Use of a computerized image analysis program to statistically characterize the ultrastructural features of chloroplasts

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During normal plant growth, the development and structure of the chloroplast is largely influenced by genetics. However, environmental and biological conditions such as light (intensity and quality), temperature, draught, herbicides, nutrition, pollutants and pathogens also affect the ultrastructure of this organelle. As a result, fine-structural investigations of higher plants frequently describe the effects of experimental treatments on the relative size of the chloroplast, as well as on the occurrence, size and number of its internal structures, which include the starch and osmiophilic bodies and the grana and stroma lamellae. These descriptions require either a tedious examination of numerousorganelles in an effort to gain a subjective impression of the changes that have occurred or a painstaking effort of counting, measuring and averaging the various structural features to provide a statistical representation of the alterations. In an effort to gain objective data in a more efficient manner, a software program was written in Quips, a Pascal based programming language. This program, whichis used on a Cambridge Quantimet 970 image analysis system, scans the electron micrograph and assigns 256 grey levels to the structural elements. This process enables one to isolate and to measure the structural features of the chloroplast.