The influence of scion donor tree age on the growth and morphogenesis of Siberian stone pine grafts

Abstract

The influence of scions donor tree age on the morphological variability of needles, shoots, and branching pattern was studied in 7-year-old grafted scions of Siberian stone pine (Pinus sibirica Du Tour). We analyzed clones of four age groups: seedlings (4–7 years), young trees (38–62 years), mature trees (238–376 years), and old trees (549–700 years). The results showed that during the first 7 years after grafting, the age of the scion donor tree greatly affects branching patterns and leaf morphology of grafted trees. The age of the scion donor tree also significantly affects the growth of grafts in length, albeit to a lesser extent. Grafts derived from seedlings, young, mature, and old trees had different ratios of shoot elongation and branching: weak growth and abundant branching, strong growth and abundant branching, strong growth and medium branching, weak growth and branching, respectively. The degree of needle xeromorphy, the level of apical dominance, and the number of epicormic buds increased significantly with the age of scion donor trees. Premature (late summer and autumn) growth of dormant buds was typical only for grafts derived from seedlings and, to a lesser extent, from young trees. The closer the scion donor tree is to the ontogenetic growth peak, the more elongated and abundant the branching of the grafts derived from it.