Plant Hormones (part 1) | hormone | Gibberellins

Plant Hormones (part 1)

•  There are five major types of plant hormones:

1. Gibberelins
2. Cytokinins
3. Ethylene
4. Abcisic Acid
5. Auxins

  

• The structure and function of each type of hormone will be described

Gibberellins 
 

•  Gibberellins (GAs) regulate and influence:

1. cell elongation
2. seed germination
3. dormancy
4. flowering
5. sex expression
6. enzyme induction
7. leaf and fruit senescence.

 Germination




Signal starch hydrolysis through inducing the synthesis of the enzyme   
α-amylase in the aleurone cells 

Gibberellins produced in the scutellum diffuse to the aleurone cells where 
they stimulate the secretion α-amylase 

α-Amylase then hydrolyses starch into glucose 

Gibberellins cause higher levels of transcription of the gene coding for 
the α-amylase enzyme 



Gibberellins: Chemical Structure


Gibberelins have complex ring structures 

Typically contain carboxylic acid groups  

Many specific gibberelins exist

• Numeric naming system (i.e. GA#) 

May be classified into two structural types:

• C-19 Gibberelins (19 carbon)  
• C-20 Gibberelins (20 carbon

 

Type 1:  19 Carbon Gibberelins

Type 2 :  20 Carbon Gibberelins