MORPHOLOGIES OF UNFILLED GRAINS AT THE TI P OF SWEET CORN EAR

Unfilled grains (caryopses) at the tip of 'Honey Bantam 36' sweet corn ear are classified as unfertilized grains (UG) and fertilized but poo rly ripened ones (PRG) according to their morphological characteristic s. The anomaly was induced by : a) bagging the ear (female inflorescen ce) before or after the appearance of the silk (filamentous style and stigma) to obtain UG and b) cutting of leaf blade to obtain PRG. Untre ated control corn stalks were kept to obtain normal, filled grains (FG ). The effect of different plant densities and cultivars on occurrence of UG and PRG were also investigated. 1. An ear of corn usually consi sts of FG, UG, and PRG. The filled and unfilled grains are easily dist inguished by the length of the ovules. 2. The UG and PRG at the tip of an ear are differentiated anatomically because in the PRG, remnants o f an embryo and the endosperm would be present. In addition, the PRG w ould exhibit browning at the chalazae, partially developed glume, pale a, and lemma, and an intact silk. 3. Fertilized grains can be differen tiated from unfertilized ones 16 days after silk emergence by their si ze, whereas the difference between UG and PRG are detectable 20 days a fter silk emergence by their external and internal characteristics. 4. The occurrence of UG and PRG varied among cultivars and was affected by plant densities; the higher plant densities favored the formation o f PRG to lack of photosynthates.