Translocation of Uranin Within the Living Ovules of Selected Species

Three dictolydonous species having distinctive ovular characteristics were chosen for observation of uranin uptake into their living ovules. Nicotiana tabacum , which has anatropous ovules, showed uranin uptake in a nondifferential manner. Translocation occurred progressively from the funiculus toward the micropylar and chalazal portions at approximately equal rates, then chalazally until the entire ovule had adsorbed the uranin completely. Polygonum capitatum , which has atropous ovules, consistently showed differential uptake of uranin within a given ovule. After the uranin had entered the funiculus and moved about half way toward the micropyle, uranin could already be detected in a small group of cells at the micropylar tip of the ovule. Torenia fournieri , which has hemianatropous ovules with protruding, observable embryo sacs, showed uranin uptake by its ovules, including the egg and synergids, but it was not possible to determine a consistent sequential pattern of translocation. It is suggested that the synergids in the anatropous ovule of N. tabacum are strategically located for early receipt of nutrients as they enter the ovule, while the synergids of P. capitatum are positioned such that they are among the last cells to receive materials entering the ovule. Using the techniques of this study, it is possible that a species having observable embryo sacs, other than T. fournieri , may prove satisfactory for making precise observations on translocation routes within living embryo sacs.