Morphologies of Unfilled Grains at the Tip of Sweet Corn Ear

Abstract

Unfilled grains (caryopses) at the tip of 'Honey Bantam 36' sweet corn ear are classified as unfertilized grains (UG) and fertilized but poorly ripened ones (PRG) according to their morphological characteristics. The anomaly was induced by: a) bagging the ear (female inflorescence) before or after the appearance of the silk (filamentous style and stigma) to obtain UG and b) cutting of leaf blade to obtain PRG. Untreated 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 consists of FG, UG, and PRG. The filled and unfilled grains are easily distinguished 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 of an embryo and the endosperm would be present. In addition, the PRG would exhibit browning at the chalazae, partially developed glume, palea, and lemma, and an intact silk.
3. Fertilized grains can be differentiated from unfertilized ones 16 days after silk emergence by their size, whereas the difference between UG and PRG are detectable 20 days after 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 of PRG to lack of photosyn- thates.