広葉樹種におけるモジュールの機能分化

抄録

Variations in the properties of modules, together with their number and disposition within a crown, play an important role in the productive strategies of trees. For example, the differentiation of current-year shoots, which are the representative modules of tree species, into short and long shoots produces a useful division of labor. Short shoots (i.e., short current-year shoots with negligible internodes are oriented to foliage-maintenance. Long shoots (i.e., long current-year shoots with extended internodes) are oriented to crown-expansion. An efficient assimilation system is constructed by disposing the right type of shoots in the right position within a crown, according to the relative importance of foliage-maintenance and crown-expansion in the position. Also in some species without such apparent shoot dimorphism, short current-year shoots display a larger leaf area per stem length than long current-year shoots. as in species with the apparent differentiation of short and log shoots. Moreover, in species without such variations in the leaf area-stem length balance, short current-year shoots have low-cost stems with small stem mass per stem length instead of displaying a large leaf area per stem length. Consequently, their short current-year shoots have a greater leaf mass per stem mass than long current-year shoots. The diverse modes in shoot differentiation may be related to species' characteristics in terms of foliage-crown dynamics, such as the life spans of stems and leaves.