Corn Descriptions and Photomicrographs
Sponsored LinksThere are several varieties of corn (Zea mays). The yellow varieties of flint or dent corn are almost exclusively used as animal feed in Asian region; however, the white varieties are used in some locations Ground corn and corn gluten are commonly used in formula feeds.
Microscopic Features
1. The corm kernel is tooth-shaped and covered with a thin transparent bran coat showing yellow or white lustrous translucent gluten along the sides with opaque white floury starch in the center of the kernel. At the tip caps there may be some portions of glumes attached.
2. In the half-split kernel, the aleurone layer with the horny gluten located an immediately under the bran coat along sides of the kernel. The white floury starch is contained in the crown and tip. The germ, located to the front and directly to the center, extends one-half to two-thirds the length of kernel.
3. When corn kernel is ground, its basic characteristics are not changed, but differ only in particle size. Fractions of corn cob consisting of three layer: bracts or chaff, attached with glumes, are at the outer part; the hard woody middle part of xylem and phloem; and the innest part of soft, porous and spongy pith, creamy white in color-may contaminate and are easily identified in ground corn.
Stereomicroscopic Features
1. Fused horny gluten and starch appear translucent yellow, hard and irregularly shaped, being clinged by white floury starch.
2. Bran appears as glossy, semi-transparent thin, irregularly shaped pieces of shredded material.
3. The tip caps are semi-funnel shaped woody pieces. The glumes are thin, soft wavy sheathed material, irregular in shape and color varying from creamy yellow to red. On close examination, there may be some veins in the glumes. The glumes are normally attached to the bracts of ground corn cob.
4. Ground corn cob may be identified by a hard woody part occurring in irregularly shaped lumps with spongy pith attached to it. Bracts with glumes can also indicate the contamination with ground corn cob.
Histological Features
1. Bran coat or pericarps are divided into four layers:-
1.1 Epidermis Cell are long, thick-walled filamentous and attach to each other along the entire length.
1.2 Mesocarp Short, thin-walled, flat cells.
1.3 Cross cells Two to foru layers thick, thin-walled and branched.
1.4 Tube cells Long, unbranched and filamentous.
2. Seed coat or hyaline layer, a thin membrane consists of thin-walled polygonally shaped cells which are difficult to detect.
3. Endosperm or storage tissue is composed of:-
3.1 Aleurone layer Thick-walled, 4 – 6 sided irregularly-shaped cells with granular contents of spherical aleurone grains.
3.2 Starch endosperm Cells are elongated, thin-walled, joined end to end. Floury starch granules are large, rounded with distinct central hilum and radiating clefts. Horny starch granules are smaller, polygonally shaped with a central hilum.
4. Embryo is composed of scutellum and the embryonic axis with larger cells in the rudimentary root.
March 09 2008 11:56 am | Article