De-hulling facilitates seed germination and ethylene production in dormant and non-dormant rice genotypes

Abstract

SUMMARYThe hull or husk of rice, comprising the lemma and palea, provides a fitting enclosure for the caryopsis. The physiological significance of the hull in seed dormancy has been examined by comparing the effects of its removal on germination, seed vigour, assimilate mobilization and ethylene production in germinating seeds of six rice genotypes; two each belonging to dormant, semi-dormant and non-dormant groups. Hull removal promoted the above parameters in all three categories of seeds, but the effect was relatively higher in dormant seeds compared with less dormant categories. Ethylene production in non-dormant seeds was initiated after imbibition of water, normally before visible emergence of the radicle. It peaked when the radicle began to protrude and declined thereafter. In comparison, dormant seeds produced very low levels of ethylene during germination; however, hull removal resulted in a dramatic rise in its production. Overall, ethylene evolution at the radicle protrusion stage correlated negatively with germination time. It was concluded that ethylene production starts with breaking of the caryopsis coat and peaks when the radicle ruptures it completely, at the stage of radicle visible emergence. Removal of the hull facilitates germination and ethylene production can be a good indicator for the progress of germination.