Različiti aspekti inhibicije rastenja i fotosinteze kukuruza (Zea mays L.) - uzrokovanih fosfonatnim herbicidom sulfosatom - 6. Manipulacija statusom lisnog pokrova zasenjivanjem

Leaf canopy manipulation by shading (irrelevant from the plants was treated with herbicide sulfosate or not) of maize plants raised in controlled environment, did not caused large changes in partitioning of dry-mass in plant. But inhibition of dry-matter and growth of maize plants caused by sulfosate treatment is bigger in unshaded (S) in relation to shaded (Sh) plants. Our opinion is that differences caused by functional-compensation processes, before viewed in other types of manipulation of source-sink relationship in plant. Inhibition of parameters of Chla fluorescencije and photosynthesis, caused by herbicide sulfosate, beginning in 6th day of trial, but decay of maize leaf photosynthetic function is so rapidly. Meanwhile in control plants that parameters on the end of trial is larger in shaded (Sh) relative to unshaded (S) plants. We interpreted that result also as functional-compensation processes. In maize plants raised in the field conditions under full day-light and then transfered in the shade (were they acclimatized), we noticed large inhibitions of growth, accumulation of dry-matter and their allocation in root and leaves with considerable increase of stem dry-mater and also early decrease of value of RWC parameter of leaves water regime under treatment of herbicide sulfosate. Besides that treatment of sulfosate in shaded plants caused significant decrease of all parameters of photosynthesis and Chla fluorescence. That caused early degradation of Chla and Chl b photosynthetic pigments, and degradation of carotenoids only at the end of trial (according to unchanged values of NPQ parameter of leaf photoprotektion) in shaded and sulfosate treated maize plants. Conclusion is that antenic function of photosynthesis was not destroyed by sulfosate action. Accordingly that in shaded maize plants the main part of inhibitory and degradative processes caused by herbicide sulfosate to mediate by inhibition of functions and growth of root and also by inhibition of water regime of leaves. Shading of herbicide sulfosate treated maize plants, raised in controled environment is largely different in comparison to shaded and sulfosate-treated maize plants raised in the field. We interpreted that differences with fact that shading of plants raised in controlled environment is not complete and it is more shorter than in field plants, and this results we interpreted as functional-compensation processes. But in field plants shading is so longer before treatment, and in this plants raised so called phenotype of 'shade plants', particularly sensitive to inhibitory action of sulfosate. And as conclusion we stated that longevity and completeness of shading is very influential factor to inhibitory action of sulfosate on maize plants. That testify of importance of 'source-sink' relationship in this particularly case.Manipulacija statusom lisnog pokrova putem zasenjivanja (nezavisno od toga da li su tretirane ili ne herbicidom sulfosatom) biljaka kukuruza raslih u kontrolisanim uslovima, ne dovodi do značajnijih izmena u preraspodeli suve mase. Međutim, inhibicija akumulacije suve mase i rastenja biljaka kukuruza usled tretmana sulfosatom znatno je veća kod nezasenjenih (S) odnosno zasenjenih (Sh) biljaka. Smatramo da su ove razlike uslovljene funkcionalno kompenzacionim procesima, ranije primećenim kod drugih vidova manipulacija 'proizvođač-potrošač' odnosa u biljci. Do inhibicije parametara fluorescencije Chla i fotosinteze, usled dejstva herbicidom sulfosatom, dolazi tek 6-og dana ogleda, ali je tad gašenje fotosintetskih funkcija listova kukuruza naglo. Međutim, kod kontrolnih biljaka, pomenuti parametri su na kraju ogleda značajno veći kod zasenjenih (Sh) odnosno nezasenjenih (S) biljaka. Pomenuti nalaz isto tumačimo funkcionalno kompenzacionim procesima. Kod biljaka kukuruza raslih u polju, pri punoj dnevnoj svetlosti, pa prenetih u senku (gde su aklimatizovane), zapažamo znatnu inhibiciju rastenja, akumulacije ukupne suve mase i njene alokacije prema korenu i listovima, uz znatno povećanje udeone suve mase stabla i rano smanjenje vrednosti RWC parametra vodnog režima listova, pri tretmanu herbicidom sulfosatom. Pored toga tretman sulfosatom dovodi kod zasenjenih biljaka i do značajnog sniženja svih parametara fotosinteze i fluorescencije Chla. To vodi ranoj degradaciji Chla i Chl b, a tek na kraju ogleda i degradaciji karotenoida (što je saglasno nepromenjenim vrednostima NPQ parametra fotoprotekcije lista), kod zasenjenih i sulfosatom tretiranih biljaka kukuruza. Znači, antenske funkcije fotosinteze tokom ogleda nisu bitno ugrožene dejstvom sulfosata. Prema tome, kod zasenjenih biljaka kukuruza većina inhibitornih i degradativnih procesa uzrokovanih dejstvom sulfosata posredovano je inhibicijom rastenja i funkcije korena, kao inhibicijom vodnog režima listova. Zasenjivanje tretiranih biljaka kukuruza, raslih u kontrolisanim uslovima, izgleda da vodi drugačijim posledicama, nego kod zasenjenih biljaka raslih u uslovima polja i tretiranih sulfosatom. To tumačimo time da je kod kontrolisanih biljaka zasenjivanje bilo delimično i znatno kraće, pa se nastale promene mogu smatrati procesima kompenzacije, dok je kod biljaka raslih u uslovima polja zasenjivanje bilo dugotrajnije pre samog tretmana, pa se nastali fenotip 'biljaka senke' pokazao veoma osetljivim na inhibitorno dejstvo sulfosata. Znači, dužina i obim zasenjivanja veoma utiču na reakciju biljaka kukuruza na dejstvo sulfosata, što svedoči o značaju 'proizvođač-potrošač' odnosa u tom slučaju