<P> A tropism ( from Greek τρόπος , tropos , `` a turning '' ) is a biological phenomenon , indicating growth or turning movement of a biological organism , usually a plant , in response to an environmental stimulus . In tropisms , this response is dependent on the direction of the stimulus ( as opposed to nastic movements which are non-directional responses ) . Viruses and other pathogens also affect what is called `` host tropism '' , `` tissue tropism '' , or `` cell tropism '' , or in which case tropism refers to the way in which different viruses / pathogens have evolved to preferentially target specific host species , specific tissue , or specific cell types within those species . Tropisms are usually named for the stimulus involved ( for example , a phototropism is a reaction to sunlight ) and may be either positive ( towards the stimulus ) or negative ( away from the stimulus ) . </P>
<P> A tropism ( from Greek τρόπος , tropos , `` a turning '' ) is a biological phenomenon , indicating growth or turning movement of a biological organism , usually a plant , in response to an environmental stimulus . In tropisms , this response is dependent on the direction of the stimulus ( as opposed to nastic movements which are non-directional responses ) . Viruses and other pathogens also affect what is called `` host tropism '' , `` tissue tropism '' , or `` cell tropism '' , or in which case tropism refers to the way in which different viruses / pathogens have evolved to preferentially target specific host species , specific tissue , or specific cell types within those species . Tropisms are usually named for the stimulus involved ( for example , a phototropism is a reaction to sunlight ) and may be either positive ( towards the stimulus ) or negative ( away from the stimulus ) . </P>
what is significance of tropic movement in plants
what is significance of tropic movement in plants
response to an environmental stimulus
response to an environmental stimulus