Author : Myat Moe Hlaing

Summary : Rice root growth is a remarkably variable in terms of root architecture, growth patterns, and environmental adaptation to complete flooding and stagnant flooding. Three experiments were conducted from October 2014 to October 2015: one complete flooding experiment in a green house condition and two stagnant flooding experiments in a field condition at the Crop and Enviromnental Sciences Division (CESD). International Rice Research Institute (IRRI), Los Bafios, Laguna, Philippines. Experiment I studied root and shoot growth, root anatomical features (aerenchyma formation and porosity), plant survival, and relationships between root/shoot characteristics and plant survival under greenhouse condition. The greatest root reduction was noted in Swarna-Sub1 and the least was noted in FR13A after flooding. The shoot length ofSwarna-Subl showed no changes while IR42's shoot length greatly increased after complete flooding. FR13A and Swarna-Sub 1 cultivars had higher survival rate and the greater shoot elongation of IR42 resulted in the lowest rate of survival measured 21 days after de-flooding. Shoot elongation was negatively correlated with percent plant survival. Being tolerance to complete flooding, FR13A had the highest increase in total aerenchyma, % aerenchyma and % root porosity (root cross section C-4.5cm from root tip) after complete flooding. Total aerenchyma was positively correlated with % aerenchyma and % root porosity under complete flooding. Total aerenchyma in root cross section B was also positively and significantly correlated with plant survival. For Experiment II, the cultivars were subjected to stagnant flooding (SF) and non flooded (control) treatments. Root length, number of roots, root dry weight, tiller numbers, stem dry weight and leaf dry weight decreased under SF compared with the control. Plant height greatly increased under SF...