2. METHODOLOGY

For this study we worked with samples of corn from genetic material developed by Agricomseeds whose grains are protected by a genetic tool. The method that was used was to extract the pericarp to submit it to a process of tissue disassociation, according to Jeffrey’s technique (Foster, 1950). Other cuts of the fruit were obtained using a freehand knife on cross and longitudinal sections. In both cases the samples were submitted to different dyes: methylene blue (Stevens, 1916), toluidine blue, safranine (Johansen, 1940) and astra blue plus safranine. To detect starches, Lugol (Johansen, 1940) was used, and for lipid compounds, Sudan III (Foster, 1949). Afterwards they were mounted between a slide and cover glass, with a drop of water, and observed under an Olympus optic microscope. A Sony camera was used for the photographic record. Comparative photograph of 2 hybrids, on the left is the hybrid with the pericarp protector and on the right the same hybrid without the protector.

3. RESULTS
3.1. EXTERNAL AND INTERNAL STRUCTURE OF NORMAL CORN FRUIT

Corn (Zea mays L.) is a caryopsis fruit (Fig. 1) whose pericarp is attached to the seed which has no integuments and has abundant amylaceous endosperm, with only one cotyledon where the embryo axis is inserted (Fig. 2).

Fig. 1 External aspect of normal corn fruit (Zea mays)

Fig. 2 Internal aspect of normal corn fruit (Zea mays)

3.2. EXTERNAL AND INTERNAL STRUCTURE OF GENETICALLY PROTECTED CORN FRUIT
Just like in normal corn fruit, modified corn fruit presents the same structural characteristics, which are basically differentiated by the presence of a red pigment (polyphenol) in the cells of the entire pericarp; said pigmentation is evidenced in the external aspect of this fruit, as we can see in Fig. 3.

Fig. 3 General aspect of Agricomseeds’ genetically protected hybrid.

In a transverse cut the corn fruit (Zea mays) shows the following structures: pericarp and seed (Fig. 4):

Fig. 4 Transverse section of Agricomseeds’ corn fruit.

Pericarp: In the pericarp we can distinguish the epicarp, mesocarp and endocarp (Fig. 5). The epicarp is formed by a layer of epidermis cells and another hypodermic layer (Fig. 5); the epidermis cells are elongated, rectangular and have thickened cell walls, conspicuous markings (Fig. 6), as well as a cuticle with a quite thick coating of cutin in the outer layer that, due to its chemical nature and structure, provides waterproofing, a mechanical protective function, and resistance to such microorganisms as insects, fungi and bacteria, as well as sun radiation and the entry of contaminating chemical products. With respect to the hypodermis, this is formed by a layer of similar cells to those of the epidermis. On its part, the mesocarp consists of approximately 5 layers of regular cells with thick walls and conspicuous markings. In turn, two groups of cells can be distinguished in the endocarp: the outermost ones are placed in approximately 3 layers, in a transverse layout with respect to the grain’s axis, with very thick cell walls and conspicuous markings; the innermost ones, in turn, are ordered in a cell layer that has an axial layout with respect to the grain’s axis, similar to the previous ones (Fig. 7). One characteristic of the pericarp is that all its cells contain pigments in the protoplasm, i.e., inside the cell.

Fig. 5 Transverse cut of Agricomseeds corn’s pericarp.

Fig. 6 Front view of the epidermis cells of Agricomseeds corn’s pericarp

Fig. 7 Elements composing Agricomseeds corn’s mesocarp and endocarp. A. Mesocarp cells. B and C. Endocarp cells.

Seed: This has a first layer of parenchymal cells with high aleurone content (Figs. 8-9). This is followed by isodiametric parenchymal cells that form the endosperm (Fig. 10-11).

Figs. 8 and 9. Front view and transverse cut of Agricomseeds corn’s aleurone layer

Fig. 10 and 11. Transverse cut of the starch parenchyma of Agricomseeds corn’s
endosperm.

CONCLUSIONS
The structural characteristic that protects Agricomseeds hybrid corn’s grains and includes uniform polymers immersed inside the grains’ pericarp cells, is the cuticle, which covers and protects the entire surface without using synthetic chemical protectors and, rather, it uses genetic tools. This structure gives the mature grains resistance to such aggressive conditions as: rain during the harvest, high or low temperatures in the field, high relative humidity, dust (abiotic), insect attacks, bacteria or fungi (biotic). Actually, it is a complete, individual coating for each grain of corn from pre-harvest, to harvest and storage. The grain’s appearance is very smooth and it has a bright red, healthy porcelain color.

BIBLIOGRAPHY
FOSTER, A.S. 1949. Practical Plant Anatomy. Van Nostrand. New York.
JOHANSEN, D. 1940. Plant Microtechnique. McGraw-Hill Company, Inc. New York and London.
ROTH, I. 1964. Microtécnica Vegetal. Universidad Central de Venezuela. Caracas.
STEVENS, W.C. 1916. Plant Anatomy. J.& A. Churchill. London.