01121naa a2200133 a 450000100080000000500110000800800410001910000170006024500680007726000090014552007650015465000160091977300520093516490112023-05-10       1991    bl uuuu     u00u1 u    #d1 aTREWAVAS, A.  ahow do plant growth substances work? II.h[electronic resource]  c1991  aThis article continues the discussion on sensitivity prompted by the publication of an earlier paper by the author in 1981. It is indicated that appropriate measurements of sensitivity can help uncover the function of growth substances in development. The experimental constraints which are necessary for unambigous measurements of sensitivity are outlined and it is shown that a specific sensitivity measurement, termed control strength, would most readily clarify function and help obviate controversy. Methods for measuring control strenght which deal with the problem of compartmentalization are considered and it is suggested that stochastic variation in single cell biochemistry might provid a contraint on the accuracy of control strength determination.  aCrescimento  tPlant Cell and Environmentgv.14, p.1-12, 1991.