In the theory of plant morphogenesis, the process of assimilate distribution between their organs remains poorly understood. The optimal distribution of assimilates between vegetative organs plays an important role in the use of available resources, however, the processes of assimilate distribution across vegetative organs are quite complex and difficult to measure, and the result of these processes is estimated by the structure of phytomass distribution across vegetative organs. According to the optimal partitioning theory (OPT), plants allocate most of their assimilates to the organ that uses the most limited resources to optimise plant functioning. In previously published interpretations of the OPT, partitioning relative phytomasses of organs in plants was studied either in relation to their phytomass (“true plasticity”) or in relation to their age (“ontogenetic plasticity”), although the actual distribution of phytomasses is the result of the combined action of these two factors. In this study, using the database of seven forest-forming genera as aggregates of vicarious species of the boreal zone, a modification of the patterns underlying the OPT in the organs of trees was performed. A two-factor regression analysis of the relative phytomasses of aboveground and underground organs of trees was performed based on a mixed model, in which numerical independent variables are represented by the age and total phytomass of the tree, and dummy variables mediate the affiliation of the initial phytomass data to each of the seven genera. Relative phytomasses are represented by the ratio of aboveground or underground phytomass to the total phytomass of a tree. The age-related reversal of the relationship of relative phytomasses with total phytomass has been revealed: the relationship of relative aboveground phytomass with total, positive at a young age, is replaced by negative at maturity and vice versa, the negative relationship of relative underground phytomass with total at a young age is replaced by positive at maturity. Thus, the relative aboveground phytomass at a young age has priority in the distribution of assimilates in the largest trees, but as the age increases, reversion occurs and this priority shifts towards the smallest trees. On the contrary, the relative underground phytomass at a young age has priority in the distribution of assimilates in the smallest trees, but as the age increases, this priority shifts towards the largest trees. The ages of the described patterns reversal have been established, which are the same for all genera: 20±0.5 years for relative aboveground phytomass and 40±2.5years for relative underground one.
V.A. USOLTSEV (Wed,) studied this question.