Estudio sobre la estructura y variabilidad de la oca (Oxalis tuberosa Mol.)

Abstract

From the study on the morphology, structure and variability of Andean tuber "Oca" (Oxalis tuberosa Mol.), the following conclusions may be drawn: Oxalis tuberosa Mol. is an annual dicotyledonous herbaceous plant, which is usually propagated by tubers. It is a polyploid (68-70 somatic chromosomes) and as such the most promising selection work will be the establishment of clones. Under different environmental conditions outside its own habitat these plants behave in a different manner in regard to their growth habit, flower abundance and color. Stolons are cauline and their structure is similar to shoots. Oca varieties are easily identified by the color and form of their rhizomes. This is the usual way to make the identifications. It was found that the intense coloring of the stem is closely related to the color of the rhizomes. All plants with green steMON have white rhizomes. Great quantities of starch are found in the inner layers of the cortex and less in the medullar part. Cárdenas" statement that all cultivated oca flowers are yellow-orange in color is corroborated differences in stigma characteristics in regard to the flower form were found. Hill's statement that floral trimorphism is directly related to the color of the rhizomes was corroborated, as follows: plants with long styles come from yellow rhizomes plants with medium styles from white rhizomes, and plants with short styles come from red rhizomes. Of all the varieties studied, variety No. 1 "Blanca Chica" has a constant type of inflorescence in other varieties the inflorescences are quite variable. Contrary to the opinion of Rothéa, it was determined that Oxalis tuberosa has secondary tissues, but the cambium activity is rather reduced. The main structural differences between stem and rhizome are the thicker collenchyma layers in the former. Rhizome formation occurs when stolon growth ceases, producing a great proliferation of the reserve tissues which form the principal part of the ripe rhizome (medulla and cortez). The development of the vascular system follows the same lines as the aerial stem, but considerable more phloem is found in the rhizomes. These studies may be very useful in the applied aspects, such as selection and breeding, and the improvement of cultural practices.