Siberian stone pine, Siberian dwarf pine, their hybrids, and backcrosses: comparative analysis of crone formation in the first 10 years of life

Abstract

For the first time, a comparative analysis of crown morphogenesis in Siberian stone pine (Pinus sibirica), Siberian dwarf pine (P. pumila), their hybrids and backcrosses was carried out using the example of 10-year-old seed offspring from the Northern Baikal natural population. The goal is to “decompose” the life form phenomenon into elementary traits, to trace their formation at the beginning of ontogenesis on two contrasting examples (an upright tree vs. prostrate tree) and inheritance after interspecific hybridization. The parent species differed fundamentally in (1) stem inclination and (2) apical dominance at two levels (1-year-old shoots and perennial branches). The phototropic slope of the Siberian dwarf pine stem “triggered” the mechanism of prostrate tree formation. Apical dominance in the system of perennial branches was the main factor in the crown formation. It, in turn, consisted of two key characteristics: strength and selectivity. In Siberian stone pine, apical dominance was strong and nonselective. In Siberian dwarf pine, apical dominance was weak and selective: some of the largest branches did not obey him. All key traits were inherited by hybrids and backcrosses strictly intermediate in accordance with the proportion of species in the offspring genome.