PHYTOHORMONE INTERACTION IN PROTONEMA DIFFERENTIATION IN THE WILD STRAIN AND AUXIN MUTANTS OF THE MOSS FUNARIA HYGROMETRICA

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  Caulonema differentiation in the moss Funaria hygrometrica has been observed to be governed by an interaction of auxins, cyclic AMP, ethylene and calcium, contrary to earlier observations that it is strictly an auxin-mediated response. This has been demonstrated from the present work by utilizing an auxin-sensitive and auxin-insensitive mutants of Funaria. The role of auxins in protonema differentiation is both inductive (mutant 87.13 and NAR-2) and stimulatory (wild type). Similar observation has also been made using the precursor for ethylene biosynthesis i.e. 1-aminocyclopropane-1-carboxylic acid (inductive effect in the mutant 86.1 and promotory in the mutant 87.13 and wild type). It appears that the endogenous cAMP level in the protonema must be maintained low in order to discern the effect of added auxin, as demonstrated by IAA-alloxan interaction in the mutant NAR-2. Lastly, interaction of auxin with ethylene and cAMP appears to act through an elevation in the intracellular Ca²⁺ concentration, as demonstrated by the use of Ca²⁺ ionophore A 23187. Thus, auxin action on protonema differentiation appears to be mediated through multiple inputs toward the single response.