Mechanisms of adaptation of small grains to soil acidity

Abstract

Acid soils limit crop production on 30-40% of the world's arable land and up to 70% of the world's potentially arable land. Over 60% of the total arable lands in Serbia are acid soils. Soil acidity is determined by hydrogen (H+) in soil solution and it is influenced by edaphic, climatic, and biological factors. Major constraints for plant growth on acid mineral soils are toxic concentrations of mineral elements like Al of H+ and/or low mineral nutrient availability due to low solubility (e.g. P and Mo) or low reserves and impaired uptake (e.g. Mg2+) at high H+ concentrations. Aluminum (Al) toxicity is primary factor limiting crop production on acid soils. This review examines our current understanding of mechanisms of Al-toxicity, as well as the physiological and genetic basis for Al-toxicity and tolerance. Inhibition of root growth by Al leads to more shallow root systems, which may affect the capacity for mineral nutrient acquisition and increase the risk of drought stress. Of the two principal strategies (tolerance and avoidance) of plants for adaptation to adverse soil conditions, the strategy of avoidance is more common for adaptation to acid mineral soils. At the same, the short view of the most important genetics tolerance mechanisms, developed and determined in some small grains genotypes, is showed as well.Kisela zemljista ogranicavaju biljnu proizvodnju na 30-40% ukupnih, kao i do 70% potencijalno obradivih svetskih povrsina. Kisela reakcija ovih zemljista i nizak sadrzaj najvaznijih biljnih hraniva, pre svega R i Sa su ogranicavajuci faktori postizanja visokih i stabilnih prinosa gajenih biljaka. Pored kisele reakcije, ova zemljista karakterise veoma cesto i povecan sadrzaj toksicnih oblika Al, Fe i Mn, kao i nedostatak ili smanjena pristupacnost P, Ca, Mg i nekih mikroelemenata, posebno Mo, Zn i V. Toksicnost Al se smatra najvaznijim faktorom koji ogranicava rast biljaka na kiselim zemljistima. Mehanizmi adaptacije strnih zita na kisela zemljista mogu se podeliti na: spoljasnje, unutrasnje (fizioloske) i geneticke. Dejstvo spoljasnjih mehanizama tolerantnosti zasniva se na imobilizaciji Al u celijskom zidu, isticanju Al kroz plazma membranu, uspostavljanju pH barijere u rizosferi i lucenju organskih kiselina, fosfata, helata i drugih liganada korenom u spoljasnju sredinu. Unutrasnji mehanizmi tolerantnosti zasnivaju se na kompleksiranju Al sa proteinima, organskim kiselinama i enzimima, kao i helatiziranju u citoplazmi. Strna zita ispoljavaju razlicitu tolerantnost prema kiselosti zemljista i povecanom sadrzaju Al u zemljisnom rastvoru. Najosetljiviji je jecam, zatim psenica, dok vecu tolerantnost ispoljavaju ovas, tritikale i raz.