Endogenous translocation patterns of current photosynthate in post-transplant Quercus rubra seedlings

Variability between individuals can cause error in plant physiology studies when measurements or treatments occur on a chronological basis. Thus, plant growth indices such as the Quercus morphological index (QMI) were developed, enabling distinctions between exogenous treatment effects and endogenous ontological effects. Few studies have examined post-transplant northern red oak (Quercus rubra L.) seedling physiology in relation to the QMI. We used 14CO2 to label current photosynthate of post-transplant northern red oak seedlings during the first flush to assess endogenous patterns of current photosynthate translocation. Carbon translocation patterns relative to QMI growth stages of post-transplant seedlings resembled those described in pre-transplant seedlings, with expanding leaves and shoots retaining the majority of current photosynthate early in the flush, followed by increases in downward translocation to both new and old roots during the lag stage, when active aboveground growth ceased for the flush. Early post-transplant growth of new shoots relied heavily on stored carbohydrates, and old shoots demonstrated negligible sink strength for current photosynthate throughout the experiment. Our findings emphasize the importance of stored carbohydrates for early post-transplant growth and suggest that QMI-based observations regarding carbohydrate translocation patterns of pre-transplant seedlings in this species remain largely valid for post-transplant seedlings.