Indeterminate growth mutants (id) were found in collections of maize germplasm. Backcrossing was used to incorporate id in some early lines, and id versions which differed from normal counterparts by flowering dates were obtained. These versions served as models for investigation of the specificity effect of id on different biological and economic characters of maize.
Leaves of normal and id versions of four lines were studied in two periods of ontogenesis: emergence of tassel and silking. The content of photosynthetic pigments was determined spectrophotometrically. An in vivo assay was used for measuring nitrate reductase activity. The same genotypes were studied during two seasons, but it is important to note that in 1981 id versions were at the fourth generation of backcrossing and in 1982 at the fifth.
Our results showed that there are biochemical distinctions between lines (see Table). However, the distinctions between normal and id versions inside every line were the same. This fact made it possible to establish and discuss the results of photosynthetic pigment content and nitrate reductase activity in leaves of normal and id plants as average values of all genotypes. In the table we see a decrease of chlorophyll a, chlorophyll b, total carotenoids and nitrate reductase activity in leaves of the id counterpart compared to normal.
We have made some interesting comparisons with the results reported in the literature on higher sensitivity of photosynthetic pigments and nitrate reductase activity to changes of environment. So we suppose that these biochemical parameters will be used for investigation in the future of the possibility of exogenous regulation of the effect of the gene id.
V. E. Micu, I. A. Antsibor, G. E. Komarova and A. I. Rotar
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