Effects of jasmonic acid, silver nitrate and L-AOPP on the distribution of free and conjugated polyamines in roots and shoots of Solanum tuberosum in vitro

Effects of jasmonic acid on the levels of free and conjugated polyamines (PAs) were investigated in Solanum tuberosum in vitro. To test for involvement of ethylene and phenolic acids, inhibitors were used: silver ions to block ethylene action and L-alpha-aminooxy-beta-phenylpropionic acid (AOPP) to inhibit the phenylpropanoid pathway. Effects on root and shoot anatomy were examined by light microscopy. The silver treatment inhibited tuberization, increased leaf size, elongation and greening of roots and reduced shoot height and hairiness of shoots and roots. Except for tuberization, jasmonic acid induced morphological changes opposite to that of inhibition of ethylene action. Jasmonic acid-induced shoot and root thickening was due to increased cell division. AOPP promoted shoot and root growth and reduced root hair formation and tuberization. In roots, the profile of free PAs in controls was putrescine (PUT) > spermidine (SPD) > spermine (SPM). PUT accounted for about 90 % of conjugated PAs. Jasmonic acid, alone and with the inhibitors, greatly increased conjugated SPD and SPM relative to conjugated PUT: conjugated SPD+SPM rose from about 10 % up to 50-80 %. Silver and/or AOPP had small effects on the relative proportions of conjugated PAs. The relative abundance of free PAs in roots was not influenced fundamentally by jasmonic acid, silver, AOPP or any combination of these. In contrast to roots, SPD dominated the free and SPM the conjugated PAs in shoots. Nevertheless, effects of jasmonic acid and AOPP on conjugated PAs (increase and decrease, respectively, in particular of SPD and SPM) were similar to those in roots. However, silver caused a contrasting response: levels of free PUT increased to make it most abundant. Conjugated SPD and SPM increased by up to 10-fold. As AOPP partly counteracted this effect, conjugation is apparently dependent on newly synthesized phenolic acids. The results provide a strong indication that both ethylene and PAL are involved in the effect of jasmonic acid on PA levels in plant tissues. Differential effects of jasmonic acid treatment on individual PAs suggest that additional modes of action also participate.