Species-specific variation in shoot production patterns of five birch species with respect to vegetative and reproductive shoots

Abstract

We tested whether the difference in shoot production patterns of reproductive and vegetative shoots is only due to resource or meristem availability or also due to species-specific factors. Rates of shoot production by four shoot types (reproductive long shoots, vegetative long shoots, reproductive short shoots, and vegetative short shoots) in Betula platyphylla Sukatchev var. japonica (Miq.) Hara, Betula davurica Pall., Betula ermanii Cham., Betula grossa Sieb. et Zucc., and Betula maximowicziana Regel were compared. In the first three species, each shoot type produced all four shoot types. However, in the latter species, limited shoot production pathways were found both in reproductive shoots and in vegetative shoots, which do not carry any costs associated with reproduction. Furthermore, shoot production by reproductive shoots was not always diminished, but rather was enhanced compared with that by vegetative shoots in B. maximowicziana. These results suggest the importance of species-specific patterns in shoot production, in addition to previously suggested explanations involving resource or meristem limitation.Key words: species specificity, cost of reproduction, Betula, reproductive shoots, vegetative shoots.