Effects of Water Stress on Biomass Partitioning of Ponderosa Pine Seedlings During Primary Root Growth and Shoot Growth Periods

Abstract

Abstract Biomass partitioning patterns of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) seedling genotypes were investigated under greenhouse conditions at different levels of water stress applied during either the early season root or shoot growth period. The growth of seedlings varied in response to the season in which water stress occurred and among water stress levels. Water stress applied during the shoot growth period resulted in a significantly higher fine root:current-year foliage biomass ratio than seedlings stressed during the root growth period. Seedlings subjected to the high water stress treatment during shoot growth also had the highest fine root:current-year foliage biomass ratio of all treatment combinations. Differences in biomass partitioning among families of ponderosa pine were also present for all treatments combined, suggesting biomass partitioning to roots and shoots is partially under genetic control. For. Sci. 41(3):594-610.