Dihidrohalkoni jabuke florizin i floretin kao nove alelopatske supstance

Abstract

Phloridzin and phloretin are dihydrochalcones highly specific to domestic apple (Malus × domestica Borkh.) and other species from genus Malus. Auto-allelopathic potential of these phenolics was recognized in‘Apple Replant Disease’(ARD) characterized by stunted growth, reduced root system and low yields in apple trees replanted on lands that previously supported apple orchards. Physiological basis of phloridzin and phloretin autotoxicity are ultrastructural and molecular alterations that include increased catalase, peroxidases and superoxide dismutase activities, raised malondialdehyde and proline contents, and high expression of genes involved in cell defence system. The latest research on model plant Arabidopsis thaliana indicates phytotoxicity of these dihydrochalcones towards other plant species. Phloretin inhibits A. thaliana seedlings growth and development inducing agravitropic phenotype and morphological and ultrastructural malformations in treated seedlings. Altered expression of CDKA1;1, CDKB2;1, CYCA3;1 and CYCB2;4 cell cycle genes and genes involved in auxin homeostasis (PINs, AUX1, LAX3, ABCBs, TAA1 and YUCs) and gibberellin biosynthesis (GA20ox2 and GA3ox1) are in the physiological bases of phloretin phytotoxicity. This mechanism makes phloretin a prospective candidate for an eco-friendly bioherbicide and paves the way for further research of phloretin role in ARD

Sekundarni metaboliti jabuke (Malus × domestica Borkh.) florizin i floretin su dihidrohalkoni visoko specifični za vrste roda Malus. Autoalelopatski potencijal ovih fenolnih jedinjenja se ogleda u suzbijanju rasta klijanca i sadnica zasađenih na mestu prvobitnih voćnjaka jabuke. U osnovi njihove fitotoksičnosti su ultrastrukturne i molekularne promene koje se ogledaju u povećanju sadržaja malondialdehida, prolina i aktivnosti antioksidativnih enzima: superoksid-dismutaze, peroksidaza i katalaza, kao i nivoa ekspresije proteina uključenih u odbrambene mehanizme ćelije. Najnovija istraživanja ukazuju na fitotoksičnost ovih dihidrohalkona i prema drugim biljnim vrstama, kao npr. korovskoj model biljci Arabidopsis thaliana. Tretman floretinom izaziva značajnu inhibiciju rastenja i razvića klijanaca A. thaliana, poremećaj gravitropskog odgovora i pojavu morfoloških i ultrastrukturnih malformacija u čijoj osnovi leži promena ekspresije CDKA1;1, CDKB2;1, CYCA3;1 i CYCB2;4 gena ćelijskog ciklusa, kao i gena uključenih u održanje homeostaze auksina (PINs, AUX1, LAX3, ABCBs, TAA1 i YUCs) i biosinteze giberelina (GA20ox2 i GA3ox1). Ovo otvara mogućnost za dalja istraživanja njihovog alelopatskog delovanja ali i potencijalnu primenu kao ekološki bezbednih bioherbicida