Syllepsis in Larixlaricina: occurrence and distribution of sylleptic long shoots and their relationships with age and vigour in young plantation-grown trees

Abstract

Production of sylleptic long shoots by 102 young Larixlaricina (Du Roi) K. Koch growing in three plantations was monitored for 5 successive years. Sylleptic long shoots were readily discernible both during development and in subsequent years because of their location, growth pattern, and distinctive morphology. Percentages of trees with current-year syllepsis increased from 67% at age 3 years to 90% at age 6 years. Mean numbers of sylleptic long shoots per sylleptic leader also increased as trees aged. Leaders with heavy syllepsis (21–39 shoots) elongated at a mean rate of 14 mm/day for 60 days; whereas, leaders without syllepsis elongated at 12 mm/day for 60 days. The former then continued elongating for a longer period. Distribution of elongation along the leaders also differed. More segments of equal initial length were marked on sylleptic than on nonsylleptic elongating leaders. Early segments elongated more on the latter than on the former. Sylleptic shoots became evident in late June and more formed acropetally until late July on some trees. They elongated at rates up to 10 mm/day and some continued elongating for as long as did their parent leaders. Syllepsis gives trees apparent advantage as they have greater capacity for foliage production.