(homologous) chromosomes have been derived from the same 

 species, cf. Amphiploid, Allopolyploid. 



Autotomy 



Loss of a part of the body of an organism by self-amputa- 

 tion followed usually by regeneration of the part, as in 

 certain arthropods and lizards. 



Autotrophic 



(1) Refers to organisms which are capable of producing 

 organic substances from inorganic materials by means of 

 energy received from outside of the organisms, e.g., plants 

 with chlorophyll and certain bacteria, cf. Parasitic, Sapro- 

 phytiCj Heterotrophic, Holophytic. (2) Refers to a pond or 

 lake that is restricted in its supply of organic material to that 

 produced within its own confines. 



Autumnal 



Refers to the fall season or Aspect (q. v.). 



Auximone 



A non-essential organic substance such as an extract 

 secured from dung, of unknown chemical composition, which 

 stimulates the growth of certain plants such as duckweeds. 



Auxin 



A substance, natural or synthetic, that controls the growth 

 of plants, cf. Hormone. 



Available Nutrient in Soil 



The part of the supply of nutrient materials such as 

 phosphates in the soil that can be absorbed by plants at rates 

 and amounts required for growth. 



Available Water (in soil) 



The part of the water in the soil that plants can absorb. 



Available Water-holding Capacity (of soil) 



The amount of water available in the soil between the 



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