Calcium-Dependent Tolerant Response of Cell Wall in Maize Mesocotyl Under Flooding Stress

AbstractThe aim of the present study was to find out the effect of calcium on floodedmaize seedlings by anatomical and ultra-structural analyses and by measuring theenzyme activity and gene expression of polygalacturonase (PG) and superoxidedismutase (SOD). For this, maize seeds were placed to germinate in germinationpaper saturated with CaCl 2 0.75 %. Then, 4-day-old seedlings were subjected toflooding in the presence or absence of CaCl 2 . Mesocotyl sections were sampleddaily for the anatomical and ultra-structural analyses, RT-qPCR and activity ofSOD and PG. The results showed that the presence of calcium in the floodingbuffer increases the tolerance of maize seedlings by 1 day when compared toseedlings flooded in the absence of this element. The reason for this longer sur-vival is that calcium maintains the integrity of the cell wall and attenuates theeffects of oxidative stress. Owing to this fact, the seedlings remained alive andfirm for up to 7 days.IntroductionThe lowoxygen pressurein soilscaused by excessof water isone of the most important environmental stresses once itsignificantly reduces the growth and productivity of cereals(Jackson and Colmer 2005). In general, precipitation insuperabundance and the poor soil drainage are the maincauses of the flooding stress. During flooding, the air in thesoil pores is replaced by water, and because of the slow dif-fusion rates of oxygen in water, coupled with the activity ofaerobic soil microorganisms, the oxygen levels fall rapidly(Pezeshki 1994). Under these conditions, the lack of oxygenhasbeen seen asthe mainproblem associatedwithflooding.Indeed,tolerancetoanoxia([O