Primordial leaves as a factor in delayed initial growth of soybean and bean plants

Analysis of the biological characteristics of grain legumes shows that soybean and bean, which have a long growing season compared to pea and chickpea varieties, form simple primordial leaves at the first epicotyledonary node. In peas and chickpeas, true compound leaves form in the first epicotyledonary node. Unlike pea and chickpea varieties, the dynamics of plant height growth in soybean and bean varieties differs by the presence of a lag-period of slow growth at the initial stages of ontogenesis. It is hypothesized that lag-period of growth in soybean and bean varieties may be caused by metabolic products of primordial leaves. To examine this hypothesis, primordial leaves were removed from soybean and bean plants at the beginning of the growing season, and changes in the dynamics of their height growth were evaluated. We found that in all the studied varieties of soybean and bean this operation led to a decrease in the growing season by 2-5 days. After removal of primordial leaves in soybean and bean varieties, we revealed a more intensive growth of internodes, and a decrease in lag-periods of growth of the first 4-5 internodes. These results support the hypothesis of growth-limiting metabolic products in primordial leaves.