Short-term treatment of potato (Solanum tuberosum L.) tuber discs with CdCl₂ solution elevated both the StPCS1 transcript level, phytochelatin synthase (PCS) activity and contents of phytochelatin (PC) and abscisic acid (ABA). Similar effects but less marked were noticed after treatment of tuber tissues with ABA solution. Cd-treatment increased also cysteine (CYS) content but did not change glutathione content. If ABA treatment preceded Cd-treatment, the elevation of CYS and PC contents were limited. The data suggest the participation of ABA in the regulation of PCS.

Soluble sugars such as sucrose, glucose and fructose in plant host cells not only play the role as donors of carbon skeletons, but they may also induce metabolic signals influencing the expression of defense genes. These metabolites function in a complex network with many bioactive molecules, which independently or in dialogue, induce successive defense mechanisms. The aim of this study was to determine the involvement of sucrose and monosaccharides as signaling molecules in the regulation of the levels of phytohormones and hydrogen peroxide participating in the defense responses of Lupinus luteus L. to a hemibiotrophic fungus Fusarium oxysporum Schlecht f. sp. lupini. A positive correlation between the level of sugars and postinfection accumulation of salicylic acid and its glucoside, as well as abscisic acid, was noted. The stimulatory effect of sugars on the production of ethylene was also reported. The protective role of soluble sugars in embryo axes of yellow lupine was seen in the limited development of infection and fusariosis. These results provide evidence for the enhanced generation of signaling molecules both by sugar alone as well as during the crosstalk between sugars and infection caused by F. oxysporum. However, a considerable postinfection increase in the level of these signaling molecules under the influence of sugars was recorded. The duration of the postinfection generation of these molecules in yellow lupine was also variable.