Abstract
Young pea plants grown as a water culture were sprayed with hydrogen peroxide and 24 h later were treated with the herbicide paraquat. The effects of paraquat and H2O2 treatment were investigated on the endogenous concentrations of free proline, and free and conjugated putrescine, spermidine and spermine. Application of PQ increased the free proline and Put, and decreased conjugated and bound polyamines. The results clearly demonstrate the oxidative damages provoked by PQ application. Single treatment with H2O2 provoked considerable decrease in the free fraction of the three PAs studied 2 h after light exposition, but caused an increase in their respective conjugated fractions. Data suggest that PA changes after H2O2 treatment are due to conversion from free to conjugated form. Three hours later free PAs in H2O2 treated-plants reached control levels; however the conjugated remained higher than the control. No alterations were detected in proline concentration after H2O2 treatment. Pretreatment with Н2О2 activated some component of the plant protection mechanisms by causing an alteration in free/conjugated PAs ratio in plants subsequently subjected to PQ treatment. Data concerning PA and proline concentrations in plants treated with both compounds supposed that H2O2 shows a protective role against PQ and improves the plant tolerance to the oxidative stress generated by paraquat.
Highlights
Polyamines (PAs) are low-weight organic molecules, widely distributed in higher and lower plants, and the PAs common for all plant species are putrescine (Put), spermidine (Spd) and spermine (Spm)
A decrease of free proline content was detected 2 h after application of H2O2, while 3 hours later its content was near the control level (Table 1)
We have established that H2O2 pretreatment prevented the inhibition of photosynthesis, and chlorophyll loss provoked by PQ, and the plant showed higher rates of survival [13]
Summary
Polyamines (PAs) are low-weight organic molecules, widely distributed in higher and lower plants, and the PAs common for all plant species are putrescine (Put), spermidine (Spd) and spermine (Spm). They occur as free molecules, but can be conjugated with small molecules such as phenolic acids or bound to macromolecules like nucleic acids and proteins for their polycationic nature [1]. Polyamines play a key role in growth, development and reproduction of plants [1] [2] Another important function of PAs is attributed to plant protection against different stresses [3] [4], including herbicides [5]-[9]. Concept exists that conjugation of polyamines could be considered as a regulatory mechanism of the free PA pool [1]
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