, progesterone, testosterone, etc. while some examples of plant hormones are auxin, cytokinin, gibberellin, abscisic acid, etc.  

Production 

Specific endocrine glands are there in the animal body to produce particular hormones while no specific organs are responsible for the production of plant hormones. 

Number of Hormones 

Moreover, animals produce a large number of hormones, while plants produce a small number of hormones.  

Complexity 

While animal hormones are complex organic substances, plant hormones are simple organic substances. 

Transport 

Also, another difference between animal and plant hormones is that animal hormones diffuse through the blood while plant hormones diffuse through xylem and phloem.  

Effect 

Animal hormones act on distant target organs while plant hormones act on nearby target organs.  

Response 

Furthermore, animal hormones produce a rapid response, while plant hormones produce a slow response.  

Regulation 

Besides, another difference between animal and plant hormones is their regulation. The production and secretion of animal hormones are regulated by the nervous system, while the production and secretion of plant hormones are not regulated by the nervous system. 

Conclusion 

Basically, animal hormones are any of the numerous signaling molecules produced by specific endocrine glands of animals. Moreover, they are complex organic substances, which diffuse through the bloodstream to a distant target organ to produce a rapid response. In contrast, plant hormones are any of the several signaling molecules produced near the target organs. However, they are simple organic substances, which diffuse either through xylem and phloem to produce a slow response. Therefore, the main difference between animal and plant hormones is their structure and other functional characteristics.    

References:

1. Kerr, Shana. “Animal Hormones.” Biology 1520, Georgia Tech Biological Sciences, 26 Feb. 2018, Available Here.
2. Farabee, M J. “PLANT HORMONES, NUTRITION, AND TRANSPORT.” Plant Hormones/Nutrition, Available Here.

Image Courtesy:

1. “Hormone” By संताजी बबन चवरे (CC BY-SA 4.0) via Commons Wikimedia   
2. “ಪರಿಸರ ವಿಜ್ಞಾನ, ವಿಕಸನ ಮತ್ತು ಸಿಸ್ಟಮ್ಯಾಟಿಕ್ಸ್” By Anjanim734 – Own work (CC BY-SA 4.0) via Commons Wikimedia