Use of derivatives of (1-cyanocyclopropyl)phenylphosphinic acid, esters thereof and/or salts thereof for enhancing tolerance in plants to abiotic stress

A derivative of (1-cyanocyclopropyl)phenylphosphinic acid or ester thereof, of the formula (I),

• where
• R1 is halogen, branched or unbranched alkyl, cycloalkyl, alkenyl, alkynyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, alkoxyalkyl, hydroxyalkyl, alkoxyalkenyl, alkylthio, haloalkylthio, alkylsulfinyl, alkylsulfonyl, haloalkyl, alkoxy, haloalkoxy, carboxyl, alkoxycarbonyl, aminocarbonyl which is optionally mono- or disubstituted, cyano, amino or nitro,
• R2 is hydrogen, branched or unbranched alkyl, cycloalkyl, cycloalkylalkyl, alkenyl, alkenylalkyl, alkynyl, alkynylalkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, alkoxyalkyl, hydroxyalkyl, alkoxyalkenyl, hydroxyalkenyl, alkylthioalkyl, haloalkyl, alkylaminoalkyl, bisalkylaminoalkyl, cycloalkylaminoalkyl, and
• n is 0, 1, 2, 3, 4, 5,
• excluding ethyl (1-cyanocyclopropyl)phenylphosphinate,
• and
• salts of the formula (II)
• where
• R1 is halogen, branched or unbranched alkyl, cycloalkyl, alkenyl, alkynyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, alkoxyalkyl, hydroxyalkyl, alkoxyalkenyl, alkylthio, haloalkylthio, alkylsulfinyl, alkylsulfonyl, haloalkyl, alkoxy, haloalkoxy, carboxyl, alkoxycarbonyl, aminocarbonyl which is optionally mono- or disubstituted, cyano, amino or nitro,
• n is 0, 1, 2, 3, 4 or 5,
• the cation (M) is
• (a) an ion of the alkali metals, or
• (b) an ion of the alkaline earth metals, or
• (c) an ion of the transition metals, or
• (d) an ammonium ion in which one, two, three or all four hydrogen atoms are optionally replaced by identical or different radicals from the group of (C1-C4)-alkyl, hydroxy-(C1-C4)-alkyl, (C3-C6)-cycloalkyl, (C1-C4)-alkoxy-(C1-C4)-alkyl, hydroxy-(C1-C4)-alkoxy-(C1-C4)-alkyl, (C1-C6)-mercaptoalkyl, phenyl or benzyl, where the aforementioned radicals are optionally substituted by one or more identical or different radicals selected from the group consisting of halogen, F, Cl, Br, I, nitro, cyano, azido, (C1-C6)-alkyl, (C1-C6)-haloalkyl, (C3-C6)-cycloalkyl, (C1-C6)-alkoxy, (C1-C6)-haloalkoxy and phenyl, and where in each case two substituents on the nitrogen atom together optionally form an unsubstituted or substituted ring, or
• (e) a phosphonium ion, or
• (f) a sulfonium ion or sulfoxonium ion, or
• (g) an oxonium ion, or
• (h) an optionally singly or multiply fused and/or (C1-C4)-alkyl-substituted saturated or unsaturated/aromatic N-containing heterocyclic ionic compound having 1-10 carbon atoms in the ring system,
• and z is 1,2 or 3.