Internal Growth Factors in Plants:

• Auxins:  best-know plant hormones.  Primarily involved in promoting plant cell elongation.

• Gibberellins: promote cell division and elongation in plant shoots.  This process, called bolting, produces long stem that raises flower up to pollinators and the wind.

• Cytokinins: stimulate cell division and leaf mesophyll growth. Concentrated in endosperm tissue.

• Ethylene: role in fruit ripening and colour change.  When transporting fruit, they keep it in conditions low in ethylene.

• Abscisic acid: growth regulator, acts as an inhibitor.  Promotes closure of stomata, inducing seed and bud dormancy, and provide resistance to water stress.

 

External Growth Factors in Plants:

• Light requirements:  less than 1% of light is captured by plants during photosynthesis.  Green plants trap light using pigments (chlorophyll, carotenoids etc..).  Both quantity and quality of light affects plants growth.

• Soil nutrients: 17 elements considered by nutritionists to be essential to plants healthy growth and reproduction.  9 macronutrients and 8 micronutrients.

• Nitrogen: nitrogen demand only surpassed by need for water and carbon dioxide.   One main reservoir is organic mater of living and dead organisms.  Other major reservoir is the atmosphere, which is 79% nitrogen.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sandner, L., & Ellis, C. (2011). Pearson investigating science BiologySource 11. Toronto: Pearson Education Canada.